poke/alac/codec/matrix_enc.c

/*
 * Copyright (c) 2011 Apple Inc. All rights reserved.
 *
 * @APPLE_APACHE_LICENSE_HEADER_START@
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *     http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 * @APPLE_APACHE_LICENSE_HEADER_END@
 */

/*
	File:		matrix_enc.c
	
	Contains:	ALAC mixing/matrixing encode routines.

	Copyright:	(c) 2004-2011 Apple, Inc.
*/

#include "matrixlib.h"
#include "ALACAudioTypes.h"

// up to 24-bit "offset" macros for the individual bytes of a 20/24-bit word
#if TARGET_RT_BIG_ENDIAN
	#define LBYTE	2
	#define MBYTE	1
	#define HBYTE	0
#else
	#define LBYTE	0
	#define MBYTE	1
	#define HBYTE	2
#endif

/*
    There is no plain middle-side option; instead there are various mixing
    modes including middle-side, each lossless, as embodied in the mix()
    and unmix() functions.  These functions exploit a generalized middle-side
    transformation:
    
    u := [(rL + (m-r)R)/m];
    v := L - R;
    
    where [ ] denotes integer floor.  The (lossless) inverse is
    
    L = u + v - [rV/m];
    R = L - v;
*/

// 16-bit routines

void mix16( int16_t * in, uint32_t stride, int32_t * u, int32_t * v, int32_t numSamples, int32_t mixbits, int32_t mixres )
{
	int16_t	*	ip = in;
	int32_t			j;

	if ( mixres != 0 )
	{
		int32_t		mod = 1 << mixbits;
		int32_t		m2;

		/* matrixed stereo */
		m2 = mod - mixres;
		for ( j = 0; j < numSamples; j++ )
		{
			int32_t		l, r;

			l = (int32_t) ip[0];
			r = (int32_t) ip[1];
			ip += stride;
			u[j] = (mixres * l + m2 * r) >> mixbits;
			v[j] = l - r;
		}
	}
	else
	{
		/* Conventional separated stereo. */
		for ( j = 0; j < numSamples; j++ )
		{
			u[j] = (int32_t) ip[0];
			v[j] = (int32_t) ip[1];
			ip += stride;
		}
	}
}

// 20-bit routines
// - the 20 bits of data are left-justified in 3 bytes of storage but right-aligned for input/output predictor buffers

void mix20( uint8_t * in, uint32_t stride, int32_t * u, int32_t * v, int32_t numSamples, int32_t mixbits, int32_t mixres )
{
	int32_t		l, r;
	uint8_t *	ip = in;
	int32_t			j;

	if ( mixres != 0 )
	{
		/* matrixed stereo */
		int32_t		mod = 1 << mixbits;
		int32_t		m2 = mod - mixres;

		for ( j = 0; j < numSamples; j++ )
		{
			l = (int32_t)( ((uint32_t)ip[HBYTE] << 16) | ((uint32_t)ip[MBYTE] << 8) | (uint32_t)ip[LBYTE] );
			l = (l << 8) >> 12;
			ip += 3;

			r = (int32_t)( ((uint32_t)ip[HBYTE] << 16) | ((uint32_t)ip[MBYTE] << 8) | (uint32_t)ip[LBYTE] );
			r = (r << 8) >> 12;
			ip += (stride - 1) * 3;

			u[j] = (mixres * l + m2 * r) >> mixbits;
			v[j] = l - r;
		} 
	}
	else
	{
		/* Conventional separated stereo. */
		for ( j = 0; j < numSamples; j++ )
		{
			l = (int32_t)( ((uint32_t)ip[HBYTE] << 16) | ((uint32_t)ip[MBYTE] << 8) | (uint32_t)ip[LBYTE] );
			u[j] = (l << 8) >> 12;
			ip += 3;

			r = (int32_t)( ((uint32_t)ip[HBYTE] << 16) | ((uint32_t)ip[MBYTE] << 8) | (uint32_t)ip[LBYTE] );
			v[j] = (r << 8) >> 12;
			ip += (stride - 1) * 3;
		}
	}
}

// 24-bit routines
// - the 24 bits of data are right-justified in the input/output predictor buffers

void mix24( uint8_t * in, uint32_t stride, int32_t * u, int32_t * v, int32_t numSamples,
			int32_t mixbits, int32_t mixres, uint16_t * shiftUV, int32_t bytesShifted )
{	
	int32_t		l, r;
	uint8_t *	ip = in;
	int32_t			shift = bytesShifted * 8;
	uint32_t	mask  = (1ul << shift) - 1;
	int32_t			j, k;

	if ( mixres != 0 )
	{
		/* matrixed stereo */
		int32_t		mod = 1 << mixbits;
		int32_t		m2 = mod - mixres;

		if ( bytesShifted != 0 )
		{
			for ( j = 0, k = 0; j < numSamples; j++, k += 2 )
			{
				l = (int32_t)( ((uint32_t)ip[HBYTE] << 16) | ((uint32_t)ip[MBYTE] << 8) | (uint32_t)ip[LBYTE] );
				l = (l << 8) >> 8;
				ip += 3;

				r = (int32_t)( ((uint32_t)ip[HBYTE] << 16) | ((uint32_t)ip[MBYTE] << 8) | (uint32_t)ip[LBYTE] );
				r = (r << 8) >> 8;
				ip += (stride - 1) * 3;

				shiftUV[k + 0] = (uint16_t)(l & mask);
				shiftUV[k + 1] = (uint16_t)(r & mask);
				
				l >>= shift;
				r >>= shift;

