freeswitch/libs/libsndfile/src/ALAC/matrix_enc.c

/*
 * Copyright (c) 2011 Apple Inc. All rights reserved.
 * Copyright (C) 2012 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_enc.c

	Contains:	ALAC mixing/matrixing encode routines.

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

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

/*
    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( int32_t * in, uint32_t stride, int32_t * u, int32_t * v, int32_t numSamples, int32_t mixbits, int32_t mixres )
{
	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 = in[0] >> 16;
			r = in[1] >> 16;
			in += stride;
			u[j] = (mixres * l + m2 * r) >> mixbits;
			v[j] = l - r;
		}
	}
	else
	{
		/* Conventional separated stereo. */
		for ( j = 0; j < numSamples; j++ )
		{
			u[j] = in[0] >> 16;
			v[j] = in[1] >> 16;
			in += 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( int32_t * in, uint32_t stride, int32_t * u, int32_t * v, int32_t numSamples, int32_t mixbits, int32_t mixres )
{
	int32_t		l, r;
	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 = in[0] >> 12;
			r = in[1] >> 12;
			in += stride;

			u[j] = (mixres * l + m2 * r) >> mixbits;
			v[j] = l - r;
		}
	}
	else
	{
		/* Conventional separated stereo. */
		for ( j = 0; j < numSamples; j++ )
		{
			u[j] = in[0] >> 12;
			v[j] = in[1] >> 12;
			in += stride;
		}
	}
}

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

void mix24( 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		l, r;
	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 = in[0] >> 8;
				r = in[1] >> 8;
				in += 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
		{
			for ( j = 0; j < numSamples; j++ )
			{
				l = in[0] >> 8;
				r = in[1] >> 8;
				in += stride;

				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 = in[0] >> 8;
				r = in[1] >> 8;
				in += 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;
			}
		}
		else
		{
			for ( j = 0; j < numSamples; j++ )
			{
				l = in[0] >> 8;
				r = in[1] >> 8;
				in += 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 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		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 = in[0];
			r = in[1];
			in += 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] = in[0];
				v[j] = in[1];
				in += stride;
			}
		}
		else
		{
			/* de-interleaving with shift */
			for ( j = 0, k = 0; j < numSamples; j++, k += 2 )
			{
				l = in[0];
				r = in[1];
				in += 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;
			}
		}
	}
}