Alsa problems (Was: Re: [Gwc-general] GWC 0.21-03 is released)

[James T. <ja...@ta...>]

On Wednesday 02 November 2005 21:51, Johan De Groote wrote:
JD> I can open it fine, load a file, make a selection etc. But if I hit
 playback I JD> get:
JD>
JD> ...
JD> ##########################################################
JD> audio_device_nonblocking_write_buffer_size: snd_pcm_avail_update
JD> Broken pipe
JD> audio_device_processed_bytes: snd_pcm_delay Broken pipe
JD> ##########################################################
JD> audio_device_nonblocking_write_buffer_size: snd_pcm_avail_update
JD> Broken pipe
JD> audio_device_processed_bytes: snd_pcm_delay Broken pipe
JD> ...
JD>
JD> Once this message starts sound stops and so does the cursor. Until I stop
JD> playback this message keeps coming in the terminal. The time to get this
 is JD> variable, but never longer than a few seconds (15 at most). Gwc
 doesn't JD> crash, and alsa continues as well. Hitting playback again will
 restart the JD> selection, until "it" happens again.
JD>

Hi, I'm back!

I think I'm making some progress on this one (which seems to be a similar 
problem to one I was having a while back (April 04) [only then it wasn't 
possible to stop it].  snd_pcm_avail_update() returns -EPIPE if the output 
buffer has emptied, and the driver has tried to get some data. Because  
audio_device_nonblocking_write_buffer_size() bails out on any error, the 
buffer never gets filled so it goes into an infinite loop. I think that the 
answer is at least in part to modify audio_alsa.c, so that a "broken pipe 
error is effectively ignored (patch at the end) -- it could be rearranged to 
eliminate the message altogether but I was trying to see what influenced the 
problem.

The other things that may help are to increase the buffer size (in 
audio_device.h) [BTW there is a redundant redefinition of MAXBUFSIZE in 
audio_util.c which ought to be removed.] and not popping windows or generally 
doing too much with X while playing back.

James

P.S. I've changed distro yet again -- Kubuntu now.

++ BEGIN PATCH ++
*** audio_alsa.c	2005-11-11 16:28:08.000000000 +0000
--- audio_alsa.c~	2005-11-11 15:57:50.000000000 +0000
***************
*** 267,273 ****
      if (frames < 0) {
          perr("audio_device_nonblocking_write_buffer_size: 
snd_pcm_avail_update",
               frames);
!        if (frames != -EPIPE ) return 0;
      }
      len = snd_pcm_frames_to_bytes(handle, frames);
  
--- 267,273 ----
      if (frames < 0) {
          perr("audio_device_nonblocking_write_buffer_size: 
snd_pcm_avail_update",
               frames);
!          return 0; 
      }
      len = snd_pcm_frames_to_bytes(handle, frames);
 ++END PATCH++


As far as I can tell 
-- 
James Tappin,             O__      "I forget the punishment for using
ja...@ta...       --  \/`    Microsoft --- Something lingering
http://www.tappin.me.uk/            with data loss in it I fancy"