downmix.cpp

mpeg2编码解码源程序代码

/* 
 *	Copyright (C) Aaron Holtzman - May 1999
 *
 *  This file is part of ac3dec, a free Dolby AC-3 stream decoder.
 *	
 *  ac3dec is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2, or (at your option)
 *  any later version.
 *   
 *  ac3dec is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *   
 *  You should have received a copy of the GNU General Public License
 *  along with GNU Make; see the file COPYING.  If not, write to
 *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. 
 *
 */

/*
 * All modifications (mpeg2decode -> DVD2AVI) are Copyright (C) Frank Zinner - Jan 2001
 */

#pragma warning(disable:4305)

#include "../global.h"
#include "ac3.h"

// Pre-scaled downmix coefficients
static float cmixlev_lut[4] = { 0.2928, 0.2468, 0.2071, 0.2468 };
static float smixlev_lut[4] = { 0.2928, 0.2071, 0.0   , 0.2071 };

static void downmix_3f_2r_to_2ch(bsi_t* bsi, stream_samples_t samples, sint_16 *s16_samples)
{
	uint_32 j;
	float right_tmp;
	float left_tmp;
	float clev, slev;
	float *centre = 0, *left = 0, *right = 0, *left_sur = 0, *right_sur = 0;

	left      = samples[0];
	centre    = samples[1];
	right     = samples[2];
	left_sur  = samples[3];
	right_sur = samples[4];

	clev = cmixlev_lut[bsi->cmixlev];
	slev = smixlev_lut[bsi->surmixlev];

	for (j = 0; j < 256; j++) 
	{
		left_tmp = 0.4142f * *left++  + clev * *centre   + slev * *left_sur++;
		right_tmp= 0.4142f * *right++ + clev * *centre++ + slev * *right_sur++;

		s16_samples[j * 2 ]    = (sint_16) (left_tmp  * 32767.0f);
		s16_samples[j * 2 + 1] = (sint_16) (right_tmp * 32767.0f);
	}
}

static void downmix_2f_2r_to_2ch(bsi_t* bsi, stream_samples_t samples, sint_16 *s16_samples)
{
	uint_32 j;
	float right_tmp;
	float left_tmp;
	float slev;
	float *left = 0, *right = 0, *left_sur = 0, *right_sur = 0;

	left      = samples[0];
	right     = samples[1];
	left_sur  = samples[2];
	right_sur = samples[3];

	slev = smixlev_lut[bsi->surmixlev];

	for (j = 0; j < 256; j++) 
	{
		left_tmp = 0.4142f * *left++  + slev * *left_sur++;
		right_tmp= 0.4142f * *right++ + slev * *right_sur++;

		s16_samples[j * 2 ]    = (sint_16) (left_tmp  * 32767.0f);
		s16_samples[j * 2 + 1] = (sint_16) (right_tmp * 32767.0f);
	}
}

static void downmix_3f_1r_to_2ch(bsi_t* bsi, stream_samples_t samples, sint_16 *s16_samples)
{
	uint_32 j;
	float right_tmp;
	float left_tmp;
	float clev,slev;
	float *centre = 0, *left = 0, *right = 0, *sur = 0;

	left      = samples[0];
	centre    = samples[1];
	right     = samples[2];
	sur       = samples[3];

	clev = cmixlev_lut[bsi->cmixlev];
	slev = smixlev_lut[bsi->surmixlev];

	for (j = 0; j < 256; j++) 
	{
		left_tmp = 0.4142f * *left++  + clev * *centre++ + slev * *sur;
		right_tmp= 0.4142f * *right++ + clev * *centre   + slev * *sur++;

		s16_samples[j * 2 ]    = (sint_16) (left_tmp  * 32767.0f);
		s16_samples[j * 2 + 1] = (sint_16) (right_tmp * 32767.0f);
	}
}

static void downmix_2f_1r_to_2ch(bsi_t* bsi, stream_samples_t samples, sint_16 *s16_samples)
{
	uint_32 j;
	float right_tmp;
	float left_tmp;
	float slev;
	float *left = 0, *right = 0, *sur = 0;

