diff mbox series

[FFmpeg-devel] avformat/movenc: Support alpha channel for AVIF

Message ID 20220518215620.1718203-1-vigneshv@google.com
State New
Headers show
Series [FFmpeg-devel] avformat/movenc: Support alpha channel for AVIF | expand

Checks

Context Check Description
yinshiyou/make_loongarch64 success Make finished
yinshiyou/make_fate_loongarch64 success Make fate finished
andriy/make_x86 success Make finished
andriy/make_fate_x86 success Make fate finished

Commit Message

Vignesh Venkat May 18, 2022, 9:56 p.m. UTC 
AVIF specification allows for alpha channel as an auxillary item (in
case of still images) or as an auxillary track (in case of animated
images).  Add support for both of these. The AVIF muxer will take
exactly two streams (when alpha is present) as input (first one being
the YUV planes and the second one being the alpha plane).

The input has to come from two different images (one of it color and
the other one being alpha), or it can come from a single file
source with the alpha channel extracted using the "alphaextract"
filter.

Example using alphaextract:
ffmpeg -i rgba.png -filter_complex "[0:v]alphaextract[a]" -map 0 -map "[a]" -still-picture 1 avif_with_alpha.avif

Example using two sources (first source can be in any pixel format and
the second source has to be in monochrome grey pixel format):
ffmpeg -i color.avif -i grey.avif -map 0 -map 1 -c copy avif_with_alpha.avif

The generated files pass the compliance checks in Compliance Warden:
https://github.com/gpac/ComplianceWarden

libavif (the reference avif library) is able to decode the files
generated using this patch.

They also play back properly (with transparent background) in:
1) Chrome
2) Firefox (only still AVIF, no animation support)

Signed-off-by: Vignesh Venkatasubramanian <vigneshv@google.com>
---
 libavformat/movenc.c | 185 +++++++++++++++++++++++++++++--------------
 libavformat/movenc.h |   4 +-
 2 files changed, 128 insertions(+), 61 deletions(-)

Comments

Zhanbang He May 19, 2022, 2:34 a.m. UTC | #1 
some error happened:

On Thu, May 19, 2022 at 5:56 AM Vignesh Venkatasubramanian <
vigneshv-at-google.com@ffmpeg.org> wrote:

> AVIF specification allows for alpha channel as an auxillary item (in
> case of still images) or as an auxillary track (in case of animated
> images).  Add support for both of these. The AVIF muxer will take
> exactly two streams (when alpha is present) as input (first one being
> the YUV planes and the second one being the alpha plane).
>
> The input has to come from two different images (one of it color and
> the other one being alpha), or it can come from a single file
> source with the alpha channel extracted using the "alphaextract"
> filter.
>
> Example using alphaextract:
> ffmpeg -i rgba.png -filter_complex "[0:v]alphaextract[a]" -map 0 -map
> "[a]" -still-picture 1 avif_with_alpha.avif
>
> Example using two sources (first source can be in any pixel format and
> the second source has to be in monochrome grey pixel format):
> ffmpeg -i color.avif -i grey.avif -map 0 -map 1 -c copy
> avif_with_alpha.avif
>
> The generated files pass the compliance checks in Compliance Warden:
> https://github.com/gpac/ComplianceWarden
>
> libavif (the reference avif library) is able to decode the files
> generated using this patch.
>
> They also play back properly (with transparent background) in:
> 1) Chrome
> 2) Firefox (only still AVIF, no animation support)
>
> Signed-off-by: Vignesh Venkatasubramanian <vigneshv@google.com>
> ---
>  libavformat/movenc.c | 185 +++++++++++++++++++++++++++++--------------
>  libavformat/movenc.h |   4 +-
>  2 files changed, 128 insertions(+), 61 deletions(-)
>
> diff --git a/libavformat/movenc.c b/libavformat/movenc.c
> index de971f94e8..00e42b7abb 100644
> --- a/libavformat/movenc.c
> +++ b/libavformat/movenc.c
> @@ -2852,7 +2852,7 @@ static int mov_write_hdlr_tag(AVFormatContext *s,
> AVIOContext *pb, MOVTrack *tra
>          hdlr = (track->mode == MODE_MOV) ? "mhlr" : "\0\0\0\0";
>          if (track->par->codec_type == AVMEDIA_TYPE_VIDEO) {
>              if (track->mode == MODE_AVIF) {
> -                hdlr_type = "pict";
> +                hdlr_type = (track == &mov->tracks[0]) ? "pict" : "auxv";
>                  descr     = "PictureHandler";
>              } else {
>                  hdlr_type = "vide";
> @@ -2940,57 +2940,83 @@ static int mov_write_iloc_tag(AVIOContext *pb,
> MOVMuxContext *mov, AVFormatConte
>      avio_wb32(pb, 0); /* Version & flags */
>      avio_w8(pb, (4 << 4) + 4); /* offset_size(4) and length_size(4) */
>      avio_w8(pb, 0); /* base_offset_size(4) and reserved(4) */
> -    avio_wb16(pb, 1); /* item_count */
> +    avio_wb16(pb, s->nb_streams); /* item_count */
>
> -    avio_wb16(pb, 1); /* item_id */
> -    avio_wb16(pb, 0); /* data_reference_index */
> -    avio_wb16(pb, 1); /* extent_count */
> -    mov->avif_extent_pos = avio_tell(pb);
> -    avio_wb32(pb, 0); /* extent_offset (written later) */
> -    // For animated AVIF, we simply write the first packet's size.
> -    avio_wb32(pb, mov->avif_extent_length); /* extent_length */
> +    for (int i = 0; i < s->nb_streams; i++) {
> +        avio_wb16(pb, i + 1); /* item_id */
> +        avio_wb16(pb, 0); /* data_reference_index */
> +        avio_wb16(pb, 1); /* extent_count */
> +        mov->avif_extent_pos[i] = avio_tell(pb);
> +        avio_wb32(pb, 0); /* extent_offset (written later) */
> +        // For animated AVIF, we simply write the first packet's size.
> +        avio_wb32(pb, mov->avif_extent_length[i]); /* extent_length */
> +    }
>
>      return update_size(pb, pos);
>  }
>
>  static int mov_write_iinf_tag(AVIOContext *pb, MOVMuxContext *mov,
> AVFormatContext *s)
>  {
> -    int64_t infe_pos;
>      int64_t iinf_pos = avio_tell(pb);
>      avio_wb32(pb, 0); /* size */
>      ffio_wfourcc(pb, "iinf");
>      avio_wb32(pb, 0); /* Version & flags */
> -    avio_wb16(pb, 1); /* entry_count */
> +    avio_wb16(pb, s->nb_streams); /* entry_count */
>
> -    infe_pos = avio_tell(pb);
> -    avio_wb32(pb, 0); /* size */
> -    ffio_wfourcc(pb, "infe");
> -    avio_w8(pb, 0x2); /* Version */
> -    avio_wb24(pb, 0); /* flags */
> -    avio_wb16(pb, 1); /* item_id */
> -    avio_wb16(pb, 0); /* item_protection_index */
> -    avio_write(pb, "av01", 4); /* item_type */
> -    avio_write(pb, "Color\0", 6); /* item_name */
> -    update_size(pb, infe_pos);
> +    for (int i = 0; i < s->nb_streams; i++) {
> +        int64_t infe_pos = avio_tell(pb);
> +        avio_wb32(pb, 0); /* size */
> +        ffio_wfourcc(pb, "infe");
> +        avio_w8(pb, 0x2); /* Version */
> +        avio_wb24(pb, 0); /* flags */
> +        avio_wb16(pb, i + 1); /* item_id */
> +        avio_wb16(pb, 0); /* item_protection_index */
> +        avio_write(pb, "av01", 4); /* item_type */
> +        avio_write(pb, !i ? "Color\0" : "Alpha\0", 6); /* item_name */
> +        update_size(pb, infe_pos);
> +    }
>
>      return update_size(pb, iinf_pos);
>  }
>
> -static int mov_write_ispe_tag(AVIOContext *pb, MOVMuxContext *mov,
> AVFormatContext *s)
> +
> +static int mov_write_iref_tag(AVIOContext *pb, MOVMuxContext *mov,
> AVFormatContext *s)
> +{
> +    int64_t auxl_pos;
> +    int64_t iref_pos = avio_tell(pb);
> +    avio_wb32(pb, 0); /* size */
> +    ffio_wfourcc(pb, "iref");
> +    avio_wb32(pb, 0); /* Version & flags */
> +
> +    auxl_pos = avio_tell(pb);
> +    avio_wb32(pb, 0); /* size */
> +    ffio_wfourcc(pb, "auxl");
> +    avio_wb16(pb, 2); /* from_item_ID */
> +    avio_wb16(pb, 1); /* reference_count */
> +    avio_wb16(pb, 1); /* to_item_ID */
> +    update_size(pb, auxl_pos);
> +
> +    return update_size(pb, iref_pos);
> +}
> +
> +static int mov_write_ispe_tag(AVIOContext *pb, MOVMuxContext *mov,
> AVFormatContext *s,
> +                              int stream_index)
>  {
>      int64_t pos = avio_tell(pb);
>      avio_wb32(pb, 0); /* size */
>      ffio_wfourcc(pb, "ispe");
>      avio_wb32(pb, 0); /* Version & flags */
> -    avio_wb32(pb, s->streams[0]->codecpar->width); /* image_width */
> -    avio_wb32(pb, s->streams[0]->codecpar->height); /* image_height */
> +    avio_wb32(pb, s->streams[stream_index]->codecpar->width); /*
> image_width */
> +    avio_wb32(pb, s->streams[stream_index]->codecpar->height); /*
> image_height */
>      return update_size(pb, pos);
>  }
>
> -static int mov_write_pixi_tag(AVIOContext *pb, MOVMuxContext *mov,
> AVFormatContext *s)
> +static int mov_write_pixi_tag(AVIOContext *pb, MOVMuxContext *mov,
> AVFormatContext *s,
> +                              int stream_index)
>  {
>      int64_t pos = avio_tell(pb);
> -    const AVPixFmtDescriptor *pixdesc =
> av_pix_fmt_desc_get(s->streams[0]->codecpar->format);
> +    const AVPixFmtDescriptor *pixdesc =
> +        av_pix_fmt_desc_get(s->streams[stream_index]->codecpar->format);
>      avio_wb32(pb, 0); /* size */
>      ffio_wfourcc(pb, "pixi");
>      avio_wb32(pb, 0); /* Version & flags */
> @@ -3001,15 +3027,30 @@ static int mov_write_pixi_tag(AVIOContext *pb,
> MOVMuxContext *mov, AVFormatConte
>      return update_size(pb, pos);
>  }
>
> +static int mov_write_auxC_tag(AVIOContext *pb)
> +{
> +    int64_t pos = avio_tell(pb);
> +    avio_wb32(pb, 0); /* size */
> +    ffio_wfourcc(pb, "auxC");
> +    avio_wb32(pb, 0); /* Version & flags */
> +    avio_write(pb, "urn:mpeg:mpegB:cicp:systems:auxiliary:alpha\0", 44);
> +    return update_size(pb, pos);
> +}
> +
>  static int mov_write_ipco_tag(AVIOContext *pb, MOVMuxContext *mov,
> AVFormatContext *s)
>  {
>      int64_t pos = avio_tell(pb);
>      avio_wb32(pb, 0); /* size */
>      ffio_wfourcc(pb, "ipco");
> -    mov_write_ispe_tag(pb, mov, s);
> -    mov_write_pixi_tag(pb, mov, s);
> -    mov_write_av1c_tag(pb, &mov->tracks[0]);
> -    mov_write_colr_tag(pb, &mov->tracks[0], 0);
> +    for (int i = 0; i < s->nb_streams; i++) {
> +        mov_write_ispe_tag(pb, mov, s, i);
> +        mov_write_pixi_tag(pb, mov, s, i);
> +        mov_write_av1c_tag(pb, &mov->tracks[i]);
> +        if (!i)
> +            mov_write_colr_tag(pb, &mov->tracks[0], 0);
> +        else
> +            mov_write_auxC_tag(pb);
> +    }
>      return update_size(pb, pos);
>  }
>
> @@ -3019,18 +3060,21 @@ static int mov_write_ipma_tag(AVIOContext *pb,
> MOVMuxContext *mov, AVFormatConte
>      avio_wb32(pb, 0); /* size */
>      ffio_wfourcc(pb, "ipma");
>      avio_wb32(pb, 0); /* Version & flags */
> -    avio_wb32(pb, 1); /* entry_count */
> -    avio_wb16(pb, 1); /* item_ID */
> -    avio_w8(pb, 4); /* association_count */
> -
> -    // ispe association.
> -    avio_w8(pb, 1); /* essential and property_index */
> -    // pixi association.
> -    avio_w8(pb, 2); /* essential and property_index */
> -    // av1C association.
> -    avio_w8(pb, 0x80 | 3); /* essential and property_index */
> -    // colr association.
> -    avio_w8(pb, 4); /* essential and property_index */
> +    avio_wb32(pb, s->nb_streams); /* entry_count */
> +
> +    for (int i = 0, index = 1; i < s->nb_streams; i++) {
> +        avio_wb16(pb, i + 1); /* item_ID */
> +        avio_w8(pb, 4); /* association_count */
> +
> +        // ispe association.
> +        avio_w8(pb, index++); /* essential and property_index */
> +        // pixi association.
> +        avio_w8(pb, index++); /* essential and property_index */
> +        // av1C association.
> +        avio_w8(pb, 0x80 | index++); /* essential and property_index */
> +        // colr/auxC association.
> +        avio_w8(pb, index++); /* essential and property_index */
> +    }
>      return update_size(pb, pos);
>  }
>
> @@ -4112,6 +4156,8 @@ static int mov_write_meta_tag(AVIOContext *pb,
> MOVMuxContext *mov,
>          mov_write_pitm_tag(pb, 1);
>          mov_write_iloc_tag(pb, mov, s);
>          mov_write_iinf_tag(pb, mov, s);
> +        if (s->nb_streams > 1)
> +            mov_write_iref_tag(pb, mov, s);
>          mov_write_iprp_tag(pb, mov, s);
>      } else {
>          /* iTunes metadata tag */
> @@ -6040,8 +6086,8 @@ int ff_mov_write_packet(AVFormatContext *s, AVPacket
> *pkt)
>              avio_write(pb, reformatted_data, size);
>          } else {
>              size = ff_av1_filter_obus(pb, pkt->data, pkt->size);
> -            if (trk->mode == MODE_AVIF && !mov->avif_extent_length) {
> -                mov->avif_extent_length = size;
> +            if (trk->mode == MODE_AVIF &&
> !mov->avif_extent_length[pkt->stream_index]) {
> +                mov->avif_extent_length[pkt->stream_index] = size;
>              }
>          }
>
> @@ -6874,14 +6920,23 @@ static int mov_init(AVFormatContext *s)
>
>      /* AVIF output must have exactly one video stream */
>      if (mov->mode == MODE_AVIF) {
> -        if (s->nb_streams > 1) {
> -            av_log(s, AV_LOG_ERROR, "AVIF output requires exactly one
> stream\n");
> +        if (s->nb_streams > 2) {
> +            av_log(s, AV_LOG_ERROR, "AVIF output requires exactly one or
> two streams\n");
>              return AVERROR(EINVAL);
>          }
> -        if (s->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO) {
> -            av_log(s, AV_LOG_ERROR, "AVIF output requires one video
> stream\n");
> +        if (s->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO &&
> +            (s->nb_streams > 1 && s->streams[1]->codecpar->codec_type !=
> AVMEDIA_TYPE_VIDEO)) {
> +            av_log(s, AV_LOG_ERROR, "AVIF output supports only video
> streams\n");
>              return AVERROR(EINVAL);
>          }
> +        if (s->nb_streams > 1) {
> +            const AVPixFmtDescriptor *pixdesc =
> +                av_pix_fmt_desc_get(s->streams[1]->codecpar->format);
> +            if (pixdesc->nb_components != 1) {
> +                av_log(s, AV_LOG_ERROR, "Second stream for AVIF (alpha)
> output must have exactly one plane\n");
> +                return AVERROR(EINVAL);
> +            }
> +        }
>          s->streams[0]->disposition |= AV_DISPOSITION_DEFAULT;
>      }
>
> @@ -7543,18 +7598,25 @@ static int avif_write_trailer(AVFormatContext *s)
>  {
>      AVIOContext *pb = s->pb;
>      MOVMuxContext *mov = s->priv_data;
> -    int64_t pos_backup, mdat_pos;
> +    int64_t pos_backup, extent_offsets[2];
>      uint8_t *buf;
> -    int buf_size, moov_size;
> +    int buf_size, moov_size, i;
>
>      if (mov->moov_written) return 0;
>
>      mov->is_animated_avif = s->streams[0]->nb_frames > 1;
> +    if (mov->is_animated_avif && s->nb_streams > 1) {
> +        // For animated avif with alpha channel, we need to write a the
> tref
> +        // tag with type "auxl".
> +        mov->tracks[1].tref_tag = MKTAG('a', 'u', 'x', 'l');
> +        mov->tracks[1].tref_id = 1;
> +    }
>      mov_write_identification(pb, s);
>      mov_write_meta_tag(pb, mov, s);
>
>      moov_size = get_moov_size(s);
> -    mov->tracks[0].data_offset = avio_tell(pb) + moov_size + 8;
> +    for (i = 0; i < s->nb_streams; i++)
> +        mov->tracks[i].data_offset = avio_tell(pb) + moov_size + 8;
>
>      if (mov->is_animated_avif) {
>          int ret;
> @@ -7565,19 +7627,24 @@ static int avif_write_trailer(AVFormatContext *s)
>      buf_size = avio_get_dyn_buf(mov->mdat_buf, &buf);
>      avio_wb32(pb, buf_size + 8);
>      ffio_wfourcc(pb, "mdat");
> -    mdat_pos = avio_tell(pb);
>
> -    if (mdat_pos != (uint32_t)mdat_pos) {
> -        av_log(s, AV_LOG_ERROR, "mdat offset does not fit in 32 bits\n");
> -        return AVERROR_INVALIDDATA;
> -    }
> +    // The offset for the YUV planes is the starting position of mdat.
> +    extent_offsets[0] = avio_tell(pb);
> +    // The offset for alpha plane is YUV offset + YUV size.
> +    extent_offsets[1] = extent_offsets[0] + mov->avif_extent_length[0];
>
>      avio_write(pb, buf, buf_size);
>
> -    // write extent offset.
> +    // write extent offsets.
>      pos_backup = avio_tell(pb);
> -    avio_seek(pb, mov->avif_extent_pos, SEEK_SET);
> -    avio_wb32(pb, mdat_pos); /* rewrite offset */
> +    for (i = 0; i < s->nb_streams; i++) {
> +        if (extent_offsets[i] != (uint32_t)extent_offsets[i]) {
> +            av_log(s, AV_LOG_ERROR, "extent offset does not fit in 32
> bits\n");
> +            return AVERROR_INVALIDDATA;
> +        }
> +        avio_seek(pb, mov->avif_extent_pos[i], SEEK_SET);
> +        avio_wb32(pb, extent_offsets[i]); /* rewrite offset */
> +    }
>      avio_seek(pb, pos_backup, SEEK_SET);
>
>      return 0;
> diff --git a/libavformat/movenc.h b/libavformat/movenc.h
> index 281576cc66..e4550f7900 100644
> --- a/libavformat/movenc.h
> +++ b/libavformat/movenc.h
> @@ -246,8 +246,8 @@ typedef struct MOVMuxContext {
>      int empty_hdlr_name;
>      int movie_timescale;
>
> -    int64_t avif_extent_pos;
> -    int avif_extent_length;
> +    int64_t avif_extent_pos[2];  // index 0 is YUV and 1 is Alpha.
> +    int avif_extent_length[2];   // index 0 is YUV and 1 is Alpha.
>      int is_animated_avif;
>  } MOVMuxContext;
>
> --
> 2.36.1.124.g0e6072fb45-goog
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
>
Zhanbang He May 19, 2022, 2:36 a.m. UTC | #2 
error happened:

