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

[Andreas Rheinhardt]

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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>>>>> ffmpeg-devel at ffmpeg.org
>>>>> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>>>>>
>>>>> To unsubscribe, visit link above, or email
>>>>> 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