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 <mich...@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.
Thanks,
- Mark
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