Re: I thought it would simple....

[Tom Watson <sdc695@yahoo.com>]

[-- Attachment #1: Type: text/plain, Size: 2657 bytes --]

OK, here is more data.  The enclosed files are:
1) The "minimal playback program" described in the original message,
modified to clear the buffer, and do the "dump" of the parameters.  The
buffer size is lengthened a bit (maybe this makes a difference??)
2) The output of 'strace' on the program, it stops at the 'poll'
instruction (broken out with a ^c at the terminal).
3) A cut/pasted copy of the output sent to the terminal.  In
particular, it has the output from "snd_pcm_dump" which ought to help a
bit.

The source was compiled with 'cc simple.c -lasound -o simple'.
It was executed with './simple surround40'.

I think I'm doing everything OK, and if I solve this goodie (on the
simple program), I suspect tha I can solve the problem with my program.

P.S.  The sound card is a Turtle Beach Santa Cruz.  It can handle the 4
channel things OK (I used 'aplay' very nicely!!)

While the C++ program is nice, I'm not really into that.  It seemed to
work OK (as given).  My program is C, thus the enclosed files.

Maybe there is a solution out there.

Thanks to all.  ALSA is the way of the future!!

--- Carlo Wood <carlo@alinoe.com> wrote:
> I found that a better example for playback is
> the 'pcm.c' file that you can find on the alsa site.
> It contains many ways to deliver the data (a nice
> sine) to your soundcard.  Playing with the parameters
> gives some insight (more than reading the overall poor
> documentation imho :().
> 
<<<deletia>>>
> On Tue, Jul 22, 2003 at 11:54:49PM -0700, Tom Watson wrote:
> > I am attempting to write a "simple" audio playback program.  Well,
> I
> > thought it would be, but...
> > Somehow (thru strace) the 'snd_pcm_writei' call goes and eventually
> > does a system 'poll' call, but it doesn't return indicating that a
> > write is OK to do.
> > I've used similar parameters in 'aplay' and I see that it works.
> > 
> > The basis of the program I'm writing is the one described in _A
> > Tutorial on Using the ALSA API_
> > (http://equalarea.com/paul/alsa-audio.html), section entitled "A
> > Minimal Playback Program".
> > 
> > One thing I've noted:  Some of the data printed out by
> "snd_pcm_dump"
> > is different between my program and 'aplay'.  I suspect that there
> is a
> > clue somewhere, but what is the "magic"??
> > 
> > If necessary, I can provide the 'strace' or the output from
> > 'snd_pcm_dump', but in the interest of brevity...
> > 
> > Any "great clue" would be appreciated.
<<<deletia of C++ program...>>>

=====
-- 
Tom Watson
tsw@johana.com

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[-- Attachment #2: simple.c --]
[-- Type: application/octet-stream, Size: 2474 bytes --]

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <alsa/asoundlib.h>
#define CHAN 4
#define BSIZ 4096	/* Number of frames */
main (int argc, char *argv[])
{
int i;
int err;
short buf[CHAN * BSIZ];
snd_pcm_t *playback_handle;
snd_pcm_hw_params_t *hw_params;
snd_output_t *log;              /* For the log goodie */

/* Just set it to something empty */
memset (buf, 0, sizeof(buf));
if ((err = snd_pcm_open (&playback_handle, argv[1], SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
	fprintf (stderr, "cannot open audio device %s (%s)\n", 
	 argv[1], snd_strerror (err));
	exit (1);
	}
	   
if ((err = snd_pcm_hw_params_malloc (&hw_params)) < 0) {
	fprintf (stderr, "cannot allocate hardware parameter structure (%s)\n",
	 snd_strerror (err));
	exit (1);
	}
			 
if ((err = snd_pcm_hw_params_any (playback_handle, hw_params)) < 0) {
	fprintf (stderr, "cannot initialize hardware parameter structure (%s)\n",
	 snd_strerror (err));
	exit (1);
	}

if ((err = snd_pcm_hw_params_set_access (playback_handle, hw_params, SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
	fprintf (stderr, "cannot set access type (%s)\n",
	 snd_strerror (err));
	exit (1);
	}

