+// In order to satisfy WASAPI's buffer requirements, we need a means of converting sample rate
+// between HW and the user. The WasapiResampler class is used to perform this conversion between
+// HwIn->UserIn and UserOut->HwOut during the stream callback loop.
+class WasapiResampler
+{
+public:
+ WasapiResampler( bool isFloat, unsigned int bitsPerSample, unsigned int channelCount,
+ unsigned int inSampleRate, unsigned int outSampleRate )
+ : _bytesPerSample( bitsPerSample / 8 )
+ , _channelCount( channelCount )
+ , _sampleRatio( ( float ) outSampleRate / inSampleRate )
+ , _transformUnk( NULL )
+ , _transform( NULL )
+ , _mediaType( NULL )
+ , _inputMediaType( NULL )
+ , _outputMediaType( NULL )
+
+ #ifdef __IWMResamplerProps_FWD_DEFINED__
+ , _resamplerProps( NULL )
+ #endif
+ {
+ // 1. Initialization
+
+ MFStartup( MF_VERSION, MFSTARTUP_NOSOCKET );
+
+ // 2. Create Resampler Transform Object
+
+ CoCreateInstance( CLSID_CResamplerMediaObject, NULL, CLSCTX_INPROC_SERVER,
+ IID_IUnknown, ( void** ) &_transformUnk );
+
+ _transformUnk->QueryInterface( IID_PPV_ARGS( &_transform ) );
+
+ #ifdef __IWMResamplerProps_FWD_DEFINED__
+ _transformUnk->QueryInterface( IID_PPV_ARGS( &_resamplerProps ) );
+ _resamplerProps->SetHalfFilterLength( 60 ); // best conversion quality
+ #endif
+
+ // 3. Specify input / output format
+
+ MFCreateMediaType( &_mediaType );
+ _mediaType->SetGUID( MF_MT_MAJOR_TYPE, MFMediaType_Audio );
+ _mediaType->SetGUID( MF_MT_SUBTYPE, isFloat ? MFAudioFormat_Float : MFAudioFormat_PCM );
+ _mediaType->SetUINT32( MF_MT_AUDIO_NUM_CHANNELS, channelCount );
+ _mediaType->SetUINT32( MF_MT_AUDIO_SAMPLES_PER_SECOND, inSampleRate );
+ _mediaType->SetUINT32( MF_MT_AUDIO_BLOCK_ALIGNMENT, _bytesPerSample * channelCount );
+ _mediaType->SetUINT32( MF_MT_AUDIO_AVG_BYTES_PER_SECOND, _bytesPerSample * channelCount * inSampleRate );
+ _mediaType->SetUINT32( MF_MT_AUDIO_BITS_PER_SAMPLE, bitsPerSample );
+ _mediaType->SetUINT32( MF_MT_ALL_SAMPLES_INDEPENDENT, TRUE );
+
+ MFCreateMediaType( &_inputMediaType );
+ _mediaType->CopyAllItems( _inputMediaType );
+
+ _transform->SetInputType( 0, _inputMediaType, 0 );
+
+ MFCreateMediaType( &_outputMediaType );
+ _mediaType->CopyAllItems( _outputMediaType );
+
+ _outputMediaType->SetUINT32( MF_MT_AUDIO_SAMPLES_PER_SECOND, outSampleRate );
+ _outputMediaType->SetUINT32( MF_MT_AUDIO_AVG_BYTES_PER_SECOND, _bytesPerSample * channelCount * outSampleRate );
+
+ _transform->SetOutputType( 0, _outputMediaType, 0 );
+
+ // 4. Send stream start messages to Resampler
+
+ _transform->ProcessMessage( MFT_MESSAGE_COMMAND_FLUSH, 0 );
+ _transform->ProcessMessage( MFT_MESSAGE_NOTIFY_BEGIN_STREAMING, 0 );
+ _transform->ProcessMessage( MFT_MESSAGE_NOTIFY_START_OF_STREAM, 0 );
+ }
+
+ ~WasapiResampler()
+ {
+ // 8. Send stream stop messages to Resampler
+
+ _transform->ProcessMessage( MFT_MESSAGE_NOTIFY_END_OF_STREAM, 0 );
+ _transform->ProcessMessage( MFT_MESSAGE_NOTIFY_END_STREAMING, 0 );
+
+ // 9. Cleanup
+
+ MFShutdown();
+
+ SAFE_RELEASE( _transformUnk );
+ SAFE_RELEASE( _transform );
+ SAFE_RELEASE( _mediaType );
+ SAFE_RELEASE( _inputMediaType );
+ SAFE_RELEASE( _outputMediaType );
