Re: [Discuss-gnuradio] Problem with valve and audio sink

[Volker Schroer]

Introducing a static variable  helps in my case, but in other situations 
it might still fail.

In between I had a deeper look to the source and I propose a solution 
depending on the state of the stream.

--- audio_alsa_sink.cc  2010-12-07 14:05:30.000000000 +0100
+++ audio_alsa_sink_new.cc      2010-12-07 14:06:42.000000000 +0100
@@ -219,9 +219,15 @@
   int nchan = ninputs;
   int err;

-  // FIXME check_topology may be called more than once.
+  // Check the state of the stream
   // Ensure that the pcm is in a state where we can still mess with 
the hw_params
-
+  snd_pcm_state_t state;
+  state=snd_pcm_state(d_pcm_handle);
+  if ( state== SND_PCM_STATE_RUNNING)
+    return true;  // If stream is running, don't change any parameters
+  else if(state == SND_PCM_STATE_XRUN )
+    snd_pcm_prepare ( d_pcm_handle ); // Prepare stream on underrun, 
and we can set parameters;
+
   bool special_case = nchan == 1 && d_special_case_mono_to_stereo;
   if (special_case)
     nchan = 2;

Thank you

Volker



> try running the same fix with the static variable, this problem will show up 
> even with simple setups because it's in the alsa audio source block.  even 
> though the fix works i wouldn't recommend it for long term solution because 
> it's a hack.  you can look into the FIXME section of the code to make a more 
> permenant solution.
>
>
> al
>
>
> -----Original Message-----
> From: Volker Schroer<address@hidden>
> To: Discuss-gnuradio<address@hidden>
> Sent: Mon, Dec 6, 2010 11:40 am
> Subject: [Discuss-gnuradio] Problem with valve and audio sink
>
>
> Hi all,
> I get an runtime error, when switching a valve.
> I saw a similar problem some months ago, but the setup was different.
> My setup is quite easy:
> A signal source ( cosine, float ) connected to a audio sink.
> he same signal source is connected to a valve and the valve is
> onnected to a scope sink.
> The valve is switched by a checkbox.
> Switching the valve leads to
> audio_alsa_sink[hw:0,0]: snd_pcm_hw_params failed: File descriptor in
> ad state
> erminate called after throwing an instance of 'std::runtime_error'
>    what():  check topology failed on audio_alsa_sink(1) using ninputs=1,
> outputs=0
> I wonder how the valve affects the audio sink.
> Any ideas ?
> Thanks in advance
> Volker
> _______________________________________________
> iscuss-gnuradio mailing list
> address@hidden
> ttp://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>
>
>