X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=alsa_write.c;h=43b26868bef5abdf3d9268cc93f7b1ca8524693f;hp=11e4504d79e78c8e613fc33baec80ef168e72f20;hb=56d75bd90d78cf44cd3984ce2a45627ef5646d38;hpb=4eb15d1cf4dbd3b2962cdd3930e2d9559acb248e

diff --git a/alsa_write.c b/alsa_write.c
index 11e4504d..43b26868 100644
--- a/alsa_write.c
+++ b/alsa_write.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2005-2013 Andre Noll <maan@systemlinux.org>
+ * Copyright (C) 2005 Andre Noll <maan@tuebingen.mpg.de>
  *
  * Licensed under the GPL v2. For licencing details see COPYING.
  */
@@ -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 milliseconds */
+	unsigned buffer_time;
 	struct timeval drain_barrier;
 	/* File descriptor for select(). */
 	int poll_fd;
@@ -77,9 +79,9 @@ 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;
 
 	PARA_INFO_LOG("opening %s\n", conf->device_arg);
 	msg = "unable to open pcm";
@@ -112,18 +114,21 @@ static int alsa_init(struct private_alsa_write_data *pad,
 		&pad->sample_rate, NULL);
 	if (ret < 0)
 		goto fail;
-	msg = "unable to get buffer time";
-	ret = snd_pcm_hw_params_get_buffer_time_max(hwparams, &buffer_time,
-		NULL);
-	if (ret < 0 || buffer_time == 0)
-		goto fail;
-	/* buffer at most 500 milliseconds */
-	buffer_time = PARA_MIN(buffer_time, 500U * 1000U);
+	/* alsa wants microseconds */
+	pad->buffer_time = conf->buffer_time_arg * 1000;
 	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;
+	pad->buffer_time /= 1000; /* we prefer milliseconds */
+	period_time = pad->buffer_time * 250; /* buffer time / 4 */
+	msg = "could not set period time";
+	ret = snd_pcm_hw_params_set_period_time_near(pad->handle, hwparams,
+		&period_time, 0);
+	if (ret < 0)
+		goto fail;
+
 	msg = "unable to install hw params";
 	ret = snd_pcm_hw_params(pad->handle, hwparams);
 	if (ret < 0)
@@ -194,10 +199,10 @@ fail:
 	return -E_ALSA;
 }
 
-static void alsa_write_pre_select(struct sched *s, struct task *t)
+static void alsa_write_pre_select(struct sched *s, void *context)
 {
 	struct pollfd pfd;
-	struct writer_node *wn = container_of(t, struct writer_node, task);
+	struct writer_node *wn = context;
 	struct private_alsa_write_data *pad = wn->private_data;
 	int ret = btr_node_status(wn->btrn, wn->min_iqs, BTR_NT_LEAF);
 
@@ -213,6 +218,8 @@ 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, s);
 	ret = snd_pcm_poll_descriptors(pad->handle, &pfd, 1);
 	if (ret < 0) {
 		PARA_ERROR_LOG("could not get alsa poll fd: %s\n",
@@ -241,10 +248,9 @@ static void alsa_close(struct writer_node *wn)
 	free(pad);
 }
 
-static int alsa_write_post_select(__a_unused struct sched *s,
-		struct task *t)
+static int alsa_write_post_select(__a_unused struct sched *s, void *context)
 {
-	struct writer_node *wn = container_of(t, struct writer_node, task);
+	struct writer_node *wn = context;
 	struct private_alsa_write_data *pad = wn->private_data;
 	struct btr_node *btrn = wn->btrn;
 	char *data;
@@ -252,7 +258,7 @@ static int alsa_write_post_select(__a_unused struct sched *s,
 	snd_pcm_sframes_t frames;
 	int ret;
 
-	ret = task_get_notification(t);
+	ret = task_get_notification(wn->task);
 	if (ret < 0)
 		goto err;
 again:
@@ -301,21 +307,13 @@ 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) {