[FFmpeg-user] ffprobe -show_frames and coded_picture_number

Robert Krüger krueger at lesspain.de
Mon Aug 12 08:57:18 CEST 2013

On Mon, Aug 12, 2013 at 12:04 AM, Richard H Lee
<ricardohenrylee at gmail.com> wrote:
> On 11/08/2013 17:53, Phil Rhodes wrote:
>> The other, better alternative would be to resample the audio and time
>> the whole playback system to the graphics card's refresh rate
> This is actually what I do. Most of the media I acquire is at NTSC
> 24000/1001 fps, but I play it on a PAL 25 fps monitor. The only way to
> get smooth motion is to speed up the frame rate.
> If I need to re-encode I pipe the raw video frames through yuvfps to set the
> frame rate or I set the PTS manually with ffmpeg. If I just need to change
> the frame rate without re-encoding, I have use MP4Box, as ffmpeg can't use
> "-vcodec copy" and setpts together. (If anybody knows how to do this, let me
> know.)
>> but nobody seems to do that, presumably because resampling audio is
>> hard.
> And the reason why resampling is hard is because there are no tools out
> there that can resample audio accurately.
> I tried every tool, ffmpeg, mencoder, sox, but they all ended up with large
> a/v desync after 10 mins. I think this is due to the rounding off of the
> decimal number I give to the various utilities. The only tool that worked
> was AVISynth, but that is a Windows tool.

If you have a reproducible test case for ffmpeg, please file a bug
report. I am not aware that this is a known limitation/bug of the
respective ffmpeg features and I have not come across it myself when
changing audio speed to achieve exactly what you describe (then again,
I am not sure I have tested with files > 10 minutes). Anyway, it is
worth taking the time to provide an input file and the exact command
line you used where you could produce an A/V desync.

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