1 files changed, 62 insertions, 0 deletions
diff --git a/engine/audio/private/voice_gain.h b/engine/audio/private/voice_gain.h
new file mode 100644
index 0000000..cd614e0
--- /dev/null
+++ b/engine/audio/private/voice_gain.h
@@ -0,0 +1,62 @@
+//========= Copyright Valve Corporation, All rights reserved. ============//
+//
+// Purpose: 
+//
+// $NoKeywords: $
+//=============================================================================//
+
+#ifndef VOICE_GAIN_H
+#define VOICE_GAIN_H
+#pragma once
+
+
+// ----------------------------------------------------------------------- //
+// CAutoGain is fed samples and figures out a gain to apply to blocks of samples.
+
+// Right now, this class applies gain one block behind. The assumption is that the blocks are
+// small enough that gain settings for one block will usually be right for the next block.
+
+// The ideal way to implement this class would be to have a delay the size of a block
+// so it can apply the right gain to the actual block it was calculated for.
+// ----------------------------------------------------------------------- //
+class CAutoGain
+{
+public:
+
+			CAutoGain();
+
+	// maxGain and avgToMaxVal are used to derive the gain amount for each block of samples.
+	// All samples are scaled by scale.
+	void	Reset(int blockSize, float maxGain, float avgToMaxVal, float scale);
+
+	// Process the specified samples and apply gain to them.
+	void	ProcessSamples(
+		short *pSamples,
+		int nSamples);
+
+private:
+
+	enum	{AG_FIX_SHIFT=7};
+	typedef long	AGFixed;
+
+	// Parameters affecting the algorithm.
+	int		m_BlockSize;			// Derive gain from blocks of this size.
+	float	m_MaxGain;
+	float	m_AvgToMaxVal;
+
+	// These are calculated as samples are passed in.
+	int		m_CurBlockOffset;
+	int		m_CurTotal;				// Total of sample values in current block.
+	int		m_CurMax;				// Highest (absolute) sample value.
+
+	float	m_Scale;				// All samples are scaled by this amount.
+
+	float	m_CurrentGain;			// Gain at sample 0 in this block.
+	float	m_NextGain;				// Gain at the last sample in this block.
+
+	AGFixed	m_FixedCurrentGain;		// Fixed-point m_CurrentGain.	
+	AGFixed	m_GainMultiplier;		// (m_NextGain - m_CurrentGain) / (m_BlockSize - 1).
+};
+
+
+#endif // VOICE_GAIN_H