[FFmpeg-devel] [PATCH] avformat/hlsenc: Fix initial setting for start_pts

[Hongcheng Zhong]

----- On Mar 6, 2020, at 11:08 AM, Andreas Rheinhardt andreas.rheinhardt at gmail.com wrote:

> Hongcheng Zhong:
>> ----- On Mar 6, 2020, at 12:55 AM, Andreas Rheinhardt
>> andreas.rheinhardt at gmail.com wrote:
>> 
>>> Hongcheng Zhong:
>>>> ----- On Mar 5, 2020, at 11:38 PM, lq lq at chinaffmpeg.org wrote:
>>>>
>>>>>> 2020年3月5日 下午9:41，Hongcheng Zhong <sj.hc_zhong at sjtu.edu.cn> 写道：
>>>>>>
>>>>>> This patch fixes Bug #8469
>>>>>> If x264 baseline profile is used with other profiles,
>>>>>> start_pts will be initialized to audio stream's first pts,
>>>>>> while the duration is calculated based on video stream's pts.
>>>>>> In this patch the start_pts is initialized with the correct stream's first pts.
>>>>>>
>>>>>> Signed-off-by: Hongcheng Zhong <sj.hc_Zhong at sjtu.edu.cn>
>>>>>> ---
>>>>>> libavformat/hlsenc.c | 10 +++++++++-
>>>>>> 1 file changed, 9 insertions(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/libavformat/hlsenc.c b/libavformat/hlsenc.c
>>>>>> index f6dd894..3b2434f 100644
>>>>>> --- a/libavformat/hlsenc.c
>>>>>> +++ b/libavformat/hlsenc.c
>>>>>> @@ -126,6 +126,7 @@ typedef struct VariantStream {
>>>>>>     int has_video;
>>>>>>     int has_subtitle;
>>>>>>     int new_start;
>>>>>> +    int start_pts_from_audio;
>>>>>>     double dpp;           // duration per packet
>>>>>>     int64_t start_pts;
>>>>>>     int64_t end_pts;
>>>>>> @@ -2274,9 +2275,15 @@ static int hls_write_packet(AVFormatContext *s, AVPacket
>>>>>> *pkt)
>>>>>>
>>>>>>     if (vs->start_pts == AV_NOPTS_VALUE) {
>>>>>>         vs->start_pts = pkt->pts;
>>>>>> +        if (st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO)
>>>>>> +            vs->start_pts_from_audio = 1;
>>>>>> +    }
>>>>>> +    if (vs->start_pts_from_audio && st->codecpar->codec_type ==
>>>>>> AVMEDIA_TYPE_VIDEO && vs->start_pts > pkt->pts) {
>>>>>> +        vs->start_pts = pkt->pts;
>>>>>> +        vs->start_pts_from_audio = 0;
>>>>>>     }
>>>>>>
>>>>>> -   if (vs->has_video) {
>>>>>> +    if (vs->has_video) {
>>>>> What’s happen with this line?
>>>>>>         can_split = st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO &&
>>>>>>                     ((pkt->flags & AV_PKT_FLAG_KEY) || (hls->flags & HLS_SPLIT_BY_TIME));
>>>>>>         is_ref_pkt = (st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) &&
>>>>>>         (pkt->stream_index == vs->reference_stream_index);
>>>>>> @@ -2751,6 +2758,7 @@ static int hls_init(AVFormatContext *s)
>>>>>>         vs->sequence       = hls->start_sequence;
>>>>>>         vs->start_pts      = AV_NOPTS_VALUE;
>>>>>>         vs->end_pts      = AV_NOPTS_VALUE;
>>>>>> +        vs->start_pts_from_audio = 0;
>>>>>>         vs->current_segment_final_filename_fmt[0] = '\0';
>>>>>>
>>>>>>         if (hls->flags & HLS_SPLIT_BY_TIME && hls->flags & HLS_INDEPENDENT_SEGMENTS) {
>>>>>> --
>>>>>> 2.7.4
>>>>>>
>>>>>> _______________________________________________
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>>>>>>
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>>>>>> ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".
>>>>
>>>> Actually, this line is useless because that vs is initialized as all zero.
>>>> Should I remove this line and submit this patch as v2 again? Thanks for your
>>>> reply.
>>>
>>> But vs->has_video is initialized to a potentially nonzero value in
>>> hls_init().
>>>
>>> - Andreas
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>> 
>> I write that line to make sure that vs->start_pts_from_audio is initialized as
>> 0.
>> Since `hls->var_streams = av_mallocz(sizeof(*hls->var_streams) *
>> nb_varstreams);`
>> in hlsenc.c: 1897, var_streams is allocated with av_mallocz(), that line is not
>> necessary.
> 
> There seems to be a misunderstanding: The line that Steven asked about
> is "if (vs->has_video) {". By changing it you mixed cosmetic changes
> and functional ones; this should not be done.
> Steven did not ask about "vs->start_pts_from_audio = 0;". But you are
> right: It is redundant.
> 
> - Andreas
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Sorry, my mistake. "Cosmetic changes should be kept in separate patches."
Thanks a lot for pointing this out.