Re: [Protux-devel] SampleRate detecting code ! [was: Good news about 0.17.1]

[Martin Herren]

Luciano Giordana wrote:

> On Sunday 09 February 2003 07:22 pm, Martin Herren wrote:
>
> > On Sun, 09 Feb 2003 21:57:58 +0100
> >
> > Martin Herren <address@hidden> wrote:
> >
> > > protux can't open hw:0,3 (digital out)
> > the reason seems to be that the SB Live's digital out can handle only a
> > 48kHz sample rate
>
>
> if the snd_pcm_...._test_....() functions worked in ALSA, the supports() 
> method, in MustuxAudioDEviceMapper, would mark this bus out as supporting 
> only 48 Khz 
> and would not let us try in 44100.
>
> but they dont work, and ALSA says that all buses supports everthing (such 
> 96Hkz in a SBLive !!!)
>
> I need to find a way to check the bus capabilities, otherwise, it will keep 
> happening...

i read myself somewhat through the alsa doc and some example code, and 
wrote a small program to detect the supported sample rates... it's 
somewhat 'heavy' as i need to open and close the device for every check, 
as it seems not possible to reassign a new sample rate when one was 
already assigned ! It uses the 'new style' API function 
snd_pcm_hw_params_set_rate_near(), so you _need_ to define 
ALSA_PCM_NEW_HW_PARAMS_API before including alsa/asoundlib.h.

i tested it with the 2 outputs of my sb live, and the result seems correct:
for hw:0,0 (analog out):
address@hidden:~/alsa$ ./detect_sample_rates hw:0,0
8000 supported
11025 supported
16000 supported
22050 supported
32000 supported
44100 supported
48000 supported

and for hw:0,3 (digital out):
address@hidden:~/alsa$ ./detect_sample_rates hw:0,3
48000 supported

(it checks the following rates: 8000, 11025, 16000, 22050, 32000, 44100, 
48000, 96000, 192000)

hope that may help you...

/Martin

/**** detect_sample_rates.c ****/
#include <stdio.h>
#include <stdlib.h>
#define ALSA_PCM_NEW_HW_PARAMS_API
#include <alsa/asoundlib.h>

int main(int argc, char **argv)
{
       int i;
       int err;
       int rate;
       int rates[10] = {8000, 11025, 16000, 22050, 32000, 44100, 48000, 
96000, 192000, 0};
       snd_pcm_t *playback_handle;
       snd_pcm_hw_params_t *hw_params;

       if (argc < 2)
       {
               fprintf(stderr, "you must give a device name as 
argument\n");
               exit(1);
       }

       for (i = 0; (rate = rates[i]) != 0; i++)
       {
               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));
               }

               if ((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, &rate, 0)) < 0)
               {
                       fprintf(stderr, "cannot set sample rate (%s)\n", 
snd_strerror(err));
                       exit(1);
               }
               if (rate == rates[i])
                       fprintf(stdout, "%i supported\n", rate);
               snd_pcm_close(playback_handle);
       }
       exit(0);
}