SALSA-Lib: Playback overrun on initial PCM start

SALSA-Lib: Playback overrun on initial PCM start

[J. Scott Merritt]

Dear List,

Using SALSA-Lib 0.0.3, I call:	

snd_pcm_open (&playback_handle, argv[1], SND_PCM_STREAM_PLAYBACK, 0);
snd_pcm_hw_params_malloc (&hw_params);
snd_pcm_hw_params_any (playback_handle, hw_params);
snd_pcm_hw_params_set_access (playback_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED);
snd_pcm_hw_params_set_format (playback_handle, hw_params, SND_PCM_FORMAT_S16_LE));
snd_pcm_hw_params_set_rate_near (playback_handle, hw_params, 44100, 0);
snd_pcm_hw_params_set_channels (playback_handle, hw_params, 2);
snd_pcm_hw_params_set_buffer_size_last (playback_handle, hw_params, &bfrsize);
snd_pcm_hw_params_get_buffer_size (hw_params, &bfrsize);
snd_pcm_hw_params (playback_handle, hw_params);
snd_pcm_hw_params_free (hw_params);
	
snd_pcm_sw_params_malloc (&sw_params);
snd_pcm_sw_params_current (playback_handle, sw_params);
snd_pcm_sw_params_set_avail_min (playback_handle, sw_params, 4096);
snd_pcm_sw_params_set_start_threshold (playback_handle, sw_params, 10000U);
snd_pcm_sw_params_set_xfer_align (playback_handle, sw_params, 1);
snd_pcm_sw_params (playback_handle, sw_params);
	
state = snd_pcm_state (playback_handle);
frames_to_deliver = snd_pcm_avail_update (playback_handle);

while ((frames_to_deliver = snd_pcm_avail_update (playback_handle)) > 4096) {
   snd_pcm_writei (playback_handle, &buf, 4096) }


As soon as the buffer start threshold is reached, or alternatively
if I manually start PCM stream, the PCM stream reports an overrun
(i.e. "Broken Pipe").  If I then examine the PCM state, it is in the
overrun (XRUN) state.

The code is being cross-compiled and tested on an ARM processor
(PXA270) which is running linux kernel 2.6.21.   This same code sequence
-does- operate properly (in the same ARM test environment) when compiled
against AlsaLib 1.0.13.

Another apparent (and perhaps relevent) difference between AlsaLib and
SALSA-Lib is that if I open the PCM stream with O_NONBLOCK and then call
snd_pcm_poll_descriptors, AlsaLib gives me a FD = 4, whereas SALSA-Lib
reports an FD = 3;

Thanks, Scott.

Re: SALSA-Lib: Playback overrun on initial PCM start

[Takashi Iwai]

At Thu, 28 Jun 2007 15:01:08 -0400,
J. Scott Merritt wrote:
> 
> Dear List,
> 
> Using SALSA-Lib 0.0.3, I call:	
> 
> snd_pcm_open (&playback_handle, argv[1], SND_PCM_STREAM_PLAYBACK, 0);
> snd_pcm_hw_params_malloc (&hw_params);
> snd_pcm_hw_params_any (playback_handle, hw_params);
> snd_pcm_hw_params_set_access (playback_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED);
> snd_pcm_hw_params_set_format (playback_handle, hw_params, SND_PCM_FORMAT_S16_LE));
> snd_pcm_hw_params_set_rate_near (playback_handle, hw_params, 44100, 0);
> snd_pcm_hw_params_set_channels (playback_handle, hw_params, 2);
> snd_pcm_hw_params_set_buffer_size_last (playback_handle, hw_params, &bfrsize);
> snd_pcm_hw_params_get_buffer_size (hw_params, &bfrsize);
> snd_pcm_hw_params (playback_handle, hw_params);
> snd_pcm_hw_params_free (hw_params);
> 	
> snd_pcm_sw_params_malloc (&sw_params);
> snd_pcm_sw_params_current (playback_handle, sw_params);
> snd_pcm_sw_params_set_avail_min (playback_handle, sw_params, 4096);
> snd_pcm_sw_params_set_start_threshold (playback_handle, sw_params, 10000U);
> snd_pcm_sw_params_set_xfer_align (playback_handle, sw_params, 1);
> snd_pcm_sw_params (playback_handle, sw_params);
> 	
> state = snd_pcm_state (playback_handle);
> frames_to_deliver = snd_pcm_avail_update (playback_handle);
> 
> while ((frames_to_deliver = snd_pcm_avail_update (playback_handle)) > 4096) {
>    snd_pcm_writei (playback_handle, &buf, 4096) }
> 
> 
> As soon as the buffer start threshold is reached, or alternatively
> if I manually start PCM stream, the PCM stream reports an overrun
> (i.e. "Broken Pipe").  If I then examine the PCM state, it is in the
> overrun (XRUN) state.

