[FFmpeg-devel] [PATCH] avcodec/mpeg4videodec: Add support for parsing and exporting video_range

[Michael Niedermayer]

On Sun, Dec 10, 2017 at 10:19:30PM +0000, Mark Thompson wrote:
> On 10/12/17 21:49, Michael Niedermayer wrote:
> > On Sun, Dec 10, 2017 at 07:56:49PM +0000, Mark Thompson wrote:
> >> On 10/12/17 15:20, Michael Niedermayer wrote:
> >>> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> >>> ---
> >>>  libavcodec/mpeg4video.h    |  3 +++
> >>>  libavcodec/mpeg4videodec.c | 32 ++++++++++++++++++++++++++++++++
> >>>  2 files changed, 35 insertions(+)
> >>>
> >>> diff --git a/libavcodec/mpeg4video.h b/libavcodec/mpeg4video.h
> >>> index 515b008ae4..0ba502d50b 100644
> >>> --- a/libavcodec/mpeg4video.h
> >>> +++ b/libavcodec/mpeg4video.h
> >>> @@ -43,6 +43,9 @@
> >>>  #define ACE_VO_TYPE             12
> >>>  #define ADV_SIMPLE_VO_TYPE      17
> >>>  
> >>> +#define VOT_VIDEO_ID 1
> >>> +#define VOT_STILL_TEXTURE_ID 2
> >>> +
> >>>  // aspect_ratio_info
> >>>  #define EXTENDED_PAR 15
> >>>  
> >>> diff --git a/libavcodec/mpeg4videodec.c b/libavcodec/mpeg4videodec.c
> >>> index cdd7077f01..852f73f02c 100644
> >>> --- a/libavcodec/mpeg4videodec.c
> >>> +++ b/libavcodec/mpeg4videodec.c
> >>> @@ -1751,6 +1751,36 @@ static int mpeg4_decode_profile_level(MpegEncContext *s, GetBitContext *gb)
> >>>          s->avctx->level = 0;
> >>>      }
> >>>  
> >>> +    return 0;
> >>> +
> >>
> >> Stray newline.
> >>
> >>> +}
> >>> +
> >>> +static int mpeg4_decode_visual_object(MpegEncContext *s, GetBitContext *gb)
> >>> +{
> >>> +    int visual_object_type;
> >>> +    int is_visual_object_identifier = get_bits1(gb);
> >>> +
> >>> +    if (is_visual_object_identifier) {
> >>> +        skip_bits(gb, 4+3);
> >>> +    }
> >>> +    visual_object_type = get_bits(gb, 4);
> >>> +
> >>> +    if (visual_object_type == VOT_VIDEO_ID ||
> >>> +        visual_object_type == VOT_STILL_TEXTURE_ID) {
> >>> +        int video_signal_type = get_bits1(gb);
> >>> +        if (video_signal_type) {
> >>> +            int video_format = get_bits(gb, 3);
> >>> +            int video_range = get_bits1(gb);
> >>> +            int color_description = get_bits1(gb);
> >>> +
> >>> +            s->avctx->color_range = video_range ? AVCOL_RANGE_JPEG : AVCOL_RANGE_MPEG;
> >>> +
> >>> +            if (color_description) {
> >>> +                skip_bits(gb, 8+8+8);
> >>
> >> Might be nice to extract the colour information as well?  (Should be able to set color_primaries/color_trc/colorspace directly, I think.)
> > 
> > will look into this
> > btw, iam a bit short on samples that use this
> > i had found just one sample after a quick look
> > more samples would be welcome, if someone has some.
> 
> From a quick look around (run over some MPEG-4 samples with an abort in the above code) I can't find any examples of video_signal_type being set at all.  Minor thing I noticed in doing that - video_format is unused so you get a warning from the compiler: since it's not useful to anyone maybe replace it with skip_bits(3) and move the other stuff around to match that?
> 
> Don't block this because of the colour part if you don't have a sample of that - I just thought from reading the relevant part of the standard that it should be easy, but if noone has ever used it then whatever.

will push with color part support.
I sadly have not found much to test it seems to be the same as mpeg2

thx

[...]
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