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engine/audio/private/voice_gain.cpp

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+//========= Copyright Valve Corporation, All rights reserved. ============//
+//
+// Purpose:
+//
+// $NoKeywords: $
+//=============================================================================//
+
+
+#include "audio_pch.h"
+#include "minmax.h"
+#include "voice_gain.h"
+
+// memdbgon must be the last include file in a .cpp file!!!
+#include "tier0/memdbgon.h"
+
+CAutoGain::CAutoGain()
+{
+	Reset(128, 5.0f, 0.5f, 1);
+}
+
+
+void CAutoGain::Reset(int blockSize, float maxGain, float avgToMaxVal, float scale)
+{
+	m_BlockSize = blockSize;
+	m_MaxGain = maxGain;
+	m_AvgToMaxVal = avgToMaxVal;
+
+	m_CurBlockOffset = 0;
+	m_CurTotal = 0;
+	m_CurMax = 0;
+
+	m_CurrentGain = 1;
+	m_NextGain = 1;
+
+	m_Scale = scale;
+
+	m_GainMultiplier = 0;
+	m_FixedCurrentGain = 1 << AG_FIX_SHIFT;
+}
+
+
+void CAutoGain::ProcessSamples(
+	short *pSamples,
+	int nSamples)
+{
+	short *pCurPos = pSamples;
+	int nSamplesLeft = nSamples;
+
+	// Continue until we hit the end of this block.
+	while(nSamplesLeft)
+	{
+		int nToProcess = min(nSamplesLeft, (m_BlockSize - m_CurBlockOffset));
+		for(int iSample=0; iSample < nToProcess; iSample++)
+		{
+			// Update running totals..
+			m_CurTotal += abs( pCurPos[iSample] );
+			m_CurMax = max( m_CurMax, (int)abs( pCurPos[iSample] ) );
+
+			// Apply gain on this sample.
+			AGFixed gain = m_FixedCurrentGain + m_CurBlockOffset * m_GainMultiplier;
+			m_CurBlockOffset++;
+
+			int newval = ((int)pCurPos[iSample] * gain) >> AG_FIX_SHIFT;
+			newval = min(32767, max(newval, -32768));
+			pCurPos[iSample] = (short)newval;
+		}
+		pCurPos += nToProcess;
+		nSamplesLeft -= nToProcess;
+
+		// Did we just end a block? Update our next gain.
+		if((m_CurBlockOffset % m_BlockSize) == 0)
+		{
+			// Now we've interpolated to our next gain, make it our current gain.
+			m_CurrentGain = m_NextGain * m_Scale;
+			m_FixedCurrentGain = (int)((double)m_CurrentGain * (1 << AG_FIX_SHIFT));
+
+			// Figure out the next gain (the gain we'll interpolate to).
+			int avg = m_CurTotal / m_BlockSize;
+			float modifiedMax = avg + (m_CurMax - avg) * m_AvgToMaxVal;
+			m_NextGain = min(32767.0f / modifiedMax, m_MaxGain) * m_Scale;
+
+			// Setup the interpolation multiplier.
+			float fGainMultiplier = (m_NextGain - m_CurrentGain) / (m_BlockSize - 1);
+			m_GainMultiplier = (AGFixed)((double)fGainMultiplier * (1 << AG_FIX_SHIFT));
+
+			// Reset counters.
+			m_CurTotal = 0;
+			m_CurMax = 0;
+			m_CurBlockOffset = 0;
+		}
+	}
+}