What are the buffer and period sizes?  Did you try alsa-lib with hw,
too, right?

> The code is being cross-compiled and tested on an ARM processor
> (PXA270) which is running linux kernel 2.6.21.   This same code sequence
> -does- operate properly (in the same ARM test environment) when compiled
> against AlsaLib 1.0.13.

Well, it might not be a bug.  SALSA-lib is more straightforward
communication to the driver, and skips many layers.  Thus it may
behave differently.

> Another apparent (and perhaps relevent) difference between AlsaLib and
> SALSA-Lib is that if I open the PCM stream with O_NONBLOCK and then call
> snd_pcm_poll_descriptors, AlsaLib gives me a FD = 4, whereas SALSA-Lib
> reports an FD = 3;

Ditto.


Takashi

Re: SALSA-Lib: Playback overrun on initial PCM start

[J. Scott Merritt]

On Fri, 29 Jun 2007 11:25:16 +0200
Takashi Iwai <tiwai@suse.de> wrote:

> At Thu, 28 Jun 2007 15:01:08 -0400,
> J. Scott Merritt wrote:
> > 
> > Dear List,
> > 
> > Using SALSA-Lib 0.0.3, I call:	
> > 
> > snd_pcm_open (&playback_handle, argv[1], SND_PCM_STREAM_PLAYBACK, 0);
> > snd_pcm_hw_params_malloc (&hw_params);
> > snd_pcm_hw_params_any (playback_handle, hw_params);
> > snd_pcm_hw_params_set_access (playback_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED);
> > snd_pcm_hw_params_set_format (playback_handle, hw_params, SND_PCM_FORMAT_S16_LE));
> > snd_pcm_hw_params_set_rate_near (playback_handle, hw_params, 44100, 0);
> > snd_pcm_hw_params_set_channels (playback_handle, hw_params, 2);
> > snd_pcm_hw_params_set_buffer_size_last (playback_handle, hw_params, &bfrsize);
> > snd_pcm_hw_params_get_buffer_size (hw_params, &bfrsize);
> > snd_pcm_hw_params (playback_handle, hw_params);
> > snd_pcm_hw_params_free (hw_params);
> > 	
> > snd_pcm_sw_params_malloc (&sw_params);
> > snd_pcm_sw_params_current (playback_handle, sw_params);
> > snd_pcm_sw_params_set_avail_min (playback_handle, sw_params, 4096);
> > snd_pcm_sw_params_set_start_threshold (playback_handle, sw_params, 10000U);
> > snd_pcm_sw_params_set_xfer_align (playback_handle, sw_params, 1);
> > snd_pcm_sw_params (playback_handle, sw_params);
> > 	
> > state = snd_pcm_state (playback_handle);
> > frames_to_deliver = snd_pcm_avail_update (playback_handle);
> > 
> > while ((frames_to_deliver = snd_pcm_avail_update (playback_handle)) > 4096) {
> >    snd_pcm_writei (playback_handle, &buf, 4096) }
> > 
> > 
> > As soon as the buffer start threshold is reached, or alternatively
> > if I manually start PCM stream, the PCM stream reports an overrun
> > (i.e. "Broken Pipe").  If I then examine the PCM state, it is in the
> > overrun (XRUN) state.
> 
> What are the buffer and period sizes?  Did you try alsa-lib with hw,
> too, right?

In sample program above, buffer size is set to "last", which results
in a buffer size of 32768 (which matches the allocation in the kernel driver).
The sample programs above does not establish a period size and is unknown.

I added code to set the period size to 1024 frames and experienced the
same (overrun) result.   I also forced the buffer size to 8192 and lowered
the sample rate to 16 kHz and did not see any improvement.

