X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=alsa_write.c;h=e75fa23067380244cd451eedc1c523fae3fb004f;hp=0824640b9560d72a1eb886a355c3f07e5271681f;hb=393c52c9e726570a2ee287e9f7e103b619a28f73;hpb=aa4a8d9c0f08687618dfcf96bc0c553ef17fbc1d

diff --git a/alsa_write.c b/alsa_write.c
index 0824640b..e75fa230 100644
--- a/alsa_write.c
+++ b/alsa_write.c
@@ -34,16 +34,21 @@ struct private_alsa_write_data {
 	snd_pcm_t *handle;
 	/** Determined and set by alsa_init(). */
 	int bytes_per_frame;
-	/**
-	 * The sample rate given by command line option or the decoder
-	 * of the writer node group.
+	/*
+	 * If the sample rate is not given at the command line and no wav
+	 * header was detected, the btr exec mechanism is employed to query the
+	 * ancestor buffer tree nodes for this information. In a typical setup
+	 * the decoder passes the sample rate back to the alsa writer.
+	 *
+	 *  \sa \ref btr_exec_up().
 	 */
 	unsigned sample_rate;
-	snd_pcm_format_t sample_format;
-	/**
-	 * The number of channels, given by command line option or the
-	 * decoder of the writer node group.
+	/*
+	 * The sample format (8/16 bit, signed/unsigned, little/big endian) is
+	 * determined in the same way as the \a sample_rate.
 	 */
+	snd_pcm_format_t sample_format;
+	/* The number of channels, again determined like \a sample_rate. */
 	unsigned channels;
 	struct timeval drain_barrier;
 	/* File descriptor for select(). */
@@ -75,6 +80,7 @@ static int alsa_init(struct private_alsa_write_data *pad,
 	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";
@@ -119,6 +125,13 @@ static int alsa_init(struct private_alsa_write_data *pad,
 		&buffer_time, NULL);
 	if (ret < 0)
 		goto fail;
+	period_time = 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)
@@ -166,15 +179,16 @@ static int alsa_init(struct private_alsa_write_data *pad,
 	if (ret == 0) {
 		char *buf, *p;
 		size_t sz;
-		PARA_INFO_LOG("dumping alsa configuration\n");
+		PARA_DEBUG_LOG("dumping alsa configuration\n");
 		snd_pcm_dump(pad->handle, output_log);
+		snd_pcm_hw_params_dump(hwparams, output_log);
 		sz = snd_output_buffer_string(output_log, &buf);
 		for (p = buf; p < buf + sz;) {
 			char *q = memchr(p, '\n', buf + sz - p);
 			if (!q)
 				break;
 			*q = '\0';
-			PARA_INFO_LOG("%s\n", p);
+			PARA_DEBUG_LOG("%s\n", p);
 			p = q + 1;
 		}
 		snd_output_close(output_log);