				u[j] = (mixres * l + m2 * r) >> mixbits;
				v[j] = l - r;
			}
		}
		else
		{
			for ( j = 0; j < numSamples; j++ )
			{
				l = (int32_t)( ((uint32_t)ip[HBYTE] << 16) | ((uint32_t)ip[MBYTE] << 8) | (uint32_t)ip[LBYTE] );
				l = (l << 8) >> 8;
				ip += 3;

				r = (int32_t)( ((uint32_t)ip[HBYTE] << 16) | ((uint32_t)ip[MBYTE] << 8) | (uint32_t)ip[LBYTE] );
				r = (r << 8) >> 8;
				ip += (stride - 1) * 3;

				u[j] = (mixres * l + m2 * r) >> mixbits;
				v[j] = l - r;
			}
		}
	}
	else
	{
		/* Conventional separated stereo. */
		if ( bytesShifted != 0 )
		{
			for ( j = 0, k = 0; j < numSamples; j++, k += 2 )
			{
				l = (int32_t)( ((uint32_t)ip[HBYTE] << 16) | ((uint32_t)ip[MBYTE] << 8) | (uint32_t)ip[LBYTE] );
				l = (l << 8) >> 8;
				ip += 3;

				r = (int32_t)( ((uint32_t)ip[HBYTE] << 16) | ((uint32_t)ip[MBYTE] << 8) | (uint32_t)ip[LBYTE] );
				r = (r << 8) >> 8;
				ip += (stride - 1) * 3;

				shiftUV[k + 0] = (uint16_t)(l & mask);
				shiftUV[k + 1] = (uint16_t)(r & mask);
				
				l >>= shift;
				r >>= shift;

				u[j] = l;
				v[j] = r;
			}
		}
		else
		{
			for ( j = 0; j < numSamples; j++ )
			{
				l = (int32_t)( ((uint32_t)ip[HBYTE] << 16) | ((uint32_t)ip[MBYTE] << 8) | (uint32_t)ip[LBYTE] );
				u[j] = (l << 8) >> 8;
				ip += 3;

				r = (int32_t)( ((uint32_t)ip[HBYTE] << 16) | ((uint32_t)ip[MBYTE] << 8) | (uint32_t)ip[LBYTE] );
				v[j] = (r << 8) >> 8;
				ip += (stride - 1) * 3;
			}
		}
	}
}

// 32-bit routines
// - note that these really expect the internal data width to be < 32 but the arrays are 32-bit
// - otherwise, the calculations might overflow into the 33rd bit and be lost
// - therefore, these routines deal with the specified "unused lower" bytes in the "shift" buffers

void mix32( int32_t * in, uint32_t stride, int32_t * u, int32_t * v, int32_t numSamples,
			int32_t mixbits, int32_t mixres, uint16_t * shiftUV, int32_t bytesShifted )
{
	int32_t	*	ip = in;
	int32_t			shift = bytesShifted * 8;
	uint32_t	mask  = (1ul << shift) - 1;
	int32_t		l, r;
	int32_t			j, k;

	if ( mixres != 0 )
	{
		int32_t		mod = 1 << mixbits;
		int32_t		m2;

		//Assert( bytesShifted != 0 );

		/* matrixed stereo with shift */
		m2 = mod - mixres;
		for ( j = 0, k = 0; j < numSamples; j++, k += 2 )
		{
			l = ip[0];
			r = ip[1];
			ip += stride;

			shiftUV[k + 0] = (uint16_t)(l & mask);
			shiftUV[k + 1] = (uint16_t)(r & mask);
			
			l >>= shift;
			r >>= shift;

			u[j] = (mixres * l + m2 * r) >> mixbits;
			v[j] = l - r;
		}
	}
	else
	{
		if ( bytesShifted == 0 )
		{
			/* de-interleaving w/o shift */
			for ( j = 0; j < numSamples; j++ )
			{
				u[j] = ip[0];
				v[j] = ip[1];
				ip += stride;
			}
		}
		else
		{
			/* de-interleaving with shift */
			for ( j = 0, k = 0; j < numSamples; j++, k += 2 )
			{
				l = ip[0];
				r = ip[1];
				ip += stride;

				shiftUV[k + 0] = (uint16_t)(l & mask);
				shiftUV[k + 1] = (uint16_t)(r & mask);
				
				l >>= shift;
				r >>= shift;

				u[j] = l;
				v[j] = r;
			}
		}
	}
}

// 20/24-bit <-> 32-bit helper routines (not really matrixing but convenient to put here)

void copy20ToPredictor( uint8_t * in, uint32_t stride, int32_t * out, int32_t numSamples )
{
	uint8_t *	ip = in;
	int32_t			j;

	for ( j = 0; j < numSamples; j++ )
	{
		int32_t			val;

		// 20-bit values are left-aligned in the 24-bit input buffer but right-aligned in the 32-bit output buffer
		val = (int32_t)( ((uint32_t)ip[HBYTE] << 16) | ((uint32_t)ip[MBYTE] << 8) | (uint32_t)ip[LBYTE] );
		out[j] = (val << 8) >> 12;
		ip += stride * 3;
	}
}

void copy24ToPredictor( uint8_t * in, uint32_t stride, int32_t * out, int32_t numSamples )
{
	uint8_t *	ip = in;
	int32_t			j;

	for ( j = 0; j < numSamples; j++ )
	{
		int32_t			val;

		val = (int32_t)( ((uint32_t)ip[HBYTE] << 16) | ((uint32_t)ip[MBYTE] << 8) | (uint32_t)ip[LBYTE] );
		out[j] = (val << 8) >> 8;
		ip += stride * 3;
	}
}