Re: [LAU] screencast using jack

On Tue, March 19, 2013 12:10 am, Federico Bruni wrote:
> Il 19/03/2013 02:25, Len Ovens ha scritto:
>>> I have another issue with the tutorial above.
>>> >It says:
>>> >"Now you have two separate files, an .mkv and a .wav file and because
>>> >jack_capture was started right after ffmpeg audio should be no more
>>> out
>>> >of sync then just a few millisecs."
>>> >
>>> >Actually my files are out of sync because they have different
>>> durations.
>>> >Video is 5:31 and audio is 9:21.

> The audio is ok, while the video is a bit too fast.
>
> Yes, they play back at the listed times.
> Here's what ffmpeg say:
>
> Input #0, matroska,webm, from 'screencast_video_20130318-23h53.mkv':
> Metadata:
> ENCODER : Lavf54.29.104
> Duration: 00:05:31.00, start: 0.000000, bitrate: 426 kb/s
> Stream #0:0: Video: h264 (High 4:4:4 Predictive), yuv444p,
> 1280x800, SAR 1:1 DAR 8:5, 30 fps, 30 tbr, 1k tbn, 60 tbc (default)

That looks pretty solid.

> But I don't understand... I've recorded at 30 fps and I'm watching at 30
> fps. Why it's playing faster than the recording?

I would think either the recording app is skipping frames because it
doesn't have time to grab them or because the next frame is the same as
the last (and so it expects to output the same frame a second time, but
somehow fails). My understanding of video in an analog context is much
better than in digital context :)

Does the video playback seem to be the same speed all the way through or
speed up and slow down?

-- 
Len Ovens
www.OvenWerks.net
_______________________________________________
Linux-audio-user mailing list
Linux-audio-user@email-addr-hidden
http://lists.linuxaudio.org/listinfo/linux-audio-user