Yes, the same exact code runs properly on the target hardware with
alsa-lib 1.0.13.
 
> > The code is being cross-compiled and tested on an ARM processor
> > (PXA270) which is running linux kernel 2.6.21.   This same code sequence
> > -does- operate properly (in the same ARM test environment) when compiled
> > against AlsaLib 1.0.13.
> 
> Well, it might not be a bug.  SALSA-lib is more straightforward
> communication to the driver, and skips many layers.  Thus it may
> behave differently.

Do you have any suggestions on how to debug an overrun problem that
occurs whenever PCM is started ?

Absent further suggestions or requests, I will simply switch back to
alsa-lib and give up on saving the extra 1/2 Mbyte of RAM.

Thanks, Scott.

Re: SALSA-Lib: Playback overrun on initial PCM start

[Takashi Iwai]

At Fri, 29 Jun 2007 11:24:09 -0400,
J. Scott Merritt wrote:
> 
> On Fri, 29 Jun 2007 11:25:16 +0200
> Takashi Iwai <tiwai@suse.de> wrote:
> 
> > At Thu, 28 Jun 2007 15:01:08 -0400,
> > J. Scott Merritt wrote:
> > > 
> > > Dear List,
> > > 
> > > Using SALSA-Lib 0.0.3, I call:	
> > > 
> > > snd_pcm_open (&playback_handle, argv[1], SND_PCM_STREAM_PLAYBACK, 0);
> > > snd_pcm_hw_params_malloc (&hw_params);
> > > snd_pcm_hw_params_any (playback_handle, hw_params);
> > > snd_pcm_hw_params_set_access (playback_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED);
> > > snd_pcm_hw_params_set_format (playback_handle, hw_params, SND_PCM_FORMAT_S16_LE));
> > > snd_pcm_hw_params_set_rate_near (playback_handle, hw_params, 44100, 0);
> > > snd_pcm_hw_params_set_channels (playback_handle, hw_params, 2);
> > > snd_pcm_hw_params_set_buffer_size_last (playback_handle, hw_params, &bfrsize);
> > > snd_pcm_hw_params_get_buffer_size (hw_params, &bfrsize);
> > > snd_pcm_hw_params (playback_handle, hw_params);
> > > snd_pcm_hw_params_free (hw_params);
> > > 	
> > > snd_pcm_sw_params_malloc (&sw_params);
> > > snd_pcm_sw_params_current (playback_handle, sw_params);
> > > snd_pcm_sw_params_set_avail_min (playback_handle, sw_params, 4096);
> > > snd_pcm_sw_params_set_start_threshold (playback_handle, sw_params, 10000U);
> > > snd_pcm_sw_params_set_xfer_align (playback_handle, sw_params, 1);
> > > snd_pcm_sw_params (playback_handle, sw_params);
> > > 	
> > > state = snd_pcm_state (playback_handle);
> > > frames_to_deliver = snd_pcm_avail_update (playback_handle);
> > > 
> > > while ((frames_to_deliver = snd_pcm_avail_update (playback_handle)) > 4096) {
> > >    snd_pcm_writei (playback_handle, &buf, 4096) }
> > > 
> > > 
> > > As soon as the buffer start threshold is reached, or alternatively
> > > if I manually start PCM stream, the PCM stream reports an overrun
> > > (i.e. "Broken Pipe").  If I then examine the PCM state, it is in the
> > > overrun (XRUN) state.
> > 
> > What are the buffer and period sizes?  Did you try alsa-lib with hw,
> > too, right?
> 
> In sample program above, buffer size is set to "last", which results
> in a buffer size of 32768 (which matches the allocation in the kernel driver).
> The sample programs above does not establish a period size and is unknown.
> 
> I added code to set the period size to 1024 frames and experienced the
> same (overrun) result.   I also forced the buffer size to 8192 and lowered
> the sample rate to 16 kHz and did not see any improvement.
> 
> Yes, the same exact code runs properly on the target hardware with
> alsa-lib 1.0.13.

