Change Audio class to optionally use SDL's internal audio stream.

Close #2215.

Source/Urho3D/Audio/Audio.cpp

@@ -87,12 +87,7 @@ bool Audio::SetMode(int bufferLengthMSec, int mixRate, bool stereo, bool interpo
 
     desired.freq = mixRate;
 
-// The concept behind the emscripten audio port is to treat it as 16 bit until the final accumulation form the clip buffer
-#ifdef __EMSCRIPTEN__
-    desired.format = AUDIO_F32LSB;
-#else
     desired.format = AUDIO_S16;
-#endif
     desired.channels = (Uint8)(stereo ? 2 : 1);
     desired.callback = SDLAudioCallback;
     desired.userdata = this;
@@ -103,30 +98,22 @@ bool Audio::SetMode(int bufferLengthMSec, int mixRate, bool stereo, bool interpo
     if (Abs((int)desired.samples / 2 - bufferSamples) < Abs((int)desired.samples - bufferSamples))
         desired.samples /= 2;
 
-    deviceID_ = SDL_OpenAudioDevice(nullptr, SDL_FALSE, &desired, &obtained, SDL_AUDIO_ALLOW_ANY_CHANGE);
+    // Intentionally disallow format change so that the obtained format will always be the desired format, even though that format
+    // is not matching the device format, however in doing it will enable the SDL's internal audio stream with audio conversion
+    deviceID_ = SDL_OpenAudioDevice(nullptr, SDL_FALSE, &desired, &obtained, SDL_AUDIO_ALLOW_ANY_CHANGE&~SDL_AUDIO_ALLOW_FORMAT_CHANGE);
     if (!deviceID_)
     {
         URHO3D_LOGERROR("Could not initialize audio output");
         return false;
     }
 
-#ifdef __EMSCRIPTEN__
-    if (obtained.format != AUDIO_F32LSB && obtained.format != AUDIO_F32MSB && obtained.format != AUDIO_F32SYS)
-    {
-        URHO3D_LOGERROR("Could not initialize audio output, 32-bit float buffer format not supported");
-        SDL_CloseAudioDevice(deviceID_);
-        deviceID_ = 0;
-        return false;
-    }
-#else
-    if (obtained.format != AUDIO_S16SYS && obtained.format != AUDIO_S16LSB && obtained.format != AUDIO_S16MSB)
+    if (obtained.format != AUDIO_S16)
     {
         URHO3D_LOGERROR("Could not initialize audio output, 16-bit buffer format not supported");
         SDL_CloseAudioDevice(deviceID_);
         deviceID_ = 0;
         return false;
     }
-#endif
 
     stereo_ = obtained.channels == 2;
     sampleSize_ = (unsigned)(stereo_ ? sizeof(int) : sizeof(short));
@@ -274,7 +261,7 @@ void SDLAudioCallback(void* userdata, Uint8* stream, int len)
     auto* audio = static_cast<Audio*>(userdata);
     {
         MutexLock Lock(audio->GetMutex());
-        audio->MixOutput(stream, len / audio->GetSampleSize() / Audio::SAMPLE_SIZE_MUL);
+        audio->MixOutput(stream, len / audio->GetSampleSize());
     }
 }
 
@@ -282,7 +269,7 @@ void Audio::MixOutput(void* dest, unsigned samples)
 {
     if (!playing_ || !clipBuffer_)
     {
-        memset(dest, 0, samples * sampleSize_ * SAMPLE_SIZE_MUL);
+        memset(dest, 0, samples * sampleSize_);
         return;
     }
 
@@ -313,17 +300,11 @@ void Audio::MixOutput(void* dest, unsigned samples)
             source->Mix(clipPtr, workSamples, mixRate_, stereo_, interpolation_);
         }
         // Copy output from clip buffer to destination
-#ifdef __EMSCRIPTEN__
-        float* destPtr = (float*)dest;
-        while (clipSamples--)
-            *destPtr++ = (float)Clamp(*clipPtr++, -32768, 32767) / 32768.0f;
-#else
         auto* destPtr = (short*)dest;
         while (clipSamples--)
             *destPtr++ = (short)Clamp(*clipPtr++, -32768, 32767);
-#endif
         samples -= workSamples;
-        ((unsigned char*&)dest) += sampleSize_ * SAMPLE_SIZE_MUL * workSamples;
+        ((unsigned char*&)dest) += sampleSize_ * workSamples;
     }
 }
 

Source/Urho3D/Audio/Audio.h

@@ -115,12 +115,6 @@ public:
     /// Mix sound sources into the buffer.
     void MixOutput(void* dest, unsigned samples);
 
-    /// Final multiplier for audio byte conversion.
-#ifdef __EMSCRIPTEN__
-    static const int SAMPLE_SIZE_MUL = 2;
-#else
-    static const int SAMPLE_SIZE_MUL = 1;
-#endif
 private:
     /// Handle render update event.
     void HandleRenderUpdate(StringHash eventType, VariantMap& eventData);