Fast ramp-up of volume on starting, to avoid 'click'

git-svn-id: svn://cook.msm.cam.ac.uk:745/thrust3d/thrust3d@117 84d2e878-0bd5-11dd-ad15-13eda11d74c5

1 files changed, 16 insertions, 0 deletions

diff --git a/src/audio.c b/src/audio.c
index 6735665..31646f0 100644
--- a/src/audio.c
+++ b/src/audio.c
@@ -70,6 +70,20 @@ static void audio_mix(void *data, Uint8 *stream8, int len) {
 		
 	}
 	
+	/* Fast ramp-up of volume when starting program, avoids 'click' */
+	if ( a->startup ) {
+		for ( j=0; j<len; j++ ) {
+			stream[j] *= a->startup_volume;
+			a->startup_volume += 0.001;
+			if ( a->startup_volume > 1.0 ) {
+				if ( a->startup ) printf("AU: Finished startup ramp.\n");
+				a->startup = 0;
+				a->startup_volume = 1.0;
+			}
+		}
+		
+	}
+	
 	if ( a->debug && (clip_count > 0) ) printf("AU: Clipped %i samples.\n", clip_count);
 	
 }
@@ -132,6 +146,8 @@ AudioContext *audio_setup(int debug) {
 	
 	/* Initialise audio context */
 	a->debug = debug;
+	a->startup = 1;
+	a->startup_volume = 0.0;
 	for ( i=0; i<AUDIO_MAX_SOUNDS; i++ ) {
 		a->sounds[i].inuse = 0;
 	}