Bug#517801: snd_pcm_start: Broken pipe

["Marcus C. Gottwald" <mcg@cheers.de>]

vk6fun wrote (Mon 2009-Mar-02 13:50:35 +0900):

> The "scope", "spectrum" and "modem" tools can key transmitter but they lock up
> the display when closing.
> The soundmodemconfig application must be crashed with control-c.
> 
> The soundmodem application itself never keys the tx.
> 
> It just crashes with Broken pipe messages.

I can report a very similar behaviour; in my case, transmitting
works fine, demodulation does not work. I am using "soundmodem"
version 0.13-1.1 with a SignaLink USB.

The problem occurs when I tell "soundmodem" to use the ALSA
hardware device. Whenever ALSA's "plug" plugin is involved, the
issue does not occur. (In that case, however, there seems to be
no way to restrict the sample rates to sane values, and the
"plug" plugin will happily convert to insanely high rates (I'm
seeing 76800 here), which (for whatever reason) makes demod not
work again. Sometimes, "soundmodem" and the "plug" plugin will
agree on a reasonably low sample rate; in that case, everything
works fine.)


An important difference between "soundmodemconfig" and
"soundmodem" seems to be that the sample rate is requested
differently. This is the console output of "soundmodemconfig"
when starting "Diagnostics / Modem":

   Minimum sampling rate: 9600
   Audio IO: type alsa
   ALSA: Using sample rate 9600, sample format 2, significant bits 16, buffer size 4800, period size 144
   ALSA: Using sample rate 9600, sample format 2, significant bits 16, buffer size 4800, period size 144
   sm[16258]: audio: starting "plug:c1r44100"
   Real sampling rate: 9600

Compare to the console output of "soundmodem -v100" on startup:

   ALSA: Using sample rate 76800, sample format 2, significant bits 16, buffer size 38400, period size 1152
   ALSA: Using sample rate 76800, sample format 2, significant bits 16, buffer size 38400, period size 1152
   sm[16320]: audio: starting "plug:c1r44100"

If "soundmodem" did the same as "soundmodemconfig", everything
should work fine for me (as long as I use the "plug" plugin).


For the sake of completeness, this is what I get from
"soundmodem -v100" when "plug" is not used:

   ALSA: Using sample rate 44100, sample format 2, significant bits 16, buffer size 22050, period size 662
   ALSA: Using sample rate 44100, sample format 2, significant bits 16, buffer size 22050, period size 662
   sm[16499]: audio: starting "c1r44100"
   sm[16499]: snd_pcm_start in iotxstart: Broken pipesm[16499]: snd_pcm_start in iotxstart: Broken pipe

It does say "iotxstart", but packets really do get modulated and
transmitted just fine; for me, receiving doesn't work.


73, Marcus DO1MCG

-- 
   Marcus C. Gottwald  ·  <mcg@cheers.de>  ·  https://cheers.de