Fix Steam Link audio latency cap

app/streaming/audio/renderers/slaud.cpp

@@ -19,6 +19,10 @@ bool SLAudioRenderer::prepareForPlayback(const OPUS_MULTISTREAM_CONFIGURATION* o
         return false;
     }
 
+    // This number is pretty conservative (especially for surround), but
+    // it's hard to avoid since we get crushed by CPU limitations.
+    m_MaxQueuedAudioMs = 40 * opusConfig->channelCount / 2;
+
     m_FrameDuration = opusConfig->samplesPerFrame / 48;
     m_AudioBufferSize = opusConfig->samplesPerFrame * sizeof(short) * opusConfig->channelCount;
     m_AudioStream = SLAudio_CreateStream(m_AudioContext,
@@ -73,8 +77,7 @@ bool SLAudioRenderer::submitAudio(int bytesWritten)
         return true;
     }
 
-    // Only allow up to 40 ms of queued audio
-    if (LiGetPendingAudioFrames() * m_FrameDuration < 40) {
+    if (LiGetPendingAudioFrames() * m_FrameDuration < m_MaxQueuedAudioMs) {
         SLAudio_SubmitFrame(m_AudioStream);
         m_AudioBuffer = nullptr;
     }

app/streaming/audio/renderers/slaud.h

@@ -25,4 +25,5 @@ private:
     void* m_AudioBuffer;
     int m_AudioBufferSize;
     int m_FrameDuration;
+    int m_MaxQueuedAudioMs;
 };

app/streaming/session.cpp

@@ -49,11 +49,13 @@ AUDIO_RENDERER_CALLBACKS Session::k_AudioCallbacks = {
     nullptr,
     Session::arCleanup,
     Session::arDecodeAndPlaySample,
-    CAPABILITY_DIRECT_SUBMIT |
-#ifdef STEAM_LINK
-    CAPABILITY_SLOW_OPUS_DECODER
+#ifndef STEAM_LINK
+    CAPABILITY_DIRECT_SUBMIT
 #else
-    0
+    // We cannot use direct submit for Steam Link because the
+    // SLAudio renderer needs to look at the audio backlog to
+    // cap latency since playback is a blocking operation.
+    CAPABILITY_SLOW_OPUS_DECODER
 #endif
 };