From c91662befabd35f448e799c047f202c337d13c32 Mon Sep 17 00:00:00 2001
From: Leon Styhre <leon@leonstyhre.com>
Date: Sat, 29 May 2021 10:52:40 +0200
Subject: [PATCH] Implemented a stable solution to video stream muting and
 clearing.

---
 es-core/src/AudioManager.cpp | 53 +++++++++++++++++++++++++++++-------
 es-core/src/AudioManager.h   |  7 ++++-
 2 files changed, 49 insertions(+), 11 deletions(-)

diff --git a/es-core/src/AudioManager.cpp b/es-core/src/AudioManager.cpp
index 54125f0e6..28073d9a1 100644
--- a/es-core/src/AudioManager.cpp
+++ b/es-core/src/AudioManager.cpp
@@ -19,7 +19,9 @@ std::vector<std::shared_ptr<Sound>> AudioManager::sSoundVector;
 SDL_AudioDeviceID AudioManager::sAudioDevice = 0;
 SDL_AudioSpec AudioManager::sAudioFormat;
 SDL_AudioStream* AudioManager::sConversionStream;
+bool AudioManager::sMuteStream = false;
 bool AudioManager::sHasAudioDevice = true;
+bool AudioManager::mIsClearingStream = false;
 
 AudioManager::AudioManager()
 {
@@ -115,8 +117,6 @@ void AudioManager::init()
     if (Settings::getInstance()->getInt("SoundVolumeVideos") < 0)
         Settings::getInstance()->setInt("SoundVolumeVideos", 0);
 
-    // Use the default sample rate initially, this will possibly be changed by the
-    // video player when a video is started.
     setupAudioStream(sRequestedAudioFormat.freq);
 }
 
@@ -163,10 +163,13 @@ void AudioManager::mixAudio(void* /*unused*/, Uint8* stream, int len)
         soundIt++;
     }
 
-    // Process video stream audio generated by VideoFFmpegComponent.
-    int streamLength = SDL_AudioStreamAvailable(sConversionStream);
+    int streamLength = 0;
 
-    if (streamLength == 0) {
+    // Process video stream audio generated by VideoFFmpegComponent.
+    if (!mIsClearingStream)
+        streamLength = SDL_AudioStreamAvailable(sConversionStream);
+
+    if (streamLength <= 0 || mIsClearingStream) {
         // If nothing is playing, pause the device until there is more audio to output.
         if (!stillPlaying)
             SDL_PauseAudioDevice(sAudioDevice, 1);
@@ -186,7 +189,7 @@ void AudioManager::mixAudio(void* /*unused*/, Uint8* stream, int len)
     int processedLength = SDL_AudioStreamGet(sConversionStream,
             static_cast<void*>(&converted.at(0)), chunkLength);
 
-    if (processedLength == -1) {
+    if (processedLength < 0) {
         LOG(LogError) << "AudioManager::mixAudio(): Couldn't convert sound chunk:";
         LOG(LogError) << SDL_GetError();
         return;
@@ -197,9 +200,17 @@ void AudioManager::mixAudio(void* /*unused*/, Uint8* stream, int len)
 //            "/ processedLength / streamLength: " << chunkLength << " / " <<
 //            " / " << processedLength << " / " << streamLength;
 
-    SDL_MixAudioFormat(stream, &converted.at(0), sAudioFormat.format, processedLength,
-            static_cast<int>(Settings::getInstance()->
-            getInt("SoundVolumeVideos") * 1.28f));
+    // This mute flag is used to make sure that the audio buffer already sent to the
+    // stream is not played when the video player has been stopped. Otherwise there would
+    // be a short time period when the audio would keep playing after the video was stopped
+    // and before the stream was cleared in clearStream().
+    if (sMuteStream) {
+        SDL_MixAudioFormat(stream, &converted.at(0), sAudioFormat.format, processedLength, 0);
+    }
+    else {
+        SDL_MixAudioFormat(stream, &converted.at(0), sAudioFormat.format, processedLength,
+                static_cast<int>(Settings::getInstance()->getInt("SoundVolumeVideos") * 1.28f));
+    }
 
     // If nothing is playing, pause the device until there is more audio to output.
     if (!stillPlaying && SDL_AudioStreamAvailable(sConversionStream) == 0)
@@ -264,6 +275,9 @@ void AudioManager::setupAudioStream(int sampleRate)
 
 void AudioManager::processStream(const void* samples, unsigned count)
 {
+    if (mIsClearingStream)
+        return;
+
     if (SDL_AudioStreamPut(sConversionStream, samples, count * sizeof(Uint8)) == -1) {
         LOG(LogError) << "Failed to put samples in the conversion stream:";
         LOG(LogError) << SDL_GetError();
@@ -276,5 +290,24 @@ void AudioManager::processStream(const void* samples, unsigned count)
 
 void AudioManager::clearStream()
 {
-    SDL_AudioStreamClear(sConversionStream);
+    // The SDL_AudioStreamClear() function is unstable and causes random crashes, so
+    // we have to implement a workaround instead where SDL_AudioStreamGet() is used
+    // to empty the stream.
+//    SDL_AudioStreamClear(sConversionStream);
+
+    mIsClearingStream = true;
+
+    int streamSize;
+    int length = sAudioFormat.samples * 4;
+
+    while ((streamSize = SDL_AudioStreamAvailable(sConversionStream)) > 0) {
+        std::vector<Uint8> readBuffer(length);
+        int processedLength = SDL_AudioStreamGet(sConversionStream,
+                static_cast<void*>(&readBuffer.at(0)), length);
+        if (processedLength <= 0) {
+            break;
+        }
+    }
+
+    mIsClearingStream = false;
 }
diff --git a/es-core/src/AudioManager.h b/es-core/src/AudioManager.h
index 5a39dc04d..e600220ed 100644
--- a/es-core/src/AudioManager.h
+++ b/es-core/src/AudioManager.h
@@ -35,7 +35,10 @@ public:
     void processStream(const void* samples, unsigned count);
     void clearStream();
 
-    bool getHasAudioDevice() { return sHasAudioDevice; };
+    void muteStream() { sMuteStream = true; }
+    void unmuteStream() { sMuteStream = false; }
+
+    bool getHasAudioDevice() { return sHasAudioDevice; }
 
     static SDL_AudioDeviceID sAudioDevice;
     static SDL_AudioSpec sAudioFormat;
@@ -48,7 +51,9 @@ private:
     static SDL_AudioStream* sConversionStream;
     static std::vector<std::shared_ptr<Sound>> sSoundVector;
     static std::shared_ptr<AudioManager> sInstance;
+    static bool sMuteStream;
     static bool sHasAudioDevice;
+    static bool mIsClearingStream;
 };
 
 #endif // ES_CORE_AUDIO_MANAGER_H