X-Git-Url: http://git.tuebingen.mpg.de/?a=blobdiff_plain;f=alsa_write.c;h=358b6346581dc813815419592823046231eab61f;hb=3ac2a1478a7ad965bb48bec7d21aa49affd95d29;hp=e75fa23067380244cd451eedc1c523fae3fb004f;hpb=393c52c9e726570a2ee287e9f7e103b619a28f73;p=paraslash.git

diff --git a/alsa_write.c b/alsa_write.c
index e75fa230..358b6346 100644
--- a/alsa_write.c
+++ b/alsa_write.c
@@ -50,6 +50,8 @@ struct private_alsa_write_data {
 	snd_pcm_format_t sample_format;
 	/* The number of channels, again determined like \a sample_rate. */
 	unsigned channels;
+	/* time until buffer underrun occurs, in microseconds */
+	unsigned buffer_time;
 	struct timeval drain_barrier;
 	/* File descriptor for select(). */
 	int poll_fd;
@@ -77,7 +79,6 @@ static int alsa_init(struct private_alsa_write_data *pad,
 	snd_pcm_uframes_t start_threshold, stop_threshold;
 	snd_pcm_uframes_t buffer_size, period_size;
 	snd_output_t *output_log;
-	unsigned buffer_time;
 	int ret;
 	const char *msg;
 	unsigned period_time;
@@ -114,18 +115,18 @@ static int alsa_init(struct private_alsa_write_data *pad,
 	if (ret < 0)
 		goto fail;
 	msg = "unable to get buffer time";
-	ret = snd_pcm_hw_params_get_buffer_time_max(hwparams, &buffer_time,
+	ret = snd_pcm_hw_params_get_buffer_time_max(hwparams, &pad->buffer_time,
 		NULL);
-	if (ret < 0 || buffer_time == 0)
+	if (ret < 0 || pad->buffer_time == 0)
 		goto fail;
 	/* buffer at most 500 milliseconds */
-	buffer_time = PARA_MIN(buffer_time, 500U * 1000U);
+	pad->buffer_time = PARA_MIN(pad->buffer_time, 500U * 1000U);
 	msg = "could not set buffer time";
 	ret = snd_pcm_hw_params_set_buffer_time_near(pad->handle, hwparams,
-		&buffer_time, NULL);
+		&pad->buffer_time, NULL);
 	if (ret < 0)
 		goto fail;
-	period_time = buffer_time / 4;
+	period_time = pad->buffer_time / 4;
 	msg = "could not set period time";
 	ret = snd_pcm_hw_params_set_period_time_near(pad->handle, hwparams,
 		&period_time, 0);
@@ -221,6 +222,8 @@ static void alsa_write_pre_select(struct sched *s, struct task *t)
 		sched_request_barrier_or_min_delay(&pad->drain_barrier, s);
 		return;
 	}
+	/* wait at most 50% of the buffer time */
+	sched_request_timeout_ms(pad->buffer_time / 2 / 1000, s);
 	ret = snd_pcm_poll_descriptors(pad->handle, &pfd, 1);
 	if (ret < 0) {
 		PARA_ERROR_LOG("could not get alsa poll fd: %s\n",
@@ -309,21 +312,13 @@ again:
 		wn->min_iqs = pad->bytes_per_frame;
 		goto again;
 	}
-	if (pad->poll_fd < 0 || !FD_ISSET(pad->poll_fd, &s->rfds))
-		return 0;
 	frames = bytes / pad->bytes_per_frame;
 	frames = snd_pcm_writei(pad->handle, data, frames);
 	if (frames == 0 || frames == -EAGAIN) {
-		/*
-		 * The alsa poll fd was ready for IO but we failed to write to
-		 * the alsa handle. This means another event is pending. We
-		 * don't care about that but we have to dispatch the event in
-		 * order to avoid a busy loop. So we simply read from the poll
-		 * fd.
-		 */
 		char buf[100];
-		if (read(pad->poll_fd, buf, 100))
-			do_nothing;
+		if (pad->poll_fd >= 0 && FD_ISSET(pad->poll_fd, &s->rfds))
+			if (read(pad->poll_fd, buf, 100))
+				do_nothing;
 		return 0;
 	}
 	if (frames > 0) {