Re: [LAU] screencast using jack

From: Federico Bruni <fedelogy@email-addr-hidden>
Date: Tue Mar 19 2013 - 09:10:11 EET

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.
> My first guess is a frame rate issue... like a half frame rate that is
> also mistranslated from 25hz to 29.*dropframe (or vise versa). It really
> doesn't matter at this point, check two things. Listen to the wave, does
> it sound right"? Watch the video stream, does it look really fast? Do they
> play back at the listed times?
>
> Are you using spdif for audio in? If so, where is it getting sync from?
>
> These are all shots in the dark. The first thing is to play them back and
> see if there is an issue with audio or video or both.

Your guess is probably right.
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)

Input #0, wav, from 'screencast_audio_20130318-23h53.wav':
   Duration: 00:09:21.79, bitrate: 2304 kb/s
     Stream #0:0: Audio: pcm_s24le ([1][0][0][0] / 0x0001), 48000 Hz,
stereo, s32, 2304 kb/s

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?

-- 
Federico
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Received on Tue Mar 19 12:15:01 2013

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