OK, looks like a bug in salsa-lib, then.
I fixed some remaining bugs and release 0.0.4 now.  Please give it a
try.  (Note that it might take some time until the ftp server is
exported / mirrored.)


thanks,

Takashi

Re: SALSA-Lib: Playback overrun on initial PCM start

[J. Scott Merritt]

On Fri, 29 Jun 2007 18:07:20 +0200
Takashi Iwai <tiwai@suse.de> wrote:

> At Fri, 29 Jun 2007 11:24:09 -0400,
> J. Scott Merritt wrote:
> > 
> > On Fri, 29 Jun 2007 11:25:16 +0200
> > Takashi Iwai <tiwai@suse.de> wrote:
> > 
> > > At Thu, 28 Jun 2007 15:01:08 -0400,
> > > J. Scott Merritt wrote:
> > > > 
> > > > Dear List,
> > > > 
> > > > Using SALSA-Lib 0.0.3, I call:	
> > > > 
> > > > snd_pcm_open (&playback_handle, argv[1], SND_PCM_STREAM_PLAYBACK, 0);
> > > > snd_pcm_hw_params_malloc (&hw_params);
> > > > snd_pcm_hw_params_any (playback_handle, hw_params);
> > > > snd_pcm_hw_params_set_access (playback_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED);
> > > > snd_pcm_hw_params_set_format (playback_handle, hw_params, SND_PCM_FORMAT_S16_LE));
> > > > snd_pcm_hw_params_set_rate_near (playback_handle, hw_params, 44100, 0);
> > > > snd_pcm_hw_params_set_channels (playback_handle, hw_params, 2);
> > > > snd_pcm_hw_params_set_buffer_size_last (playback_handle, hw_params, &bfrsize);
> > > > snd_pcm_hw_params_get_buffer_size (hw_params, &bfrsize);
> > > > snd_pcm_hw_params (playback_handle, hw_params);
> > > > snd_pcm_hw_params_free (hw_params);
> > > > 	
> > > > snd_pcm_sw_params_malloc (&sw_params);
> > > > snd_pcm_sw_params_current (playback_handle, sw_params);
> > > > snd_pcm_sw_params_set_avail_min (playback_handle, sw_params, 4096);
> > > > snd_pcm_sw_params_set_start_threshold (playback_handle, sw_params, 10000U);
> > > > snd_pcm_sw_params_set_xfer_align (playback_handle, sw_params, 1);
> > > > snd_pcm_sw_params (playback_handle, sw_params);
> > > > 	
> > > > state = snd_pcm_state (playback_handle);
> > > > frames_to_deliver = snd_pcm_avail_update (playback_handle);
> > > > 
> > > > while ((frames_to_deliver = snd_pcm_avail_update (playback_handle)) > 4096) {
> > > >    snd_pcm_writei (playback_handle, &buf, 4096) }
> > > > 
> > > > 
> > > > As soon as the buffer start threshold is reached, or alternatively
> > > > if I manually start PCM stream, the PCM stream reports an overrun
> > > > (i.e. "Broken Pipe").  If I then examine the PCM state, it is in the
> > > > overrun (XRUN) state.
> > > 
> > > What are the buffer and period sizes?  Did you try alsa-lib with hw,
> > > too, right?
> > 
> > In sample program above, buffer size is set to "last", which results
> > in a buffer size of 32768 (which matches the allocation in the kernel driver).
> > The sample programs above does not establish a period size and is unknown.
> > 
> > I added code to set the period size to 1024 frames and experienced the
> > same (overrun) result.   I also forced the buffer size to 8192 and lowered
> > the sample rate to 16 kHz and did not see any improvement.
> > 
> > Yes, the same exact code runs properly on the target hardware with
> > alsa-lib 1.0.13.
> 
> OK, looks like a bug in salsa-lib, then.
> I fixed some remaining bugs and release 0.0.4 now.  Please give it a
> try.  (Note that it might take some time until the ftp server is
> exported / mirrored.)

Much better :)

I no longer get the PlayBack overrun on PCM start.  However, it appears
that "poll" or the snd_pcm_sw_params_set_avail_min (=4096) is not being
properly honored.  With the normal alsa-lib, when the "poll" returns
snd_pcm_avail_update reports that space is available for 4096 frames.
However, in my initial testing, when running with SALSA lib, only about
100 frames or so are available when the poll returns.

