[FFmpeg-devel,28/31] vp9_metadata: Improve spec-compliance and warnings

The earlier version had three deficits:
1. It allowed to set the stream to RGB although this is not allowed when
the profile is 0 or 2.
2. If it set the stream to RGB, then it did not automatically set the
range to full range; the result was that one got a warning every time a
frame with color_config element was processed if the frame originally
had TV range and the user didn't explicitly choose PC range. Now one
gets only one warning in such a situation.
3. Intra-only frames in profile 0 are automatically BT.601, but if the
user wished another color space, he was not informed about his wishes
being unfulfillable.

The commit also improves the documentation about this.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
---
 doc/bitstream_filters.texi    |  8 ++++---
 libavcodec/vp9_metadata_bsf.c | 40 ++++++++++++++++++++++++-----------
 2 files changed, 33 insertions(+), 15 deletions(-)

On 09/07/2019 02:10, Andreas Rheinhardt wrote:
> The earlier version had three deficits:
> 1. It allowed to set the stream to RGB although this is not allowed when
> the profile is 0 or 2.
> 2. If it set the stream to RGB, then it did not automatically set the
> range to full range; the result was that one got a warning every time a
> frame with color_config element was processed if the frame originally
> had TV range and the user didn't explicitly choose PC range. Now one
> gets only one warning in such a situation.
> 3. Intra-only frames in profile 0 are automatically BT.601, but if the
> user wished another color space, he was not informed about his wishes
> being unfulfillable.
> 
> The commit also improves the documentation about this.
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
> ---
>  doc/bitstream_filters.texi    |  8 ++++---
>  libavcodec/vp9_metadata_bsf.c | 40 ++++++++++++++++++++++++-----------
>  2 files changed, 33 insertions(+), 15 deletions(-)
> 
> diff --git a/doc/bitstream_filters.texi b/doc/bitstream_filters.texi
> index a6a5a331f5..47de4c7116 100644
> --- a/doc/bitstream_filters.texi
> +++ b/doc/bitstream_filters.texi
> @@ -657,7 +657,9 @@ Modify metadata embedded in a VP9 stream.
>  
>  @table @option
>  @item color_space
> -Set the color space value in the frame header.
> +Set the color space value in the frame header. Note that any frame
> +set to RGB will be implicitly set to PC range and that RGB is
> +incompatible with profiles 0 and 2.
>  @table @samp
>  @item unknown
>  @item bt601
> @@ -669,8 +671,8 @@ Set the color space value in the frame header.
>  @end table
>  
>  @item color_range
> -Set the color range value in the frame header.  Note that this cannot
> -be set in RGB streams.
> +Set the color range value in the frame header. Note that any value
> +imposed by the color space will take precedence over this value.
>  @table @samp
>  @item tv
>  @item pc
> diff --git a/libavcodec/vp9_metadata_bsf.c b/libavcodec/vp9_metadata_bsf.c
> index 1bde1b96aa..52e962b1c0 100644
> --- a/libavcodec/vp9_metadata_bsf.c
> +++ b/libavcodec/vp9_metadata_bsf.c
> @@ -33,7 +33,7 @@ typedef struct VP9MetadataContext {
>      int color_space;
>      int color_range;
>  
> -    int color_range_rgb_warned;
> +    int color_warnings;
>  } VP9MetadataContext;
>  
>  
> @@ -56,20 +56,36 @@ static int vp9_metadata_filter(AVBSFContext *bsf, AVPacket *pkt)
>      for (i = 0; i < frag->nb_units; i++) {
>          VP9RawFrame *frame = frag->units[i].content;
>          VP9RawFrameHeader *header = &frame->header;
> +        int profile = (header->profile_high_bit << 1) + header->profile_low_bit;
> +
> +        if (header->frame_type == VP9_KEY_FRAME ||
> +            header->intra_only && profile > 0) {
> +            if (ctx->color_space >= 0) {
> +                if (!(profile & 1) && ctx->color_space == VP9_CS_RGB) {
> +                    if (!(ctx->color_warnings & 2)) {
> +                        av_log(bsf, AV_LOG_WARNING, "Warning: RGB "
> +                               "incompatible with profiles 0 and 2.\n");
> +                        ctx->color_warnings |= 2;
> +                    }
> +                } else
> +                    header->color_space = ctx->color_space;
> +            }
>  
> -        if (ctx->color_space >= 0) {
> -            header->color_space = ctx->color_space;
> -        }
> -        if (ctx->color_range >= 0) {
> -            if (ctx->color_range == 0 &&
> -                header->color_space == VP9_CS_RGB &&
> -                !ctx->color_range_rgb_warned) {
> -                av_log(bsf, AV_LOG_WARNING, "Warning: color_range cannot "
> -                       "be set to limited in RGB streams.\n");
> -                ctx->color_range_rgb_warned = 1;
> -            } else {
> +            if (ctx->color_range >= 0)
>                  header->color_range = ctx->color_range;
> +            if (header->color_space == VP9_CS_RGB) {
> +                if (!(ctx->color_warnings & 1) && !header->color_range) {
> +                    av_log(bsf, AV_LOG_WARNING, "Warning: Color space RGB "
> +                           "implicitly sets color range to PC range.\n");
> +                    ctx->color_warnings |= 1;
> +                }
> +                header->color_range = 1;
>              }
> +        } else if (!(ctx->color_warnings & 4) && header->intra_only && !profile &&
> +                   ctx->color_space >= 0 && ctx->color_space != VP9_CS_BT_601) {
> +            av_log(bsf, AV_LOG_WARNING, "Warning: Intra-only frames in "
> +                   "profile 0 are automatically BT.601.\n");
> +            ctx->color_warnings |= 4;
>          }
>      }
>  
> 

LGTM, applied.

Thanks,

- Mark