./ffmpeg -i alpha.png -filter_complex [0:v]alphaextract[a] -map 0 -map [a]
-still-picture 1 avif_with_alpha.avif
ffmpeg version N-106936-gff5ea89da2 Copyright (c) 2000-2022 the FFmpeg
developers
  built with gcc 11 (Ubuntu 11.2.0-19ubuntu1)
  configuration: --disable-ffplay --disable-ffprobe --enable-gpl
--enable-nonfree --prefix=/home/bang/Desktop/out
  libavutil      57. 24.101 / 57. 24.101
  libavcodec     59. 28.100 / 59. 28.100
  libavformat    59. 24.100 / 59. 24.100
  libavdevice    59.  6.100 / 59.  6.100
  libavfilter     8. 38.100 /  8. 38.100
  libswscale      6.  6.100 /  6.  6.100
  libswresample   4.  6.100 /  4.  6.100
  libpostproc    56.  5.100 / 56.  5.100
Unrecognized option 'still-picture'.
Error splitting the argument list: Option not found

On Thu, May 19, 2022 at 5:56 AM Vignesh Venkatasubramanian <
vigneshv-at-google.com@ffmpeg.org> wrote:

> AVIF specification allows for alpha channel as an auxillary item (in
> case of still images) or as an auxillary track (in case of animated
> images).  Add support for both of these. The AVIF muxer will take
> exactly two streams (when alpha is present) as input (first one being
> the YUV planes and the second one being the alpha plane).
>
> The input has to come from two different images (one of it color and
> the other one being alpha), or it can come from a single file
> source with the alpha channel extracted using the "alphaextract"
> filter.
>
> Example using alphaextract:
> ffmpeg -i rgba.png -filter_complex "[0:v]alphaextract[a]" -map 0 -map
> "[a]" -still-picture 1 avif_with_alpha.avif
>
> Example using two sources (first source can be in any pixel format and
> the second source has to be in monochrome grey pixel format):
> ffmpeg -i color.avif -i grey.avif -map 0 -map 1 -c copy
> avif_with_alpha.avif
>
> The generated files pass the compliance checks in Compliance Warden:
> https://github.com/gpac/ComplianceWarden
>
> libavif (the reference avif library) is able to decode the files
> generated using this patch.
>
> They also play back properly (with transparent background) in:
> 1) Chrome
> 2) Firefox (only still AVIF, no animation support)
>
> Signed-off-by: Vignesh Venkatasubramanian <vigneshv@google.com>
> ---
>  libavformat/movenc.c | 185 +++++++++++++++++++++++++++++--------------
>  libavformat/movenc.h |   4 +-
>  2 files changed, 128 insertions(+), 61 deletions(-)
>
> diff --git a/libavformat/movenc.c b/libavformat/movenc.c
> index de971f94e8..00e42b7abb 100644
> --- a/libavformat/movenc.c
> +++ b/libavformat/movenc.c
> @@ -2852,7 +2852,7 @@ static int mov_write_hdlr_tag(AVFormatContext *s,
> AVIOContext *pb, MOVTrack *tra
>          hdlr = (track->mode == MODE_MOV) ? "mhlr" : "\0\0\0\0";
>          if (track->par->codec_type == AVMEDIA_TYPE_VIDEO) {
>              if (track->mode == MODE_AVIF) {
> -                hdlr_type = "pict";
> +                hdlr_type = (track == &mov->tracks[0]) ? "pict" : "auxv";
>                  descr     = "PictureHandler";
>              } else {
>                  hdlr_type = "vide";
> @@ -2940,57 +2940,83 @@ static int mov_write_iloc_tag(AVIOContext *pb,
> MOVMuxContext *mov, AVFormatConte
>      avio_wb32(pb, 0); /* Version & flags */
>      avio_w8(pb, (4 << 4) + 4); /* offset_size(4) and length_size(4) */
>      avio_w8(pb, 0); /* base_offset_size(4) and reserved(4) */
> -    avio_wb16(pb, 1); /* item_count */
> +    avio_wb16(pb, s->nb_streams); /* item_count */
>
> -    avio_wb16(pb, 1); /* item_id */
> -    avio_wb16(pb, 0); /* data_reference_index */
> -    avio_wb16(pb, 1); /* extent_count */
> -    mov->avif_extent_pos = avio_tell(pb);
> -    avio_wb32(pb, 0); /* extent_offset (written later) */
> -    // For animated AVIF, we simply write the first packet's size.
> -    avio_wb32(pb, mov->avif_extent_length); /* extent_length */
> +    for (int i = 0; i < s->nb_streams; i++) {
> +        avio_wb16(pb, i + 1); /* item_id */
> +        avio_wb16(pb, 0); /* data_reference_index */
> +        avio_wb16(pb, 1); /* extent_count */
> +        mov->avif_extent_pos[i] = avio_tell(pb);
> +        avio_wb32(pb, 0); /* extent_offset (written later) */
> +        // For animated AVIF, we simply write the first packet's size.
> +        avio_wb32(pb, mov->avif_extent_length[i]); /* extent_length */
> +    }
>
>      return update_size(pb, pos);
>  }
>
>  static int mov_write_iinf_tag(AVIOContext *pb, MOVMuxContext *mov,
> AVFormatContext *s)
>  {
> -    int64_t infe_pos;
>      int64_t iinf_pos = avio_tell(pb);
>      avio_wb32(pb, 0); /* size */
>      ffio_wfourcc(pb, "iinf");
>      avio_wb32(pb, 0); /* Version & flags */
> -    avio_wb16(pb, 1); /* entry_count */
> +    avio_wb16(pb, s->nb_streams); /* entry_count */
>
> -    infe_pos = avio_tell(pb);
> -    avio_wb32(pb, 0); /* size */
> -    ffio_wfourcc(pb, "infe");
> -    avio_w8(pb, 0x2); /* Version */
> -    avio_wb24(pb, 0); /* flags */
> -    avio_wb16(pb, 1); /* item_id */
> -    avio_wb16(pb, 0); /* item_protection_index */
> -    avio_write(pb, "av01", 4); /* item_type */
> -    avio_write(pb, "Color\0", 6); /* item_name */
> -    update_size(pb, infe_pos);
> +    for (int i = 0; i < s->nb_streams; i++) {
> +        int64_t infe_pos = avio_tell(pb);
> +        avio_wb32(pb, 0); /* size */
> +        ffio_wfourcc(pb, "infe");
> +        avio_w8(pb, 0x2); /* Version */
> +        avio_wb24(pb, 0); /* flags */
> +        avio_wb16(pb, i + 1); /* item_id */
> +        avio_wb16(pb, 0); /* item_protection_index */
> +        avio_write(pb, "av01", 4); /* item_type */
> +        avio_write(pb, !i ? "Color\0" : "Alpha\0", 6); /* item_name */
> +        update_size(pb, infe_pos);
> +    }
>
>      return update_size(pb, iinf_pos);
>  }
>
> -static int mov_write_ispe_tag(AVIOContext *pb, MOVMuxContext *mov,
> AVFormatContext *s)
> +
> +static int mov_write_iref_tag(AVIOContext *pb, MOVMuxContext *mov,
> AVFormatContext *s)
> +{
> +    int64_t auxl_pos;
> +    int64_t iref_pos = avio_tell(pb);
> +    avio_wb32(pb, 0); /* size */
> +    ffio_wfourcc(pb, "iref");
> +    avio_wb32(pb, 0); /* Version & flags */
> +
> +    auxl_pos = avio_tell(pb);
> +    avio_wb32(pb, 0); /* size */
> +    ffio_wfourcc(pb, "auxl");
> +    avio_wb16(pb, 2); /* from_item_ID */
> +    avio_wb16(pb, 1); /* reference_count */
> +    avio_wb16(pb, 1); /* to_item_ID */
> +    update_size(pb, auxl_pos);
> +
> +    return update_size(pb, iref_pos);
> +}
> +
> +static int mov_write_ispe_tag(AVIOContext *pb, MOVMuxContext *mov,
> AVFormatContext *s,
> +                              int stream_index)
>  {
>      int64_t pos = avio_tell(pb);
>      avio_wb32(pb, 0); /* size */
>      ffio_wfourcc(pb, "ispe");
>      avio_wb32(pb, 0); /* Version & flags */
> -    avio_wb32(pb, s->streams[0]->codecpar->width); /* image_width */
> -    avio_wb32(pb, s->streams[0]->codecpar->height); /* image_height */
> +    avio_wb32(pb, s->streams[stream_index]->codecpar->width); /*
> image_width */
> +    avio_wb32(pb, s->streams[stream_index]->codecpar->height); /*
> image_height */
>      return update_size(pb, pos);
>  }
>
> -static int mov_write_pixi_tag(AVIOContext *pb, MOVMuxContext *mov,
> AVFormatContext *s)
> +static int mov_write_pixi_tag(AVIOContext *pb, MOVMuxContext *mov,
> AVFormatContext *s,
> +                              int stream_index)
>  {
>      int64_t pos = avio_tell(pb);
> -    const AVPixFmtDescriptor *pixdesc =
> av_pix_fmt_desc_get(s->streams[0]->codecpar->format);
> +    const AVPixFmtDescriptor *pixdesc =
> +        av_pix_fmt_desc_get(s->streams[stream_index]->codecpar->format);
>      avio_wb32(pb, 0); /* size */
>      ffio_wfourcc(pb, "pixi");
>      avio_wb32(pb, 0); /* Version & flags */
> @@ -3001,15 +3027,30 @@ static int mov_write_pixi_tag(AVIOContext *pb,
> MOVMuxContext *mov, AVFormatConte
>      return update_size(pb, pos);
>  }
>
> +static int mov_write_auxC_tag(AVIOContext *pb)
> +{
> +    int64_t pos = avio_tell(pb);
> +    avio_wb32(pb, 0); /* size */
> +    ffio_wfourcc(pb, "auxC");
> +    avio_wb32(pb, 0); /* Version & flags */
> +    avio_write(pb, "urn:mpeg:mpegB:cicp:systems:auxiliary:alpha\0", 44);
> +    return update_size(pb, pos);
> +}
> +
>  static int mov_write_ipco_tag(AVIOContext *pb, MOVMuxContext *mov,
> AVFormatContext *s)
>  {
>      int64_t pos = avio_tell(pb);
>      avio_wb32(pb, 0); /* size */
>      ffio_wfourcc(pb, "ipco");
> -    mov_write_ispe_tag(pb, mov, s);
> -    mov_write_pixi_tag(pb, mov, s);
> -    mov_write_av1c_tag(pb, &mov->tracks[0]);