I will examine this more closely.

Re: SALSA-Lib: Playback overrun on initial PCM start

[Takashi Iwai]

At Fri, 29 Jun 2007 12:26:45 -0400,
J. Scott Merritt wrote:
> 
> On Fri, 29 Jun 2007 18:07:20 +0200
> Takashi Iwai <tiwai@suse.de> wrote:
> 
> > At Fri, 29 Jun 2007 11:24:09 -0400,
> > J. Scott Merritt wrote:
> > > 
> > > On Fri, 29 Jun 2007 11:25:16 +0200
> > > Takashi Iwai <tiwai@suse.de> wrote:
> > > 
> > > > At Thu, 28 Jun 2007 15:01:08 -0400,
> > > > J. Scott Merritt wrote:
> > > > > 
> > > > > Dear List,
> > > > > 
> > > > > Using SALSA-Lib 0.0.3, I call:	
> > > > > 
> > > > > snd_pcm_open (&playback_handle, argv[1], SND_PCM_STREAM_PLAYBACK, 0);
> > > > > snd_pcm_hw_params_malloc (&hw_params);
> > > > > snd_pcm_hw_params_any (playback_handle, hw_params);
> > > > > snd_pcm_hw_params_set_access (playback_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED);
> > > > > snd_pcm_hw_params_set_format (playback_handle, hw_params, SND_PCM_FORMAT_S16_LE));
> > > > > snd_pcm_hw_params_set_rate_near (playback_handle, hw_params, 44100, 0);
> > > > > snd_pcm_hw_params_set_channels (playback_handle, hw_params, 2);
> > > > > snd_pcm_hw_params_set_buffer_size_last (playback_handle, hw_params, &bfrsize);
> > > > > snd_pcm_hw_params_get_buffer_size (hw_params, &bfrsize);
> > > > > snd_pcm_hw_params (playback_handle, hw_params);
> > > > > snd_pcm_hw_params_free (hw_params);
> > > > > 	
> > > > > snd_pcm_sw_params_malloc (&sw_params);
> > > > > snd_pcm_sw_params_current (playback_handle, sw_params);
> > > > > snd_pcm_sw_params_set_avail_min (playback_handle, sw_params, 4096);
> > > > > snd_pcm_sw_params_set_start_threshold (playback_handle, sw_params, 10000U);
> > > > > snd_pcm_sw_params_set_xfer_align (playback_handle, sw_params, 1);
> > > > > snd_pcm_sw_params (playback_handle, sw_params);
> > > > > 	
> > > > > state = snd_pcm_state (playback_handle);
> > > > > frames_to_deliver = snd_pcm_avail_update (playback_handle);
> > > > > 
> > > > > while ((frames_to_deliver = snd_pcm_avail_update (playback_handle)) > 4096) {
> > > > >    snd_pcm_writei (playback_handle, &buf, 4096) }
> > > > > 
> > > > > 
> > > > > As soon as the buffer start threshold is reached, or alternatively
> > > > > if I manually start PCM stream, the PCM stream reports an overrun
> > > > > (i.e. "Broken Pipe").  If I then examine the PCM state, it is in the
> > > > > overrun (XRUN) state.
> > > > 
> > > > What are the buffer and period sizes?  Did you try alsa-lib with hw,
> > > > too, right?
> > > 
> > > In sample program above, buffer size is set to "last", which results
> > > in a buffer size of 32768 (which matches the allocation in the kernel driver).
> > > The sample programs above does not establish a period size and is unknown.
> > > 
> > > I added code to set the period size to 1024 frames and experienced the
> > > same (overrun) result.   I also forced the buffer size to 8192 and lowered
> > > the sample rate to 16 kHz and did not see any improvement.
> > > 
> > > Yes, the same exact code runs properly on the target hardware with
> > > alsa-lib 1.0.13.
> > 
> > OK, looks like a bug in salsa-lib, then.
> > I fixed some remaining bugs and release 0.0.4 now.  Please give it a
> > try.  (Note that it might take some time until the ftp server is
> > exported / mirrored.)
> 
> Much better :)
> 
> I no longer get the PlayBack overrun on PCM start.  However, it appears
> that "poll" or the snd_pcm_sw_params_set_avail_min (=4096) is not being
> properly honored.  With the normal alsa-lib, when the "poll" returns
> snd_pcm_avail_update reports that space is available for 4096 frames.
> However, in my initial testing, when running with SALSA lib, only about
> 100 frames or so are available when the poll returns.
> 
> I will examine this more closely.

