[alsa-devel] [PATCH] alsa-plugins: Pulse: only underrun if no more data has been written

[Takashi Iwai]

At Tue, 23 Aug 2011 13:56:58 +0200,
David Henningsson wrote:
> 
> Behold the third version of the patch.
> 
> On 08/19/2011 02:46 PM, Takashi Iwai wrote:
> > At Fri, 19 Aug 2011 11:49:25 +0200,
> > David Henningsson wrote:
> >>
> >> > From 8098c77a447a80d2860588387d18b3aa6d23b6bb Mon Sep 17 00:00:00 2001
> >> From: David Henningsson<david.henningsson at canonical.com>
> >> Date: Fri, 19 Aug 2011 11:47:07 +0200
> >> Subject: [PATCH] alsa-plugins: Pulse: only underrun if no more data has been
> >>   written
> >>
> >> If more data has already been written after the underrun, the underrun
> >> will automatically end and therefore we should not report it or
> >> restart the stream.
> >>
> >> Signed-off-by: David Henningsson<david.henningsson at canonical.com>
> >> ---
> >>   configure.in      |    7 +++++++
> >>   pulse/pcm_pulse.c |   28 ++++++++++++++++++++++++++--
> >>   2 files changed, 33 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/configure.in b/configure.in
> >> index ccf59ba..f6886b1 100644
> >> --- a/configure.in
> >> +++ b/configure.in
> >> @@ -31,8 +31,14 @@ AC_ARG_ENABLE([pulseaudio],
> >>
> >>   if test "x$enable_pulseaudio" != "xno"; then
> >>     PKG_CHECK_MODULES(pulseaudio, [libpulse>= 0.9.11], [HAVE_PULSE=yes], [HAVE_PULSE=no])
> >> +  PKG_CHECK_MODULES(pulseaudio_099, [libpulse>= 0.99.1],
> >> +    [HAVE_PULSE_UNDERRUN_INDEX=yes], [HAVE_PULSE_UNDERRUN_INDEX=no])
> >
> > Hm, can we use PA_CHECK_VERSION() or such simply in the code?
> 
> Ok, good idea.
> 
> >
> >> diff --git a/pulse/pcm_pulse.c b/pulse/pcm_pulse.c
> >> index d6c6792..61f1c0c 100644
> >> --- a/pulse/pcm_pulse.c
> >> +++ b/pulse/pcm_pulse.c
> >> @@ -26,6 +26,10 @@
> >>   #include<alsa/asoundlib.h>
> >>   #include<alsa/pcm_external.h>
> >>
> >> +#ifdef HAVE_CONFIG_H
> >> +#include<config.h>
> >> +#endif
> >> +
> >>   #include "pulse.h"
> >>
> >>   typedef struct snd_pcm_pulse {
> >> @@ -39,9 +43,10 @@ typedef struct snd_pcm_pulse {
> >>   	size_t last_size;
> >>   	size_t ptr;
> >>   	int underrun;
> >> -	int handle_underrun;
> >> +	int handle_underrun; /* can be 0=never, 1=always or 2,3=only if more data has not been written */
> >
> > I think it'd be simpler to introduce one more boolean variable.
> > Otherwise the logic looks too complex than needed.
> 
> I've now done that. I don't know if it became simpler though.

Hm, indeed.

I think we can start off from more simple.  With the new PA, the
underrun detection should work better.  So why we do we need yet
another mode to disable it?  It should be enough just to have a
boolean for underrun_detect yes/no.

So, the patch would be like below.

What do you think?


Takashi

---
diff --git a/pulse/pcm_pulse.c b/pulse/pcm_pulse.c
index d6c6792..b0e52ab 100644
--- a/pulse/pcm_pulse.c
+++ b/pulse/pcm_pulse.c
@@ -42,6 +42,7 @@ typedef struct snd_pcm_pulse {
 	int handle_underrun;
 
 	size_t offset;
+	int64_t written;
 
 	pa_stream *stream;
 
@@ -460,6 +461,7 @@ static snd_pcm_sframes_t pulse_write(snd_pcm_ioplug_t * io,
 
 	/* Make sure the buffer pointer is in sync */
 	pcm->last_size -= writebytes;
+	pcm->written += writebytes;
 	ret = update_ptr(pcm);
 	if (ret < 0)
 		goto finish;
@@ -585,6 +587,15 @@ static void stream_request_cb(pa_stream * p, size_t length, void *userdata)
 	update_active(pcm);
 }
 
+#if defined(PA_CHECK_VERSION) && PA_CHECK_VERSION(0,99,0)
+#define DEFAULT_HANDLE_UNDERRUN		1
+#define do_underrun_detect(pcm, p) \
+	((pcm)->written <= pa_stream_get_underflow_index(p))
+#else
+#define DEFAULT_HANDLE_UNDERRUN		0
+#define do_underrun_detect(pcm, p)	1	/* always true */
+#endif
+
 static void stream_underrun_cb(pa_stream * p, void *userdata)
 {
 	snd_pcm_pulse_t *pcm = userdata;
@@ -594,7 +605,8 @@ static void stream_underrun_cb(pa_stream * p, void *userdata)
 	if (!pcm->p)
 		return;
 
-	pcm->underrun = 1;
+	if (do_underrun_detect(pcm, p))
+		pcm->underrun = 1;
 }
 
 static void stream_latency_cb(pa_stream *p, void *userdata) {
@@ -739,6 +751,7 @@ static int pulse_prepare(snd_pcm_ioplug_t * io)
 
 	pcm->offset = 0;
 	pcm->underrun = 0;
+	pcm->written = 0;
 
 	/* Reset fake ringbuffer */
 	pcm->last_size = 0;
@@ -983,7 +996,7 @@ SND_PCM_PLUGIN_DEFINE_FUNC(pulse)
 	const char *server = NULL;
 	const char *device = NULL;
 	const char *fallback_name = NULL;
-	int handle_underrun = 0;
+	int handle_underrun = DEFAULT_HANDLE_UNDERRUN;
 	int err;
 	snd_pcm_pulse_t *pcm;