Cap queued audio at 40 ms on Steam Link

app/streaming/audio/audio.cpp

@@ -156,16 +156,22 @@ void Session::arDecodeAndPlaySample(char* sampleData, int sampleLength)
                                                  (short*)buffer,
                                                  desiredSize / sizeof(short) / s_ActiveSession->m_AudioConfig.channelCount,
                                                  0);
+
+        // Update desiredSize with the number of bytes actually populated by the decoding operation
         if (samplesDecoded > 0) {
             SDL_assert(desiredSize >= sizeof(short) * samplesDecoded * s_ActiveSession->m_AudioConfig.channelCount);
             desiredSize = sizeof(short) * samplesDecoded * s_ActiveSession->m_AudioConfig.channelCount;
-            if (!s_ActiveSession->m_AudioRenderer->submitAudio(desiredSize)) {
-                SDL_LogWarn(SDL_LOG_CATEGORY_APPLICATION,
-                            "Reinitializing audio renderer after failure");
+        }
+        else {
+            desiredSize = 0;
+        }
 
-                delete s_ActiveSession->m_AudioRenderer;
-                s_ActiveSession->m_AudioRenderer = nullptr;
-            }
+        if (!s_ActiveSession->m_AudioRenderer->submitAudio(desiredSize)) {
+            SDL_LogWarn(SDL_LOG_CATEGORY_APPLICATION,
+                        "Reinitializing audio renderer after failure");
+
+            delete s_ActiveSession->m_AudioRenderer;
+            s_ActiveSession->m_AudioRenderer = nullptr;
         }
     }
 

app/streaming/audio/renderers/renderer.h

@@ -2,9 +2,6 @@
 
 #include <Limelight.h>
 
-#define MAX_CHANNELS 6
-#define SAMPLES_PER_FRAME 240
-
 class IAudioRenderer
 {
 public:

app/streaming/audio/renderers/sdlaud.cpp

@@ -87,6 +87,11 @@ void* SdlAudioRenderer::getAudioBuffer(int*)
 
 bool SdlAudioRenderer::submitAudio(int bytesWritten)
 {
+    if (bytesWritten == 0) {
+        // Nothing to do
+        return true;
+    }
+
     if (SDL_QueueAudio(m_AudioDevice, m_AudioBuffer, bytesWritten) < 0) {
         SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
                      "Failed to queue audio sample: %s",

app/streaming/audio/renderers/slaud.cpp

@@ -4,7 +4,8 @@
 
 SLAudioRenderer::SLAudioRenderer()
     : m_AudioContext(nullptr),
-      m_AudioStream(nullptr)
+      m_AudioStream(nullptr),
+      m_AudioBuffer(nullptr)
 {
     SLAudio_SetLogFunction(SLAudioRenderer::slLogCallback, nullptr);
 }
@@ -18,6 +19,7 @@ bool SLAudioRenderer::prepareForPlayback(const OPUS_MULTISTREAM_CONFIGURATION* o
         return false;
     }
 
+    m_FrameDuration = opusConfig->samplesPerFrame / 48;
     m_AudioBufferSize = opusConfig->samplesPerFrame * sizeof(short) * opusConfig->channelCount;
     m_AudioStream = SLAudio_CreateStream(m_AudioContext,
                                          opusConfig->sampleRate,
@@ -31,7 +33,8 @@ bool SLAudioRenderer::prepareForPlayback(const OPUS_MULTISTREAM_CONFIGURATION* o
     }
 
     SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
-                "Using SLAudio renderer");
+                "Using SLAudio renderer with %d ms frames",
+                m_FrameDuration);
 
     return true;
 }
@@ -39,11 +42,21 @@ bool SLAudioRenderer::prepareForPlayback(const OPUS_MULTISTREAM_CONFIGURATION* o
 void* SLAudioRenderer::getAudioBuffer(int* size)
 {
     SDL_assert(*size == m_AudioBufferSize);
-    return SLAudio_BeginFrame(m_AudioStream);
+
+    if (m_AudioBuffer == nullptr) {
+        m_AudioBuffer = SLAudio_BeginFrame(m_AudioStream);
+    }
+
+    return m_AudioBuffer;
 }
 
 SLAudioRenderer::~SLAudioRenderer()
 {
+    if (m_AudioBuffer != nullptr) {
+        memset(m_AudioBuffer, 0, m_AudioBufferSize);
+        SLAudio_SubmitFrame(m_AudioStream);
+    }
+
     if (m_AudioStream != nullptr) {
         SLAudio_FreeStream(m_AudioStream);
     }
@@ -53,9 +66,24 @@ SLAudioRenderer::~SLAudioRenderer()
     }
 }
 
-bool SLAudioRenderer::submitAudio(int)
+bool SLAudioRenderer::submitAudio(int bytesWritten)
 {
-    SLAudio_SubmitFrame(m_AudioStream);
+    if (bytesWritten == 0) {
+        // This buffer will be reused next time
+        return true;
+    }
+
+    // Only allow up to 40 ms of queued audio
+    if (LiGetPendingAudioFrames() * m_FrameDuration < 40) {
+        SLAudio_SubmitFrame(m_AudioStream);
+        m_AudioBuffer = nullptr;
+    }
+    else {
+        SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
+                    "Too many queued audio frames: %d",
+                    LiGetPendingAudioFrames());
+    }
+
     return true;
 }
 

app/streaming/audio/renderers/slaud.h

@@ -22,5 +22,7 @@ private:
     CSLAudioContext* m_AudioContext;
     CSLAudioStream* m_AudioStream;
 
+    void* m_AudioBuffer;
     int m_AudioBufferSize;
+    int m_FrameDuration;
 };

app/streaming/audio/renderers/soundioaudiorenderer.cpp

@@ -303,6 +303,11 @@ bool SoundIoAudioRenderer::submitAudio(int bytesWritten)
         return false;
     }
 
+    if (bytesWritten == 0) {
+        // Nothing to do
+        return true;
+    }
+
     // Flush events to update with new device arrivals
     soundio_flush_events(m_SoundIo);
 

moonlight-common-c/moonlight-common-c

@@ -1 +1 @@
-Subproject commit 59481c085a7f774c5d30374636f8bc75da7c676c
+Subproject commit dffe51e885bcb5e09f90288f30268846f08c25de