Skip to content

Commit

Permalink
Browse files Browse the repository at this point in the history
Editors Note: The original patch was modified to use SDL_Delay() inst…
…ead of

              nanosleep because nanosleep may not be portable to all systems
              using SDL with the ALSA backend.  This may be a moot point with
              the switch to blocking writes anyway...

Date: Sat, 27 Dec 2003 21:47:36 +0100
From: Michel Daenzer
To: Debian Bug Tracking System
Subject: [SDL] Bug#225252: [PATCH] ALSA fixes

Package: libsdl1.2debian-all
Version: 1.2.6-2
Severity: normal
Tags: patch

For SDL 1.2.6, the ALSA backend was changed to call snd_pcm_open() with
SND_PCM_NONBLOCK. That's a good idea per se, however, it causes high CPU
usage, interrupted sound and stuttering in some games here. Taking a nanosleep
whenever snd_pcm_writei() returns -EAGAIN fixes this, but I think it's more
efficient to use blocking mode for the actual sound playback. Feedback from the
SDL and ALSA lists appreciated.

The patch also fixes the default ALSA device to be used.
  • Loading branch information
slouken committed Jan 4, 2004
1 parent 8bce08f commit cff4587
Showing 1 changed file with 7 additions and 2 deletions.
9 changes: 7 additions & 2 deletions src/audio/alsa/SDL_alsa_audio.c
Expand Up @@ -45,7 +45,7 @@
#define DRIVER_NAME "alsa"

/* The default ALSA audio driver */
#define DEFAULT_DEVICE "plughw:0,0"
#define DEFAULT_DEVICE "default"

/* Audio driver functions */
static int ALSA_OpenAudio(_THIS, SDL_AudioSpec *spec);
Expand Down Expand Up @@ -146,17 +146,19 @@ static void ALSA_PlayAudio(_THIS)
int status;
int sample_len;
signed short *sample_buf;

sample_len = this->spec.samples;
sample_buf = (signed short *)mixbuf;
while ( sample_len > 0 ) {
status = snd_pcm_writei(pcm_handle, sample_buf, sample_len);
if ( status < 0 ) {
if ( status == -EAGAIN ) {
SDL_Delay(1);
continue;
}
if ( status == -ESTRPIPE ) {
do {
SDL_Delay(1);
status = snd_pcm_resume(pcm_handle);
} while ( status == -EAGAIN );
}
Expand Down Expand Up @@ -316,6 +318,9 @@ static int ALSA_OpenAudio(_THIS, SDL_AudioSpec *spec)
/* Get the parent process id (we're the parent of the audio thread) */
parent = getpid();

/* Switch to blocking mode for playback */
snd_pcm_nonblock(pcm_handle, 0);

/* We're ready to rock and roll. :-) */
return(0);
}

0 comments on commit cff4587

Please sign in to comment.