lame.c

音频编码

/* -*- mode: C; mode: fold -*- */
/*
 *	LAME MP3 encoding engine
 *
 *	Copyright (c) 1999-2000 Mark Taylor
 *	Copyright (c) 2000-2005 Takehiro Tominaga
 *	Copyright (c) 2000-2005 Robert Hegemann
 *	Copyright (c) 2000-2005 Gabriel Bouvigne
 *	Copyright (c) 2000-2004 Alexander Leidinger
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

/* $Id: lame.c,v 1.278.2.2 2005/11/20 14:08:24 bouvigne Exp $ */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif


#include <assert.h>
#include "lame-analysis.h"
#include "lame.h"
#include "util.h"
#include "bitstream.h"
#include "version.h"
#include "tables.h"
#include "quantize_pvt.h"
#include "psymodel.h"
#include "VbrTag.h"
#include "machine.h"
#include "gain_analysis.h"
#include "set_get.h"

#if defined(__FreeBSD__) && !defined(__alpha__)
#include <floatingpoint.h>
#endif
#ifdef __riscos__
#include "asmstuff.h"
#endif

#ifdef WITH_DMALLOC
#include <dmalloc.h>
#endif

#ifdef __sun__
/* woraround for SunOS 4.x, it has SEEK_* defined here */
#include <unistd.h>
#endif


#define LAME_DEFAULT_QUALITY 3

static FLOAT
filter_coef(FLOAT x)
{
    if (x > 1.0) return 0.0;
    if (x <= 0.0) return 1.0;

    return cos(PI/2 * x);
}

static void
lame_init_params_ppflt(lame_global_flags * gfp)
{
    lame_internal_flags *gfc = gfp->internal_flags;
    /***************************************************************/
    /* compute info needed for polyphase filter (filter type==0, default) */
    /***************************************************************/

    int     band, maxband, minband;
    FLOAT   freq;
    int lowpass_band = 32;
    int highpass_band = -1;

    if (gfc->lowpass1 > 0) {
	minband = 999;
	for (band = 0; band <= 31; band++) {
	    freq = band / 31.0;
	    /* this band and above will be zeroed: */
	    if (freq >= gfc->lowpass2) {
		lowpass_band = Min(lowpass_band, band);
	    }
	    if (gfc->lowpass1 < freq && freq < gfc->lowpass2) {
		minband = Min(minband, band);
	    }
	}

        /* compute the *actual* transition band implemented by
         * the polyphase filter */
        if (minband == 999) {
            gfc->lowpass1 = (lowpass_band - .75) / 31.0;
        }
        else {
            gfc->lowpass1 = (minband - .75) / 31.0;
        }
        gfc->lowpass2 = lowpass_band / 31.0;
    }

    /* make sure highpass filter is within 90% of what the effective
     * highpass frequency will be */
    if (gfc->highpass2 > 0) {
        if (gfc->highpass2 < .9 * (.75 / 31.0)) {
            gfc->highpass1 = 0;
            gfc->highpass2 = 0;
            MSGF(gfc, "Warning: highpass filter disabled.  "
                 "highpass frequency too small\n");
        }
    }

    if (gfc->highpass2 > 0) {
        maxband = -1;
        for (band = 0; band <= 31; band++) {
            freq = band / 31.0;
            /* this band and below will be zereod */
            if (freq <= gfc->highpass1) {
                highpass_band = Max(highpass_band, band);
            }
            if (gfc->highpass1 < freq && freq < gfc->highpass2) {
                maxband = Max(maxband, band);
            }
        }
        /* compute the *actual* transition band implemented by
         * the polyphase filter */
        gfc->highpass1 = highpass_band / 31.0;
        if (maxband == -1) {
            gfc->highpass2 = (highpass_band + .75) / 31.0;
        }
        else {
            gfc->highpass2 = (maxband + .75) / 31.0;
        }
    }

    for (band = 0; band < 32; band++) {
	freq = band / 31.0;
	gfc->amp_filter[band]
	    = filter_coef((gfc->highpass2 - freq)
			  / (gfc->highpass2 - gfc->highpass1 + 1e-37))
	    * filter_coef((freq - gfc->lowpass1)
			  / (gfc->lowpass2 - gfc->lowpass1 - 1e-37));
    }
}


