src/ALAC/matrix_dec.c

/*
 * Copyright (c) 2011 Apple Inc. All rights reserved.
 * Copyright (C) 2012-2014 Erik de Castro Lopo <erikd@mega-nerd.com>
 *
 * @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_dec.c

	Contains:	ALAC mixing/matrixing decode routines.

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

#include "matrixlib.h"
#include "ALACAudioTypes.h"
#include "shift.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
unmix16 (const int32_t * u, int32_t * v, int32_t * out, uint32_t stride, int32_t numSamples, int32_t mixbits, int32_t mixres)
{
	int32_t 	j ;

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

			l = u [j] + v [j] - ((mixres * v [j]) >> mixbits) ;
			r = l - v [j] ;

			out [0] = arith_shift_left (l, 16) ;
			out [1] = arith_shift_left (r, 16) ;
			out += stride ;
		}
	}
	else
	{
		/* Conventional separated stereo. */
		for (j = 0 ; j < numSamples ; j++)
		{
			out [0] = u [j] << 16 ;
			out [1] = v [j] << 16 ;
			out += 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
unmix20 (const int32_t * u, int32_t * v, int32_t * out, uint32_t stride, int32_t numSamples, int32_t mixbits, int32_t mixres)
{
	int32_t 	j ;

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

			l = u [j] + v [j] - ((mixres * v [j]) >> mixbits) ;
			r = l - v [j] ;

			out [0] = arith_shift_left (l, 12) ;
			out [1] = arith_shift_left (r, 12) ;
			out += stride ;
		}
	}
	else
	{
		/* Conventional separated stereo. */
		for (j = 0 ; j < numSamples ; j++)
		{
			out [0] = arith_shift_left (u [j], 12) ;
			out [1] = arith_shift_left (v [j], 12) ;
			out += stride ;
		}
	}
}

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

void
unmix24 (const int32_t * u, int32_t * v, int32_t * out, uint32_t stride, int32_t numSamples,
				int32_t mixbits, int32_t mixres, uint16_t * shiftUV, int32_t bytesShifted)
{
	int32_t		shift = bytesShifted * 8 ;
	int32_t		l, r ;
	int32_t 		j, k ;

	if (mixres != 0)
	{
		/* matrixed stereo */
		if (bytesShifted != 0)
		{
			for (j = 0, k = 0 ; j < numSamples ; j++, k += 2)
			{
				l = u [j] + v [j] - ((mixres * v [j]) >> mixbits) ;
				r = l - v [j] ;

				l = arith_shift_left (l, shift) | (uint32_t) shiftUV [k + 0] ;
				r = arith_shift_left (r, shift) | (uint32_t) shiftUV [k + 1] ;

				out [0] = arith_shift_left (l, 8) ;
				out [1] = arith_shift_left (r, 8) ;
				out += stride ;
			}
		}
		else
		{
			for (j = 0 ; j < numSamples ; j++)
			{
				l = u [j] + v [j] - ((mixres * v [j]) >> mixbits) ;
				r = l - v [j] ;

				out [0] = l << 8 ;
				out [1] = r << 8 ;
				out += stride ;
			}
		}
	}
	else
	{
		/* Conventional separated stereo. */
		if (bytesShifted != 0)
		{
			for (j = 0, k = 0 ; j < numSamples ; j++, k += 2)
			{
				l = u [j] ;
				r = v [j] ;

				l = (l << shift) | (uint32_t) shiftUV [k + 0] ;
				r = (r << shift) | (uint32_t) shiftUV [k + 1] ;

				out [0] = l << 8 ;
				out [1] = r << 8 ;
				out += stride ;
			}
		}
		else
		{
			for (j = 0 ; j < numSamples ; j++)
			{
				out [0] = u [j] << 8 ;
				out [1] = v [j] << 8 ;
				out += stride ;
			}
		}
	}
}

// 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
unmix32 (const int32_t * u, int32_t * v, int32_t * out, uint32_t stride, int32_t numSamples,
				int32_t mixbits, int32_t mixres, uint16_t * shiftUV, int32_t bytesShifted)
{
	int32_t		shift = bytesShifted * 8 ;
	int32_t		l, r ;
	int32_t 	j, k ;

	if (mixres != 0)
	{
		//Assert (bytesShifted != 0) ;

		/* matrixed stereo with shift */
		for (j = 0, k = 0 ; j < numSamples ; j++, k += 2)
		{
			int32_t		lt, rt ;

			lt = u [j] ;
			rt = v [j] ;

			l = lt + rt - ((mixres * rt) >> mixbits) ;
			r = l - rt ;

			out [0] = arith_shift_left (l, shift) | (uint32_t) shiftUV [k + 0] ;
			out [1] = arith_shift_left (r, shift) | (uint32_t) shiftUV [k + 1] ;
			out += stride ;
		}
	}
	else
	{
		if (bytesShifted == 0)
		{
			/* interleaving w/o shift */
			for (j = 0 ; j < numSamples ; j++)
			{
				out [0] = u [j] ;
				out [1] = v [j] ;
				out += stride ;
			}
		}
		else
		{
			/* interleaving with shift */
			for (j = 0, k = 0 ; j < numSamples ; j++, k += 2)
			{
				out [0] = (u [j] << shift) | (uint32_t) shiftUV [k + 0] ;
				out [1] = (v [j] << shift) | (uint32_t) shiftUV [k + 1] ;
				out += stride ;
			}
		}
	}
}

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

void
copyPredictorTo24 (const int32_t * in, int32_t * out, uint32_t stride, int32_t numSamples)
{
	int32_t		j ;

	for (j = 0 ; j < numSamples ; j++)
	{
		out [0] = in [j] << 8 ;
		out += stride ;
	}
}

void
copyPredictorTo24Shift (const int32_t * in, uint16_t * shift, int32_t * out, uint32_t stride, int32_t numSamples, int32_t bytesShifted)
{
	int32_t		shiftVal = bytesShifted * 8 ;
	int32_t		j ;

	//Assert (bytesShifted != 0) ;

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

		val = arith_shift_left (val, shiftVal) | (uint32_t) shift [j] ;
		out [0] = arith_shift_left (val, 8) ;
		out += stride ;
	}
}

void
copyPredictorTo20 (const int32_t * in, int32_t * out, uint32_t stride, int32_t numSamples)
{
	int32_t		j ;

	// 32-bit predictor values are right-aligned but 20-bit output values should be left-aligned
	// in the 24-bit output buffer
	for (j = 0 ; j < numSamples ; j++)
	{
		out [0] = arith_shift_left (in [j], 12) ;
		out += stride ;
	}
}

void
copyPredictorTo32 (const int32_t * in, int32_t * out, uint32_t stride, int32_t numSamples)
{
	int32_t			i, j ;

	// this is only a subroutine to abstract the "iPod can only output 16-bit data" problem
	for (i = 0, j = 0 ; i < numSamples ; i++, j += stride)
		out [j] = arith_shift_left (in [i], 8) ;
}

void
copyPredictorTo32Shift (const int32_t * in, uint16_t * shift, int32_t * out, uint32_t stride, int32_t numSamples, int32_t bytesShifted)
{
	int32_t *		op = out ;
	uint32_t		shiftVal = bytesShifted * 8 ;
	int32_t			j ;

	//Assert (bytesShifted != 0) ;

	// this is only a subroutine to abstract the "iPod can only output 16-bit data" problem
	for (j = 0 ; j < numSamples ; j++)
	{
		op [0] = arith_shift_left (in [j], shiftVal) | (uint32_t) shift [j] ;
		op += stride ;
	}
}