Summary:ASTERISK-02950: [request] Console/dsp extension does not work with AC97 (48kHz stereo-only) audio chips
Reporter:dcarter (dcarter)Labels:
Date Opened:2004-12-09 12:00:19.000-0600Date Closed:2011-06-07 14:05:31
Versions:Frequency of
Description:When I try to use the on-board audio in my Asterisk box (using an nForce2 chipset) as an extension (for connection to an overhead paging amplifier) it does not work.

If I use the OSS driver (i810_audio.o) I get an error on the console that it cannot set the device to the correct mode.  (Since the hardware only supports 48kHz/2-channel, and Asterisk is presumably trying to use 8kHz/1-channel, this makes sense.)

I tried the ALSA driver (in OSS compatability mode, as I couldn't get chan_alsa to load) which got me further.  With this driver loaded, Asterisk can open the device, but the audio which results is not usable (it's basically pulses of chirps, which I'm guessing are resulting from playing 8kHz audio data at 48kHz, and then waiting until a buffer is full before doing it again.)

To fix this, I'm assuming Asterisk would need to be able to format convert the normal console extension audio (8kHz ulaw) into 48kHz stereo PCM for the sound chip.
Comments:By: twisted (twisted) 2004-12-10 20:39:20.000-0600

I can confirm that this does in fact work properly on AC97 chipsets, however, devices that use the nForce2 chipsets do indeed sound like garbage using the console driver. (i can prove this on the xbox console - don't laugh.)

By: Mark Spencer (markster) 2004-12-10 21:30:29.000-0600

so can we close this out?

By: Russell Bryant (russell) 2004-12-10 21:45:21.000-0600

AC97 sounds like garbage to begin with.  You should be able to hear something though.  Maybe you're not using the right driver.  In any case, this is an issue with the sound system and not an Asterisk bug.

IMHO, the best option here is to buy a decent sound card for your overhead paging.