Re: [FFmpeg-devel] [PATCH] avformat/pcmdec: add pts and dts calculation for pcmdec

[Hiccup Zhu <hiccupzhu@gmail.com>]

The purpose of this patch is to calculate pts and dts when using pcmdemux.
Is there anything wrong with doing this, or do you have any suggestions for
improvement?

Andreas Rheinhardt <andreas.rheinhardt@outlook.com> 于2024年5月14日周二 19:41写道：

> Shiqi Zhu:
> > Signed-off-by: Shiqi Zhu <hiccupzhu@gmail.com>
> > ---
> >  libavformat/pcmdec.c | 37 +++++++++++++++++++++++++++++++++++--
> >  1 file changed, 35 insertions(+), 2 deletions(-)
> >
> > diff --git a/libavformat/pcmdec.c b/libavformat/pcmdec.c
> > index 2f6508b75a..d879aefaad 100644
> > --- a/libavformat/pcmdec.c
> > +++ b/libavformat/pcmdec.c
> > @@ -36,6 +36,7 @@ typedef struct PCMAudioDemuxerContext {
> >      AVClass *class;
> >      int sample_rate;
> >      AVChannelLayout ch_layout;
> > +    int64_t nb_samples;
> >  } PCMAudioDemuxerContext;
> >
> >  static int pcm_read_header(AVFormatContext *s)
> > @@ -46,6 +47,7 @@ static int pcm_read_header(AVFormatContext *s)
> >      uint8_t *mime_type = NULL;
> >      int ret;
> >
> > +    s1->nb_samples = 0;
> >      st = avformat_new_stream(s, NULL);
> >      if (!st)
> >          return AVERROR(ENOMEM);
> > @@ -104,6 +106,37 @@ static int pcm_read_header(AVFormatContext *s)
> >      return 0;
> >  }
> >
> > +static int pcm_dec_read_packet(AVFormatContext *s, AVPacket *pkt)
> > +{
> > +    PCMAudioDemuxerContext *s1 = s->priv_data;
> > +    AVCodecParameters *par = s->streams[0]->codecpar;
> > +    int ret;
> > +
> > +    ret = ff_pcm_read_packet(s, pkt);
> > +    if (ret < 0)
> > +        return ret;
> > +
> > +    pkt->time_base = s->streams[0]->time_base;
> > +    pkt->dts = pkt->pts = s1->nb_samples;
> > +    s1->nb_samples += pkt->size / par->block_align;
> > +
> > +    return ret;
> > +}
> > +
> > +static int pcm_dec_read_seek(AVFormatContext *s,
> > +                             int stream_index, int64_t timestamp, int
> flags)
> > +{
> > +    PCMAudioDemuxerContext *s1 = s->priv_data;
> > +    int ret;
> > +
> > +    ret = ff_pcm_read_seek(s, stream_index, timestamp, flags);
> > +    if (ret < 0)
> > +        return ret;
> > +
> > +    s1->nb_samples = ffstream(s->streams[0])->cur_dts;
> > +    return ret;
> > +}
> > +
> >  static const AVOption pcm_options[] = {
> >      { "sample_rate", "", offsetof(PCMAudioDemuxerContext, sample_rate),
> AV_OPT_TYPE_INT, {.i64 = 44100}, 0, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },
> >      { "ch_layout",   "", offsetof(PCMAudioDemuxerContext, ch_layout),
>  AV_OPT_TYPE_CHLAYOUT, {.str = "mono"}, 0, 0, AV_OPT_FLAG_DECODING_PARAM },
> > @@ -126,8 +159,8 @@ const FFInputFormat ff_pcm_ ## name_ ## _demuxer =
> {        \
> >      .p.priv_class   = &pcm_demuxer_class,                   \
> >      .priv_data_size = sizeof(PCMAudioDemuxerContext),       \
> >      .read_header    = pcm_read_header,                      \
> > -    .read_packet    = ff_pcm_read_packet,                   \
> > -    .read_seek      = ff_pcm_read_seek,                     \
> > +    .read_packet    = pcm_dec_read_packet,                  \
> > +    .read_seek      = pcm_dec_read_seek,                    \
> >      .raw_codec_id   = codec,                                \
> >      __VA_ARGS__                                             \
> >  };
>
> A quick test shows that PTS and DTS are already set generically for pcm
> formats (unless the AVFMT_FLAG_NOFILLIN flag is set). If it is not in
> your usecase, then you should provide details about this (preferably by
> opening a ticket on trac).
>
> - Andreas
>
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