Re: hdsp vs 16bit vs dmix

[Takashi Iwai <tiwai@suse.de>]

At Thu, 08 Jan 2004 02:29:13 +0900,
Patrick Shirkey wrote:
> 
> I am seeing strange things happen while using the hdsp and dmix plugin 
> and aplay as a test app.
> 
> JACK works perfectly.
> 
> I can get sound from aplay if I use this commandline:
> 
> aplay -f cd -D plughw audio.wav
> Playing WAVE 'audio.wav' : Signed 16 bit Little Endian, Rate 44100 Hz, 
> Stereo
> underrun!!! (at least 40.147 ms long)
> underrun!!! (at least 86.223 ms long)
> underrun!!! (at least 145.116 ms long)
> underrun!!! (at least 79.109 ms long)
> underrun!!! (at least 248.555 ms long)
> underrun!!! (at least 180.442 ms long)
> underrun!!! (at least 96.117 ms long)
> Aborted by signal Interrupt...	
> 
> But I get an xrun every second or so which makes the card useless for 
> native alsa apps .

i'm not sure which plugin plays wrong yet.

run aplay with -v option and see which plugins and what configurations
are used.  for example, if the native hardware requires 32bit samples,
prepare 32bit samples WAV instead of 16bit, and reduce the plugin.
i don't think the rate conversion is used, so the plugins are linear,
route, and copy plugins.

my rough guess is the copy plugin.  try aplay -M option, so that mmap
mode is used.

> 
> aplay -f cd -D hw:0 audio.wav
> Playing WAVE 'audio.wav' : Signed 16 bit Little Endian, Rate 44100 Hz, 
> Stereo
> aplay: set_params:822: Access type not available

hdsp supports only MMAP access.
aplay uses the RW access as default.


> If I try the dmix plugin (which also works with the pci card):
> 
> 
>   pcm.!default {
>             type plug
>             slave.pcm "dmixer"
>          }
> 
> pcm.dmixer  {
>      type dmix
>      ipc_key 1234
>      slave {
>          pcm "hw:0"
>          period_time 0
>          period_size 1024
>          buffer_size 4096
> #        periods 128
>          rate 44100
>          format s16_le
>      }
>      bindings {
>          0 0
>          1 1
>      }
> }
> 
> ctl.dmixer {
>      type hw
>      card 0
> }
> 
> ------
>   aplay -f cd -D default audio.wav
> ALSA lib pcm_hw.c:324:(snd_pcm_hw_hw_params) SNDRV_PCM_IOCTL_HW_PARAMS 
> failed: Device or resource busy
> ALSA lib pcm_direct.c:712:(snd_pcm_direct_initialize_slave) unable to 
> install hw params
> ALSA lib pcm_dmix.c:827:(snd_pcm_dmix_open) unable to initialize slave
> aplay: main:502: audio open error: Device or resource busy

hmm, it's wierd.  -ENODEV ?

> ------
> 
> For fun I tried this syntax:
> 
> 
>   pcm.!default {
>             type plughw
>             slave.pcm "dmixer"
>          }
> 
> 
> ------
>   aplay -f cd -D default audio.wav
> ALSA lib pcm.c:1900:(snd_pcm_open_conf) Cannot open shared library 
> /usr/lib/alsa-lib/libasound_module_pcm_plughw.so
> aplay: main:502: audio open error: No such file or directory

this one is clear.  there is no plughw type.
it's a defined pcm name.


Takashi


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