Re: Looking for help with dmix plug-in on ARM

[Takashi Iwai <tiwai@suse.de>]

At Thu, 8 Feb 2007 10:44:10 -0800,
<daniel.car@cox.net> wrote:
> 
> Hi,
> 
> I'm working on an unannounced SOC audio driver on an ARM system.  I have a problem were audio works fine with out dmix, but when I try to use dmix no audio data gets to the driver.  The dmix plug-in does work when attaching external usb audio device.  Trying to use dmix so that more then one application can generate audio simultaneously.
> 
> If I try with version 1.0.11 of ALSA the audio driver doesn't receive any data after the snd_pcm_period_elapsed() function call.  If I try with version 1.0.13 of ALSA, aplay returns an error saying: 
> # aplay -D hw:0,0 pcm48khz_2ch_stereo.wav open_stream success
>   Playing WAVE 'pcm48khz_2ch_stereo.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Stereo
>   aplay: set_params:882: Broken configuration for this PCM: no configurations available
> 
> I'm planning on building a debug version of 1.0.14rc2 and tracing thru the code to see why aplay fails.  Is there a better way to debug this?  Are there any tricks for building ALSA with debug info?

So, actually it's a problem of driver / alsa-lib hw layer rather than
dmix?  You can get more verbose messages by setting LIBASOUND_DEBUG
variable.  See alsa-lib/NOTES for details.

> Here is how the driver is set up:
> static snd_pcm_hardware_t snd_oloriver_playback_hw = {
>  .info = (SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_INTERLEAVED |
> 	   SNDRV_PCM_INFO_MMAP_VALID),
>  .formats 	    = SNDRV_PCM_FMTBIT_S16_LE,
>   .rates 	    = SNDRV_PCM_RATE_48000,
>   .rate_min	    = 48000, 
>   .rate_max	    = 48000,
>   .channels_min     = 2,
>   .channels_max     = 2,
>   .buffer_bytes_max = 65536,
>   .period_bytes_min = 32768,
>   .period_bytes_max = 32768,
>   .periods_min 	    = 2,
>   .periods_max 	    = 2,

My rough guess is that the buffer and period size constraints are too
restrictive.  You can try to pass the exact period/buffer sizes to
aplay via --period-size=8192 --buffer-size=16384 options.


Takashi

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