> -    mov_write_colr_tag(pb, &mov->tracks[0], 0);
> +    for (int i = 0; i < s->nb_streams; i++) {
> +        mov_write_ispe_tag(pb, mov, s, i);
> +        mov_write_pixi_tag(pb, mov, s, i);
> +        mov_write_av1c_tag(pb, &mov->tracks[i]);
> +        if (!i)
> +            mov_write_colr_tag(pb, &mov->tracks[0], 0);
> +        else
> +            mov_write_auxC_tag(pb);
> +    }
>      return update_size(pb, pos);
>  }
>
> @@ -3019,18 +3060,21 @@ static int mov_write_ipma_tag(AVIOContext *pb,
> MOVMuxContext *mov, AVFormatConte
>      avio_wb32(pb, 0); /* size */
>      ffio_wfourcc(pb, "ipma");
>      avio_wb32(pb, 0); /* Version & flags */
> -    avio_wb32(pb, 1); /* entry_count */
> -    avio_wb16(pb, 1); /* item_ID */
> -    avio_w8(pb, 4); /* association_count */
> -
> -    // ispe association.
> -    avio_w8(pb, 1); /* essential and property_index */
> -    // pixi association.
> -    avio_w8(pb, 2); /* essential and property_index */
> -    // av1C association.
> -    avio_w8(pb, 0x80 | 3); /* essential and property_index */
> -    // colr association.
> -    avio_w8(pb, 4); /* essential and property_index */
> +    avio_wb32(pb, s->nb_streams); /* entry_count */
> +
> +    for (int i = 0, index = 1; i < s->nb_streams; i++) {
> +        avio_wb16(pb, i + 1); /* item_ID */
> +        avio_w8(pb, 4); /* association_count */
> +
> +        // ispe association.
> +        avio_w8(pb, index++); /* essential and property_index */
> +        // pixi association.
> +        avio_w8(pb, index++); /* essential and property_index */
> +        // av1C association.
> +        avio_w8(pb, 0x80 | index++); /* essential and property_index */
> +        // colr/auxC association.
> +        avio_w8(pb, index++); /* essential and property_index */
> +    }
>      return update_size(pb, pos);
>  }
>
> @@ -4112,6 +4156,8 @@ static int mov_write_meta_tag(AVIOContext *pb,
> MOVMuxContext *mov,
>          mov_write_pitm_tag(pb, 1);
>          mov_write_iloc_tag(pb, mov, s);
>          mov_write_iinf_tag(pb, mov, s);
> +        if (s->nb_streams > 1)
> +            mov_write_iref_tag(pb, mov, s);
>          mov_write_iprp_tag(pb, mov, s);
>      } else {
>          /* iTunes metadata tag */
> @@ -6040,8 +6086,8 @@ int ff_mov_write_packet(AVFormatContext *s, AVPacket
> *pkt)
>              avio_write(pb, reformatted_data, size);
>          } else {
>              size = ff_av1_filter_obus(pb, pkt->data, pkt->size);
> -            if (trk->mode == MODE_AVIF && !mov->avif_extent_length) {
> -                mov->avif_extent_length = size;
> +            if (trk->mode == MODE_AVIF &&
> !mov->avif_extent_length[pkt->stream_index]) {
> +                mov->avif_extent_length[pkt->stream_index] = size;
>              }
>          }
>
> @@ -6874,14 +6920,23 @@ static int mov_init(AVFormatContext *s)
>
>      /* AVIF output must have exactly one video stream */
>      if (mov->mode == MODE_AVIF) {
> -        if (s->nb_streams > 1) {
> -            av_log(s, AV_LOG_ERROR, "AVIF output requires exactly one
> stream\n");
> +        if (s->nb_streams > 2) {
> +            av_log(s, AV_LOG_ERROR, "AVIF output requires exactly one or
> two streams\n");
>              return AVERROR(EINVAL);
>          }
> -        if (s->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO) {
> -            av_log(s, AV_LOG_ERROR, "AVIF output requires one video
> stream\n");
> +        if (s->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO &&
> +            (s->nb_streams > 1 && s->streams[1]->codecpar->codec_type !=
> AVMEDIA_TYPE_VIDEO)) {
> +            av_log(s, AV_LOG_ERROR, "AVIF output supports only video
> streams\n");
>              return AVERROR(EINVAL);
>          }
> +        if (s->nb_streams > 1) {
> +            const AVPixFmtDescriptor *pixdesc =
> +                av_pix_fmt_desc_get(s->streams[1]->codecpar->format);
> +            if (pixdesc->nb_components != 1) {
> +                av_log(s, AV_LOG_ERROR, "Second stream for AVIF (alpha)
> output must have exactly one plane\n");
> +                return AVERROR(EINVAL);
> +            }
> +        }
>          s->streams[0]->disposition |= AV_DISPOSITION_DEFAULT;
>      }
>
> @@ -7543,18 +7598,25 @@ static int avif_write_trailer(AVFormatContext *s)
>  {
>      AVIOContext *pb = s->pb;
>      MOVMuxContext *mov = s->priv_data;
> -    int64_t pos_backup, mdat_pos;
> +    int64_t pos_backup, extent_offsets[2];
>      uint8_t *buf;
> -    int buf_size, moov_size;
> +    int buf_size, moov_size, i;
>
>      if (mov->moov_written) return 0;
>
>      mov->is_animated_avif = s->streams[0]->nb_frames > 1;
> +    if (mov->is_animated_avif && s->nb_streams > 1) {
> +        // For animated avif with alpha channel, we need to write a the
> tref
> +        // tag with type "auxl".
> +        mov->tracks[1].tref_tag = MKTAG('a', 'u', 'x', 'l');
> +        mov->tracks[1].tref_id = 1;
> +    }
>      mov_write_identification(pb, s);
>      mov_write_meta_tag(pb, mov, s);
>
>      moov_size = get_moov_size(s);
> -    mov->tracks[0].data_offset = avio_tell(pb) + moov_size + 8;
> +    for (i = 0; i < s->nb_streams; i++)
> +        mov->tracks[i].data_offset = avio_tell(pb) + moov_size + 8;
>
>      if (mov->is_animated_avif) {
>          int ret;
> @@ -7565,19 +7627,24 @@ static int avif_write_trailer(AVFormatContext *s)
>      buf_size = avio_get_dyn_buf(mov->mdat_buf, &buf);
>      avio_wb32(pb, buf_size + 8);
>      ffio_wfourcc(pb, "mdat");
> -    mdat_pos = avio_tell(pb);
>
> -    if (mdat_pos != (uint32_t)mdat_pos) {
> -        av_log(s, AV_LOG_ERROR, "mdat offset does not fit in 32 bits\n");
> -        return AVERROR_INVALIDDATA;
> -    }
> +    // The offset for the YUV planes is the starting position of mdat.
> +    extent_offsets[0] = avio_tell(pb);
> +    // The offset for alpha plane is YUV offset + YUV size.
> +    extent_offsets[1] = extent_offsets[0] + mov->avif_extent_length[0];
>
>      avio_write(pb, buf, buf_size);
>
> -    // write extent offset.
> +    // write extent offsets.
>      pos_backup = avio_tell(pb);
> -    avio_seek(pb, mov->avif_extent_pos, SEEK_SET);
> -    avio_wb32(pb, mdat_pos); /* rewrite offset */
> +    for (i = 0; i < s->nb_streams; i++) {
> +        if (extent_offsets[i] != (uint32_t)extent_offsets[i]) {
> +            av_log(s, AV_LOG_ERROR, "extent offset does not fit in 32
> bits\n");
> +            return AVERROR_INVALIDDATA;
> +        }
> +        avio_seek(pb, mov->avif_extent_pos[i], SEEK_SET);
> +        avio_wb32(pb, extent_offsets[i]); /* rewrite offset */
> +    }
>      avio_seek(pb, pos_backup, SEEK_SET);
>
>      return 0;
> diff --git a/libavformat/movenc.h b/libavformat/movenc.h
> index 281576cc66..e4550f7900 100644
> --- a/libavformat/movenc.h
> +++ b/libavformat/movenc.h
> @@ -246,8 +246,8 @@ typedef struct MOVMuxContext {
>      int empty_hdlr_name;
>      int movie_timescale;
>
> -    int64_t avif_extent_pos;
> -    int avif_extent_length;
> +    int64_t avif_extent_pos[2];  // index 0 is YUV and 1 is Alpha.
> +    int avif_extent_length[2];   // index 0 is YUV and 1 is Alpha.
>      int is_animated_avif;
>  } MOVMuxContext;
>
> --
> 2.36.1.124.g0e6072fb45-goog
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
>
Vignesh Venkat May 19, 2022, 4:08 p.m. UTC | #3 
On Wed, May 18, 2022 at 7:36 PM Bang He <hezhanbang@gmail.com> wrote:
>
> error happened:
>
> ./ffmpeg -i alpha.png -filter_complex [0:v]alphaextract[a] -map 0 -map [a]
> -still-picture 1 avif_with_alpha.avif
> ffmpeg version N-106936-gff5ea89da2 Copyright (c) 2000-2022 the FFmpeg
> developers
>   built with gcc 11 (Ubuntu 11.2.0-19ubuntu1)
>   configuration: --disable-ffplay --disable-ffprobe --enable-gpl
> --enable-nonfree --prefix=/home/bang/Desktop/out
>   libavutil      57. 24.101 / 57. 24.101
>   libavcodec     59. 28.100 / 59. 28.100
>   libavformat    59. 24.100 / 59. 24.100
>   libavdevice    59.  6.100 / 59.  6.100
>   libavfilter     8. 38.100 /  8. 38.100
>   libswscale      6.  6.100 /  6.  6.100
>   libswresample   4.  6.100 /  4.  6.100
>   libpostproc    56.  5.100 / 56.  5.100
> Unrecognized option 'still-picture'.
> Error splitting the argument list: Option not found
>

You would have to build ffmpeg with libaom enabled for AVIF encoding
to work (since AVIF is backed by an AV1 encoder). From the logs you
posted, it seems like you don't have an AV1 encoder available in your
ffmpeg build.

The "-still-picture" flag was added in ab05e9a7f2. Please make sure
that you are sync'ed past that to pick up that option.