	left      = samples[0];
	right     = samples[1];
	sur       = samples[2];

	slev = smixlev_lut[bsi->surmixlev];

	for (j = 0; j < 256; j++) 
	{
		left_tmp = 0.4142f * *left++  + slev * *sur;
		right_tmp= 0.4142f * *right++ + slev * *sur++;

		s16_samples[j * 2 ]    = (sint_16) (left_tmp  * 32767.0f);
		s16_samples[j * 2 + 1] = (sint_16) (right_tmp * 32767.0f);
	}
}

static void downmix_3f_0r_to_2ch(bsi_t* bsi, stream_samples_t samples, sint_16 *s16_samples)
{
	uint_32 j;
	float right_tmp;
	float left_tmp;
	float clev;
	float *centre = 0, *left = 0, *right = 0;

	left      = samples[0];
	centre    = samples[1];
	right     = samples[2];

	clev = cmixlev_lut[bsi->cmixlev];

	for (j = 0; j < 256; j++) 
	{
		left_tmp = 0.4142f * *left++  + clev * *centre; 
		right_tmp= 0.4142f * *right++ + clev * *centre++;   

		s16_samples[j * 2]    = (sint_16) (left_tmp  * 32767.0f);
		s16_samples[j * 2 + 1] = (sint_16) (right_tmp * 32767.0f);
	}
}
				
static void downmix_2f_0r_to_2ch(bsi_t* bsi, stream_samples_t samples, sint_16 *s16_samples)
{
	uint_32 j;
	float *left = 0, *right = 0;

	left      = samples[0];
	right     = samples[1];

	for (j = 0; j < 256; j++) 
	{
		s16_samples[j * 2]     = (sint_16) (*left++  * 32767.0f);
		s16_samples[j * 2 + 1] = (sint_16) (*right++ * 32767.0f);
	}
}

static void downmix_1f_0r_to_2ch(float *centre, sint_16 *s16_samples)
{
	uint_32 j;
	float tmp;

	for (j = 0; j < 256; j++) 
	{
		tmp =  32767.0f * 0.7071f * *centre++;

		s16_samples[j * 2] = s16_samples[j * 2 + 1] = (sint_16) tmp;
	}
}

//-------------------------------------------------------------------------

static void downmix_3f_2r_to_2ch_dolby(bsi_t* bsi, stream_samples_t samples, sint_16 *s16_samples)
{
//	static float lspr1, lspr2, rspr1, rspr2;

	uint_32 j;
	float right_tmp;
	float left_tmp;
	float *centre = 0, *left = 0, *right = 0, *left_sur = 0, *right_sur = 0;

	left      = samples[0];
	centre    = samples[1];
	right     = samples[2];
	left_sur  = samples[3];
	right_sur = samples[4];

//	*left = *left * 0.1253f - lspr2 * 0.2812f + lspr1 * 0.7800f;
//	lspr2 = lspr1;
//	lspr1 = *left;

	for (j = 0; j < 256; j++) 
	{
		left_tmp = 0.3204f * *left++  + 0.2265f * (*centre - *left_sur - *right_sur);
		right_tmp= 0.3204f * *right++ + 0.2265f * (*centre++ + *left_sur++ + *right_sur++);

		s16_samples[j * 2 ]    = (sint_16) (left_tmp  * 32767.0f);
		s16_samples[j * 2 + 1] = (sint_16) (right_tmp * 32767.0f);
	}
}

static void downmix_2f_2r_to_2ch_dolby(bsi_t* bsi, stream_samples_t samples, sint_16 *s16_samples)
{
	uint_32 j;
	float right_tmp;
	float left_tmp;
	float *left = 0, *right = 0, *left_sur = 0, *right_sur = 0;

	left      = samples[0];
	right     = samples[1];
	left_sur  = samples[2];
	right_sur = samples[3];

