James Courtier-Dutton wrote:
I have a Motherboard with the ICH5 and ALC650 so I use the intel8x0 alsa kernel driver. (Currently the version from 2.6.0-test4.)
I have managed to get SPDIF passthru working. (I posted the patch some time ago, and it is now in 2.6.0-test4)
I cannot get multichannel working.
The motherboard has 5 audio jacks. mic, line-in, front, rear, center-lfe.
If I output just 2 channels, the sound comes out perfectly from the "front" jack.
If I output in 4 or 6 channels, the sound fails on all channels.
Sometime I hear a short burst of sound on the front channel, but hardly ever.
I am pretty sure that this is a buffer/period size problem.
My application has code is (see below)
Which function in intel8x0.c interacts with the buffer and period sizes?
The "snd_pcm_hw_params_set_buffer_time_near" gets full buffer_time for stereo, but for 6 channels it does not, and has to reduce the buffer size to some limits determined by the hardware. I think it is this "limiting/contraint" code that is not working correctly.
Can anyone provide me with pointers so that I could fix this bug ?
Cheers James
/* set the ring-buffer time [us] (large enough for x us|y samples ...) */
dir=0;
err = snd_pcm_hw_params_set_buffer_time_near(this->audio_fd, params, &buffer_time, &dir); /* buffer_time before call = 1000000 */
if (err < 0) {
printf ("audio_alsa_out: buffer time not available\n");
goto __close;
}
printf ("audio_alsa_out: Got %d buffer_time, wanted %d\n",buffer_time, BUFFER_TIME);
err = snd_pcm_hw_params_get_buffer_size(params, &(this->buffer_size));
/* set the period time [us] (interrupt every x us|y samples ...) */
dir=0;
period_size=this->buffer_size/8;
err = snd_pcm_hw_params_set_period_size_near(this->audio_fd, params, &period_size, &dir);
if (err < 0) {
printf ("audio_alsa_out: period time not available");
goto __close;
}
dir=0;
err = snd_pcm_hw_params_get_period_size(params, &period_size, &dir);
if (2*period_size > this->buffer_size) {
printf ("audio_alsa_out: buffer to small, could not use. period_size=%ld, buffer_size=%ld\n", period_size, this->buffer_s
ize);
goto __close;
}
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