> On Thu, May 19, 2022 at 5:56 AM Vignesh Venkatasubramanian <
> vigneshv-at-google.com@ffmpeg.org> wrote:
>
> > AVIF specification allows for alpha channel as an auxillary item (in
> > case of still images) or as an auxillary track (in case of animated
> > images).  Add support for both of these. The AVIF muxer will take
> > exactly two streams (when alpha is present) as input (first one being
> > the YUV planes and the second one being the alpha plane).
> >
> > The input has to come from two different images (one of it color and
> > the other one being alpha), or it can come from a single file
> > source with the alpha channel extracted using the "alphaextract"
> > filter.
> >
> > Example using alphaextract:
> > ffmpeg -i rgba.png -filter_complex "[0:v]alphaextract[a]" -map 0 -map
> > "[a]" -still-picture 1 avif_with_alpha.avif
> >
> > Example using two sources (first source can be in any pixel format and
> > the second source has to be in monochrome grey pixel format):
> > ffmpeg -i color.avif -i grey.avif -map 0 -map 1 -c copy
> > avif_with_alpha.avif
> >
> > The generated files pass the compliance checks in Compliance Warden:
> > https://github.com/gpac/ComplianceWarden
> >
> > libavif (the reference avif library) is able to decode the files
> > generated using this patch.
> >
> > They also play back properly (with transparent background) in:
> > 1) Chrome
> > 2) Firefox (only still AVIF, no animation support)
> >
> > Signed-off-by: Vignesh Venkatasubramanian <vigneshv@google.com>
> > ---
> >  libavformat/movenc.c | 185 +++++++++++++++++++++++++++++--------------
> >  libavformat/movenc.h |   4 +-
> >  2 files changed, 128 insertions(+), 61 deletions(-)
> >
> > diff --git a/libavformat/movenc.c b/libavformat/movenc.c
> > index de971f94e8..00e42b7abb 100644
> > --- a/libavformat/movenc.c
> > +++ b/libavformat/movenc.c
> > @@ -2852,7 +2852,7 @@ static int mov_write_hdlr_tag(AVFormatContext *s,
> > AVIOContext *pb, MOVTrack *tra
> >          hdlr = (track->mode == MODE_MOV) ? "mhlr" : "\0\0\0\0";
> >          if (track->par->codec_type == AVMEDIA_TYPE_VIDEO) {
> >              if (track->mode == MODE_AVIF) {
> > -                hdlr_type = "pict";
> > +                hdlr_type = (track == &mov->tracks[0]) ? "pict" : "auxv";
> >                  descr     = "PictureHandler";
> >              } else {
> >                  hdlr_type = "vide";
> > @@ -2940,57 +2940,83 @@ static int mov_write_iloc_tag(AVIOContext *pb,
> > MOVMuxContext *mov, AVFormatConte
> >      avio_wb32(pb, 0); /* Version & flags */
> >      avio_w8(pb, (4 << 4) + 4); /* offset_size(4) and length_size(4) */
> >      avio_w8(pb, 0); /* base_offset_size(4) and reserved(4) */
> > -    avio_wb16(pb, 1); /* item_count */
> > +    avio_wb16(pb, s->nb_streams); /* item_count */
> >
> > -    avio_wb16(pb, 1); /* item_id */
> > -    avio_wb16(pb, 0); /* data_reference_index */
> > -    avio_wb16(pb, 1); /* extent_count */
> > -    mov->avif_extent_pos = avio_tell(pb);
> > -    avio_wb32(pb, 0); /* extent_offset (written later) */
> > -    // For animated AVIF, we simply write the first packet's size.
> > -    avio_wb32(pb, mov->avif_extent_length); /* extent_length */
> > +    for (int i = 0; i < s->nb_streams; i++) {
> > +        avio_wb16(pb, i + 1); /* item_id */
> > +        avio_wb16(pb, 0); /* data_reference_index */
> > +        avio_wb16(pb, 1); /* extent_count */
> > +        mov->avif_extent_pos[i] = avio_tell(pb);
> > +        avio_wb32(pb, 0); /* extent_offset (written later) */
> > +        // For animated AVIF, we simply write the first packet's size.
> > +        avio_wb32(pb, mov->avif_extent_length[i]); /* extent_length */
> > +    }
> >
> >      return update_size(pb, pos);
> >  }
> >
> >  static int mov_write_iinf_tag(AVIOContext *pb, MOVMuxContext *mov,
> > AVFormatContext *s)
> >  {
> > -    int64_t infe_pos;
> >      int64_t iinf_pos = avio_tell(pb);
> >      avio_wb32(pb, 0); /* size */
> >      ffio_wfourcc(pb, "iinf");
> >      avio_wb32(pb, 0); /* Version & flags */
> > -    avio_wb16(pb, 1); /* entry_count */
> > +    avio_wb16(pb, s->nb_streams); /* entry_count */
> >
> > -    infe_pos = avio_tell(pb);
> > -    avio_wb32(pb, 0); /* size */
> > -    ffio_wfourcc(pb, "infe");
> > -    avio_w8(pb, 0x2); /* Version */
> > -    avio_wb24(pb, 0); /* flags */
> > -    avio_wb16(pb, 1); /* item_id */
> > -    avio_wb16(pb, 0); /* item_protection_index */
> > -    avio_write(pb, "av01", 4); /* item_type */
> > -    avio_write(pb, "Color\0", 6); /* item_name */
> > -    update_size(pb, infe_pos);
> > +    for (int i = 0; i < s->nb_streams; i++) {
> > +        int64_t infe_pos = avio_tell(pb);
> > +        avio_wb32(pb, 0); /* size */
> > +        ffio_wfourcc(pb, "infe");
> > +        avio_w8(pb, 0x2); /* Version */
> > +        avio_wb24(pb, 0); /* flags */
> > +        avio_wb16(pb, i + 1); /* item_id */
> > +        avio_wb16(pb, 0); /* item_protection_index */
> > +        avio_write(pb, "av01", 4); /* item_type */
> > +        avio_write(pb, !i ? "Color\0" : "Alpha\0", 6); /* item_name */
> > +        update_size(pb, infe_pos);
> > +    }
> >
> >      return update_size(pb, iinf_pos);
> >  }
> >
> > -static int mov_write_ispe_tag(AVIOContext *pb, MOVMuxContext *mov,
> > AVFormatContext *s)
> > +
> > +static int mov_write_iref_tag(AVIOContext *pb, MOVMuxContext *mov,
> > AVFormatContext *s)
> > +{
> > +    int64_t auxl_pos;
> > +    int64_t iref_pos = avio_tell(pb);
> > +    avio_wb32(pb, 0); /* size */
> > +    ffio_wfourcc(pb, "iref");
> > +    avio_wb32(pb, 0); /* Version & flags */
> > +
> > +    auxl_pos = avio_tell(pb);
> > +    avio_wb32(pb, 0); /* size */
> > +    ffio_wfourcc(pb, "auxl");
> > +    avio_wb16(pb, 2); /* from_item_ID */
> > +    avio_wb16(pb, 1); /* reference_count */
> > +    avio_wb16(pb, 1); /* to_item_ID */
> > +    update_size(pb, auxl_pos);
> > +
> > +    return update_size(pb, iref_pos);
> > +}
> > +
> > +static int mov_write_ispe_tag(AVIOContext *pb, MOVMuxContext *mov,
> > AVFormatContext *s,
> > +                              int stream_index)
> >  {
> >      int64_t pos = avio_tell(pb);
> >      avio_wb32(pb, 0); /* size */
> >      ffio_wfourcc(pb, "ispe");
> >      avio_wb32(pb, 0); /* Version & flags */
> > -    avio_wb32(pb, s->streams[0]->codecpar->width); /* image_width */
> > -    avio_wb32(pb, s->streams[0]->codecpar->height); /* image_height */
> > +    avio_wb32(pb, s->streams[stream_index]->codecpar->width); /*
> > image_width */
> > +    avio_wb32(pb, s->streams[stream_index]->codecpar->height); /*
> > image_height */
> >      return update_size(pb, pos);
> >  }
> >
> > -static int mov_write_pixi_tag(AVIOContext *pb, MOVMuxContext *mov,
> > AVFormatContext *s)
> > +static int mov_write_pixi_tag(AVIOContext *pb, MOVMuxContext *mov,
> > AVFormatContext *s,
> > +                              int stream_index)
> >  {
> >      int64_t pos = avio_tell(pb);
> > -    const AVPixFmtDescriptor *pixdesc =
> > av_pix_fmt_desc_get(s->streams[0]->codecpar->format);
> > +    const AVPixFmtDescriptor *pixdesc =
> > +        av_pix_fmt_desc_get(s->streams[stream_index]->codecpar->format);
> >      avio_wb32(pb, 0); /* size */
> >      ffio_wfourcc(pb, "pixi");
> >      avio_wb32(pb, 0); /* Version & flags */
> > @@ -3001,15 +3027,30 @@ static int mov_write_pixi_tag(AVIOContext *pb,
> > MOVMuxContext *mov, AVFormatConte
> >      return update_size(pb, pos);
> >  }
> >
> > +static int mov_write_auxC_tag(AVIOContext *pb)
> > +{
> > +    int64_t pos = avio_tell(pb);
> > +    avio_wb32(pb, 0); /* size */
> > +    ffio_wfourcc(pb, "auxC");
> > +    avio_wb32(pb, 0); /* Version & flags */
> > +    avio_write(pb, "urn:mpeg:mpegB:cicp:systems:auxiliary:alpha\0", 44);
> > +    return update_size(pb, pos);
> > +}
> > +
> >  static int mov_write_ipco_tag(AVIOContext *pb, MOVMuxContext *mov,
> > AVFormatContext *s)
> >  {
> >      int64_t pos = avio_tell(pb);
> >      avio_wb32(pb, 0); /* size */
> >      ffio_wfourcc(pb, "ipco");
> > -    mov_write_ispe_tag(pb, mov, s);
> > -    mov_write_pixi_tag(pb, mov, s);
> > -    mov_write_av1c_tag(pb, &mov->tracks[0]);
> > -    mov_write_colr_tag(pb, &mov->tracks[0], 0);
> > +    for (int i = 0; i < s->nb_streams; i++) {
> > +        mov_write_ispe_tag(pb, mov, s, i);
> > +        mov_write_pixi_tag(pb, mov, s, i);
> > +        mov_write_av1c_tag(pb, &mov->tracks[i]);
> > +        if (!i)
> > +            mov_write_colr_tag(pb, &mov->tracks[0], 0);
> > +        else
> > +            mov_write_auxC_tag(pb);
> > +    }
> >      return update_size(pb, pos);
> >  }
> >
> > @@ -3019,18 +3060,21 @@ static int mov_write_ipma_tag(AVIOContext *pb,
> > MOVMuxContext *mov, AVFormatConte
> >      avio_wb32(pb, 0); /* size */
> >      ffio_wfourcc(pb, "ipma");
> >      avio_wb32(pb, 0); /* Version & flags */
> > -    avio_wb32(pb, 1); /* entry_count */
> > -    avio_wb16(pb, 1); /* item_ID */
> > -    avio_w8(pb, 4); /* association_count */
> > -
> > -    // ispe association.
> > -    avio_w8(pb, 1); /* essential and property_index */
> > -    // pixi association.
> > -    avio_w8(pb, 2); /* essential and property_index */
> > -    // av1C association.
> > -    avio_w8(pb, 0x80 | 3); /* essential and property_index */
> > -    // colr association.
> > -    avio_w8(pb, 4); /* essential and property_index */
> > +    avio_wb32(pb, s->nb_streams); /* entry_count */
> > +
> > +    for (int i = 0, index = 1; i < s->nb_streams; i++) {
> > +        avio_wb16(pb, i + 1); /* item_ID */
> > +        avio_w8(pb, 4); /* association_count */
> > +
> > +        // ispe association.
> > +        avio_w8(pb, index++); /* essential and property_index */
> > +        // pixi association.
> > +        avio_w8(pb, index++); /* essential and property_index */
> > +        // av1C association.
> > +        avio_w8(pb, 0x80 | index++); /* essential and property_index */
> > +        // colr/auxC association.
> > +        avio_w8(pb, index++); /* essential and property_index */
> > +    }
> >      return update_size(pb, pos);
> >  }
> >
> > @@ -4112,6 +4156,8 @@ static int mov_write_meta_tag(AVIOContext *pb,
> > MOVMuxContext *mov,
> >          mov_write_pitm_tag(pb, 1);
> >          mov_write_iloc_tag(pb, mov, s);
> >          mov_write_iinf_tag(pb, mov, s);
> > +        if (s->nb_streams > 1)
> > +            mov_write_iref_tag(pb, mov, s);
> >          mov_write_iprp_tag(pb, mov, s);
> >      } else {
> >          /* iTunes metadata tag */
> > @@ -6040,8 +6086,8 @@ int ff_mov_write_packet(AVFormatContext *s, AVPacket
> > *pkt)
> >              avio_write(pb, reformatted_data, size);
> >          } else {
> >              size = ff_av1_filter_obus(pb, pkt->data, pkt->size);
> > -            if (trk->mode == MODE_AVIF && !mov->avif_extent_length) {
> > -                mov->avif_extent_length = size;
> > +            if (trk->mode == MODE_AVIF &&
> > !mov->avif_extent_length[pkt->stream_index]) {
> > +                mov->avif_extent_length[pkt->stream_index] = size;
> >              }
> >          }
> >
> > @@ -6874,14 +6920,23 @@ static int mov_init(AVFormatContext *s)
> >
> >      /* AVIF output must have exactly one video stream */
> >      if (mov->mode == MODE_AVIF) {
> > -        if (s->nb_streams > 1) {
> > -            av_log(s, AV_LOG_ERROR, "AVIF output requires exactly one
> > stream\n");
> > +        if (s->nb_streams > 2) {
> > +            av_log(s, AV_LOG_ERROR, "AVIF output requires exactly one or
> > two streams\n");
> >              return AVERROR(EINVAL);
> >          }
