[FFmpeg-devel,v3] avformat, ffmpeg: deprecate old rotation API

The old "API" that signaled rotation as a metadata value has been
replaced by DISPLAYMATRIX side data quite a while ago.

There is no reason to make muxers/demuxers/API users support both. In
addition, the metadata API is dangerous, as user tags could "leak" into
it, creating unintended features or bugs.

ffmpeg CLI has to be updated to use the new API. In particular, we must
not allow to leak the "rotate" tag into the muxer. Some muxers will
catch this properly (like mov), but others (like mkv) can add it as
generic tag. Note applications, which use libavformat and assume the
old rotate API, will interpret such "rotate" user tags as rotate
metadata (which it is not), and incorrectly rotate the video.

The ffmpeg/ffplay tools drop the use of the old API for muxing and
demuxing, as all muxers/demuxers support the new API. This will mean
that the tools will not mistakenly interpret per-track "rotate" user
tags as rotate metadata. It will _not_ be treated as regression.

Unfortunately, hacks have been added, that allow the user to override
rotation by setting metadata explicitly, e.g. via

  -metadata:s:v:0 rotate=0

See references to trac #4560. fate-filter-meta-4560-rotate0 tests this.
It's easier to adjust the hack for supporting it than arguing for its
removal, so ffmpeg CLI now explicitly catches this case, and essentially
replaces the "rotate" value with a display matrix side data. (It would
be easier for both user and implementation to create an explicit option
for rotation.)

When the code under FF_API_OLD_ROTATE_API is disabled, one FATE
reference file has to be updated (because "rotate" is not exported
anymore).
---
Not sure what happened - probably removed some redundant code and failed
to retest properly. Maybe now?
---
 cmdutils.c            | 10 +---------
 ffmpeg.c              | 41 ++++++++++++++++++++++++++++++++++++-----
 ffmpeg.h              |  1 +
 ffmpeg_opt.c          | 12 ++++++++----
 libavformat/mov.c     |  2 ++
 libavformat/movenc.c  |  4 ++++
 libavformat/version.h |  3 +++
 7 files changed, 55 insertions(+), 18 deletions(-)

On Sat, 25 Mar 2017 12:28:26 +0100
wm4 <nfxjfg@googlemail.com> wrote:

> The old "API" that signaled rotation as a metadata value has been
> replaced by DISPLAYMATRIX side data quite a while ago.
> 
> There is no reason to make muxers/demuxers/API users support both. In
> addition, the metadata API is dangerous, as user tags could "leak" into
> it, creating unintended features or bugs.
> 
> ffmpeg CLI has to be updated to use the new API. In particular, we must
> not allow to leak the "rotate" tag into the muxer. Some muxers will
> catch this properly (like mov), but others (like mkv) can add it as
> generic tag. Note applications, which use libavformat and assume the
> old rotate API, will interpret such "rotate" user tags as rotate
> metadata (which it is not), and incorrectly rotate the video.
> 
> The ffmpeg/ffplay tools drop the use of the old API for muxing and
> demuxing, as all muxers/demuxers support the new API. This will mean
> that the tools will not mistakenly interpret per-track "rotate" user
> tags as rotate metadata. It will _not_ be treated as regression.
> 
> Unfortunately, hacks have been added, that allow the user to override
> rotation by setting metadata explicitly, e.g. via
> 
>   -metadata:s:v:0 rotate=0
> 
> See references to trac #4560. fate-filter-meta-4560-rotate0 tests this.
> It's easier to adjust the hack for supporting it than arguing for its
> removal, so ffmpeg CLI now explicitly catches this case, and essentially
> replaces the "rotate" value with a display matrix side data. (It would
> be easier for both user and implementation to create an explicit option
> for rotation.)
> 
> When the code under FF_API_OLD_ROTATE_API is disabled, one FATE
> reference file has to be updated (because "rotate" is not exported
> anymore).
> ---
> Not sure what happened - probably removed some redundant code and failed
> to retest properly. Maybe now?
> ---
>  cmdutils.c            | 10 +---------
>  ffmpeg.c              | 41 ++++++++++++++++++++++++++++++++++++-----
>  ffmpeg.h              |  1 +
>  ffmpeg_opt.c          | 12 ++++++++----
>  libavformat/mov.c     |  2 ++
>  libavformat/movenc.c  |  4 ++++
>  libavformat/version.h |  3 +++
>  7 files changed, 55 insertions(+), 18 deletions(-)
> 
> diff --git a/cmdutils.c b/cmdutils.c
> index 2373dbf841..3d428f3eea 100644
> --- a/cmdutils.c
> +++ b/cmdutils.c
> @@ -2097,18 +2097,10 @@ void *grow_array(void *array, int elem_size, int *size, int new_size)
>  
>  double get_rotation(AVStream *st)
>  {
> -    AVDictionaryEntry *rotate_tag = av_dict_get(st->metadata, "rotate", NULL, 0);
>      uint8_t* displaymatrix = av_stream_get_side_data(st,
>                                                       AV_PKT_DATA_DISPLAYMATRIX, NULL);
>      double theta = 0;
> -
> -    if (rotate_tag && *rotate_tag->value && strcmp(rotate_tag->value, "0")) {
> -        char *tail;
> -        theta = av_strtod(rotate_tag->value, &tail);
> -        if (*tail)
> -            theta = 0;
> -    }
> -    if (displaymatrix && !theta)
> +    if (displaymatrix)
>          theta = -av_display_rotation_get((int32_t*) displaymatrix);
>  
>      theta -= 360*floor(theta/360 + 0.9/360);
> diff --git a/ffmpeg.c b/ffmpeg.c
> index 532db80e0b..90441224f9 100644
> --- a/ffmpeg.c
> +++ b/ffmpeg.c
> @@ -50,6 +50,7 @@
>  #include "libavutil/internal.h"
>  #include "libavutil/intreadwrite.h"
>  #include "libavutil/dict.h"
> +#include "libavutil/display.h"
>  #include "libavutil/mathematics.h"
>  #include "libavutil/pixdesc.h"
>  #include "libavutil/avstring.h"
> @@ -3067,9 +3068,6 @@ static int init_output_stream_streamcopy(OutputStream *ost)
>              const AVPacketSideData *sd_src = &ist->st->side_data[i];
>              AVPacketSideData *sd_dst = &ost->st->side_data[ost->st->nb_side_data];
>  
> -            if (ost->rotate_overridden && sd_src->type == AV_PKT_DATA_DISPLAYMATRIX)
> -                continue;
> -
>              sd_dst->data = av_malloc(sd_src->size);
>              if (!sd_dst->data)
>                  return AVERROR(ENOMEM);
> @@ -3080,6 +3078,13 @@ static int init_output_stream_streamcopy(OutputStream *ost)
>          }
>      }
>  
> +    if (ost->rotate_overridden) {
> +        uint8_t *sd = av_stream_new_side_data(ost->st, AV_PKT_DATA_DISPLAYMATRIX,
> +                                              sizeof(int32_t) * 9);
> +        if (sd)
> +            av_display_rotation_set((int32_t *)sd, -ost->rotate_override_value);
> +    }
> +
>      ost->parser = av_parser_init(par_dst->codec_id);
>      ost->parser_avctx = avcodec_alloc_context3(NULL);
>      if (!ost->parser_avctx)
> @@ -3233,6 +3238,11 @@ static int init_output_stream_encode(OutputStream *ost)
>  
>      set_encoder_id(output_files[ost->file_index], ost);
>  
> +    // Muxers use AV_PKT_DATA_DISPLAYMATRIX to signal rotation. On the other
> +    // hand, the legacy API makes demuxers set "rotate" metadata entries,
> +    // which have to be filtered out to prevent leaking them to output files.
> +    av_dict_set(&ost->st->metadata, "rotate", NULL, 0);
> +
>      if (ist) {
>          ost->st->disposition          = ist->st->disposition;
>  
> @@ -3470,6 +3480,26 @@ static int init_output_stream(OutputStream *ost, char *error, int error_len)
>              }
>          }
>  
> +        /*
> +         * Add global input side data. For now this is naive, and copies it
> +         * from the input stream's global side data. All side data should
> +         * really be funneled over AVFrame and libavfilter, then added back to
> +         * packet side data, and then potentially using the first packet for
> +         * global side data.
> +         */
> +        if (ist) {
> +            int i;
> +            for (i = 0; i < ist->st->nb_side_data; i++) {
