[vlc-devel] Re: How to indicate the audio device created by saa7134-oss

David Liontooth liontooth at cogweb.net
Wed Mar 29 11:18:06 CEST 2006

Jean-Paul Saman wrote:
> David Liontooth wrote:
>> To record from VLC using a v4l card, I issue
>> vlc v4l:/dev/video2:norm=ntsc:frequency=77250:size=640x480:channel=5:\
>> adev=/dev/dsp2:samplerate=32000:audio=0:stop-time=$TIM \
>> --sout "#transcode{vcodec=h264,fps=29.97,acodec=mpga}\
>> :std{access=file,mux=asf,dst=$DIR/$FIL.mpg}" aspect-ratio "4:3" -I dummy
>> I get in response,
>> /usr/sbin/alsactl: load_state:1250: Cannot find soundcard '2'...
>> ALSA lib pcm_hw.c:1305:(_snd_pcm_hw_open) Invalid value for card
>> Error opening audio: No such device
>> This is true -- there is no soundcard 2 as far as alsa is concerned:
>>    $ cat /proc/asound/cards
>>     0 [CK8S           ]: NFORCE - NVidia CK8S
>>                      NVidia CK8S with ALC850 at 0xfc003000, irq 17
>> However, /dev/dsp2 exists -- in dmesg I have this, showing that the 
>> saa7134-oss module has created its device nodes:
>> saa7134 OSS driver for DMA sound loaded
>> saa7133[0]: registered device dsp2
>> saa7133[0]: registered device mixer2
>> Is there a way to instruct VLC to use an audio device that alsactl 
>> doesn't see? Or perhaps to make alsactl see it?
> It is an oss driver and no ALSA !. Make sure your kernel supports ALSA 
> OSS emulation.
> kind greetings,
> Jean-Paul Saman.
Thank you. There's a problem with OSS emulation in Debian. In 
/etc/modprobe.d is a symlink, linux-sound-base_noOSS, to 
/lib/linux-sound-base/noOSS.modprobe.conf from the package 
linux-sound-base. While I built OSS emulation into the kernel (as 
modules), I didn't select an OSS driver for my sound card, and ALSA may 
have noticed this and put in this symlink to block all OSS sound card 
drivers (?).

When I load saa7134-oss, I get "saa7134 OSS driver for DMA sound loaded" 
and the dsp1 and mixer1 device receipts, then:

 saa7134 ALSA: can't load, DMA sound handler already assigned (probably 
to OSS)

It looks like the symlink was designed to tell the system there is no 
OSS to compete with.

I rebuilt the kernel with all sound built-in, and the problem went away. 
The symlink got recreated on reboot.

Thank you for helping pinpoint what the problem was.


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