> > -        if (s->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO) {
> > -            av_log(s, AV_LOG_ERROR, "AVIF output requires one video
> > stream\n");
> > +        if (s->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO &&
> > +            (s->nb_streams > 1 && s->streams[1]->codecpar->codec_type !=
> > AVMEDIA_TYPE_VIDEO)) {
> > +            av_log(s, AV_LOG_ERROR, "AVIF output supports only video
> > streams\n");
> >              return AVERROR(EINVAL);
> >          }
> > +        if (s->nb_streams > 1) {
> > +            const AVPixFmtDescriptor *pixdesc =
> > +                av_pix_fmt_desc_get(s->streams[1]->codecpar->format);
> > +            if (pixdesc->nb_components != 1) {
> > +                av_log(s, AV_LOG_ERROR, "Second stream for AVIF (alpha)
> > output must have exactly one plane\n");
> > +                return AVERROR(EINVAL);
> > +            }
> > +        }
> >          s->streams[0]->disposition |= AV_DISPOSITION_DEFAULT;
> >      }
> >
> > @@ -7543,18 +7598,25 @@ static int avif_write_trailer(AVFormatContext *s)
> >  {
> >      AVIOContext *pb = s->pb;
> >      MOVMuxContext *mov = s->priv_data;
> > -    int64_t pos_backup, mdat_pos;
> > +    int64_t pos_backup, extent_offsets[2];
> >      uint8_t *buf;
> > -    int buf_size, moov_size;
> > +    int buf_size, moov_size, i;
> >
> >      if (mov->moov_written) return 0;
> >
> >      mov->is_animated_avif = s->streams[0]->nb_frames > 1;
> > +    if (mov->is_animated_avif && s->nb_streams > 1) {
> > +        // For animated avif with alpha channel, we need to write a the
> > tref
> > +        // tag with type "auxl".
> > +        mov->tracks[1].tref_tag = MKTAG('a', 'u', 'x', 'l');
> > +        mov->tracks[1].tref_id = 1;
> > +    }
> >      mov_write_identification(pb, s);
> >      mov_write_meta_tag(pb, mov, s);
> >
> >      moov_size = get_moov_size(s);
> > -    mov->tracks[0].data_offset = avio_tell(pb) + moov_size + 8;
> > +    for (i = 0; i < s->nb_streams; i++)
> > +        mov->tracks[i].data_offset = avio_tell(pb) + moov_size + 8;
> >
> >      if (mov->is_animated_avif) {
> >          int ret;
> > @@ -7565,19 +7627,24 @@ static int avif_write_trailer(AVFormatContext *s)
> >      buf_size = avio_get_dyn_buf(mov->mdat_buf, &buf);
> >      avio_wb32(pb, buf_size + 8);
> >      ffio_wfourcc(pb, "mdat");
> > -    mdat_pos = avio_tell(pb);
> >
> > -    if (mdat_pos != (uint32_t)mdat_pos) {
> > -        av_log(s, AV_LOG_ERROR, "mdat offset does not fit in 32 bits\n");
> > -        return AVERROR_INVALIDDATA;
> > -    }
> > +    // The offset for the YUV planes is the starting position of mdat.
> > +    extent_offsets[0] = avio_tell(pb);
> > +    // The offset for alpha plane is YUV offset + YUV size.
> > +    extent_offsets[1] = extent_offsets[0] + mov->avif_extent_length[0];
> >
> >      avio_write(pb, buf, buf_size);
> >
> > -    // write extent offset.
> > +    // write extent offsets.
> >      pos_backup = avio_tell(pb);
> > -    avio_seek(pb, mov->avif_extent_pos, SEEK_SET);
> > -    avio_wb32(pb, mdat_pos); /* rewrite offset */
> > +    for (i = 0; i < s->nb_streams; i++) {
> > +        if (extent_offsets[i] != (uint32_t)extent_offsets[i]) {
> > +            av_log(s, AV_LOG_ERROR, "extent offset does not fit in 32
> > bits\n");
> > +            return AVERROR_INVALIDDATA;
> > +        }
> > +        avio_seek(pb, mov->avif_extent_pos[i], SEEK_SET);
> > +        avio_wb32(pb, extent_offsets[i]); /* rewrite offset */
> > +    }
> >      avio_seek(pb, pos_backup, SEEK_SET);
> >
> >      return 0;
> > diff --git a/libavformat/movenc.h b/libavformat/movenc.h
> > index 281576cc66..e4550f7900 100644
> > --- a/libavformat/movenc.h
> > +++ b/libavformat/movenc.h
> > @@ -246,8 +246,8 @@ typedef struct MOVMuxContext {
> >      int empty_hdlr_name;
> >      int movie_timescale;
> >
> > -    int64_t avif_extent_pos;
> > -    int avif_extent_length;
> > +    int64_t avif_extent_pos[2];  // index 0 is YUV and 1 is Alpha.
> > +    int avif_extent_length[2];   // index 0 is YUV and 1 is Alpha.
> >      int is_animated_avif;
> >  } MOVMuxContext;
> >
> > --
> > 2.36.1.124.g0e6072fb45-goog
> >
> > _______________________________________________
> > ffmpeg-devel mailing list
> > ffmpeg-devel@ffmpeg.org
> > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> >
> > To unsubscribe, visit link above, or email
> > ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
> >
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel@ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
Vignesh Venkat May 31, 2022, 7:12 p.m. UTC | #4 
On Thu, May 19, 2022 at 9:08 AM Vignesh Venkatasubramanian
<vigneshv@google.com> wrote:
>
> On Wed, May 18, 2022 at 7:36 PM Bang He <hezhanbang@gmail.com> wrote:
> >
> > error happened:
> >
> > ./ffmpeg -i alpha.png -filter_complex [0:v]alphaextract[a] -map 0 -map [a]
> > -still-picture 1 avif_with_alpha.avif
> > ffmpeg version N-106936-gff5ea89da2 Copyright (c) 2000-2022 the FFmpeg
> > developers
> >   built with gcc 11 (Ubuntu 11.2.0-19ubuntu1)
> >   configuration: --disable-ffplay --disable-ffprobe --enable-gpl
> > --enable-nonfree --prefix=/home/bang/Desktop/out
> >   libavutil      57. 24.101 / 57. 24.101
> >   libavcodec     59. 28.100 / 59. 28.100
> >   libavformat    59. 24.100 / 59. 24.100
> >   libavdevice    59.  6.100 / 59.  6.100
> >   libavfilter     8. 38.100 /  8. 38.100
> >   libswscale      6.  6.100 /  6.  6.100
> >   libswresample   4.  6.100 /  4.  6.100
> >   libpostproc    56.  5.100 / 56.  5.100
> > Unrecognized option 'still-picture'.
> > Error splitting the argument list: Option not found
> >
>
> You would have to build ffmpeg with libaom enabled for AVIF encoding
> to work (since AVIF is backed by an AV1 encoder). From the logs you
> posted, it seems like you don't have an AV1 encoder available in your
> ffmpeg build.
>
> The "-still-picture" flag was added in ab05e9a7f2. Please make sure
> that you are sync'ed past that to pick up that option.
>
> > On Thu, May 19, 2022 at 5:56 AM Vignesh Venkatasubramanian <
> > vigneshv-at-google.com@ffmpeg.org> wrote:
> >
> > > AVIF specification allows for alpha channel as an auxillary item (in
> > > case of still images) or as an auxillary track (in case of animated
> > > images).  Add support for both of these. The AVIF muxer will take
> > > exactly two streams (when alpha is present) as input (first one being
> > > the YUV planes and the second one being the alpha plane).
> > >
> > > The input has to come from two different images (one of it color and
> > > the other one being alpha), or it can come from a single file
> > > source with the alpha channel extracted using the "alphaextract"
> > > filter.
> > >
> > > Example using alphaextract:
> > > ffmpeg -i rgba.png -filter_complex "[0:v]alphaextract[a]" -map 0 -map
> > > "[a]" -still-picture 1 avif_with_alpha.avif
> > >
> > > Example using two sources (first source can be in any pixel format and
> > > the second source has to be in monochrome grey pixel format):
> > > ffmpeg -i color.avif -i grey.avif -map 0 -map 1 -c copy
> > > avif_with_alpha.avif
> > >
> > > The generated files pass the compliance checks in Compliance Warden:
> > > https://github.com/gpac/ComplianceWarden
> > >
> > > libavif (the reference avif library) is able to decode the files
> > > generated using this patch.
> > >
> > > They also play back properly (with transparent background) in:
> > > 1) Chrome
> > > 2) Firefox (only still AVIF, no animation support)
> > >
> > > Signed-off-by: Vignesh Venkatasubramanian <vigneshv@google.com>
> > > ---
> > >  libavformat/movenc.c | 185 +++++++++++++++++++++++++++++--------------
> > >  libavformat/movenc.h |   4 +-
> > >  2 files changed, 128 insertions(+), 61 deletions(-)
> > >
> > > diff --git a/libavformat/movenc.c b/libavformat/movenc.c
> > > index de971f94e8..00e42b7abb 100644
> > > --- a/libavformat/movenc.c
> > > +++ b/libavformat/movenc.c
> > > @@ -2852,7 +2852,7 @@ static int mov_write_hdlr_tag(AVFormatContext *s,
> > > AVIOContext *pb, MOVTrack *tra
> > >          hdlr = (track->mode == MODE_MOV) ? "mhlr" : "\0\0\0\0";
> > >          if (track->par->codec_type == AVMEDIA_TYPE_VIDEO) {
> > >              if (track->mode == MODE_AVIF) {
> > > -                hdlr_type = "pict";
> > > +                hdlr_type = (track == &mov->tracks[0]) ? "pict" : "auxv";
> > >                  descr     = "PictureHandler";
> > >              } else {
> > >                  hdlr_type = "vide";
> > > @@ -2940,57 +2940,83 @@ static int mov_write_iloc_tag(AVIOContext *pb,
> > > MOVMuxContext *mov, AVFormatConte
> > >      avio_wb32(pb, 0); /* Version & flags */
> > >      avio_w8(pb, (4 << 4) + 4); /* offset_size(4) and length_size(4) */
> > >      avio_w8(pb, 0); /* base_offset_size(4) and reserved(4) */
> > > -    avio_wb16(pb, 1); /* item_count */
> > > +    avio_wb16(pb, s->nb_streams); /* item_count */
> > >
> > > -    avio_wb16(pb, 1); /* item_id */
> > > -    avio_wb16(pb, 0); /* data_reference_index */
> > > -    avio_wb16(pb, 1); /* extent_count */
> > > -    mov->avif_extent_pos = avio_tell(pb);
> > > -    avio_wb32(pb, 0); /* extent_offset (written later) */
> > > -    // For animated AVIF, we simply write the first packet's size.
> > > -    avio_wb32(pb, mov->avif_extent_length); /* extent_length */
> > > +    for (int i = 0; i < s->nb_streams; i++) {
> > > +        avio_wb16(pb, i + 1); /* item_id */
> > > +        avio_wb16(pb, 0); /* data_reference_index */
> > > +        avio_wb16(pb, 1); /* extent_count */
> > > +        mov->avif_extent_pos[i] = avio_tell(pb);
> > > +        avio_wb32(pb, 0); /* extent_offset (written later) */
> > > +        // For animated AVIF, we simply write the first packet's size.
> > > +        avio_wb32(pb, mov->avif_extent_length[i]); /* extent_length */
> > > +    }
> > >
> > >      return update_size(pb, pos);
> > >  }
> > >
> > >  static int mov_write_iinf_tag(AVIOContext *pb, MOVMuxContext *mov,
> > > AVFormatContext *s)
> > >  {
> > > -    int64_t infe_pos;
> > >      int64_t iinf_pos = avio_tell(pb);
> > >      avio_wb32(pb, 0); /* size */
> > >      ffio_wfourcc(pb, "iinf");
> > >      avio_wb32(pb, 0); /* Version & flags */
> > > -    avio_wb16(pb, 1); /* entry_count */
> > > +    avio_wb16(pb, s->nb_streams); /* entry_count */
> > >
> > > -    infe_pos = avio_tell(pb);
> > > -    avio_wb32(pb, 0); /* size */
> > > -    ffio_wfourcc(pb, "infe");
> > > -    avio_w8(pb, 0x2); /* Version */
> > > -    avio_wb24(pb, 0); /* flags */
> > > -    avio_wb16(pb, 1); /* item_id */
> > > -    avio_wb16(pb, 0); /* item_protection_index */
> > > -    avio_write(pb, "av01", 4); /* item_type */
> > > -    avio_write(pb, "Color\0", 6); /* item_name */
> > > -    update_size(pb, infe_pos);
> > > +    for (int i = 0; i < s->nb_streams; i++) {
> > > +        int64_t infe_pos = avio_tell(pb);
> > > +        avio_wb32(pb, 0); /* size */
> > > +        ffio_wfourcc(pb, "infe");
> > > +        avio_w8(pb, 0x2); /* Version */
> > > +        avio_wb24(pb, 0); /* flags */
> > > +        avio_wb16(pb, i + 1); /* item_id */
> > > +        avio_wb16(pb, 0); /* item_protection_index */
> > > +        avio_write(pb, "av01", 4); /* item_type */
> > > +        avio_write(pb, !i ? "Color\0" : "Alpha\0", 6); /* item_name */
> > > +        update_size(pb, infe_pos);
> > > +    }
> > >
> > >      return update_size(pb, iinf_pos);
> > >  }
> > >
> > > -static int mov_write_ispe_tag(AVIOContext *pb, MOVMuxContext *mov,
> > > AVFormatContext *s)
> > > +