	for (j = 0; j < 256; j++) 
	{
		left_tmp = 0.4142f * *left++  - 0.2928f * (*left_sur   + *right_sur);
		right_tmp= 0.4142f * *right++ + 0.2928f * (*left_sur++ + *right_sur++);

		s16_samples[j * 2 ]    = (sint_16) (left_tmp  * 32767.0f);
		s16_samples[j * 2 + 1] = (sint_16) (right_tmp * 32767.0f);
	}
}

static void downmix_3f_1r_to_2ch_dolby(bsi_t* bsi, stream_samples_t samples, sint_16 *s16_samples)
{
	uint_32 j;
	float right_tmp;
	float left_tmp;
	float *centre = 0, *left = 0, *right = 0, *sur = 0;

	left      = samples[0];
	centre    = samples[1];
	right     = samples[2];
	sur       = samples[3];

	for (j = 0; j < 256; j++) 
	{
		left_tmp = 0.4142f * *left++  + 0.2928f * (*centre - *sur);
		right_tmp= 0.4142f * *right++ + 0.2928f * (*centre++ + *sur++);

		s16_samples[j * 2 ]    = (sint_16) (left_tmp  * 32767.0f);
		s16_samples[j * 2 + 1] = (sint_16) (right_tmp * 32767.0f);
	}
}

static void downmix_2f_1r_to_2ch_dolby(bsi_t* bsi, stream_samples_t samples, sint_16 *s16_samples)
{
	uint_32 j;
	float right_tmp;
	float left_tmp;
	float *left = 0, *right = 0, *sur = 0;

	left      = samples[0];
	right     = samples[1];
	sur	      = samples[2];

	for (j = 0; j < 256; j++) 
	{
		left_tmp = 0.5858f * *left++  - 0.4142f * *sur;
		right_tmp= 0.5858f * *right++ + 0.4142f * *sur++;

		s16_samples[j * 2 ]    = (sint_16) (left_tmp  * 32767.0f);
		s16_samples[j * 2 + 1] = (sint_16) (right_tmp * 32767.0f);
	}
}

//-------------------------------------------------------------------------

//
// Downmix into 2 or 4 channels  (4 ch isn't in quite yet)
//
// The downmix function names have the following format
//
// downmix_Xf_Yr_to_[2|4]ch[_dolby]
//
// where X        = number of front channels
//       Y        = number of rear channels
//       [2|4]    = number of output channels
//       [_dolby] = with or without dolby surround mix
//

void downmix(bsi_t* bsi, stream_samples_t samples, sint_16 *s16_samples)
{
	switch (bsi->acmod)
	{
		// 3/2
		case 7:
			if (Surround_Flag)
				downmix_3f_2r_to_2ch_dolby(bsi,samples,s16_samples);
			else
				downmix_3f_2r_to_2ch(bsi,samples,s16_samples);
			break;

		// 2/2
		case 6:
			if (Surround_Flag)
				downmix_2f_2r_to_2ch_dolby(bsi,samples,s16_samples);
			else
				downmix_2f_2r_to_2ch(bsi,samples,s16_samples);
			break;

		// 3/1
		case 5:
			if (Surround_Flag)
				downmix_3f_1r_to_2ch_dolby(bsi,samples,s16_samples);
			else
				downmix_3f_1r_to_2ch(bsi,samples,s16_samples);
			break;

		// 2/1
		case 4:
			if (Surround_Flag)
				downmix_2f_1r_to_2ch_dolby(bsi,samples,s16_samples);
			else
				downmix_2f_1r_to_2ch(bsi,samples,s16_samples);
			break;

		// 3/0
		case 3:
			downmix_3f_0r_to_2ch(bsi,samples,s16_samples);
			break;

		case 2:
			downmix_2f_0r_to_2ch(bsi,samples,s16_samples);
			break;

		// 1/0
		case 1:
			downmix_1f_0r_to_2ch(samples[0],s16_samples);
			break;

		// 1+1
		case 0:
			downmix_1f_0r_to_2ch(samples[ac3_config.dual_mono_ch_sel],s16_samples);
			break;
	}
}