try to keep API boundaries passing frames, instead of bytes

stepmania/src/arch/Sound/CAHelpers.cpp

@@ -40,7 +40,8 @@ OSStatus AudioConverter::FormatConverterInputProc(UInt32& ioNumberDataPackets,
     }
     buf.mData = mBuffer;
 
-	mDriver->FillConverter( buf.mData, buf.mDataByteSize );
+	const int frames = buf.mDataByteSize / kBytesPerPacket;
+	mDriver->FillConverter( buf.mData, frames );
     return noErr;
 }
 

stepmania/src/arch/Sound/RageSoundDriver_CA.cpp

@@ -239,10 +239,9 @@ int64_t RageSound_CA::GetPosition(const RageSoundBase *sound) const
 	return int64_t(time.mSampleTime);
 }
 
-void RageSound_CA::FillConverter(void *data, UInt32 dataByteSize)
+void RageSound_CA::FillConverter( void *data, UInt32 frames )
 {
-	int frames = dataByteSize / gConverter->GetInputFormat().mBytesPerPacket;
-	this->Mix((int16_t *)data, frames, mDecodePos, int64_t(mNow->mSampleTime));
+	this->Mix( (int16_t *)data, frames, mDecodePos, int64_t(mNow->mSampleTime) );
 }
 
 OSStatus RageSound_CA::GetData(AudioDeviceID inDevice,

stepmania/src/arch/Sound/RageSoundDriver_CA.h

@@ -35,7 +35,7 @@ private:
                                      void *inData);
                               
 public:
-    void FillConverter(void *data, UInt32 dataByteSize);
+    void FillConverter( void *data, UInt32 frames );
     RageSound_CA();
     ~RageSound_CA();
     float GetPlayLatency() const { return mLatency; }