[FFmpeg-user] R: Generete one second of black video and relative silence audio with the same duration

[Richard Mikesell]

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Richard Mikesell


On Sat, Jan 25, 2020 at 4:20 PM Gian Maria Allibrante <chanof at hotmail.com>
wrote:

> Thanks Moritz, sorry for the confusion, may ask:
>
>   *   How to remove this audio packet? (i need this trick to concatenate
> videos with total duration multiple of the GOP destined to infinite mpeg
> dash pseudo live loop, mp4box will fail after some cycles with this
> duration dicrepance, it's unable to skip it)
>   *   How you see this information: side_data_type=Skip Samples etc.
>
> Gian
>
> ________________________________
> Da: ffmpeg-user <ffmpeg-user-bounces at ffmpeg.org> per conto di Moritz
> Barsnick <barsnick at gmx.net>
> Inviato: sabato 25 gennaio 2020 22:53
> A: FFmpeg user discussions <ffmpeg-user at ffmpeg.org>
> Oggetto: Re: [FFmpeg-user] Generete one second of black video and relative
> silence audio with the same duration
>
> On Sat, Jan 25, 2020 at 22:26:31 +0000, Gian Maria Allibrante wrote:
> > Hi Moritz, thanks for reply, this one, im always unable to get round
> match duration:
> >
> > echo VIDEO FORMAT CONTAINER DURATION:
> > ffprobe -v error -show_entries format=duration \
> >   -of default=noprint_wrappers=1:nokey=1 output.mp4
> > echo VIDEO STREAM DURATION:
> > ffprobe -v error -select_streams v:0 -show_entries stream=duration \
> >   -of default=noprint_wrappers=1:nokey=1 output.mp4
>
> Ah, I think I understand now. You are trying to get the same duration
> from the container as from the video stream.
>
> Honestly, I was looking for a totally different problem:
>
> > > VIDEO FORMAT CONTAINER DURATION: 3.026000
> > > VIDEO STREAM DURATION: 3.000000
>
> You showed us *three* seconds results, not one second. This totally
> distracted from your actual issue! ;-)
>
> Regarding the approx 0.026 extra seconds:
> For some reason, ffmpeg creates an additional initial audio packet,
> marked with
> side_data_type=Skip Samples
> skip_samples=1105
>
> If those initial samples are skipped, the total length is exactly okay.
> I'm not sure whether ffmpeg does this due to restrictions regaring the
> audio packet size.
>
> Moritz
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