> > > +static int mov_write_iref_tag(AVIOContext *pb, MOVMuxContext *mov,
> > > AVFormatContext *s)
> > > +{
> > > +    int64_t auxl_pos;
> > > +    int64_t iref_pos = avio_tell(pb);
> > > +    avio_wb32(pb, 0); /* size */
> > > +    ffio_wfourcc(pb, "iref");
> > > +    avio_wb32(pb, 0); /* Version & flags */
> > > +
> > > +    auxl_pos = avio_tell(pb);
> > > +    avio_wb32(pb, 0); /* size */
> > > +    ffio_wfourcc(pb, "auxl");
> > > +    avio_wb16(pb, 2); /* from_item_ID */
> > > +    avio_wb16(pb, 1); /* reference_count */
> > > +    avio_wb16(pb, 1); /* to_item_ID */
> > > +    update_size(pb, auxl_pos);
> > > +
> > > +    return update_size(pb, iref_pos);
> > > +}
> > > +
> > > +static int mov_write_ispe_tag(AVIOContext *pb, MOVMuxContext *mov,
> > > AVFormatContext *s,
> > > +                              int stream_index)
> > >  {
> > >      int64_t pos = avio_tell(pb);
> > >      avio_wb32(pb, 0); /* size */
> > >      ffio_wfourcc(pb, "ispe");
> > >      avio_wb32(pb, 0); /* Version & flags */
> > > -    avio_wb32(pb, s->streams[0]->codecpar->width); /* image_width */
> > > -    avio_wb32(pb, s->streams[0]->codecpar->height); /* image_height */
> > > +    avio_wb32(pb, s->streams[stream_index]->codecpar->width); /*
> > > image_width */
> > > +    avio_wb32(pb, s->streams[stream_index]->codecpar->height); /*
> > > image_height */
> > >      return update_size(pb, pos);
> > >  }
> > >
> > > -static int mov_write_pixi_tag(AVIOContext *pb, MOVMuxContext *mov,
> > > AVFormatContext *s)
> > > +static int mov_write_pixi_tag(AVIOContext *pb, MOVMuxContext *mov,
> > > AVFormatContext *s,
> > > +                              int stream_index)
> > >  {
> > >      int64_t pos = avio_tell(pb);
> > > -    const AVPixFmtDescriptor *pixdesc =
> > > av_pix_fmt_desc_get(s->streams[0]->codecpar->format);
> > > +    const AVPixFmtDescriptor *pixdesc =
> > > +        av_pix_fmt_desc_get(s->streams[stream_index]->codecpar->format);
> > >      avio_wb32(pb, 0); /* size */
> > >      ffio_wfourcc(pb, "pixi");
> > >      avio_wb32(pb, 0); /* Version & flags */
> > > @@ -3001,15 +3027,30 @@ static int mov_write_pixi_tag(AVIOContext *pb,
> > > MOVMuxContext *mov, AVFormatConte
> > >      return update_size(pb, pos);
> > >  }
> > >
> > > +static int mov_write_auxC_tag(AVIOContext *pb)
> > > +{
> > > +    int64_t pos = avio_tell(pb);
> > > +    avio_wb32(pb, 0); /* size */
> > > +    ffio_wfourcc(pb, "auxC");
> > > +    avio_wb32(pb, 0); /* Version & flags */
> > > +    avio_write(pb, "urn:mpeg:mpegB:cicp:systems:auxiliary:alpha\0", 44);
> > > +    return update_size(pb, pos);
> > > +}
> > > +
> > >  static int mov_write_ipco_tag(AVIOContext *pb, MOVMuxContext *mov,
> > > AVFormatContext *s)
> > >  {
> > >      int64_t pos = avio_tell(pb);
> > >      avio_wb32(pb, 0); /* size */
> > >      ffio_wfourcc(pb, "ipco");
> > > -    mov_write_ispe_tag(pb, mov, s);
> > > -    mov_write_pixi_tag(pb, mov, s);
> > > -    mov_write_av1c_tag(pb, &mov->tracks[0]);
> > > -    mov_write_colr_tag(pb, &mov->tracks[0], 0);
> > > +    for (int i = 0; i < s->nb_streams; i++) {
> > > +        mov_write_ispe_tag(pb, mov, s, i);
> > > +        mov_write_pixi_tag(pb, mov, s, i);
> > > +        mov_write_av1c_tag(pb, &mov->tracks[i]);
> > > +        if (!i)
> > > +            mov_write_colr_tag(pb, &mov->tracks[0], 0);
> > > +        else
> > > +            mov_write_auxC_tag(pb);
> > > +    }
> > >      return update_size(pb, pos);
> > >  }
> > >
> > > @@ -3019,18 +3060,21 @@ static int mov_write_ipma_tag(AVIOContext *pb,
> > > MOVMuxContext *mov, AVFormatConte
> > >      avio_wb32(pb, 0); /* size */
> > >      ffio_wfourcc(pb, "ipma");
> > >      avio_wb32(pb, 0); /* Version & flags */
> > > -    avio_wb32(pb, 1); /* entry_count */
> > > -    avio_wb16(pb, 1); /* item_ID */
> > > -    avio_w8(pb, 4); /* association_count */
> > > -
> > > -    // ispe association.
> > > -    avio_w8(pb, 1); /* essential and property_index */
> > > -    // pixi association.
> > > -    avio_w8(pb, 2); /* essential and property_index */
> > > -    // av1C association.
> > > -    avio_w8(pb, 0x80 | 3); /* essential and property_index */
> > > -    // colr association.
> > > -    avio_w8(pb, 4); /* essential and property_index */
> > > +    avio_wb32(pb, s->nb_streams); /* entry_count */
> > > +
> > > +    for (int i = 0, index = 1; i < s->nb_streams; i++) {
> > > +        avio_wb16(pb, i + 1); /* item_ID */
> > > +        avio_w8(pb, 4); /* association_count */
> > > +
> > > +        // ispe association.
> > > +        avio_w8(pb, index++); /* essential and property_index */
> > > +        // pixi association.
> > > +        avio_w8(pb, index++); /* essential and property_index */
> > > +        // av1C association.
> > > +        avio_w8(pb, 0x80 | index++); /* essential and property_index */
> > > +        // colr/auxC association.
> > > +        avio_w8(pb, index++); /* essential and property_index */
> > > +    }
> > >      return update_size(pb, pos);
> > >  }
> > >
> > > @@ -4112,6 +4156,8 @@ static int mov_write_meta_tag(AVIOContext *pb,
> > > MOVMuxContext *mov,
> > >          mov_write_pitm_tag(pb, 1);
> > >          mov_write_iloc_tag(pb, mov, s);
> > >          mov_write_iinf_tag(pb, mov, s);
> > > +        if (s->nb_streams > 1)
> > > +            mov_write_iref_tag(pb, mov, s);
> > >          mov_write_iprp_tag(pb, mov, s);
> > >      } else {
> > >          /* iTunes metadata tag */
> > > @@ -6040,8 +6086,8 @@ int ff_mov_write_packet(AVFormatContext *s, AVPacket
> > > *pkt)
> > >              avio_write(pb, reformatted_data, size);
> > >          } else {
> > >              size = ff_av1_filter_obus(pb, pkt->data, pkt->size);
> > > -            if (trk->mode == MODE_AVIF && !mov->avif_extent_length) {
> > > -                mov->avif_extent_length = size;
> > > +            if (trk->mode == MODE_AVIF &&
> > > !mov->avif_extent_length[pkt->stream_index]) {
> > > +                mov->avif_extent_length[pkt->stream_index] = size;
> > >              }
> > >          }
> > >
> > > @@ -6874,14 +6920,23 @@ static int mov_init(AVFormatContext *s)
> > >
> > >      /* AVIF output must have exactly one video stream */
> > >      if (mov->mode == MODE_AVIF) {
> > > -        if (s->nb_streams > 1) {
> > > -            av_log(s, AV_LOG_ERROR, "AVIF output requires exactly one
> > > stream\n");
> > > +        if (s->nb_streams > 2) {
> > > +            av_log(s, AV_LOG_ERROR, "AVIF output requires exactly one or
> > > two streams\n");
> > >              return AVERROR(EINVAL);
> > >          }
> > > -        if (s->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO) {
> > > -            av_log(s, AV_LOG_ERROR, "AVIF output requires one video
> > > stream\n");
> > > +        if (s->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO &&
> > > +            (s->nb_streams > 1 && s->streams[1]->codecpar->codec_type !=
> > > AVMEDIA_TYPE_VIDEO)) {
> > > +            av_log(s, AV_LOG_ERROR, "AVIF output supports only video
> > > streams\n");
> > >              return AVERROR(EINVAL);
> > >          }
> > > +        if (s->nb_streams > 1) {
> > > +            const AVPixFmtDescriptor *pixdesc =
> > > +                av_pix_fmt_desc_get(s->streams[1]->codecpar->format);
> > > +            if (pixdesc->nb_components != 1) {
> > > +                av_log(s, AV_LOG_ERROR, "Second stream for AVIF (alpha)
> > > output must have exactly one plane\n");
> > > +                return AVERROR(EINVAL);
> > > +            }
> > > +        }
> > >          s->streams[0]->disposition |= AV_DISPOSITION_DEFAULT;
> > >      }
> > >
> > > @@ -7543,18 +7598,25 @@ static int avif_write_trailer(AVFormatContext *s)
> > >  {
> > >      AVIOContext *pb = s->pb;
> > >      MOVMuxContext *mov = s->priv_data;
> > > -    int64_t pos_backup, mdat_pos;
> > > +    int64_t pos_backup, extent_offsets[2];
> > >      uint8_t *buf;
> > > -    int buf_size, moov_size;
> > > +    int buf_size, moov_size, i;
> > >
> > >      if (mov->moov_written) return 0;
> > >
> > >      mov->is_animated_avif = s->streams[0]->nb_frames > 1;
> > > +    if (mov->is_animated_avif && s->nb_streams > 1) {
> > > +        // For animated avif with alpha channel, we need to write a the
> > > tref
> > > +        // tag with type "auxl".
> > > +        mov->tracks[1].tref_tag = MKTAG('a', 'u', 'x', 'l');
> > > +        mov->tracks[1].tref_id = 1;
> > > +    }
> > >      mov_write_identification(pb, s);
> > >      mov_write_meta_tag(pb, mov, s);
> > >
> > >      moov_size = get_moov_size(s);
> > > -    mov->tracks[0].data_offset = avio_tell(pb) + moov_size + 8;
> > > +    for (i = 0; i < s->nb_streams; i++)
> > > +        mov->tracks[i].data_offset = avio_tell(pb) + moov_size + 8;
> > >
> > >      if (mov->is_animated_avif) {
> > >          int ret;
> > > @@ -7565,19 +7627,24 @@ static int avif_write_trailer(AVFormatContext *s)
> > >      buf_size = avio_get_dyn_buf(mov->mdat_buf, &buf);
> > >      avio_wb32(pb, buf_size + 8);
> > >      ffio_wfourcc(pb, "mdat");
> > > -    mdat_pos = avio_tell(pb);
> > >
> > > -    if (mdat_pos != (uint32_t)mdat_pos) {
> > > -        av_log(s, AV_LOG_ERROR, "mdat offset does not fit in 32 bits\n");
> > > -        return AVERROR_INVALIDDATA;
> > > -    }
> > > +    // The offset for the YUV planes is the starting position of mdat.
> > > +    extent_offsets[0] = avio_tell(pb);
> > > +    // The offset for alpha plane is YUV offset + YUV size.
> > > +    extent_offsets[1] = extent_offsets[0] + mov->avif_extent_length[0];
> > >
> > >      avio_write(pb, buf, buf_size);
> > >
> > > -    // write extent offset.
> > > +    // write extent offsets.
> > >      pos_backup = avio_tell(pb);
> > > -    avio_seek(pb, mov->avif_extent_pos, SEEK_SET);
> > > -    avio_wb32(pb, mdat_pos); /* rewrite offset */
> > > +    for (i = 0; i < s->nb_streams; i++) {
> > > +        if (extent_offsets[i] != (uint32_t)extent_offsets[i]) {
> > > +            av_log(s, AV_LOG_ERROR, "extent offset does not fit in 32
> > > bits\n");
> > > +            return AVERROR_INVALIDDATA;
> > > +        }
> > > +        avio_seek(pb, mov->avif_extent_pos[i], SEEK_SET);
> > > +        avio_wb32(pb, extent_offsets[i]); /* rewrite offset */
> > > +    }
> > >      avio_seek(pb, pos_backup, SEEK_SET);
> > >
> > >      return 0;
> > > diff --git a/libavformat/movenc.h b/libavformat/movenc.h
> > > index 281576cc66..e4550f7900 100644
> > > --- a/libavformat/movenc.h
> > > +++ b/libavformat/movenc.h
> > > @@ -246,8 +246,8 @@ typedef struct MOVMuxContext {
> > >      int empty_hdlr_name;
> > >      int movie_timescale;
> > >
> > > -    int64_t avif_extent_pos;
> > > -    int avif_extent_length;
> > > +    int64_t avif_extent_pos[2];  // index 0 is YUV and 1 is Alpha.
> > > +    int avif_extent_length[2];   // index 0 is YUV and 1 is Alpha.
> > >      int is_animated_avif;
> > >  } MOVMuxContext;
> > >
> > > --
> > > 2.36.1.124.g0e6072fb45-goog
> > >
> > > _______________________________________________
> > > ffmpeg-devel mailing list
> > > ffmpeg-devel@ffmpeg.org
> > > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> > >
> > > To unsubscribe, visit link above, or email
> > > ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
> > >
> > _______________________________________________
> > ffmpeg-devel mailing list
> > ffmpeg-devel@ffmpeg.org
> > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> >
> > To unsubscribe, visit link above, or email
> > ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe".
>
>
>
> --
> Vignesh

