[alsa-devel] [Alsa-devel] Read the input of a soundcard with ALSA

[Nyx]

Hi,

I have some problems to read the input of my soundcard using Alsa and I
don't really understand how to have access to the input of my soundcard.
I follow :
http://www.alsa-project.org/alsa-doc/alsa-lib/_2test_2pcm_8c-example.html
http://www.alsa-project.org/alsa-doc/alsa-lib/_2test_2latency_8c-example.html

# So, in my program, I have created two handles for capture and playback :
char *device = "hw:0,0";
snd_output_t *output;
snd_input_t *input;
snd_pcm_t *phandle, *chandle;

# then I connect the phandle to the out
err = snd_output_stdio_attach(&output, stdout, 0);
if (..)

# Do I have to connect the chandle with the input ?
# err = snd_input_stdio_attach(&input, stdin, 0);

# I open the access to PCM
err = snd_pcm_open(&phandle, pdevice, SND_PCM_STREAM_PLAYBACK, 0)
if (..)
err = snd_pcm_open(&chandle, pdevice, SND_PCM_STREAM_CAPTURE, 0)
if(..)

# Hardware and software Parameters
## Hardware Parameters
snd_pcm_hw_params;
int err;

err = snd_pcm_hw_params_any(phandle, params); if(..);
err = snd_pcm_hw_params_set_access(phandle,
params,SND_PCM_ACCESS_RW_INTERLEAVED); if(..);
err = snd_pcm_hw_params_set_format(phandle, params,SND_PCM_FORMAT_S16);
if(..);
err = snd_pcm_hw_params_set_channels(phandle, params, 1); if(..);
err = snd_pcm_hw_params_set_rate_near(phandle, params, 44100, 0); if(..);
err = snd_pcm_hw_params_set_buffer_time_near(phandle, params, 500000, &dir);
if(..);
err = snd_pcm_hw_params_set_time_near(phandle, params, 100000, &dir),
if(..);
err = snd_pcm_hw_params(phandle, params);

##Software parameters
err = snd_pcm_sw_params(phandle, params); if(..);
err = snd_pcm_sw_params_set_start_threshold(phandle, swparams, 0x7fffffff);
if(..);
err = snd_pcm_sw_params_set_avail_min(phandle, swparams, 4);

# same configuration for phandle

# Link output to input and start
err = snd_pcm_link(chandle, phandle); if(..);
err = snd_pcm_start(chandle); if(..);

#Then I want to read my input
frames_in = 0;
in_max = 0;
latency = 28;
buffer = malloc((latency_max * snd_pcm_format_width(format) / 8) * 2);
while (1) {
        r = readbuf(chandle, buffer, latency, &frames_in, &in_max)); if(..);
}

# description of the function
long readbuf(snd_pcm_t *handle, char *buf, long len, size_t *frames, size_t
*max)
{
        long r;
        do {
      r = snd_pcm_readi(handle, buf, len);
} while (r == -EAGAIN);

if  (r > 0) {
*frames += r;
if ((long)*max < r)
*max = r;
}
printf ("r = %s,  len %li and buf[%d] %f \r", snd_strerror(r), len,i,
buf[i]);
return r;
}

So I compile it and I run it, and I have
$ read = Broken Pipe, len = 28 and buf[..] = 0.000

Anyone can help me to read the input of my sound card ?

Thank you
-- 
K