Fixes to SDL audio renderer and autodetection support

app/app.pro

@@ -1,4 +1,4 @@
-QT += core quick network quickcontrols2 svg
+QT += core quick network quickcontrols2 svg multimedia
 CONFIG += c++11
 
 unix:!macx {

app/gui/SettingsView.qml

@@ -386,14 +386,10 @@ ScrollView {
                     textRole: "text"
                     model: ListModel {
                         id: audioListModel
-                        // Detection of audio channels only works on Windows
+                        ListElement {
-                        // and even so, it's still unreliable because audio devices
-                        // lie about how many channels they can support. Hide the
-                        // option to autodetect until this is resolved.
-                        /*ListElement {
                             text: "Autodetect"
                             val: StreamingPreferences.AC_AUTO
-                        }*/
+                        }
                         ListElement {
                             text: "Stereo"
                             val: StreamingPreferences.AC_FORCE_STEREO

app/settings/streamingpreferences.cpp

@@ -43,7 +43,7 @@ void StreamingPreferences::reload()
     enableMdns = settings.value(SER_MDNS, true).toBool();
     mouseAcceleration = settings.value(SER_MOUSEACCELERATION, false).toBool();
     audioConfig = static_cast<AudioConfig>(settings.value(SER_AUDIOCFG,
-                                                  static_cast<int>(AudioConfig::AC_FORCE_STEREO)).toInt());
+                                                  static_cast<int>(AudioConfig::AC_AUTO)).toInt());
     videoCodecConfig = static_cast<VideoCodecConfig>(settings.value(SER_VIDEOCFG,
                                                   static_cast<int>(VideoCodecConfig::VCC_AUTO)).toInt());
     videoDecoderSelection = static_cast<VideoDecoderSelection>(settings.value(SER_VIDEODEC,

app/streaming/audio/audio.cpp

@@ -70,8 +70,7 @@ int Session::arInit(int /* audioConfiguration */,
         return -2;
     }
 
-    s_ActiveSession->m_AudioRenderer->prepareForPlayback(opusConfig);
+    if (!s_ActiveSession->m_AudioRenderer->prepareForPlayback(opusConfig)) {
-    if (s_ActiveSession->m_AudioRenderer == nullptr) {
         delete s_ActiveSession->m_AudioRenderer;
         opus_multistream_decoder_destroy(s_ActiveSession->m_OpusDecoder);
         return -3;
@@ -86,12 +85,21 @@ int Session::arInit(int /* audioConfiguration */,
 
 void Session::arCleanup()
 {
-    delete s_ActiveSession->m_AudioRenderer;
+    // m_AudioRenderer is deleted in cleanupAudioRenderer()
 
     opus_multistream_decoder_destroy(s_ActiveSession->m_OpusDecoder);
     s_ActiveSession->m_OpusDecoder = nullptr;
 }
 
+// This is called on the main thread
+void Session::cleanupAudioRendererOnMainThread()
+{
+    SDL_AtomicLock(&m_AudioRendererLock);
+    delete m_AudioRenderer;
+    m_AudioRenderer = nullptr;
+    SDL_AtomicUnlock(&m_AudioRendererLock);
+}
+
 void Session::arDecodeAndPlaySample(char* sampleData, int sampleLength)
 {
     int samplesDecoded;
@@ -103,9 +111,13 @@ void Session::arDecodeAndPlaySample(char* sampleData, int sampleLength)
                                              SAMPLES_PER_FRAME,
                                              0);
     if (samplesDecoded > 0) {
+        SDL_AtomicLock(&s_ActiveSession->m_AudioRendererLock);
+        if (s_ActiveSession->m_AudioRenderer != nullptr) {
             s_ActiveSession->m_AudioRenderer->submitAudio(s_ActiveSession->m_OpusDecodeBuffer,
                                                           static_cast<int>(sizeof(short) *
                                                             samplesDecoded *
                                                             s_ActiveSession->m_AudioConfig.channelCount));
         }
+        SDL_AtomicUnlock(&s_ActiveSession->m_AudioRendererLock);
+    }
 }

app/streaming/audio/renderers/sdlaud.cpp

@@ -3,6 +3,7 @@
 #include <Limelight.h>
 #include <SDL.h>
 
+#include <QAudioDeviceInfo>
 #include <QtGlobal>
 
 #define MIN_QUEUED_FRAMES 2
@@ -10,69 +11,31 @@
 #define STOP_THE_WORLD_LIMIT 20
 #define DROP_RATIO_DENOM 32
 