if ((err = snd_pcm_hw_params_set_format (playback_handle, hw_params, SND_PCM_FORMAT_S16_LE)) < 0) {
	fprintf (stderr, "cannot set sample format (%s)\n",
	 snd_strerror (err));
	exit (1);
	}

if ((err = snd_pcm_hw_params_set_rate_near (playback_handle, hw_params, 44100, 0)) < 0) {
	fprintf (stderr, "cannot set sample rate (%s)\n",
	 snd_strerror (err));
	exit (1);
	}

if ((err = snd_pcm_hw_params_set_channels (playback_handle, hw_params, CHAN)) < 0) {
	fprintf (stderr, "cannot set channel count (%s)\n",
	 snd_strerror (err));
	exit (1);
	}

if ((err = snd_pcm_hw_params (playback_handle, hw_params)) < 0) {
	fprintf (stderr, "cannot set parameters (%s)\n",
	 snd_strerror (err));
	exit (1);
	}
err = snd_output_stdio_attach(&log, stderr, 0);
if (err < 0)
	{
	fprintf (stderr, "Can\'t do stdio attach (%d)\n", err);
	exit (1);
	}
snd_pcm_dump (playback_handle, log);
      
/* snd_pcm_hw_params_free (hw_params); */

if ((err = snd_pcm_prepare (playback_handle)) < 0) {
	fprintf (stderr, "cannot prepare audio interface for use (%s)\n",
	 snd_strerror (err));
	exit (1);
	}

for (i = 0; i < 10; ++i) {
	if ((err = snd_pcm_writei (playback_handle, buf, BSIZ)) != BSIZ) {
		fprintf (stderr, "write to audio interface failed (%s)\n",
			 snd_strerror (err));
		exit (1);
		}
	}

snd_pcm_close (playback_handle);
exit (0);
}


[-- Attachment #3: simple.tr --]
[-- Type: application/x-troff, Size: 26330 bytes --]

[-- Attachment #4: simple.sout --]
[-- Type: application/octet-stream, Size: 1682 bytes --]

Multi PCM

Channel bindings:
0: slave 0, channel 0
1: slave 0, channel 1
2: slave 1, channel 0
3: slave 1, channel 1

Its setup is:
stream       : PLAYBACK
access       : RW_INTERLEAVED
format       : S16_LE
subformat    : STD
channels     : 4
rate         : 44100
exact rate   : 44100 (44100/1)
msbits       : 16
buffer_size  : 8192
period_size  : 8
period_time  : 181
tick_time    : 10000
tstamp_mode  : NONE
period_step  : 1
sleep_min    : 0
avail_min    : 8
xfer_align   : 8
start_threshold  : 1
stop_threshold   : 8192
silence_threshold: 0
silence_size : 0
boundary     : 1073741824

Slave #0: Hardware PCM card 0 'Sound Fusion CS46xx' device 0 subdevice 0

Its setup is:
stream       : PLAYBACK
access       : MMAP_INTERLEAVED
format       : S16_LE
subformat    : STD
channels     : 2
rate         : 44100
exact rate   : 44100 (44100/1)
msbits       : 16
buffer_size  : 8192
period_size  : 8
period_time  : 181
tick_time    : 10000
tstamp_mode  : NONE
period_step  : 1
sleep_min    : 0
avail_min    : 8
xfer_align   : 8
start_threshold  : 1
stop_threshold   : 8192
silence_threshold: 0
silence_size : 0
boundary     : 1073741824

Slave #1: Hardware PCM card 0 'Sound Fusion CS46xx' device 1 subdevice 0

Its setup is:
stream       : PLAYBACK
access       : MMAP_INTERLEAVED
format       : S16_LE
subformat    : STD
channels     : 2
rate         : 44100
exact rate   : 44100 (44100/1)
msbits       : 16
buffer_size  : 8192
period_size  : 8
period_time  : 181
tick_time    : 10000
tstamp_mode  : NONE
period_step  : 1
sleep_min    : 0
avail_min    : 8
xfer_align   : 8
start_threshold  : 1
stop_threshold   : 8192
silence_threshold: 0
silence_size : 0
boundary     : 1073741824