Found out another bug.  Try the patch below.

Thanks for reporting!


Takashi

diff -r ad2c81608e10 src/pcm.c
--- a/src/pcm.c	Fri Jun 29 17:59:52 2007 +0200
+++ b/src/pcm.c	Fri Jun 29 19:12:04 2007 +0200
@@ -857,6 +857,7 @@ static int snd_pcm_hw_mmap_status(snd_pc
 		pcm->mmap_status = NULL;
 		goto no_mmap;
 	}
+	pcm->mmap_control->avail_min = 1;
 	return 0;
 
  no_mmap:
@@ -865,6 +866,7 @@ static int snd_pcm_hw_mmap_status(snd_pc
 		return -ENOMEM;
 	pcm->mmap_status = &pcm->sync_ptr->s.status;
 	pcm->mmap_control = &pcm->sync_ptr->c.control;
+	pcm->mmap_control->avail_min = 1;
 	_snd_pcm_sync_ptr(pcm, 0);
 	return 0;
 }
diff -r ad2c81608e10 src/pcm_params.c
--- a/src/pcm_params.c	Fri Jun 29 17:59:52 2007 +0200
+++ b/src/pcm_params.c	Fri Jun 29 19:12:04 2007 +0200
@@ -1052,6 +1052,7 @@ int snd_pcm_sw_params(snd_pcm_t *pcm, sn
 	if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_SW_PARAMS, params) < 0)
 		return -errno;
 	pcm->sw_params = *params;
+	pcm->mmap_control->avail_min = params->avail_min;
 	return 0;
 }

Re: SALSA-Lib: Playback overrun on initial PCM start

[J. Scott Merritt]

On Fri, 29 Jun 2007 19:15:00 +0200
Takashi Iwai <tiwai@suse.de> wrote:

> At Fri, 29 Jun 2007 12:26:45 -0400,
> J. Scott Merritt wrote:
> > 
> > I no longer get the PlayBack overrun on PCM start.  However, it appears
> > that "poll" or the snd_pcm_sw_params_set_avail_min (=4096) is not being
> > properly honored.  With the normal alsa-lib, when the "poll" returns
> > snd_pcm_avail_update reports that space is available for 4096 frames.
> > However, in my initial testing, when running with SALSA lib, only about
> > 100 frames or so are available when the poll returns.
> > 
> > I will examine this more closely.
> 
> Found out another bug.  Try the patch below.
> 
> Thanks for reporting!
> 
> 
> Takashi
> 
> diff -r ad2c81608e10 src/pcm.c
> --- a/src/pcm.c	Fri Jun 29 17:59:52 2007 +0200
> +++ b/src/pcm.c	Fri Jun 29 19:12:04 2007 +0200
> @@ -857,6 +857,7 @@ static int snd_pcm_hw_mmap_status(snd_pc
>  		pcm->mmap_status = NULL;
>  		goto no_mmap;
>  	}
> +	pcm->mmap_control->avail_min = 1;
>  	return 0;
>  
>   no_mmap:
> @@ -865,6 +866,7 @@ static int snd_pcm_hw_mmap_status(snd_pc
>  		return -ENOMEM;
>  	pcm->mmap_status = &pcm->sync_ptr->s.status;
>  	pcm->mmap_control = &pcm->sync_ptr->c.control;
> +	pcm->mmap_control->avail_min = 1;
>  	_snd_pcm_sync_ptr(pcm, 0);
>  	return 0;
>  }
> diff -r ad2c81608e10 src/pcm_params.c
> --- a/src/pcm_params.c	Fri Jun 29 17:59:52 2007 +0200
> +++ b/src/pcm_params.c	Fri Jun 29 19:12:04 2007 +0200
> @@ -1052,6 +1052,7 @@ int snd_pcm_sw_params(snd_pcm_t *pcm, sn
>  	if (ioctl(pcm->fd, SNDRV_PCM_IOCTL_SW_PARAMS, params) < 0)
>  		return -errno;
>  	pcm->sw_params = *params;
> +	pcm->mmap_control->avail_min = params->avail_min;
>  	return 0;
>  }

That did the trick :)

Many thanks for the extremely quick and accurate assistance !