+// Detecting this with SDL is quite problematic, so we'll use Qt's
+// multimedia framework to do so. It appears to be actually
+// accurate on Linux and macOS, unlike using SDL and relying
+// on a channel change in the format received.
 int SdlAudioRenderer::detectAudioConfiguration()
 {
-    SDL_AudioSpec want, have;
+    int preferredChannelCount = QAudioDeviceInfo::defaultOutputDevice().preferredFormat().channelCount();
-    SDL_AudioDeviceID dev;
-    int ret;
-
-    if (SDL_InitSubSystem(SDL_INIT_AUDIO) != 0) {
-        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
-                     "SDL_InitSubSystem(SDL_INIT_AUDIO) failed: %s",
-                     SDL_GetError());
-        return AUDIO_CONFIGURATION_STEREO;
-    }
-
-    SDL_zero(want);
-    want.freq = 48000;
-    want.format = AUDIO_S16;
-    want.channels = 6;
-    want.samples = 1024;
-
-    // Try to open for 5.1 surround sound, but allow SDL to tell us that's
-    // not available.
-    dev = SDL_OpenAudioDevice(NULL, 0, &want, &have, SDL_AUDIO_ALLOW_CHANNELS_CHANGE);
-    if (dev == 0) {
-        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
-                     "Failed to open audio device");
-        // We'll probably have issues during audio stream init, but we'll
-        // try anyway
-        ret = AUDIO_CONFIGURATION_STEREO;
-        goto Exit;
-    }
-
-    SDL_CloseAudioDevice(dev);
 
     SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
-                "Audio device has %d channels", have.channels);
+                "Audio output device prefers %d channel configuration",
+                preferredChannelCount);
 
-    if (have.channels > 2) {
+    // We can better downmix 5.1 to quad than we can upmix stereo
-        // We don't support quadraphonic or 7.1 surround, but SDL
+    if (preferredChannelCount > 2) {
-        // should be able to downmix or upmix better from 5.1 than
+        return AUDIO_CONFIGURATION_51_SURROUND;
-        // from stereo, so use 5.1 in non-stereo cases.
-        ret = AUDIO_CONFIGURATION_51_SURROUND;
     }
     else {
-        ret = AUDIO_CONFIGURATION_STEREO;
+        return AUDIO_CONFIGURATION_STEREO;
     }
-
-Exit:
-    SDL_QuitSubSystem(SDL_INIT_AUDIO);
-    return ret;
 }
 
 bool SdlAudioRenderer::testAudio(int audioConfiguration)
 {
     SDL_AudioSpec want, have;
     SDL_AudioDeviceID dev;
-    bool ret;
-
-    if (SDL_InitSubSystem(SDL_INIT_AUDIO) != 0) {
-        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
-                     "Audio test - SDL_InitSubSystem(SDL_INIT_AUDIO) failed: %s",
-                     SDL_GetError());
-        return false;
-    }
 
     SDL_zero(want);
     want.freq = 48000;
@@ -88,8 +51,7 @@ bool SdlAudioRenderer::testAudio(int audioConfiguration)
         break;
     default:
         SDL_assert(false);
-        ret = false;
+        return false;
-        goto Exit;
     }
 
     // Test audio device for functionality
@@ -98,8 +60,7 @@ bool SdlAudioRenderer::testAudio(int audioConfiguration)
         SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
                      "Audio test - Failed to open audio device: %s",
                      SDL_GetError());
-        ret = false;
+        return false;
-        goto Exit;
     }
 
     SDL_CloseAudioDevice(dev);
@@ -107,12 +68,7 @@ bool SdlAudioRenderer::testAudio(int audioConfiguration)
     SDL_LogInfo(SDL_LOG_CATEGORY_APPLICATION,
                 "Audio test - Successful with %d channels",
                 want.channels);
-
+    return true;
-    ret = true;
-
-Exit:
-    SDL_QuitSubSystem(SDL_INIT_AUDIO);
-    return ret;
 }
 