> +                AVPacketSideData *sd = &ist->st->side_data[i];
> +                uint8_t *dst = av_stream_new_side_data(ost->st, sd->type, sd->size);
> +                if (!dst)
> +                    return AVERROR(ENOMEM);
> +                memcpy(dst, sd->data, sd->size);
> +                if (ist->autorotate && sd->type == AV_PKT_DATA_DISPLAYMATRIX)
> +                    av_display_rotation_set((uint32_t *)dst, 0);
> +            }
> +        }
> +
>          // copy timebase while removing common factors
>          if (ost->st->time_base.num <= 0 || ost->st->time_base.den <= 0)
>              ost->st->time_base = av_add_q(ost->enc_ctx->time_base, (AVRational){0, 1});
> @@ -4266,9 +4296,10 @@ static int process_input(int file_index)
>              AVPacketSideData *src_sd = &ist->st->side_data[i];
>              uint8_t *dst_data;
>  
> -            if (av_packet_get_side_data(&pkt, src_sd->type, NULL))
> +            if (src_sd->type == AV_PKT_DATA_DISPLAYMATRIX)
>                  continue;
> -            if (ist->autorotate && src_sd->type == AV_PKT_DATA_DISPLAYMATRIX)
> +
> +            if (av_packet_get_side_data(&pkt, src_sd->type, NULL))
>                  continue;
>  
>              dst_data = av_packet_new_side_data(&pkt, src_sd->type, src_sd->size);
> diff --git a/ffmpeg.h b/ffmpeg.h
> index c3ed6ced78..4d0456c1fb 100644
> --- a/ffmpeg.h
> +++ b/ffmpeg.h
> @@ -475,6 +475,7 @@ typedef struct OutputStream {
>      int force_fps;
>      int top_field_first;
>      int rotate_overridden;
> +    double rotate_override_value;
>  
>      AVRational frame_aspect_ratio;
>  
> diff --git a/ffmpeg_opt.c b/ffmpeg_opt.c
> index fc885dfac3..ffe1abdb38 100644
> --- a/ffmpeg_opt.c
> +++ b/ffmpeg_opt.c
> @@ -2549,8 +2549,6 @@ loop_end:
>              av_dict_copy(&output_streams[i]->st->metadata, ist->st->metadata, AV_DICT_DONT_OVERWRITE);
>              if (!output_streams[i]->stream_copy) {
>                  av_dict_set(&output_streams[i]->st->metadata, "encoder", NULL, 0);
> -                if (ist->autorotate)
> -                    av_dict_set(&output_streams[i]->st->metadata, "rotate", NULL, 0);
>              }
>          }
>  
> @@ -2640,9 +2638,15 @@ loop_end:
>              for (j = 0; j < oc->nb_streams; j++) {
>                  ost = output_streams[nb_output_streams - oc->nb_streams + j];
>                  if ((ret = check_stream_specifier(oc, oc->streams[j], stream_spec)) > 0) {
> -                    av_dict_set(&oc->streams[j]->metadata, o->metadata[i].u.str, *val ? val : NULL, 0);
>                      if (!strcmp(o->metadata[i].u.str, "rotate")) {
> -                        ost->rotate_overridden = 1;
> +                        char *tail;
> +                        double theta = av_strtod(val, &tail);
> +                        if (!*tail) {
> +                            ost->rotate_overridden = 1;
> +                            ost->rotate_override_value = theta;
> +                        }
> +                    } else {
> +                        av_dict_set(&oc->streams[j]->metadata, o->metadata[i].u.str, *val ? val : NULL, 0);
>                      }
>                  } else if (ret < 0)
>                      exit_program(1);
> diff --git a/libavformat/mov.c b/libavformat/mov.c
> index 3754346f9e..a00c53a676 100644
> --- a/libavformat/mov.c
> +++ b/libavformat/mov.c
> @@ -4030,6 +4030,7 @@ static int mov_read_tkhd(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>              for (j = 0; j < 3; j++)
>                  sc->display_matrix[i * 3 + j] = res_display_matrix[i][j];
>  
> +#if FF_API_OLD_ROTATE_API
>          rotate = av_display_rotation_get(sc->display_matrix);
>          if (!isnan(rotate)) {
>              char rotate_buf[64];
> @@ -4039,6 +4040,7 @@ static int mov_read_tkhd(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>              snprintf(rotate_buf, sizeof(rotate_buf), "%g", rotate);
>              av_dict_set(&st->metadata, "rotate", rotate_buf, 0);
>          }
> +#endif
>      }
>  
>      // transform the display width/height according to the matrix
> diff --git a/libavformat/movenc.c b/libavformat/movenc.c
> index 11b26708ae..3b4e3b519c 100644
> --- a/libavformat/movenc.c
> +++ b/libavformat/movenc.c
> @@ -2496,19 +2496,23 @@ static int mov_write_tkhd_tag(AVIOContext *pb, MOVMuxContext *mov,
>      avio_wb16(pb, 0); /* reserved */
>  
>      /* Matrix structure */
> +#if FF_API_OLD_ROTATE_API
>      if (st && st->metadata) {
>          AVDictionaryEntry *rot = av_dict_get(st->metadata, "rotate", NULL, 0);
>          rotation = (rot && rot->value) ? atoi(rot->value) : 0;
>      }
> +#endif
>      if (display_matrix) {
>          for (i = 0; i < 9; i++)
>              avio_wb32(pb, display_matrix[i]);
> +#if FF_API_OLD_ROTATE_API
>      } else if (rotation == 90) {
>          write_matrix(pb,  0,  1, -1,  0, track->par->height, 0);
>      } else if (rotation == 180) {
>          write_matrix(pb, -1,  0,  0, -1, track->par->width, track->par->height);
>      } else if (rotation == 270) {
>          write_matrix(pb,  0, -1,  1,  0, 0, track->par->width);
> +#endif
>      } else {
>          write_matrix(pb,  1,  0,  0,  1, 0, 0);
>      }
> diff --git a/libavformat/version.h b/libavformat/version.h
> index dd4c680803..7b92255bea 100644
> --- a/libavformat/version.h
> +++ b/libavformat/version.h
> @@ -94,6 +94,9 @@
>  #ifndef FF_API_LAVF_KEEPSIDE_FLAG
>  #define FF_API_LAVF_KEEPSIDE_FLAG       (LIBAVFORMAT_VERSION_MAJOR < 58)
>  #endif
> +#ifndef FF_API_OLD_ROTATE_API
> +#define FF_API_OLD_ROTATE_API           (LIBAVFORMAT_VERSION_MAJOR < 58)
> +#endif
>  
>  
>  #ifndef FF_API_R_FRAME_RATE

Pushed, with added version bump + APIchanges entry. Thanks for review.