Best regards, Scott.

SALSA-Lib: Playback Select/Poll not effective

[J. Scott Merritt]

Dear List,

Using SALSA-Lib 0.0.4, I call:	

snd_pcm_open (&playback_handle, argv[1], SND_PCM_STREAM_PLAYBACK, O_NONBLOCK);
snd_pcm_hw_params_malloc (&hw_params)
snd_pcm_hw_params_any (playback_handle, hw_params)
snd_pcm_hw_params_set_access (playback_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED)
snd_pcm_hw_params_set_format (playback_handle, hw_params, SND_PCM_FORMAT_S16_LE)
snd_pcm_hw_params_set_rate (playback_handle, hw_params, 16000, 0)
snd_pcm_hw_params_set_channels (playback_handle, hw_params, 2)
snd_pcm_hw_params_set_buffer_size_last (playback_handle, hw_params, &bfrsize)
snd_pcm_hw_params_set_period_size (playback_handle, hw_params, 1024, 0)
snd_pcm_hw_params (playback_handle, hw_params)
snd_pcm_hw_params_free (hw_params);
	
snd_pcm_sw_params_malloc (&sw_params)
snd_pcm_sw_params_current (playback_handle, sw_params)
snd_pcm_sw_params_set_avail_min (playback_handle, sw_params, 1024)
snd_pcm_sw_params_set_start_threshold (playback_handle, sw_params, 4096U)
snd_pcm_sw_params (playback_handle, sw_params)
	
snd_pcm_prepare (playback_handle)

int pdcount = snd_pcm_poll_descriptors_count (playback_handle);
struct pollfd fds [10];
pdcount = snd_pcm_poll_descriptors (playback_handle, fds, 10);

while ((frames_to_deliver = snd_pcm_avail_update (playback_handle)) > 1024) {
   snd_pcm_writei (playback_handle, &buf, 1024) } 

while (1) {
   retval = poll (fds, 1, 5000);

   frames_to_deliver = snd_pcm_avail_update (playback_handle);
   fprintf (stderr, "Frames to deliver was: %ld\n", frames_to_deliver);

   frames_to_deliver = frames_to_deliver > 4096 ? 4096 : frames_to_deliver;
   playback_callback (frames_to_deliver);
}


The "retval = poll (fds, 1, 5000)" statement does not appear to wait for the
playback buffer to be sufficiently emptied.  When this same program is run with
the standard alsa-lib, the POLL statement will wait until there is room in the
buffer to accomodate 1024 additional samples.  When run with SALSA-lib, it
appears to return immediately and snd_pcm_avail_update indicates that there
is only space for about 80 more samples.

The code is being cross-compiled and tested on an ARM processor
(PXA270) which is running linux kernel 2.6.21.   This same code sequence
-does- operate properly (in the same ARM test environment) when compiled
against AlsaLib 1.0.13.

Another apparent (and perhaps relevent) difference between AlsaLib and
SALSA-Lib is that if I open the PCM stream with O_NONBLOCK and then call
snd_pcm_poll_descriptors, AlsaLib gives me a FD = 4, whereas SALSA-Lib
reports an FD = 3;

Thanks, Scott.

Re: SALSA-Lib: Playback overrun on initial PCM start

[J. Scott Merritt]

On Fri, 29 Jun 2007 18:07:20 +0200
Takashi Iwai <tiwai@suse.de> wrote:

> OK, looks like a bug in salsa-lib, then.
> I fixed some remaining bugs and release 0.0.4 now.  Please give it a
> try.  (Note that it might take some time until the ftp server is
> exported / mirrored.)

Much better :)

I no longer get the PlayBack overrun on PCM start.  However, it appears
that "poll" or the snd_pcm_sw_params_set_avail_min (=4096) is not being
properly honored.  With the normal alsa-lib, when the "poll" returns
snd_pcm_avail_update reports that space is available for 4096 frames.
However, in my initial testing, when running with SALSA lib, only about
100 frames or so are available when the poll returns.

I will examine this more closely.