On Mon, 2013-12-09 at 13:23 +0800, Raymond Yau wrote:

2013/12/6 Tanu Kaskinen tanu.kaskinen@linux.intel.com

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On Sat, 2013-11-30 at 18:07 +0100, Lars-Peter Clausen wrote:

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PCM Devices which have the BATCH flag set update the PCM pointer only

with

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period size granularity. Using timer based scheduling does not have any advantage in this mode. For one devices which have that flag set usually

update

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the position pointer in software after getting the period interrupt. So disabling the period interrupt is not possible for this kind of devices. Furthermore writing to or reading from the buffer slice for the current

period

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is not possible since the position inside the buffer is not known. On

the other

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hand the tsched algorithm seems to get easily confused for this kind of hardware, which results in garbled audio output. This typically means

that timer

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based scheduling needs to be manually disabled on systems with such

devices.

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Auto disabling tsched in this case allows these systems to run with the

default

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configuration.

Signed-off-by: Lars-Peter Clausen lars@metafoo.de

src/modules/alsa/alsa-util.c | 4 ++++ 1 file changed, 4 insertions(+)

diff --git a/src/modules/alsa/alsa-util.c b/src/modules/alsa/alsa-util.c index 75f5858..4b24e47 100644 --- a/src/modules/alsa/alsa-util.c +++ b/src/modules/alsa/alsa-util.c @@ -245,6 +245,10 @@ int pa_alsa_set_hw_params( if (!pa_alsa_pcm_is_hw(pcm_handle)) _use_tsched = false;

• /* The PCM pointer is only updated with period granularity */
• if (snd_pcm_hw_params_is_batch(hwparams))

•    _use_tsched = false;
  

#if (SND_LIB_VERSION >= ((1<<16)|(0<<8)|24)) /* API additions in 1.0.24

*/

...

 if (_use_tsched) {

Thanks! I applied the patch.

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Are you patch sufficient ?

In alsa-lib , snd_pcm_sw_params_set_avail_min always return zero

int snd_pcm_sw_params_set_avail_min(snd_pcm_t *pcm, snd_pcm_sw_params_t *params, snd_pcm_uframes_t val) { assert(pcm && params); /* Fix avail_min if it's below period size. The period_size * defines the minimal wake-up timing accuracy, so it doesn't * make sense to set below that. */ if (val < pcm->period_size) val = pcm->period_size; params->avail_min = val; return 0; }

http://cgit.freedesktop.org/pulseaudio/pulseaudio/commit/src/modules/alsa/al...

/* We need at last one frame in the used part of the buffer */

• avail_min = (snd_pcm_uframes_t) u->hwbuf_unused_frames + 1;

• avail_min = (snd_pcm_uframes_t) u->hwbuf_unused / u->frame_size + 1;

do pulseaudio need to keep at least one periods instead of more than 1 frames for those driver which update hwptr in periods ?

I don't know.