Re: [FFmpeg-devel] [PATCH] avcodec/h264_mp4toannexb: fix missing SPS/PPS to IDR frames

["\"zhilizhao(赵志立)\"" <quinkblack@foxmail.com>]

> On Jan 10, 2023, at 23:31, Zhao Zhili <quinkblack@foxmail.com> wrote:
> 
> On Tue, 2023-01-10 at 07:41 +0100, Andreas Rheinhardt wrote:
>> Zhao Zhili:
>>> From: Zhao Zhili <zhilizhao@tencent.com>
>>> 
>>> If there is a single group of SPS/PPS before an IDR frame, but no
>>> SPS/PPS after that, we will miss the chance to reset
>>> idr_sps_seen/idr_pps_seen. The result is missing SPS/PPS for all
>>> IDR frames except the first one.
>>> 
>>> Signed-off-by: Zhao Zhili <zhilizhao@tencent.com>
>>> ---
>>> libavcodec/h264_mp4toannexb_bsf.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>> 
>>> diff --git a/libavcodec/h264_mp4toannexb_bsf.c
>>> b/libavcodec/h264_mp4toannexb_bsf.c
>>> index d11be455c2..bbdeca9c44 100644
>>> --- a/libavcodec/h264_mp4toannexb_bsf.c
>>> +++ b/libavcodec/h264_mp4toannexb_bsf.c
>>> @@ -259,7 +259,7 @@ static int h264_mp4toannexb_filter(AVBSFContext
>>> *ctx, AVPacket *opkt)
>>> 
>>>             count_or_copy(&out, &out_size, buf, nal_size,
>>>                           unit_type == H264_NAL_SPS || unit_type
>>> == H264_NAL_PPS, j);
>>> -            if (!new_idr && unit_type == H264_NAL_SLICE) {
>>> +            if (unit_type == H264_NAL_SLICE) {
>>>                 new_idr  = 1;
>>>                 sps_seen = 0;
>>>                 pps_seen = 0;
>> 
>> If I understand you correctly, you want that to include the parameter
>> sets from the extradata to every IDR frame without extradata if said
>> IDR
>> frame follows a non-IDR frame after in-band parameter sets. There is
>> just one problem with this: Said in-band parameter sets might
>> overwrite
>> parameter sets from extradata and inserting the outdated parameter
>> sets
>> from extradata lateron might make the stream undecodable.
> 
> It's a good question. Current code works when an IDR has in-band
> parameter set, which is different than the out-of-band parameter set,
> and the decoder doesn't miss the in-band parameter set. But there is a
> high chance the decoder will miss the in-band parameter set for annexb
> bitstream, e.g., playback at the middle of a live mpegts streams. It's
> a serious issue of missing periodic in-band parameter set for annexb
> for a lot of usecases. Handle new parameter set isn't as common as the
> need of periodic in-band parameter set (I guess).
> 
> It's not a new issue that this bitstream failed to update the parameter
> set, for example, it doesn't handle AV_PKT_DATA_NEW_EXTRADATA. I can
> add support for
> 1. handling AV_PKT_DATA_NEW_EXTRADATA
> 2. handling in-band sps/pps
> 
> But it won't be soon.

Ping.

> 
>> 
>> - Andreas
>> 
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