Option to fix bug #851

For some people setting the period size works better (and is what SDL 1.2.13 did), but for most people it's the same or worse.  You can use an environment variable to pick which one you want.

--HG--
branch : SDL-1.2
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/branches/SDL-1.2%404099

src/audio/alsa/SDL_alsa_audio.c

@@ -43,8 +43,6 @@
 /* The tag name used by ALSA audio */
 #define DRIVER_NAME         "alsa"
 
-/* Whether we should set the buffer size or the period size */
-/*#define SET_PERIOD_SIZE*/
 /*#define DEBUG_PERIOD_SIZE*/
 
 /* Audio driver functions */
@@ -377,9 +375,7 @@ static int ALSA_OpenAudio(_THIS, SDL_AudioSpec *spec)
 	snd_pcm_format_t     format;
 	snd_pcm_uframes_t    frames;
 	unsigned int         rate;
-#ifdef SET_PERIOD_SIZE
 	unsigned int         periods;
-#endif
 	unsigned int 	     channels;
 	Uint16               test_format;
 
@@ -475,28 +471,33 @@ static int ALSA_OpenAudio(_THIS, SDL_AudioSpec *spec)
 	spec->freq = rate;
 
 	/* Set the buffer size, in samples */
-#ifdef SET_PERIOD_SIZE
-	frames = spec->samples;
-	status = SDL_NAME(snd_pcm_hw_params_set_period_size_near)(pcm_handle, hwparams, &frames, NULL);
-	if ( status < 0 ) {
-		SDL_SetError("Couldn't set period size: %s", SDL_NAME(snd_strerror)(status));
-		ALSA_CloseAudio(this);
-		return(-1);
-	}
+	if (getenv("SDL_AUDIO_ALSA_SET_PERIOD_SIZE")) {
+		frames = spec->samples;
+		status = SDL_NAME(snd_pcm_hw_params_set_period_size_near)(pcm_handle, hwparams, &frames, NULL);
+		if ( status < 0 ) {
+			SDL_SetError("Couldn't set period size: %s", SDL_NAME(snd_strerror)(status));
+			ALSA_CloseAudio(this);
+			return(-1);
+		}
 
-	spec->samples = frames;
+		spec->samples = frames;
 
-	periods = 2;
-	status = SDL_NAME(snd_pcm_hw_params_set_periods_near)(pcm_handle, hwparams, &periods, NULL);
-	if ( status < 0 ) {
-		SDL_SetError("Couldn't set period count: %s", SDL_NAME(snd_strerror)(status));
-		ALSA_CloseAudio(this);
-		return(-1);
+		periods = 2;
+		status = SDL_NAME(snd_pcm_hw_params_set_periods_near)(pcm_handle, hwparams, &periods, NULL);
+		if ( status < 0 ) {
+			SDL_SetError("Couldn't set period count: %s", SDL_NAME(snd_strerror)(status));
+			ALSA_CloseAudio(this);
+			return(-1);
+		}
+	} else {
+		frames = spec->samples * 2;
+		status = SDL_NAME(snd_pcm_hw_params_set_buffer_size_near)(pcm_handle, hwparams, &frames);
+		if ( status < 0 ) {
+			SDL_SetError("Couldn't set buffer size: %s", SDL_NAME(snd_strerror)(status));
+			ALSA_CloseAudio(this);
+			return(-1);
+		}
 	}
-#else
-	frames = spec->samples * 2;
-	status = SDL_NAME(snd_pcm_hw_params_set_buffer_size_near)(pcm_handle, hwparams, &frames);
-#endif
 
 	/* "set" the hardware with the desired parameters */
 	status = SDL_NAME(snd_pcm_hw_params)(pcm_handle, hwparams);