Add support for start delays to sound groups.

research/ma_engine.c

@@ -38,6 +38,7 @@ int main(int argc, char** argv)
     //ma_engine_sound_group_set_pan(&engine, NULL, -1);
     ma_engine_sound_group_set_pitch(&engine, NULL, 1.0f);
     ma_engine_sound_group_set_fade_in(&engine, NULL, 4000);
+    ma_engine_sound_group_set_start_delay(&engine, NULL, 2000);
     
     /*ma_engine_sound_set_volume(&engine, &sound, 0.25f);*/
     //ma_engine_sound_set_pitch(&engine, &sound, 2.0f);

research/ma_engine.h

@@ -913,6 +913,8 @@ struct ma_sound_group
     ma_engine_effect effect;                /* The main effect for panning, etc. This is set on the mixer at initialisation time. */
     ma_mixer mixer;
     ma_mutex lock;                          /* Only used by ma_engine_sound_init_*() and ma_engine_sound_uninit(). Not used in the mixing thread. */
+    ma_uint64 runningTimeInEngineFrames;    /* The amount of time the sound has been running in engine frames, including start delays. */
+    ma_uint64 startDelayInEngineFrames;
     ma_bool32 isPlaying;                    /* True by default. Sound groups can be stopped with ma_engine_sound_stop() and resumed with ma_engine_sound_start(). Also affects children. */
 };
 
@@ -998,6 +1000,7 @@ MA_API ma_result ma_engine_sound_group_set_effect(ma_engine* pEngine, ma_sound_g
 MA_API ma_result ma_engine_sound_group_set_pan(ma_engine* pEngine, ma_sound_group* pGroup, float pan);
 MA_API ma_result ma_engine_sound_group_set_pitch(ma_engine* pEngine, ma_sound_group* pGroup, float pitch);
 MA_API ma_result ma_engine_sound_group_set_fade_in(ma_engine* pEngine, ma_sound_group* pGroup, ma_uint64 fadeTimeInMilliseconds);
+MA_API ma_result ma_engine_sound_group_set_start_delay(ma_engine* pEngine, ma_sound_group* pGroup, ma_uint64 delayInMilliseconds);
 
 MA_API ma_result ma_engine_listener_set_position(ma_engine* pEngine, ma_vec3 position);
 MA_API ma_result ma_engine_listener_set_rotation(ma_engine* pEngine, ma_quat rotation);
@@ -5336,7 +5339,7 @@ static void ma_engine_mix_sound(ma_engine* pEngine, ma_sound_group* pGroup, ma_s
                     c89atomic_exchange_32(&pSound->atEnd, MA_TRUE); /* This will be set to false in ma_engine_sound_start(). */
                 }
 
-                pSound->runningTimeInEngineFrames += framesProcessed;
+                pSound->runningTimeInEngineFrames += offsetInFrames + framesProcessed;
             } else {
                 /* The sound hasn't started yet. Just keep advancing time forward, but leave the data source alone. */
                 pSound->runningTimeInEngineFrames += frameCount;
@@ -5372,16 +5375,26 @@ static void ma_engine_mix_sound_group(ma_engine* pEngine, ma_sound_group* pGroup
     frameCountOut = frameCount;
     frameCountIn  = frameCount;
 
+    /* If the group is being delayed we don't want to mix anything. */
+    if ((pGroup->runningTimeInEngineFrames + frameCount) > pGroup->startDelayInEngineFrames) {
+        /* We're not delayed so we can mix or seek. In order to get frame-exact playback timing we need to start mixing from an offset. */
+        ma_uint64 offsetInFrames = 0;
+        if (pGroup->startDelayInEngineFrames > pGroup->runningTimeInEngineFrames) {
+            offsetInFrames = pGroup->startDelayInEngineFrames - pGroup->runningTimeInEngineFrames;
+        }
+
+        MA_ASSERT(offsetInFrames < frameCount);
+
         /* We need to loop here to ensure we fill every frame. This won't necessarily be able to be done in one iteration due to resampling within the effect. */
         totalFramesProcessed = 0;
-    while (totalFramesProcessed < frameCount) {
-        frameCountOut = frameCount - totalFramesProcessed;
-        frameCountIn  = frameCount - totalFramesProcessed;
+        while (totalFramesProcessed < (frameCount - offsetInFrames)) {
+            frameCountOut = frameCount - offsetInFrames - totalFramesProcessed;
+            frameCountIn  = frameCount - offsetInFrames - totalFramesProcessed;
 
             /* Before can mix the group we need to mix it's children. */
             result = ma_mixer_begin(&pGroup->mixer, pParentMixer, &frameCountOut, &frameCountIn);
             if (result != MA_SUCCESS) {
-            return;
+                break;
             }
 
             MA_ASSERT(frameCountIn < 0xFFFFFFFF);
@@ -5397,13 +5410,19 @@ static void ma_engine_mix_sound_group(ma_engine* pEngine, ma_sound_group* pGroup
             }
 
             /* Now mix into the parent. */
-        result = ma_mixer_end(&pGroup->mixer, pParentMixer, pFramesOut, totalFramesProcessed);
+            result = ma_mixer_end(&pGroup->mixer, pParentMixer, pFramesOut, offsetInFrames + totalFramesProcessed);
             if (result != MA_SUCCESS) {
-            return;
+                break;
             }
 
             totalFramesProcessed += frameCountOut;
         }
+
+        pGroup->runningTimeInEngineFrames += offsetInFrames + totalFramesProcessed;
+    } else {
+        /* The group hasn't started yet. Just keep advancing time forward, but leave the data source alone. */
+        pGroup->runningTimeInEngineFrames += frameCount;
+    }
 }
 
 static void ma_engine_listener__data_callback_fixed(ma_engine* pEngine, void* pFramesOut, ma_uint32 frameCount)
@@ -6568,6 +6587,21 @@ MA_API ma_result ma_engine_sound_group_set_fade_in(ma_engine* pEngine, ma_sound_
     return ma_dual_fader_set_fade(&pGroup->effect.fader, 0, 0, 1, pGroup->effect.fader.timeInFramesCur, pGroup->effect.fader.timeInFramesCur + (fadeTimeInMilliseconds * pGroup->effect.fader.config.sampleRate) / 1000);
 }
 
+MA_API ma_result ma_engine_sound_group_set_start_delay(ma_engine* pEngine, ma_sound_group* pGroup, ma_uint64 delayInMilliseconds)
+{
+    if (pEngine == NULL) {
+        return MA_INVALID_ARGS;
+    }
+
+    if (pGroup == NULL) {
+        pGroup = &pEngine->masterSoundGroup;
+    }
+
+    pGroup->startDelayInEngineFrames = (pEngine->sampleRate * delayInMilliseconds) / 1000;
+
+    return MA_SUCCESS;
+}
+
 
 MA_API ma_result ma_engine_listener_set_position(ma_engine* pEngine, ma_vec3 position)
 {