static void
optimum_bandwidth(double *const lowerlimit,
                  double *const upperlimit,
                  const unsigned bitrate)
{
/* 
 *  Input:
 *      bitrate     total bitrate in kbps
 *
 *   Output:
 *      lowerlimit: best lowpass frequency limit for input filter in Hz
 *      upperlimit: best highpass frequency limit for input filter in Hz
 */
    int index;

    typedef struct {
        int bitrate; /* only indicative value */
        int lowpass;
    } band_pass_t;

    const band_pass_t freq_map[] = {
        {  8,  2000},
        { 16,  3700},
        { 24,  3900},
        { 32,  5500},
        { 40,  7000},
        { 48,  7500},
        { 56, 10000},
        { 64, 11000},
        { 80, 13500},
        { 96, 15100},
        {112, 15600},
        {128, 17000},
        {160, 17500},
        {192, 18600},
        {224, 19400},
        {256, 19700},
        {320, 20500}
    };


    index = nearestBitrateFullIndex(bitrate);

    *lowerlimit = freq_map[index].lowpass;


/*
 *  Now we try to choose a good high pass filtering frequency.
 *  This value is currently not used.
 *    For fu < 16 kHz:  sqrt(fu*fl) = 560 Hz
 *    For fu = 18 kHz:  no high pass filtering
 *  This gives:
 *
 *   2 kHz => 160 Hz
 *   3 kHz => 107 Hz
 *   4 kHz =>  80 Hz
 *   8 kHz =>  40 Hz
 *  16 kHz =>  20 Hz
 *  17 kHz =>  10 Hz
 *  18 kHz =>   0 Hz
 *
 *  These are ad hoc values and these can be optimized if a high pass is available.
 */
/*    if (f_low <= 16000)
        f_high = 16000. * 20. / f_low;
    else if (f_low <= 18000)
        f_high = 180. - 0.01 * f_low;
    else
        f_high = 0.;*/

    /*  
     *  When we sometimes have a good highpass filter, we can add the highpass
     *  frequency to the lowpass frequency
     */

    /*if (upperlimit != NULL)
        *upperlimit = f_high;*/
}


static int
optimum_samplefreq(int lowpassfreq, int input_samplefreq)
{
/*
 * Rules:
 *  - if possible, sfb21 should NOT be used
 *
 */
    int suggested_samplefreq;
    
    if (input_samplefreq >= 48000)
        suggested_samplefreq = 48000;
    else if (input_samplefreq >= 44100)
        suggested_samplefreq = 44100;
    else if (input_samplefreq >= 32000)
        suggested_samplefreq = 32000;
    else if (input_samplefreq >= 24000)
        suggested_samplefreq = 24000;
    else if (input_samplefreq >= 22050)
        suggested_samplefreq = 22050;
    else if (input_samplefreq >= 16000)
        suggested_samplefreq = 16000;
    else if (input_samplefreq >= 12000)
        suggested_samplefreq = 12000;
    else if (input_samplefreq >= 11025)
        suggested_samplefreq = 11025;
    else if (input_samplefreq >= 8000)
        suggested_samplefreq = 8000;

    if (lowpassfreq == -1)
        return suggested_samplefreq;

    if (lowpassfreq <= 15960)
        suggested_samplefreq = 44100;
    if (lowpassfreq <= 15250)
        suggested_samplefreq = 32000;
    if (lowpassfreq <= 11220)
        suggested_samplefreq = 24000;
    if (lowpassfreq <= 9970)
        suggested_samplefreq = 22050;
    if (lowpassfreq <= 7230)
        suggested_samplefreq = 16000;
    if (lowpassfreq <= 5420)
        suggested_samplefreq = 12000;
    if (lowpassfreq <= 4510)
        suggested_samplefreq = 11025;
    if (lowpassfreq <= 3970)
        suggested_samplefreq = 8000;

    if (input_samplefreq < suggested_samplefreq)
        suggested_samplefreq = input_samplefreq;
    return suggested_samplefreq;
}