 SdlAudioRenderer::SdlAudioRenderer()
@@ -123,20 +79,18 @@ SdlAudioRenderer::SdlAudioRenderer()
       m_SampleIndex(0),
       m_BaselinePendingData(0)
 {
-
-}
-
-bool SdlAudioRenderer::prepareForPlayback(const OPUS_MULTISTREAM_CONFIGURATION* opusConfig)
-{
-    SDL_AudioSpec want, have;
-
     SDL_assert(!SDL_WasInit(SDL_INIT_AUDIO));
     if (SDL_InitSubSystem(SDL_INIT_AUDIO) != 0) {
         SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
                      "SDL_InitSubSystem(SDL_INIT_AUDIO) failed: %s",
                      SDL_GetError());
-        return -1;
+        SDL_assert(SDL_WasInit(SDL_INIT_AUDIO));
     }
+}
+
+bool SdlAudioRenderer::prepareForPlayback(const OPUS_MULTISTREAM_CONFIGURATION* opusConfig)
+{
+    SDL_AudioSpec want, have;
 
     SDL_zero(want);
     want.freq = opusConfig->sampleRate;
@@ -155,7 +109,7 @@ bool SdlAudioRenderer::prepareForPlayback(const OPUS_MULTISTREAM_CONFIGURATION*
                      "Failed to open audio device: %s",
                      SDL_GetError());
         SDL_QuitSubSystem(SDL_INIT_AUDIO);
-        return -1;
+        return false;
     }
 
     // SDL counts pending samples in the queued
@@ -182,14 +136,16 @@ bool SdlAudioRenderer::prepareForPlayback(const OPUS_MULTISTREAM_CONFIGURATION*
     // Start playback
     SDL_PauseAudioDevice(m_AudioDevice, 0);
 
-    return 0;
+    return true;
 }
 
 SdlAudioRenderer::~SdlAudioRenderer()
 {
+    if (m_AudioDevice != 0) {
         // Stop playback
         SDL_PauseAudioDevice(m_AudioDevice, 1);
         SDL_CloseAudioDevice(m_AudioDevice);
+    }
 
     SDL_QuitSubSystem(SDL_INIT_AUDIO);
     SDL_assert(!SDL_WasInit(SDL_INIT_AUDIO));

app/streaming/session.cpp

@@ -279,7 +279,8 @@ Session::Session(NvComputer* computer, NvApp& app)
       m_DisplayOriginY(0),
       m_PendingWindowedTransition(false),
       m_OpusDecoder(nullptr),
-      m_AudioRenderer(nullptr)
+      m_AudioRenderer(nullptr),
+      m_AudioRendererLock(0)
 {
 
 }
@@ -1110,6 +1111,9 @@ DispatchDeferredCleanup:
     m_VideoDecoder = nullptr;
     SDL_AtomicUnlock(&m_DecoderLock);
 
+    // Destroy the audio renderer which must also be done on the main thread
+    cleanupAudioRendererOnMainThread();
+
     SDL_DestroyWindow(m_Window);
     if (iconSurface != nullptr) {
         SDL_FreeSurface(iconSurface);

app/streaming/session.hpp

@@ -54,6 +54,8 @@ private:
 
     int detectAudioConfiguration();
 
+    void cleanupAudioRendererOnMainThread();
+
     bool testAudio(int audioConfiguration);
 
     void getWindowDimensions(int& x, int& y,
@@ -124,6 +126,7 @@ private:
     short m_OpusDecodeBuffer[MAX_CHANNELS * SAMPLES_PER_FRAME];
     IAudioRenderer* m_AudioRenderer;
     OPUS_MULTISTREAM_CONFIGURATION m_AudioConfig;
+    SDL_SpinLock m_AudioRendererLock;
 
     static AUDIO_RENDERER_CALLBACKS k_AudioCallbacks;
     static CONNECTION_LISTENER_CALLBACKS k_ConnCallbacks;