Bug#362847: Further information

[Stéphane Magnenat]

Hi,

I've made a test-case in the form of a simple C program which generates 10 sec 
of 440 Hz sinus. With a define, it can generate samples at 44.1 kHz or et 48 
kHz. Direct output at 48 kHz sounds perfect but output at 44.1 kHz through 
the alsa rate plugin clearly shows a problem generating high frequencies.
I've attached the test case to this mail. It can be compiled with:
gcc -lasound alsatest.c -o alsatest
Please chane the samplingRate define to test with 44100 and 48000

Thanks, have a nice day,

Steph

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <alsa/asoundlib.h>

#define samplingRate 44100
#define duration 10
#define sampleCount (samplingRate * duration * 2)

int main (int argc, char *argv[])
{
		int i;
		int err;
		int rate = samplingRate;
		short buf[sampleCount];
		snd_pcm_t *playback_handle;
		snd_pcm_hw_params_t *hw_params;

		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, &rate, 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, 2)) < 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);
		}

		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);
		}

		/* fill the buffer */
		for (i = 0; i < samplingRate * duration; i++)
		{
			const double sinF = 440.0;
			double val = sin( ((double)i * 2.0 * M_PI * sinF) / (samplingRate));
			buf[i * 2] = val * 32767;
			buf[i * 2 + 1] = val * 32767;
		}

		if ((err = snd_pcm_writei (playback_handle, buf, sampleCount)) != sampleCount) {
			fprintf (stderr, "write to audio interface failed (%s)\n",
								snd_strerror (err));
			exit (1);
		}

		snd_pcm_close (playback_handle);
		exit (0);
}