/* set internal feature flags.  USER should not access these since
 * some combinations will produce strange results */
void
lame_init_qval(lame_global_flags * gfp)
{
    lame_internal_flags *gfc = gfp->internal_flags;

    switch (gfp->quality) {
    case 9:            /* no psymodel, no noise shaping */
        gfc->filter_type = 0;
        gfc->psymodel = 0;
        gfc->quantization = 0;
        gfc->noise_shaping = 0;
        gfc->noise_shaping_amp = 0;
        gfc->noise_shaping_stop = 0;
        gfc->use_best_huffman = 0;
        gfc->full_outer_loop = 0;
        break;

    case 8:
        gfp->quality = 7;
    case 7:            /* use psymodel (for short block and m/s switching), but no noise shapping */
        gfc->filter_type = 0;
        gfc->psymodel = 1;
        gfc->quantization = 0;
        gfc->noise_shaping = 0;
        gfc->noise_shaping_amp = 0;
        gfc->noise_shaping_stop = 0;
        gfc->use_best_huffman = 0;
        gfc->full_outer_loop = 0;
        break;

    case 6:
        gfc->filter_type = 0;
        gfc->psymodel = 1;
        gfc->quantization = 0;
        if (gfc->noise_shaping == 0)
            gfc->noise_shaping = 1;
        gfc->noise_shaping_amp = 0;
        gfc->noise_shaping_stop = 0;
        if (gfc->subblock_gain == -1)
            gfc->subblock_gain = 1;
        gfc->use_best_huffman = 0;
        gfc->full_outer_loop = 0;
        break;

    case 5:
        gfc->filter_type = 0;
        gfc->psymodel = 1;
        gfc->quantization = 1;
        if (gfc->noise_shaping == 0)
            gfc->noise_shaping = 1;
        gfc->noise_shaping_amp = 0;
        gfc->noise_shaping_stop = 0;
        if (gfc->subblock_gain == -1)
            gfc->subblock_gain = 1;
        gfc->use_best_huffman = 0;
        gfc->full_outer_loop = 0;
        break;

    case 4:
        gfc->filter_type = 0;
        gfc->psymodel = 1;
        gfc->quantization = 1;
        if (gfc->noise_shaping == 0)
            gfc->noise_shaping = 1;
        gfc->noise_shaping_amp = 0;
        gfc->noise_shaping_stop = 0;
        if (gfc->subblock_gain == -1)
            gfc->subblock_gain = 1;
        gfc->use_best_huffman = 1;
        gfc->full_outer_loop = 0;
        break;

    case 3:
        gfc->filter_type = 0;
        gfc->psymodel = 1;
        gfc->quantization = 1;
        if (gfc->noise_shaping == 0)
            gfc->noise_shaping = 1;
        gfc->noise_shaping_amp = 1;
        gfc->noise_shaping_stop = 1;
        if (gfc->subblock_gain == -1)
            gfc->subblock_gain = 1;
        gfc->use_best_huffman = 1;
        gfc->full_outer_loop = 0;
        break;

    case 2:
        gfc->filter_type = 0;
        gfc->psymodel = 1;
        gfc->quantization = 1;
        if (gfc->noise_shaping == 0)
            gfc->noise_shaping = 1;
        if (gfc->substep_shaping == 0)
	        gfc->substep_shaping = 2;
        gfc->noise_shaping_amp = 1;
        gfc->noise_shaping_stop = 1;
        if (gfc->subblock_gain == -1)
            gfc->subblock_gain = 1;
        gfc->use_best_huffman = 1; /* inner loop */
        gfc->full_outer_loop = 0;
        break;

    case 1:
        gfc->filter_type = 0; /* 1 not yet coded */
        gfc->psymodel = 1;
        gfc->quantization = 1;
        if (gfc->noise_shaping == 0)
            gfc->noise_shaping = 1;
        if (gfc->substep_shaping == 0)
	        gfc->substep_shaping = 2;
        gfc->noise_shaping_amp = 2;
        gfc->noise_shaping_stop = 1;
        if (gfc->subblock_gain == -1)
            gfc->subblock_gain = 1;
        gfc->use_best_huffman = 1;
        gfc->full_outer_loop = 0;
        break;

    case 0:
        gfc->filter_type = 0; /* 1 not yet coded */
        gfc->psymodel = 1;
        gfc->quantization = 1;
        if (gfc->noise_shaping == 0)
            gfc->noise_shaping = 1;
        if (gfc->substep_shaping == 0)
	        gfc->substep_shaping = 2;
        gfc->noise_shaping_amp = 2;
        gfc->noise_shaping_stop = 1;
        if (gfc->subblock_gain == -1)
            gfc->subblock_gain = 1;
        gfc->use_best_huffman = 1; /*type 2 disabled because of it slowness,
                                     in favor of full outer loop search */
        gfc->full_outer_loop = 1;
        break;
    }