Re: [FFmpeg-devel] [PATCH] libavformat/concatdev.c: use the unified time base

[Gyan Doshi <ffmpeg@gyani.pro>]

On 2022-03-01 09:46 am, Ye Chuan wrote:
> In some case, the input files have different time base
> even though they  share the same codec and codec parameters,
>
> So when we replace the packet, we need use the unified time base
> instead of it of each stream own, which may lead to wrong pts/dts
> of the output packet.
Make this optional. This 'bug' has been used to effect speed change in 
some inputs.

Regards,
Gyan

>
> Signed-off-by: Chuan Ye <yechuan0102@hotmail.com>
> ---
> libavformat/concatdec.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/libavformat/concatdec.c b/libavformat/concatdec.c
> index 0603c6e254..f7067d5059 100644
> --- a/libavformat/concatdec.c
> +++ b/libavformat/concatdec.c
> @@ -740,6 +740,7 @@ static int concat_read_packet(AVFormatContext *avf, AVPacket *pkt)
>      ConcatStream *cs;
>      AVStream *st;
>      FFStream *sti;
> +    AVRational output_tb;
>
>      if (cat->eof)
>          return AVERROR_EOF;
> @@ -782,13 +783,15 @@ static int concat_read_packet(AVFormatContext *avf, AVPacket *pkt)
>             av_ts2str(pkt->pts), av_ts2timestr(pkt->pts, &st->time_base),
>             av_ts2str(pkt->dts), av_ts2timestr(pkt->dts, &st->time_base));
>
> +    /* replace the pkt base on the time base of target output stream */
> +    output_tb = avf->streams[cs->out_stream_index]->time_base;
>      delta = av_rescale_q(cat->cur_file->start_time - cat->cur_file->file_inpoint,
>                           AV_TIME_BASE_Q,
> -                         cat->avf->streams[pkt->stream_index]->time_base);
> +                         output_tb);
>      if (pkt->pts != AV_NOPTS_VALUE)
> -        pkt->pts += delta;
> +        pkt->pts = av_rescale_q(pkt->pts, st->time_base, output_tb) + delta;
>      if (pkt->dts != AV_NOPTS_VALUE)
> -        pkt->dts += delta;
> +        pkt->dts = av_rescale_q(pkt->dts, st->time_base, output_tb) + delta;
>      av_log(avf, AV_LOG_DEBUG, " -> pts:%s pts_time:%s dts:%s dts_time:%s\n",
>             av_ts2str(pkt->pts), av_ts2timestr(pkt->pts, &st->time_base),
>             av_ts2str(pkt->dts), av_ts2timestr(pkt->dts, &st->time_base));

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