Re: [PATCH] improved snd-aloop quality when using certain samplerates and kernel HZ

["Ahmet İnan" <ainan@mathematik.uni-freiburg.de>]

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when the time interval for a period is smaller than kernel HZ, then
snd-aloop and snd-dummy cannot call snd_pcm_period_elapsed as fast enough
annymore. this happens for example with games. but the app still needs to
see, that the buffer actually did go further, which is provided by these
patches.

[snd-aloop - better realtime app support]
http://www.mathematik.uni-freiburg.de/IAM/homepages/ainan/alsa-driver-hg-aloop-ainan-patch2.diff
[Signed-off-by: Ahmet İnan <ainan <at> mathematik.uni-freiburg.de>]

[snd-dummy - better realtime app support]
http://www.mathematik.uni-freiburg.de/IAM/homepages/ainan/alsa-kernel-hg-dummy-ainan-patch1.diff
[Signed-off-by: Ahmet İnan <ainan <at> mathematik.uni-freiburg.de>]

patches are relative to current hg-tree.

finally even realtime apps like games work smooth.
only one thing left for perfection :)

ahmet

--
admin der abteilung für angewandte mathematik, tel. 0761-203-5626

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diff -r 89222d702376 drivers/aloop-kernel.c
--- a/drivers/aloop-kernel.c	Thu Feb 21 07:54:16 2008 +0100
+++ b/drivers/aloop-kernel.c	Fri Feb 22 18:16:56 2008 +0100
@@ -198,10 +198,10 @@ static void snd_card_loopback_timer_func
 	spin_lock_irq(&dpcm->lock);
 
 	dpcm->pcm_irq_pos += dpcm->pcm_bps;
+	dpcm->pcm_buf_pos += dpcm->pcm_bps;
+	dpcm->pcm_buf_pos %= dpcm->pcm_buffer_size * dpcm->pcm_hz;
 	if (dpcm->pcm_irq_pos >= dpcm->pcm_period_size * dpcm->pcm_hz) {
 		dpcm->pcm_irq_pos %= dpcm->pcm_period_size * dpcm->pcm_hz;
-		dpcm->pcm_buf_pos += dpcm->pcm_period_size;
-		dpcm->pcm_buf_pos %= dpcm->pcm_buffer_size;
 		spin_unlock_irq(&dpcm->lock);	
 		snd_pcm_period_elapsed(dpcm->substream);
 	} else {
@@ -213,7 +213,7 @@ static snd_pcm_uframes_t snd_card_loopba
 {
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	snd_card_loopback_pcm_t *dpcm = runtime->private_data;
-	return bytes_to_frames(runtime, dpcm->pcm_buf_pos);
+	return bytes_to_frames(runtime, dpcm->pcm_buf_pos / dpcm->pcm_hz);
 }
 
 static struct snd_pcm_hardware snd_card_loopback_info =

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diff -r 1d499d7e155e drivers/dummy.c
--- a/drivers/dummy.c	Thu Feb 21 12:40:00 2008 +0100
+++ b/drivers/dummy.c	Fri Feb 22 18:25:20 2008 +0100
@@ -259,10 +259,10 @@ static void snd_card_dummy_pcm_timer_fun
 	dpcm->timer.expires = 1 + jiffies;
 	add_timer(&dpcm->timer);
 	dpcm->pcm_irq_pos += dpcm->pcm_bps;
+	dpcm->pcm_buf_pos += dpcm->pcm_bps;
+	dpcm->pcm_buf_pos %= dpcm->pcm_buffer_size * dpcm->pcm_hz;
 	if (dpcm->pcm_irq_pos >= dpcm->pcm_period_size * dpcm->pcm_hz) {
 		dpcm->pcm_irq_pos %= dpcm->pcm_period_size * dpcm->pcm_hz;
-		dpcm->pcm_buf_pos += dpcm->pcm_period_size;
-		dpcm->pcm_buf_pos %= dpcm->pcm_buffer_size;
 		spin_unlock_irqrestore(&dpcm->lock, flags);
 		snd_pcm_period_elapsed(dpcm->substream);
 	} else
@@ -274,7 +274,7 @@ static snd_pcm_uframes_t snd_card_dummy_
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	struct snd_dummy_pcm *dpcm = runtime->private_data;
 
-	return bytes_to_frames(runtime, dpcm->pcm_buf_pos);
+	return bytes_to_frames(runtime, dpcm->pcm_buf_pos / dpcm->pcm_hz);
 }
 
 static struct snd_pcm_hardware snd_card_dummy_playback =

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