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Old 05-02-2006, 12:30 PM   #1
juanjavier_xxx
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Registered: Aug 2004
Location: Madrid, Spain
Distribution: Debian stable.
Posts: 186

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Only mono sound when capturing audio thru mencoder.


I don't manage to get stereo stream when capturing full screen 720x576
analog video with stereo sound from mencoder. I get the video ok, but
audio is mono. Monitoring the input via ALSA mixer GUI thru the headphones
the sound *is* and *arrive* in stereo to the soundcard (an Ensoniq Audio
PCI SoundBlaster with a SigmaTel STAC9708/11 chipset).

Mencoder claims like this when actually recording from analog video with
stereo sound:


Code:
Building audio filter chain for 44100 Hz/1ch/s16le -> 0Hz/0ch/??...
Building audio filter chain for 44100 Hz/1ch/s16le -> 44100Hz/1ch/s16le...

Audio stream: 705.600 kbit/s (88200 B/s)
It seems it gets only the signal from one of the channels instead of both.

Needless to say I get the correct sound source selected from within the Alsa
mixer; otherwhise NO sound will come out of the recorded video during playback
at all...

What am I missing?

Cheers,

Juan.
 
Old 05-03-2006, 02:26 PM   #2
juanjavier_xxx
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Registered: Aug 2004
Location: Madrid, Spain
Distribution: Debian stable.
Posts: 186

Original Poster
Rep: Reputation: 30
Uupss...forgot to mention...no physical connection, jack or cable issue here....

....Window$ captures full resolution moving pictures with stereo PCM 44.1 khz sound without physically touching any cord or plug. The physical connection configuration is ok.

Any idea? Thanks in advance,
Juan Javier Martínez.
 
Old 05-04-2006, 01:21 AM   #3
juanjavier_xxx
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Registered: Aug 2004
Location: Madrid, Spain
Distribution: Debian stable.
Posts: 186

Original Poster
Rep: Reputation: 30
Well, I think it has got something to do with the v4l2 audio output mode: it is set to «LANG1» instead of «stereo».

Hence the decoded audio output shows 705 kbits/sec and one channel instead of full 1411 kbits/sec and two full channels.


Now that I (hopefully) found the problem...how do I find the solution?

The question lies: How do I change the audio output mode for V4l2 driver?

Still googling about v4l2 like mad.... ;-)

Any help about this v4l2 tweaking would be *much* appreciated.


Cheers,

Juan Javier.
 
  


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