+
+ #ifdef __IWMResamplerProps_FWD_DEFINED__
+ SAFE_RELEASE( _resamplerProps );
+ #endif
+ }
+
+ void Convert( char* outBuffer, const char* inBuffer, unsigned int inSampleCount, unsigned int& outSampleCount, int maxOutSampleCount = -1 )
+ {
+ unsigned int inputBufferSize = _bytesPerSample * _channelCount * inSampleCount;
+ if ( _sampleRatio == 1 )
+ {
+ // no sample rate conversion required
+ memcpy( outBuffer, inBuffer, inputBufferSize );
+ outSampleCount = inSampleCount;
+ return;
+ }
+
+ unsigned int outputBufferSize = 0;
+ if ( maxOutSampleCount != -1 )
+ {
+ outputBufferSize = _bytesPerSample * _channelCount * maxOutSampleCount;
+ }
+ else
+ {
+ outputBufferSize = ( unsigned int ) ceilf( inputBufferSize * _sampleRatio ) + ( _bytesPerSample * _channelCount );
+ }
+
+ IMFMediaBuffer* rInBuffer;
+ IMFSample* rInSample;
+ BYTE* rInByteBuffer = NULL;
+
+ // 5. Create Sample object from input data
+
+ MFCreateMemoryBuffer( inputBufferSize, &rInBuffer );
+
+ rInBuffer->Lock( &rInByteBuffer, NULL, NULL );
+ memcpy( rInByteBuffer, inBuffer, inputBufferSize );
+ rInBuffer->Unlock();
+ rInByteBuffer = NULL;
+
+ rInBuffer->SetCurrentLength( inputBufferSize );
+
+ MFCreateSample( &rInSample );
+ rInSample->AddBuffer( rInBuffer );
+
+ // 6. Pass input data to Resampler
+
+ _transform->ProcessInput( 0, rInSample, 0 );
+
+ SAFE_RELEASE( rInBuffer );
+ SAFE_RELEASE( rInSample );
+
+ // 7. Perform sample rate conversion
+
+ IMFMediaBuffer* rOutBuffer = NULL;
+ BYTE* rOutByteBuffer = NULL;
+
+ MFT_OUTPUT_DATA_BUFFER rOutDataBuffer;
+ DWORD rStatus;
+ DWORD rBytes = outputBufferSize; // maximum bytes accepted per ProcessOutput
+
+ // 7.1 Create Sample object for output data
+
+ memset( &rOutDataBuffer, 0, sizeof rOutDataBuffer );
+ MFCreateSample( &( rOutDataBuffer.pSample ) );
+ MFCreateMemoryBuffer( rBytes, &rOutBuffer );
+ rOutDataBuffer.pSample->AddBuffer( rOutBuffer );
+ rOutDataBuffer.dwStreamID = 0;
+ rOutDataBuffer.dwStatus = 0;
+ rOutDataBuffer.pEvents = NULL;
+
+ // 7.2 Get output data from Resampler
+
+ if ( _transform->ProcessOutput( 0, 1, &rOutDataBuffer, &rStatus ) == MF_E_TRANSFORM_NEED_MORE_INPUT )
+ {
+ outSampleCount = 0;
+ SAFE_RELEASE( rOutBuffer );
+ SAFE_RELEASE( rOutDataBuffer.pSample );
+ return;
+ }
+
+ // 7.3 Write output data to outBuffer
+
+ SAFE_RELEASE( rOutBuffer );
+ rOutDataBuffer.pSample->ConvertToContiguousBuffer( &rOutBuffer );
+ rOutBuffer->GetCurrentLength( &rBytes );
+
+ rOutBuffer->Lock( &rOutByteBuffer, NULL, NULL );
+ memcpy( outBuffer, rOutByteBuffer, rBytes );
+ rOutBuffer->Unlock();
+ rOutByteBuffer = NULL;
+
+ outSampleCount = rBytes / _bytesPerSample / _channelCount;
+ SAFE_RELEASE( rOutBuffer );
+ SAFE_RELEASE( rOutDataBuffer.pSample );
+ }
+
+private:
+ unsigned int _bytesPerSample;
+ unsigned int _channelCount;
+ float _sampleRatio;
+
+ IUnknown* _transformUnk;
+ IMFTransform* _transform;
+ IMFMediaType* _mediaType;
+ IMFMediaType* _inputMediaType;
+ IMFMediaType* _outputMediaType;
+
+ #ifdef __IWMResamplerProps_FWD_DEFINED__
+ IWMResamplerProps* _resamplerProps;
+ #endif
+};
+
+//-----------------------------------------------------------------------------
+