At Wed, 2 Apr 2008 18:27:13 +0300, Alexander Indenbaum wrote:
Takashi & alsa-devel,
I am playing with embedded Linux box based on kernel 2.4.36. Our box is equipped with proprietary chip which allows PCM playback using user space DMA pool API. My target is to enable audio playback for ALSA clients by redirecting PCM stream into proprietary chip. I did a little RTFM and with a lot of help from this list discovered that fortunately ALSA expendable architecture allows such things as a part of PCM External Plugin SDK.
So I downloaded and installed following ALSA 1.0.16 distribution components:
- driver configured with "./configure --with-cards=seq-dummy,dummy
--with-kernel=/path/to/my/linux-2.4.36"
- lib configured with "./configure --with-pcm-plugins=all"
I looked at Jack IO plugin at plugins and started with skeleton plugin of my own: pcm_sigma.c (attached). I hope to redirect PCM into my plugin using following /etc/asound.conf ============= pcm.!default { type sigma } =============
What I see when I fire ALSA client ( friefox with YouTube flash ) that ALSA
- loads/links my module: ALSA lib dlmisc.c:51:(snd_dlopen) snd_dlopen
name = (/usr/lib/alsa-lib/libasound_module_pcm_sigma.so) 2. calls open interface of the module: _snd_pcm_sigma_open @ pcm_sigma.c:118
snd_pcm_sigma_open @ pcm_sigma.c:86 3. calls close interface of the module: snd_pcm_sigma_close @ pcm_sigma.c:23 4. goto 2
So basically what I see is an infinite open/close loop without any call to other interfaces of the module. I hoped to get my hands on PCM stream and start to push it into our proprietary chip :(.
QUESTIONS: Is my PCM IO Plugin approach correct?
I think yes.
Is my configuration (/etc/asound.conf) correct?
If the plugin object gets called anyhow, it should be correct.
Is my implemention of PCM IO plugin interface correct? Should I implement additional methods?
Did you try any other program such as aplay? Flashplayer is the hardest thing to debug...
Takashi