[FFmpeg-devel] [PATCH] avformat/dv: fix timestamps of audio packets in case of dropped corrupt audio frames

[Michael Niedermayer]

On Sat, Oct 31, 2020 at 05:56:24PM +0100, Marton Balint wrote:
> Fixes out of sync timestamps in ticket #8762.
> 
> Signed-off-by: Marton Balint <cus at passwd.hu>
> ---
>  libavformat/dv.c       | 16 ++--------------
>  tests/ref/seek/lavf-dv | 18 +++++++++---------
>  2 files changed, 11 insertions(+), 23 deletions(-)
> 
> diff --git a/libavformat/dv.c b/libavformat/dv.c
> index 3e0d12c0e3..26a78139f5 100644
> --- a/libavformat/dv.c
> +++ b/libavformat/dv.c
> @@ -49,7 +49,6 @@ struct DVDemuxContext {
>      uint8_t           audio_buf[4][8192];
>      int               ach;
>      int               frames;
> -    uint64_t          abytes;
>  };
>  
>  static inline uint16_t dv_audio_12to16(uint16_t sample)
> @@ -258,7 +257,7 @@ static int dv_extract_audio_info(DVDemuxContext *c, const uint8_t *frame)
>              c->ast[i] = avformat_new_stream(c->fctx, NULL);
>              if (!c->ast[i])
>                  break;
> -            avpriv_set_pts_info(c->ast[i], 64, 1, 30000);
> +            avpriv_set_pts_info(c->ast[i], 64, c->sys->time_base.num, c->sys->time_base.den);
>              c->ast[i]->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
>              c->ast[i]->codecpar->codec_id   = AV_CODEC_ID_PCM_S16LE;
>  
> @@ -387,8 +386,7 @@ int avpriv_dv_produce_packet(DVDemuxContext *c, AVPacket *pkt,
>      for (i = 0; i < c->ach; i++) {
>          c->audio_pkt[i].pos  = pos;
>          c->audio_pkt[i].size = size;
> -        c->audio_pkt[i].pts  = c->abytes * 30000 * 8 /
> -                               c->ast[i]->codecpar->bit_rate;
> +        c->audio_pkt[i].pts  = (c->sys->height == 720) ? (c->frames & ~1) : c->frames;
>          ppcm[i] = c->audio_buf[i];
>      }
>      if (c->ach)
> @@ -401,10 +399,7 @@ int avpriv_dv_produce_packet(DVDemuxContext *c, AVPacket *pkt,
>              c->audio_pkt[2].size = c->audio_pkt[3].size = 0;
>          } else {
>              c->audio_pkt[0].size = c->audio_pkt[1].size = 0;
> -            c->abytes           += size;
>          }
> -    } else {
> -        c->abytes += size;
>      }
>  
>      /* Now it's time to return video packet */

Please correct me if iam wrong but
in cases where no audio is missing or damaged, this would also ignore how much
audio is in each packet. So you could have lets say a timestamp difference
of excatly 1 second between 2 packets while their is actually not exactly
1 second worth of audio samples between them. 


[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I have often repented speaking, but never of holding my tongue.
-- Xenocrates
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