audio playback fixes

VoidLink/Stream/Connection.m

@@ -48,6 +48,7 @@ static SDL_AudioDeviceID audioDevice;
 static OPUS_MULTISTREAM_CONFIGURATION audioConfig;
 static void* audioBuffer;
 static float volume = 1.0;
+static bool sysAudioQueueReset = false;
 static int audioFrameSize;
 
 static bool useSystemAudioEngine;
@@ -56,6 +57,8 @@ static AVAudioEngine *audioEngine;
 static AVAudioPlayerNode *audioPlayerNode;
 static AVAudioPCMBuffer *pcmBuffer;
 static AVAudioFormat *audioFormat;
+static int64_t systemAudioScheduledFrames;
+static CFTimeInterval systemAudioLastFlushTime;
 
 static bool muteInBackground;
 static bool fullColorRange;
@@ -64,6 +67,32 @@ static VideoDecoderRenderer* renderer;
 
 static BandwidthTracker *bwTracker;
 
+static int64_t GetSystemAudioQueuedFrames(void)
+{
+    if (audioPlayerNode == nil) {
+        return 0;
+    }
+
+    AVAudioTime *nodeTime = audioPlayerNode.lastRenderTime;
+    if (nodeTime == nil) {
+        return systemAudioScheduledFrames;
+    }
+
+    AVAudioTime *playerTime = [audioPlayerNode playerTimeForNodeTime:nodeTime];
+    if (playerTime == nil) {
+        return systemAudioScheduledFrames;
+    }
+
+    int64_t queuedFrames = systemAudioScheduledFrames - playerTime.sampleTime;
+    return queuedFrames > 0 ? queuedFrames : 0;
+}
+
+static void ResetSystemAudioBackpressureState(void)
+{
+    systemAudioScheduledFrames = 0;
+    systemAudioLastFlushTime = 0;
+}
+
 int DrDecoderSetup(int videoFormat, int width, int height, int redrawRate, void* context, int drFlags)
 {
     [renderer setupWithVideoFormat:videoFormat width:width height:height frameRate:redrawRate fullRange:fullColorRange];
@@ -348,6 +377,7 @@ void ArCleanup(void)
 }
 
 void AudioEngineInit(int sampleRate, int channelCount) {
+    ResetSystemAudioBackpressureState();
     
     audioEngine = [[AVAudioEngine alloc] init];
     audioPlayerNode = [[AVAudioPlayerNode alloc] init];
@@ -426,20 +456,41 @@ void ArDecodeAndPlaySample(char* sampleData, int sampleLength)
         float* fbuf = (float*)audioBuffer;
         
         if(useSystemAudioEngine){
-            // 创建 AVAudioPCMBuffer
+            int64_t maxQueuedFrames = (int64_t)audioConfig.samplesPerFrame * 10;
+            CFTimeInterval now = CACurrentMediaTime();
+            if (GetSystemAudioQueuedFrames() > maxQueuedFrames &&
+                now - systemAudioLastFlushTime >= 5) {
+                // Drop stale local backlog without slowing down upstream packet
+                // consumption, which keeps background playback stable.
+                
+                NSLog(@"sdfasfdsfasdfasfasfasdfasfasfdfasf");
+                
+                sysAudioQueueReset = true;
+                dispatch_time_t delayTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(2 * NSEC_PER_SEC));
+                dispatch_after(dispatch_time(DISPATCH_TIME_NOW, delayTime), dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+                    sysAudioQueueReset = false;
+                });
+
+                [audioPlayerNode reset];
+                ResetSystemAudioBackpressureState();
+                systemAudioLastFlushTime = now;
+            }
+
             AVAudioFrameCount frameCount = decodeLen;
             AVAudioPCMBuffer *buffer = [[AVAudioPCMBuffer alloc] initWithPCMFormat:audioFormat frameCapacity:frameCount];
             buffer.frameLength = frameCount;
             
-            // 拷贝数据到 buffer
             for (int ch = 0; ch < audioConfig.channelCount; ch++) {
                 float *dst = buffer.floatChannelData[ch];
                 for (int i = 0; i < decodeLen; i++) {
-                    dst[i] = fbuf[i * audioConfig.channelCount + ch] * volume; // 非交错数据
+                    dst[i] = fbuf[i * audioConfig.channelCount + ch] * (sysAudioQueueReset ? 0 : volume); // 非交错数据
                 }
             }
-            // 播放
+
-            if(!audioSessionInterrupted) [audioPlayerNode scheduleBuffer:buffer completionHandler:nil];
+            if(!audioSessionInterrupted) {
+                [audioPlayerNode scheduleBuffer:buffer completionHandler:nil];
+                systemAudioScheduledFrames += frameCount;
+            }
         }
         
         else{
@@ -535,6 +586,7 @@ void ClSetControllerLED(uint16_t controllerNumber, uint8_t r, uint8_t g, uint8_t
     // won't be able to acquire it if LiStartConnection is in
     // progress.
     LiInterruptConnection();
+    ResetSystemAudioBackpressureState();
     [audioPlayerNode stop];
     [audioEngine stop];
     [[NSNotificationCenter defaultCenter] removeObserver:self];
@@ -557,6 +609,7 @@ void ClSetControllerLED(uint16_t controllerNumber, uint8_t r, uint8_t g, uint8_t
     switch (type) {
         case AVAudioSessionInterruptionTypeBegan:
             audioSessionInterrupted = true;
+            ResetSystemAudioBackpressureState();
             [audioPlayerNode stop];
             [audioEngine stop];
             break;