Another alsa newbie seeks help

Another alsa newbie seeks help

[Sol]

Hello,

I have been using the example "pcm.c" in the alsa-lib/test directory to
learn about alsa and my soundcard(audiophile 2496 ice1712).

I have found something strange that I do not understand. 
async_direct(mmap) method will produce no sound for my card.  However,
if I change the format to S32_LE in pcm.c and first specify 10 channels
using async method- then I get sound when I use the async_direct method
afterwards.

If I haven't confused myself writing this, it looks like this:

./pcm -c 10 -m async_direct
Playback device is plughw:0,0
Stream parameters are 44100Hz, S32_LE, 10 channels
Sine wave rate is 440.0000Hz
Using transfer method: async_direct

(No sound here)

./pcm -c 10 -m async
Playback device is plughw:0,0
Stream parameters are 44100Hz, S32_LE, 10 channels
Sine wave rate is 440.0000Hz
Using transfer method: async

(Sound plays)

./pcm -c 10 -m async_direct
Playback device is plughw:0,0
Stream parameters are 44100Hz, S32_LE, 10 channels
Sine wave rate is 440.0000Hz
Using transfer method: async_direct

(Sound plays)

I see the hw_params change from RW_INTERLEAVED to MMAP_INTERLEAVED.  Do
I need to specify my channels somewhere for the mmap to work correctly
with my card?  Am I smoking crack!?

Thanks,

Sol




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Re: Another alsa newbie seeks help

[Clemens Ladisch]

Sol wrote:
> I have been using the example "pcm.c" in the alsa-lib/test directory to
> learn about alsa and my soundcard(audiophile 2496 ice1712).
>
> I have found something strange that I do not understand.
> async_direct(mmap) method will produce no sound for my card.  However,
> if I change the format to S32_LE in pcm.c and first specify 10 channels
> using async method- then I get sound when I use the async_direct method
> afterwards.
>
> If I haven't confused myself writing this, it looks like this:
>
> ./pcm -c 10 -m async_direct
> Playback device is plughw:0,0

This uses the plug plugin, which does all kinds of intelligent or
"intelligent" conversions. Please try to use hw:0,0 directly.


HTH
Clemens




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