Ping on this please. Any comments on this one?
James Zern June 1, 2022, 5:52 p.m. UTC | #5 
On Wed, May 18, 2022 at 2:56 PM Vignesh Venkatasubramanian
<vigneshv-at-google.com@ffmpeg.org> wrote:
>
> AVIF specification allows for alpha channel as an auxillary item (in

auxiliary

> case of still images) or as an auxillary track (in case of animated
> images).  Add support for both of these. The AVIF muxer will take
> exactly two streams (when alpha is present) as input (first one being
> the YUV planes and the second one being the alpha plane).
>
> The input has to come from two different images (one of it color and
> the other one being alpha), or it can come from a single file
> source with the alpha channel extracted using the "alphaextract"
> filter.
>
> Example using alphaextract:
> ffmpeg -i rgba.png -filter_complex "[0:v]alphaextract[a]" -map 0 -map "[a]" -still-picture 1 avif_with_alpha.avif
>
> Example using two sources (first source can be in any pixel format and
> the second source has to be in monochrome grey pixel format):
> ffmpeg -i color.avif -i grey.avif -map 0 -map 1 -c copy avif_with_alpha.avif
>
> The generated files pass the compliance checks in Compliance Warden:
> https://github.com/gpac/ComplianceWarden
>
> libavif (the reference avif library) is able to decode the files
> generated using this patch.
>
> They also play back properly (with transparent background) in:
> 1) Chrome
> 2) Firefox (only still AVIF, no animation support)
>
> Signed-off-by: Vignesh Venkatasubramanian <vigneshv@google.com>
> ---
>  libavformat/movenc.c | 185 +++++++++++++++++++++++++++++--------------
>  libavformat/movenc.h |   4 +-
>  2 files changed, 128 insertions(+), 61 deletions(-)
>
> diff --git a/libavformat/movenc.c b/libavformat/movenc.c
> index de971f94e8..00e42b7abb 100644
> --- a/libavformat/movenc.c
> +++ b/libavformat/movenc.c
> @@ -2852,7 +2852,7 @@ static int mov_write_hdlr_tag(AVFormatContext *s, AVIOContext *pb, MOVTrack *tra
>          hdlr = (track->mode == MODE_MOV) ? "mhlr" : "\0\0\0\0";
>          if (track->par->codec_type == AVMEDIA_TYPE_VIDEO) {
>              if (track->mode == MODE_AVIF) {
> -                hdlr_type = "pict";
> +                hdlr_type = (track == &mov->tracks[0]) ? "pict" : "auxv";
>                  descr     = "PictureHandler";
>              } else {
>                  hdlr_type = "vide";
> @@ -2940,57 +2940,83 @@ static int mov_write_iloc_tag(AVIOContext *pb, MOVMuxContext *mov, AVFormatConte
>      avio_wb32(pb, 0); /* Version & flags */
>      avio_w8(pb, (4 << 4) + 4); /* offset_size(4) and length_size(4) */
>      avio_w8(pb, 0); /* base_offset_size(4) and reserved(4) */
> -    avio_wb16(pb, 1); /* item_count */
> +    avio_wb16(pb, s->nb_streams); /* item_count */

This assumes at most 2 streams for AVIF, the use of nb_streams here and
elsewhere carry any risk for other formats?

> [...]
>
> @@ -6874,14 +6920,23 @@ static int mov_init(AVFormatContext *s)
>
>      /* AVIF output must have exactly one video stream */

This is no longer true.

>      if (mov->mode == MODE_AVIF) {
> -        if (s->nb_streams > 1) {
> -            av_log(s, AV_LOG_ERROR, "AVIF output requires exactly one stream\n");
> +        if (s->nb_streams > 2) {
> +            av_log(s, AV_LOG_ERROR, "AVIF output requires exactly one or two streams\n");
>              return AVERROR(EINVAL);
>          }
> -        if (s->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO) {
> -            av_log(s, AV_LOG_ERROR, "AVIF output requires one video stream\n");
> +        if (s->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO &&
> +            (s->nb_streams > 1 && s->streams[1]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO)) {
> +            av_log(s, AV_LOG_ERROR, "AVIF output supports only video streams\n");
>              return AVERROR(EINVAL);
>          }
> +        if (s->nb_streams > 1) {
> +            const AVPixFmtDescriptor *pixdesc =
> +                av_pix_fmt_desc_get(s->streams[1]->codecpar->format);
> +            if (pixdesc->nb_components != 1) {
> +                av_log(s, AV_LOG_ERROR, "Second stream for AVIF (alpha) output must have exactly one plane\n");
> +                return AVERROR(EINVAL);
> +            }
> +        }
>          s->streams[0]->disposition |= AV_DISPOSITION_DEFAULT;
>      }
>
> @@ -7543,18 +7598,25 @@ static int avif_write_trailer(AVFormatContext *s)
>  {
>      AVIOContext *pb = s->pb;
>      MOVMuxContext *mov = s->priv_data;
> -    int64_t pos_backup, mdat_pos;
> +    int64_t pos_backup, extent_offsets[2];
>      uint8_t *buf;
> -    int buf_size, moov_size;
> +    int buf_size, moov_size, i;
>
>      if (mov->moov_written) return 0;
>
>      mov->is_animated_avif = s->streams[0]->nb_frames > 1;
> +    if (mov->is_animated_avif && s->nb_streams > 1) {
> +        // For animated avif with alpha channel, we need to write a the tref

...write a tref...
Vignesh Venkat June 1, 2022, 6:05 p.m. UTC | #6 
On Wed, Jun 1, 2022 at 10:52 AM James Zern <jzern@google.com> wrote:
>
> On Wed, May 18, 2022 at 2:56 PM Vignesh Venkatasubramanian
> <vigneshv-at-google.com@ffmpeg.org> wrote:
> >
> > AVIF specification allows for alpha channel as an auxillary item (in
>
> auxiliary
>

Done.

> > case of still images) or as an auxillary track (in case of animated
> > images).  Add support for both of these. The AVIF muxer will take
> > exactly two streams (when alpha is present) as input (first one being
> > the YUV planes and the second one being the alpha plane).
> >
> > The input has to come from two different images (one of it color and
> > the other one being alpha), or it can come from a single file
> > source with the alpha channel extracted using the "alphaextract"
> > filter.
> >
> > Example using alphaextract:
> > ffmpeg -i rgba.png -filter_complex "[0:v]alphaextract[a]" -map 0 -map "[a]" -still-picture 1 avif_with_alpha.avif
> >
> > Example using two sources (first source can be in any pixel format and
> > the second source has to be in monochrome grey pixel format):
> > ffmpeg -i color.avif -i grey.avif -map 0 -map 1 -c copy avif_with_alpha.avif
> >
> > The generated files pass the compliance checks in Compliance Warden:
> > https://github.com/gpac/ComplianceWarden
> >
> > libavif (the reference avif library) is able to decode the files
> > generated using this patch.
> >
> > They also play back properly (with transparent background) in:
> > 1) Chrome
> > 2) Firefox (only still AVIF, no animation support)
> >
> > Signed-off-by: Vignesh Venkatasubramanian <vigneshv@google.com>
> > ---
> >  libavformat/movenc.c | 185 +++++++++++++++++++++++++++++--------------
> >  libavformat/movenc.h |   4 +-
> >  2 files changed, 128 insertions(+), 61 deletions(-)
> >
> > diff --git a/libavformat/movenc.c b/libavformat/movenc.c
> > index de971f94e8..00e42b7abb 100644
> > --- a/libavformat/movenc.c
> > +++ b/libavformat/movenc.c
> > @@ -2852,7 +2852,7 @@ static int mov_write_hdlr_tag(AVFormatContext *s, AVIOContext *pb, MOVTrack *tra
> >          hdlr = (track->mode == MODE_MOV) ? "mhlr" : "\0\0\0\0";
> >          if (track->par->codec_type == AVMEDIA_TYPE_VIDEO) {
> >              if (track->mode == MODE_AVIF) {
> > -                hdlr_type = "pict";
> > +                hdlr_type = (track == &mov->tracks[0]) ? "pict" : "auxv";
> >                  descr     = "PictureHandler";
> >              } else {
> >                  hdlr_type = "vide";
> > @@ -2940,57 +2940,83 @@ static int mov_write_iloc_tag(AVIOContext *pb, MOVMuxContext *mov, AVFormatConte
> >      avio_wb32(pb, 0); /* Version & flags */
> >      avio_w8(pb, (4 << 4) + 4); /* offset_size(4) and length_size(4) */
> >      avio_w8(pb, 0); /* base_offset_size(4) and reserved(4) */
> > -    avio_wb16(pb, 1); /* item_count */
> > +    avio_wb16(pb, s->nb_streams); /* item_count */
>
> This assumes at most 2 streams for AVIF, the use of nb_streams here and
> elsewhere carry any risk for other formats?
>

For AVIF, we check and ensure we only have at most 2 streams in
mov_init. iloc box is written only for AVIF as of now. So there is no
risk for other formats.

> > [...]
> >
> > @@ -6874,14 +6920,23 @@ static int mov_init(AVFormatContext *s)
> >
> >      /* AVIF output must have exactly one video stream */
>
> This is no longer true.
>

Updated.

> >      if (mov->mode == MODE_AVIF) {
> > -        if (s->nb_streams > 1) {
> > -            av_log(s, AV_LOG_ERROR, "AVIF output requires exactly one stream\n");
> > +        if (s->nb_streams > 2) {
> > +            av_log(s, AV_LOG_ERROR, "AVIF output requires exactly one or two streams\n");
> >              return AVERROR(EINVAL);
> >          }
> > -        if (s->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO) {
> > -            av_log(s, AV_LOG_ERROR, "AVIF output requires one video stream\n");
> > +        if (s->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO &&
> > +            (s->nb_streams > 1 && s->streams[1]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO)) {
> > +            av_log(s, AV_LOG_ERROR, "AVIF output supports only video streams\n");
> >              return AVERROR(EINVAL);
> >          }
> > +        if (s->nb_streams > 1) {
> > +            const AVPixFmtDescriptor *pixdesc =
> > +                av_pix_fmt_desc_get(s->streams[1]->codecpar->format);
> > +            if (pixdesc->nb_components != 1) {
> > +                av_log(s, AV_LOG_ERROR, "Second stream for AVIF (alpha) output must have exactly one plane\n");
> > +                return AVERROR(EINVAL);
> > +            }
> > +        }
> >          s->streams[0]->disposition |= AV_DISPOSITION_DEFAULT;
> >      }
> >
> > @@ -7543,18 +7598,25 @@ static int avif_write_trailer(AVFormatContext *s)
> >  {
> >      AVIOContext *pb = s->pb;
> >      MOVMuxContext *mov = s->priv_data;
> > -    int64_t pos_backup, mdat_pos;
> > +    int64_t pos_backup, extent_offsets[2];
> >      uint8_t *buf;
> > -    int buf_size, moov_size;
> > +    int buf_size, moov_size, i;
> >
> >      if (mov->moov_written) return 0;
> >
> >      mov->is_animated_avif = s->streams[0]->nb_frames > 1;
> > +    if (mov->is_animated_avif && s->nb_streams > 1) {
> > +        // For animated avif with alpha channel, we need to write a the tref
>
> ...write a tref...

