libmp3lame编码解码mp3文件

/* -*- mode: C; mode: fold -*- */ /* * LAME MP3 encoding engine * * Copyright (c) 1999-2000 Mark Taylor * Copyright (c) 2000-2005 Takehiro Tominaga * Copyright (c) 2000-2017 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 1.377 2017/09/26 12:14:02 robert Exp $ */ #include "config.h" #include "lame.h" #include "machine.h" #include "encoder.h" #include "util.h" #include "lame_global_flags.h" #include "gain_analysis.h" #include "bitstream.h" #include "quantize_pvt.h" #include "set_get.h" #include "quantize.h" #include "psymodel.h" #include "version.h" #include "VbrTag.h" #include "tables.h" #if defined(__FreeBSD__) && !defined(__alpha__) #include <floatingpoint.h> #endif #ifdef __riscos__ #include "asmstuff.h" #endif #ifdef __sun__ /* woraround for SunOS 4.x, it has SEEK_* defined here */ #include <unistd.h> #endif #define LAME_DEFAULT_QUALITY 3 int is_lame_global_flags_valid(const lame_global_flags * gfp) { if (gfp == NULL) return 0; if (gfp->class_id != LAME_ID) return 0; return 1; } int is_lame_internal_flags_valid(const lame_internal_flags * gfc) { if (gfc == NULL) return 0; if (gfc->class_id != LAME_ID) return 0; if (gfc->lame_init_params_successful <=0) return 0; return 1; } 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_internal_flags * gfc) { SessionConfig_t *const cfg = &gfc->cfg; /***************************************************************/ /* 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 (cfg->lowpass1 > 0) { minband = 999; for (band = 0; band <= 31; band++) { freq = band / 31.0; /* this band and above will be zeroed: */ if (freq >= cfg->lowpass2) { lowpass_band = Min(lowpass_band, band); } if (cfg->lowpass1 < freq && freq < cfg->lowpass2) { minband = Min(minband, band); } } /* compute the *actual* transition band implemented by * the polyphase filter */ if (minband == 999) { cfg->lowpass1 = (lowpass_band - .75) / 31.0; } else { cfg->lowpass1 = (minband - .75) / 31.0; } cfg->lowpass2 = lowpass_band / 31.0; } /* make sure highpass filter is within 90% of what the effective * highpass frequency will be */ if (cfg->highpass2 > 0) { if (cfg->highpass2 < .9 * (.75 / 31.0)) { cfg->highpass1 = 0; cfg->highpass2 = 0; MSGF(gfc, "Warning: highpass filter disabled. " "highpass frequency too small\n"); } } if (cfg->highpass2 > 0) { maxband = -1; for (band = 0; band <= 31; band++) { freq = band / 31.0; /* this band and below will be zereod */ if (freq <= cfg->highpass1) { highpass_band = Max(highpass_band, band); } if (cfg->highpass1 < freq && freq < cfg->highpass2) { maxband = Max(maxband, band); } } /* compute the *actual* transition band implemented by * the polyphase filter */ cfg->highpass1 = highpass_band / 31.0; if (maxband == -1) { cfg->highpass2 = (highpass_band + .75) / 31.0; } else { cfg->highpass2 = (maxband + .75) / 31.0; } } for (band = 0; band < 32; band++) { FLOAT fc1, fc2; freq = band / 31.0f; if (cfg->highpass2 > cfg->highpass1) { fc1 = filter_coef((cfg->highpass2 - freq) / (cfg->highpass2 - cfg->highpass1 + 1e-20)); } else { fc1 = 1.0f; } if (cfg->lowpass2 > cfg->lowpass1) { fc2 = filter_coef((freq - cfg->lowpass1) / (cfg->lowpass2 - cfg->lowpass1 + 1e-20)); } else { fc2 = 1.0f; } gfc->sv_enc.amp_filter[band] = fc1 * fc2; } } 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 table_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} }; table_index = nearestBitrateFullIndex(bitrate); (void) freq_map[table_index].bitrate; *lowerlimit = freq_map[table_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;*/ (void) upperlimit; } static int optimum_samplefreq(int lowpassfreq, int input_samplefreq) { /* * Rules: * - if possible, sfb21 should NOT be used * */ int suggested_samplefreq = 44100; 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 <=