From 554a34fb958cfa15c00a81671a72079cae00ca5f Mon Sep 17 00:00:00 2001 From: Max Kellermann Date: Sun, 8 Mar 2009 03:55:01 +0100 Subject: alsa: better period_time default value for high sample rates The default values for buffer_time and period_time were both capped by the hardware limits on practically all chips. The result was a period_time which was half as big as the buffer_time. On some chips, this led to lots of underruns when using a high sample rate (192 kHz), because MPD had very little time to send new samples to ALSA. A period time which is one fourth of the buffer time turned out to be much better. If no period_time is configured, see how much buffer_time the hardware accepts, and try to configure one fourth of it as period_time, instead of hard-coding the default period_time value. This is yet another attempt to provide a solution which is valid for all sound chips. Using the SND_PCM_NONBLOCK flag also seemed to solve the underruns, but put a lot more CPU load to MPD. --- src/output/alsa_plugin.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) (limited to 'src') diff --git a/src/output/alsa_plugin.c b/src/output/alsa_plugin.c index fb748fdec..489d4f32b 100644 --- a/src/output/alsa_plugin.c +++ b/src/output/alsa_plugin.c @@ -32,7 +32,6 @@ static const char default_device[] = "default"; enum { MPD_ALSA_BUFFER_TIME_US = 500000, - MPD_ALSA_PERIOD_TIME_US = 125000, }; #define MPD_ALSA_RETRY_NR 5 @@ -118,8 +117,7 @@ alsa_configure(struct alsa_data *ad, const struct config_param *param) ad->buffer_time = config_get_block_unsigned(param, "buffer_time", MPD_ALSA_BUFFER_TIME_US); - ad->period_time = config_get_block_unsigned(param, "period_time", - MPD_ALSA_PERIOD_TIME_US); + ad->period_time = config_get_block_unsigned(param, "period_time", 0); #ifdef SND_PCM_NO_AUTO_RESAMPLE if (!config_get_block_bool(param, "auto_resample", true)) @@ -313,6 +311,13 @@ configure_hw: goto error; } + if (period_time_ro == 0 && buffer_time >= 10000) { + period_time_ro = period_time = buffer_time / 4; + + g_debug("default period_time = buffer_time/4 = %u/4 = %u", + buffer_time, period_time); + } + if (period_time_ro > 0) { period_time = period_time_ro; cmd = "snd_pcm_hw_params_set_period_time_near"; -- cgit v1.2.3