From b103d7c810fa11cf3ea70ef289885ae57cde8f77 Mon Sep 17 00:00:00 2001
From: joq <joq@0c269be4-1314-0410-8aa9-9f06e86f4224>
Date: Tue, 4 Jul 2006 03:14:01 +0000
Subject: [PATCH]  r3403@lithium:  joq | 2006-07-03 21:04:52 -0500  Committed
 dummy backend timing improvements.

git-svn-id: svn+ssh://jackaudio.org/trunk/jack@980 0c269be4-1314-0410-8aa9-9f06e86f4224
---
 configure.ac                 |  3 ++-
 drivers/dummy/dummy_driver.c | 44 +++++++++++++++++++++++-------------
 drivers/dummy/dummy_driver.h |  1 +
 3 files changed, 31 insertions(+), 17 deletions(-)

diff --git a/configure.ac b/configure.ac
index f644fed..0a81a5a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -17,7 +17,7 @@ dnl                 changes are made
 dnl ---
 JACK_MAJOR_VERSION=0
 JACK_MINOR_VERSION=102
-JACK_MICRO_VERSION=18
+JACK_MICRO_VERSION=19
 
 dnl ---
 dnl HOWTO: updating the jack protocol version
@@ -699,6 +699,7 @@ echo \| Build with FreeBob support............................ : $HAVE_FREEBOB
 echo \| Build with OSS support................................ : $HAVE_OSS
 echo \| Build with CoreAudio support.......................... : $HAVE_COREAUDIO
 echo \| Build with PortAudio support.......................... : $HAVE_PA
+echo \| Install prefix........................................ : $prefix
 echo \| Compiler optimization flags........................... : $JACK_OPT_CFLAGS
 echo \| Compiler full flags................................... : $CFLAGS
 echo \| Install dir for libjack + backends.................... : $libdir/jack
diff --git a/drivers/dummy/dummy_driver.c b/drivers/dummy/dummy_driver.c
index 76a3a39..897735a 100644
--- a/drivers/dummy/dummy_driver.c
+++ b/drivers/dummy/dummy_driver.c
@@ -38,19 +38,38 @@
 
 #undef DEBUG_WAKEUP
 
+/* this is used for calculate what counts as an xrun */
+#define PRETEND_BUFFER_SIZE 4096
 
 static jack_nframes_t 
 dummy_driver_wait (dummy_driver_t *driver, int extra_fd, int *status,
 		   float *delayed_usecs)
 {
-	jack_time_t starting_time = jack_get_microseconds();
-	jack_time_t processing_time = (driver->last_wait_ust?
-				       starting_time - driver->last_wait_ust:
-				       0);
-
-	/* wait until time for next cycle */
-	if (driver->wait_time > processing_time)
-		usleep (driver->wait_time - processing_time);
+	jack_time_t now = jack_get_microseconds();
+
+	if (driver->next_time < now) {
+		if (driver->next_time == 0) {
+			/* first time through */
+			driver->next_time = now + driver->wait_time;
+		}  else if (now - driver->next_time
+			    > (PRETEND_BUFFER_SIZE * 1000000LL
+			       / driver->sample_rate)) {
+			/* xrun */
+			fprintf(stderr,"**** dummy: xrun of %ju usec\n",
+				(uintmax_t)now - driver->next_time);
+			driver->next_time = now + driver->wait_time;
+		} else {
+			/* late, but handled by our "buffer"; try to
+			 * get back on track */
+			driver->next_time += driver->wait_time;
+		}
+	} else {
+		jack_time_t wait = driver->next_time - now;
+		struct timespec ts = { .tv_sec = wait / 1000000,
+				       .tv_nsec = (wait % 1000000) * 1000 };
+		nanosleep(&ts,NULL);
+		driver->next_time += driver->wait_time;
+	}
 
 	driver->last_wait_ust = jack_get_microseconds ();
 	driver->engine->transport_cycle_start (driver->engine,
@@ -96,14 +115,6 @@ dummy_driver_null_cycle (dummy_driver_t* driver, jack_nframes_t nframes)
 static int
 dummy_driver_bufsize (dummy_driver_t* driver, jack_nframes_t nframes)
 {
-	/* This is a somewhat arbitrary size restriction.  The dummy
-	 * driver doesn't work well with smaller buffer sizes,
-	 * apparantly due to usleep() inaccuracy under Linux 2.4.  If
-	 * you can get it working with smaller buffers, lower the
-	 * limit.  (JOQ) */
-	if (nframes < 128)
-		return EINVAL;
-
 	driver->period_size = nframes;  
 	driver->period_usecs = driver->wait_time =
 		(jack_time_t) floor ((((float) nframes) / driver->sample_rate)
@@ -243,6 +254,7 @@ dummy_driver_new (jack_client_t * client,
 	driver->sample_rate = sample_rate;
 	driver->period_size = period_size;
 	driver->wait_time   = wait_time;
+	driver->next_time   = 0;
 	driver->last_wait_ust = 0;
 
 	driver->capture_channels  = capture_ports;
diff --git a/drivers/dummy/dummy_driver.h b/drivers/dummy/dummy_driver.h
index 57f6e48..7fd9d22 100644
--- a/drivers/dummy/dummy_driver.h
+++ b/drivers/dummy/dummy_driver.h
@@ -36,6 +36,7 @@ struct _dummy_driver
     jack_nframes_t  sample_rate;
     jack_nframes_t  period_size;
     unsigned long   wait_time;
+    jack_time_t     next_time;
 
     unsigned int    capture_channels;
     unsigned int    playback_channels;