Re: [FFmpeg-devel] [FFmpeg-cvslog] avformat/dump: Print stream start offsets for input streams

Re: [FFmpeg-devel] [FFmpeg-cvslog] avformat/dump: Print stream start offsets for input streams

[Gyan Doshi]

On 2025-04-19 08:35 pm, softworkz wrote:
> ffmpeg | branch: master | softworkz <softworkz@hotmail.com> | Sat Feb 23 04:59:10 2019 +0100| [02d7384ed5eec0152056c081b536c16cb86e6361] | committer: softworkz
>
> avformat/dump: Print stream start offsets for input streams
>
> Seeing the offset of video and audio streams to each other is often
> a useful metric in diagnosing and understanding issues with playback
> or transcoding.
> This commit adds those offsets to the stream info print.
>
> Signed-off-by: softworkz <softworkz@hotmail.com>
>
>> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=02d7384ed5eec0152056c081b536c16cb86e6361
> ---
>
>   libavformat/dump.c | 5 +++++
>   1 file changed, 5 insertions(+)
>
> diff --git a/libavformat/dump.c b/libavformat/dump.c
> index 3d37623a41..8c7db7b275 100644
> --- a/libavformat/dump.c
> +++ b/libavformat/dump.c
> @@ -678,6 +678,11 @@ FF_ENABLE_DEPRECATION_WARNINGS
>               print_fps(1 / av_q2d(st->time_base), "tbn", log_level);
>       }
>   
> +    if (st->start_time != AV_NOPTS_VALUE && st->start_time != 0 && st->time_base.den && st->time_base.num) {
> +        const double stream_start = av_q2d(st->time_base) * st->start_time;
> +        av_log(NULL, AV_LOG_INFO, ", Start-Time %.3fs", stream_start);

This should use the same precision as the other timestamp printouts, to 
avoid subtle inaccuracies.
For a single-stream MPEG-TS , ffmpeg prints "start: 1.466667" for the 
format and "Start-Time 1.467s" for the stream.

Regards,
Gyan


> +    }
> +
>       dump_disposition(st->disposition, log_level);
>       av_log(NULL, log_level, "\n");
>   
>
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Re: [FFmpeg-devel] [FFmpeg-cvslog] avformat/dump: Print stream start offsets for input streams

[softworkz .]

> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces@ffmpeg.org> On Behalf Of Gyan
> Doshi
> Sent: Sonntag, 20. April 2025 13:25
> To: ffmpeg-devel@ffmpeg.org
> Subject: Re: [FFmpeg-devel] [FFmpeg-cvslog] avformat/dump: Print
> stream start offsets for input streams
> 
> 
> 
> On 2025-04-19 08:35 pm, softworkz wrote:
> > ffmpeg | branch: master | softworkz <softworkz@hotmail.com> | Sat
> Feb 23 04:59:10 2019 +0100| [02d7384ed5eec0152056c081b536c16cb86e6361]
> | committer: softworkz
> >
> > avformat/dump: Print stream start offsets for input streams
> >
> > Seeing the offset of video and audio streams to each other is often
> > a useful metric in diagnosing and understanding issues with playback
> > or transcoding.
> > This commit adds those offsets to the stream info print.
> >
> > Signed-off-by: softworkz <softworkz@hotmail.com>
> >
> >>
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=02d7384ed5ee
> c0152056c081b536c16cb86e6361
> > ---
> >
> >   libavformat/dump.c | 5 +++++
> >   1 file changed, 5 insertions(+)
> >
> > diff --git a/libavformat/dump.c b/libavformat/dump.c
> > index 3d37623a41..8c7db7b275 100644
> > --- a/libavformat/dump.c
> > +++ b/libavformat/dump.c
> > @@ -678,6 +678,11 @@ FF_ENABLE_DEPRECATION_WARNINGS
> >               print_fps(1 / av_q2d(st->time_base), "tbn",
> log_level);
> >       }
> >
> > +    if (st->start_time != AV_NOPTS_VALUE && st->start_time != 0 &&
> st->time_base.den && st->time_base.num) {
> > +        const double stream_start = av_q2d(st->time_base) * st-
> >start_time;
> > +        av_log(NULL, AV_LOG_INFO, ", Start-Time %.3fs",
> stream_start);
> 
> This should use the same precision as the other timestamp printouts,
> to
> avoid subtle inaccuracies.
> For a single-stream MPEG-TS , ffmpeg prints "start: 1.466667" for the
> format and "Start-Time 1.467s" for the stream.
> 
> Regards,
> Gyan
> 


Yup, that makes sense. New patch coming.

Thank you,
sw

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