Done.
diff mbox series

Patch

diff --git a/libavformat/movenc.c b/libavformat/movenc.c
index de971f94e8..00e42b7abb 100644
--- a/libavformat/movenc.c
+++ b/libavformat/movenc.c
@@ -2852,7 +2852,7 @@  static int mov_write_hdlr_tag(AVFormatContext *s, AVIOContext *pb, MOVTrack *tra
         hdlr = (track->mode == MODE_MOV) ? "mhlr" : "\0\0\0\0";
         if (track->par->codec_type == AVMEDIA_TYPE_VIDEO) {
             if (track->mode == MODE_AVIF) {
-                hdlr_type = "pict";
+                hdlr_type = (track == &mov->tracks[0]) ? "pict" : "auxv";
                 descr     = "PictureHandler";
             } else {
                 hdlr_type = "vide";
@@ -2940,57 +2940,83 @@  static int mov_write_iloc_tag(AVIOContext *pb, MOVMuxContext *mov, AVFormatConte
     avio_wb32(pb, 0); /* Version & flags */
     avio_w8(pb, (4 << 4) + 4); /* offset_size(4) and length_size(4) */
     avio_w8(pb, 0); /* base_offset_size(4) and reserved(4) */
-    avio_wb16(pb, 1); /* item_count */
+    avio_wb16(pb, s->nb_streams); /* item_count */
 
-    avio_wb16(pb, 1); /* item_id */
-    avio_wb16(pb, 0); /* data_reference_index */
-    avio_wb16(pb, 1); /* extent_count */
-    mov->avif_extent_pos = avio_tell(pb);
-    avio_wb32(pb, 0); /* extent_offset (written later) */
-    // For animated AVIF, we simply write the first packet's size.
-    avio_wb32(pb, mov->avif_extent_length); /* extent_length */
+    for (int i = 0; i < s->nb_streams; i++) {
+        avio_wb16(pb, i + 1); /* item_id */
+        avio_wb16(pb, 0); /* data_reference_index */
+        avio_wb16(pb, 1); /* extent_count */
+        mov->avif_extent_pos[i] = avio_tell(pb);
+        avio_wb32(pb, 0); /* extent_offset (written later) */
+        // For animated AVIF, we simply write the first packet's size.
+        avio_wb32(pb, mov->avif_extent_length[i]); /* extent_length */
+    }
 
     return update_size(pb, pos);
 }
 
 static int mov_write_iinf_tag(AVIOContext *pb, MOVMuxContext *mov, AVFormatContext *s)
 {
-    int64_t infe_pos;
     int64_t iinf_pos = avio_tell(pb);
     avio_wb32(pb, 0); /* size */
     ffio_wfourcc(pb, "iinf");
     avio_wb32(pb, 0); /* Version & flags */
-    avio_wb16(pb, 1); /* entry_count */
+    avio_wb16(pb, s->nb_streams); /* entry_count */
 
-    infe_pos = avio_tell(pb);
-    avio_wb32(pb, 0); /* size */
-    ffio_wfourcc(pb, "infe");
-    avio_w8(pb, 0x2); /* Version */
-    avio_wb24(pb, 0); /* flags */
-    avio_wb16(pb, 1); /* item_id */
-    avio_wb16(pb, 0); /* item_protection_index */
-    avio_write(pb, "av01", 4); /* item_type */
-    avio_write(pb, "Color\0", 6); /* item_name */
-    update_size(pb, infe_pos);
+    for (int i = 0; i < s->nb_streams; i++) {
+        int64_t infe_pos = avio_tell(pb);
+        avio_wb32(pb, 0); /* size */
+        ffio_wfourcc(pb, "infe");
+        avio_w8(pb, 0x2); /* Version */
+        avio_wb24(pb, 0); /* flags */
+        avio_wb16(pb, i + 1); /* item_id */
+        avio_wb16(pb, 0); /* item_protection_index */
+        avio_write(pb, "av01", 4); /* item_type */
+        avio_write(pb, !i ? "Color\0" : "Alpha\0", 6); /* item_name */
+        update_size(pb, infe_pos);
+    }
 
     return update_size(pb, iinf_pos);
 }
 
-static int mov_write_ispe_tag(AVIOContext *pb, MOVMuxContext *mov, AVFormatContext *s)
+
+static int mov_write_iref_tag(AVIOContext *pb, MOVMuxContext *mov, AVFormatContext *s)
+{
+    int64_t auxl_pos;
+    int64_t iref_pos = avio_tell(pb);
+    avio_wb32(pb, 0); /* size */
+    ffio_wfourcc(pb, "iref");
+    avio_wb32(pb, 0); /* Version & flags */
+
+    auxl_pos = avio_tell(pb);
+    avio_wb32(pb, 0); /* size */
+    ffio_wfourcc(pb, "auxl");
+    avio_wb16(pb, 2); /* from_item_ID */
+    avio_wb16(pb, 1); /* reference_count */
+    avio_wb16(pb, 1); /* to_item_ID */
+    update_size(pb, auxl_pos);
+
+    return update_size(pb, iref_pos);
+}
+
+static int mov_write_ispe_tag(AVIOContext *pb, MOVMuxContext *mov, AVFormatContext *s,
+                              int stream_index)
 {
     int64_t pos = avio_tell(pb);
     avio_wb32(pb, 0); /* size */
     ffio_wfourcc(pb, "ispe");
     avio_wb32(pb, 0); /* Version & flags */
-    avio_wb32(pb, s->streams[0]->codecpar->width); /* image_width */
-    avio_wb32(pb, s->streams[0]->codecpar->height); /* image_height */
+    avio_wb32(pb, s->streams[stream_index]->codecpar->width); /* image_width */
+    avio_wb32(pb, s->streams[stream_index]->codecpar->height); /* image_height */
     return update_size(pb, pos);
 }
 
-static int mov_write_pixi_tag(AVIOContext *pb, MOVMuxContext *mov, AVFormatContext *s)
+static int mov_write_pixi_tag(AVIOContext *pb, MOVMuxContext *mov, AVFormatContext *s,
+                              int stream_index)
 {
     int64_t pos = avio_tell(pb);
-    const AVPixFmtDescriptor *pixdesc = av_pix_fmt_desc_get(s->streams[0]->codecpar->format);
+    const AVPixFmtDescriptor *pixdesc =
+        av_pix_fmt_desc_get(s->streams[stream_index]->codecpar->format);
     avio_wb32(pb, 0); /* size */
     ffio_wfourcc(pb, "pixi");
     avio_wb32(pb, 0); /* Version & flags */
@@ -3001,15 +3027,30 @@  static int mov_write_pixi_tag(AVIOContext *pb, MOVMuxContext *mov, AVFormatConte
     return update_size(pb, pos);
 }
 
+static int mov_write_auxC_tag(AVIOContext *pb)
+{
+    int64_t pos = avio_tell(pb);
+    avio_wb32(pb, 0); /* size */
+    ffio_wfourcc(pb, "auxC");
+    avio_wb32(pb, 0); /* Version & flags */
+    avio_write(pb, "urn:mpeg:mpegB:cicp:systems:auxiliary:alpha\0", 44);
+    return update_size(pb, pos);
+}
+
 static int mov_write_ipco_tag(AVIOContext *pb, MOVMuxContext *mov, AVFormatContext *s)
 {
     int64_t pos = avio_tell(pb);
     avio_wb32(pb, 0); /* size */
     ffio_wfourcc(pb, "ipco");
-    mov_write_ispe_tag(pb, mov, s);
-    mov_write_pixi_tag(pb, mov, s);
-    mov_write_av1c_tag(pb, &mov->tracks[0]);
-    mov_write_colr_tag(pb, &mov->tracks[0], 0);
+    for (int i = 0; i < s->nb_streams; i++) {
+        mov_write_ispe_tag(pb, mov, s, i);
+        mov_write_pixi_tag(pb, mov, s, i);
+        mov_write_av1c_tag(pb, &mov->tracks[i]);
+        if (!i)
+            mov_write_colr_tag(pb, &mov->tracks[0], 0);
+        else
+            mov_write_auxC_tag(pb);
+    }
     return update_size(pb, pos);
 }
 
@@ -3019,18 +3060,21 @@  static int mov_write_ipma_tag(AVIOContext *pb, MOVMuxContext *mov, AVFormatConte
     avio_wb32(pb, 0); /* size */
     ffio_wfourcc(pb, "ipma");
     avio_wb32(pb, 0); /* Version & flags */
-    avio_wb32(pb, 1); /* entry_count */
-    avio_wb16(pb, 1); /* item_ID */
-    avio_w8(pb, 4); /* association_count */
-
-    // ispe association.
-    avio_w8(pb, 1); /* essential and property_index */
-    // pixi association.
-    avio_w8(pb, 2); /* essential and property_index */
-    // av1C association.
-    avio_w8(pb, 0x80 | 3); /* essential and property_index */
-    // colr association.
-    avio_w8(pb, 4); /* essential and property_index */
+    avio_wb32(pb, s->nb_streams); /* entry_count */
+
+    for (int i = 0, index = 1; i < s->nb_streams; i++) {
+        avio_wb16(pb, i + 1); /* item_ID */
+        avio_w8(pb, 4); /* association_count */
+
+        // ispe association.
+        avio_w8(pb, index++); /* essential and property_index */
+        // pixi association.
+        avio_w8(pb, index++); /* essential and property_index */
+        // av1C association.
+        avio_w8(pb, 0x80 | index++); /* essential and property_index */
+        // colr/auxC association.
+        avio_w8(pb, index++); /* essential and property_index */
+    }
     return update_size(pb, pos);
 }
 
@@ -4112,6 +4156,8 @@  static int mov_write_meta_tag(AVIOContext *pb, MOVMuxContext *mov,
         mov_write_pitm_tag(pb, 1);
         mov_write_iloc_tag(pb, mov, s);
         mov_write_iinf_tag(pb, mov, s);
+        if (s->nb_streams > 1)
+            mov_write_iref_tag(pb, mov, s);
         mov_write_iprp_tag(pb, mov, s);
     } else {
         /* iTunes metadata tag */
@@ -6040,8 +6086,8 @@  int ff_mov_write_packet(AVFormatContext *s, AVPacket *pkt)
             avio_write(pb, reformatted_data, size);
         } else {
             size = ff_av1_filter_obus(pb, pkt->data, pkt->size);
-            if (trk->mode == MODE_AVIF && !mov->avif_extent_length) {
-                mov->avif_extent_length = size;
+            if (trk->mode == MODE_AVIF && !mov->avif_extent_length[pkt->stream_index]) {
+                mov->avif_extent_length[pkt->stream_index] = size;
             }
         }
 
@@ -6874,14 +6920,23 @@  static int mov_init(AVFormatContext *s)
 
     /* AVIF output must have exactly one video stream */
     if (mov->mode == MODE_AVIF) {
-        if (s->nb_streams > 1) {
-            av_log(s, AV_LOG_ERROR, "AVIF output requires exactly one stream\n");
+        if (s->nb_streams > 2) {
+            av_log(s, AV_LOG_ERROR, "AVIF output requires exactly one or two streams\n");
             return AVERROR(EINVAL);
         }
-        if (s->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO) {
-            av_log(s, AV_LOG_ERROR, "AVIF output requires one video stream\n");
+        if (s->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO &&
+            (s->nb_streams > 1 && s->streams[1]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO)) {
+            av_log(s, AV_LOG_ERROR, "AVIF output supports only video streams\n");
             return AVERROR(EINVAL);
         }
+        if (s->nb_streams > 1) {
+            const AVPixFmtDescriptor *pixdesc =
+                av_pix_fmt_desc_get(s->streams[1]->codecpar->format);
+            if (pixdesc->nb_components != 1) {
+                av_log(s, AV_LOG_ERROR, "Second stream for AVIF (alpha) output must have exactly one plane\n");
+                return AVERROR(EINVAL);
+            }
+        }
         s->streams[0]->disposition |= AV_DISPOSITION_DEFAULT;
     }
 
@@ -7543,18 +7598,25 @@  static int avif_write_trailer(AVFormatContext *s)
 {
     AVIOContext *pb = s->pb;
     MOVMuxContext *mov = s->priv_data;
-    int64_t pos_backup, mdat_pos;
+    int64_t pos_backup, extent_offsets[2];
     uint8_t *buf;
-    int buf_size, moov_size;
+    int buf_size, moov_size, i;
 
     if (mov->moov_written) return 0;
 
     mov->is_animated_avif = s->streams[0]->nb_frames > 1;
+    if (mov->is_animated_avif && s->nb_streams > 1) {
+        // For animated avif with alpha channel, we need to write a the tref
+        // tag with type "auxl".
+        mov->tracks[1].tref_tag = MKTAG('a', 'u', 'x', 'l');
+        mov->tracks[1].tref_id = 1;
+    }
     mov_write_identification(pb, s);
     mov_write_meta_tag(pb, mov, s);
 
     moov_size = get_moov_size(s);
-    mov->tracks[0].data_offset = avio_tell(pb) + moov_size + 8;
+    for (i = 0; i < s->nb_streams; i++)
+        mov->tracks[i].data_offset = avio_tell(pb) + moov_size + 8;
 
     if (mov->is_animated_avif) {
         int ret;
@@ -7565,19 +7627,24 @@  static int avif_write_trailer(AVFormatContext *s)
     buf_size = avio_get_dyn_buf(mov->mdat_buf, &buf);
     avio_wb32(pb, buf_size + 8);
     ffio_wfourcc(pb, "mdat");
-    mdat_pos = avio_tell(pb);
 
-    if (mdat_pos != (uint32_t)mdat_pos) {
-        av_log(s, AV_LOG_ERROR, "mdat offset does not fit in 32 bits\n");
-        return AVERROR_INVALIDDATA;
-    }
+    // The offset for the YUV planes is the starting position of mdat.
+    extent_offsets[0] = avio_tell(pb);
+    // The offset for alpha plane is YUV offset + YUV size.
+    extent_offsets[1] = extent_offsets[0] + mov->avif_extent_length[0];
 
     avio_write(pb, buf, buf_size);
 
-    // write extent offset.
+    // write extent offsets.
     pos_backup = avio_tell(pb);
-    avio_seek(pb, mov->avif_extent_pos, SEEK_SET);
-    avio_wb32(pb, mdat_pos); /* rewrite offset */
+    for (i = 0; i < s->nb_streams; i++) {
+        if (extent_offsets[i] != (uint32_t)extent_offsets[i]) {
+            av_log(s, AV_LOG_ERROR, "extent offset does not fit in 32 bits\n");
+            return AVERROR_INVALIDDATA;
+        }
+        avio_seek(pb, mov->avif_extent_pos[i], SEEK_SET);
+        avio_wb32(pb, extent_offsets[i]); /* rewrite offset */
+    }
     avio_seek(pb, pos_backup, SEEK_SET);
 
     return 0;
diff --git a/libavformat/movenc.h b/libavformat/movenc.h
index 281576cc66..e4550f7900 100644
--- a/libavformat/movenc.h
+++ b/libavformat/movenc.h
@@ -246,8 +246,8 @@  typedef struct MOVMuxContext {
     int empty_hdlr_name;
     int movie_timescale;
 
-    int64_t avif_extent_pos;
-    int avif_extent_length;
+    int64_t avif_extent_pos[2];  // index 0 is YUV and 1 is Alpha.
+    int avif_extent_length[2];   // index 0 is YUV and 1 is Alpha.
     int is_animated_avif;
 } MOVMuxContext;