linuxaudio.org

On Tue, March 19, 2013 6:10 pm, Federico Bruni wrote:

quoted text
> 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?

>

It possible that your machine was dropping frames while recording. You can

slow down playback 'stretch" the video to the timelength you require.
http://ffmpeg.org/trac/ffmpeg/wiki/How%20to%20speed%20up%20/%20slow%20do...
--

Patrick Shirkey

Boost Hardware Ltd

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