Re: device underruns

[Daniel Mack <daniel@caiaq.de>]

On Mon, Apr 27, 2009 at 12:12:14PM +0200, Takashi Iwai wrote:
> > > The ALSA PCM core just relies upon two things from the lowlevel driver:
> > > 
> > > 1. The lowlevel driver calls snd_pcm_period_elapsed() at each time
> > >    when the set-up period size has been processed by the hardware.
> > > 2. The pointer callback reports the sane position as the current
> > >    position; not below the previous position and not above the next
> > >    period boundary.
> > > 
> > > Especially pulseaudio is very sensitive about these two things,
> > > because it always asks the driver the current position.  Thus, if your
> > > driver doesn't fulfill the above conditions, it won't work properly.
> > 
> > Oh well. Stupid me. I think I fixed it, and wonder why it didn't break
> > more things. Could you apply the patch below?
> 
> If you provide a proper changelog and your sign-off ;)

Oops :)


>From d50433f1047b85b150737c2f2588763ead2096ce Mon Sep 17 00:00:00 2001
From: Daniel Mack <daniel@caiaq.de>
Date: Mon, 27 Apr 2009 12:14:23 +0200
Subject: [PATCH] ALSA: snd-usb-caiaq: fix reported elapsed periods

Reset the internal period position counter upon stream startup. This
fixes initial aplay underruns and problems related to latency picky
applications such as pulseaudio.

Bumped the version number to 1.3.14.

Signed-off-by: Daniel Mack <daniel@caiaq.de>
---
 sound/usb/caiaq/audio.c  |   12 +++++++-----
 sound/usb/caiaq/device.c |    2 +-
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/sound/usb/caiaq/audio.c b/sound/usb/caiaq/audio.c
index 3f45c0f..b13ce76 100644
--- a/sound/usb/caiaq/audio.c
+++ b/sound/usb/caiaq/audio.c
@@ -195,11 +195,14 @@ static int snd_usb_caiaq_pcm_prepare(struct snd_pcm_substream *substream)
 
 	debug("%s(%p)\n", __func__, substream);
 	
-	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
+		dev->period_out_count[index] = BYTES_PER_SAMPLE + 1;
 		dev->audio_out_buf_pos[index] = BYTES_PER_SAMPLE + 1;
-	else
+	} else {
+		dev->period_in_count[index] = BYTES_PER_SAMPLE;
 		dev->audio_in_buf_pos[index] = BYTES_PER_SAMPLE;
-	
+	}
+
 	if (dev->streaming)
 		return 0;
 	
@@ -300,8 +303,7 @@ static void check_for_elapsed_periods(struct snd_usb_caiaqdev *dev,
 		if (!sub)
 			continue;
 
-		pb = frames_to_bytes(sub->runtime, 
-				     sub->runtime->period_size);
+		pb = snd_pcm_lib_period_bytes(sub);
 		cnt = (sub->stream == SNDRV_PCM_STREAM_PLAYBACK) ?
 					&dev->period_out_count[stream] :
 					&dev->period_in_count[stream];
diff --git a/sound/usb/caiaq/device.c b/sound/usb/caiaq/device.c
index 6d51770..515de1c 100644
--- a/sound/usb/caiaq/device.c
+++ b/sound/usb/caiaq/device.c
@@ -35,7 +35,7 @@
 #include "input.h"
 
 MODULE_AUTHOR("Daniel Mack <daniel@caiaq.de>");
-MODULE_DESCRIPTION("caiaq USB audio, version 1.3.13");
+MODULE_DESCRIPTION("caiaq USB audio, version 1.3.14");
 MODULE_LICENSE("GPL");
 MODULE_SUPPORTED_DEVICE("{{Native Instruments, RigKontrol2},"
 			 "{Native Instruments, RigKontrol3},"
-- 
1.6.2.1