flacenc.c

ffmpeg的完整源代码和作者自己写的文档。不但有在Linux的工程哦

/**
 * FLAC audio encoder
 * Copyright (c) 2006  Justin Ruggles <[e-mail]>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "avcodec.h"
#include "bitstream.h"
#include "crc.h"
#include "dsputil.h"
#include "golomb.h"
#include "lls.h"

#define FLAC_MAX_CH  8
#define FLAC_MIN_BLOCKSIZE  16
#define FLAC_MAX_BLOCKSIZE  65535

#define FLAC_SUBFRAME_CONSTANT  0
#define FLAC_SUBFRAME_VERBATIM  1
#define FLAC_SUBFRAME_FIXED     8
#define FLAC_SUBFRAME_LPC      32

#define FLAC_CHMODE_NOT_STEREO      0
#define FLAC_CHMODE_LEFT_RIGHT      1
#define FLAC_CHMODE_LEFT_SIDE       8
#define FLAC_CHMODE_RIGHT_SIDE      9
#define FLAC_CHMODE_MID_SIDE       10

#define ORDER_METHOD_EST     0
#define ORDER_METHOD_2LEVEL  1
#define ORDER_METHOD_4LEVEL  2
#define ORDER_METHOD_8LEVEL  3
#define ORDER_METHOD_SEARCH  4
#define ORDER_METHOD_LOG     5

#define FLAC_STREAMINFO_SIZE  34

#define MIN_LPC_ORDER       1
#define MAX_LPC_ORDER      32
#define MAX_FIXED_ORDER     4
#define MAX_PARTITION_ORDER 8
#define MAX_PARTITIONS     (1 << MAX_PARTITION_ORDER)
#define MAX_LPC_PRECISION  15
#define MAX_LPC_SHIFT      15
#define MAX_RICE_PARAM     14

typedef struct CompressionOptions {
    int compression_level;
    int block_time_ms;
    int use_lpc;
    int lpc_coeff_precision;
    int min_prediction_order;
    int max_prediction_order;
    int prediction_order_method;
    int min_partition_order;
    int max_partition_order;
} CompressionOptions;

typedef struct RiceContext {
    int porder;
    int params[MAX_PARTITIONS];
} RiceContext;

typedef struct FlacSubframe {
    int type;
    int type_code;
    int obits;
    int order;
    int32_t coefs[MAX_LPC_ORDER];
    int shift;
    RiceContext rc;
    int32_t samples[FLAC_MAX_BLOCKSIZE];
    int32_t residual[FLAC_MAX_BLOCKSIZE+1];
} FlacSubframe;

typedef struct FlacFrame {
    FlacSubframe subframes[FLAC_MAX_CH];
    int blocksize;
    int bs_code[2];
    uint8_t crc8;
    int ch_mode;
} FlacFrame;

typedef struct FlacEncodeContext {
    PutBitContext pb;
    int channels;
    int ch_code;
    int samplerate;
    int sr_code[2];
    int blocksize;
    int max_framesize;
    uint32_t frame_count;
    FlacFrame frame;
    CompressionOptions options;
    AVCodecContext *avctx;
    DSPContext dsp;
} FlacEncodeContext;

static const int flac_samplerates[16] = {
    0, 0, 0, 0,
    8000, 16000, 22050, 24000, 32000, 44100, 48000, 96000,
    0, 0, 0, 0
};

static const int flac_blocksizes[16] = {
    0,
    192,
    576, 1152, 2304, 4608,
    0, 0,
    256, 512, 1024, 2048, 4096, 8192, 16384, 32768
};

/**
 * Writes streaminfo metadata block to byte array
 */
static void write_streaminfo(FlacEncodeContext *s, uint8_t *header)
{
    PutBitContext pb;

    memset(header, 0, FLAC_STREAMINFO_SIZE);
    init_put_bits(&pb, header, FLAC_STREAMINFO_SIZE);

    /* streaminfo metadata block */
    put_bits(&pb, 16, s->blocksize);
    put_bits(&pb, 16, s->blocksize);
    put_bits(&pb, 24, 0);
    put_bits(&pb, 24, s->max_framesize);
    put_bits(&pb, 20, s->samplerate);
    put_bits(&pb, 3, s->channels-1);
    put_bits(&pb, 5, 15);       /* bits per sample - 1 */
    flush_put_bits(&pb);
    /* total samples = 0 */
    /* MD5 signature = 0 */
}

/**
 * Sets blocksize based on samplerate
 * Chooses the closest predefined blocksize >= BLOCK_TIME_MS milliseconds
 */
static int select_blocksize(int samplerate, int block_time_ms)
{
    int i;
    int target;
    int blocksize;

    assert(samplerate > 0);
    blocksize = flac_blocksizes[1];
    target = (samplerate * block_time_ms) / 1000;
    for(i=0; i<16; i++) {
        if(target >= flac_blocksizes[i] && flac_blocksizes[i] > blocksize) {
            blocksize = flac_blocksizes[i];
        }
    }
    return blocksize;
}

static int flac_encode_init(AVCodecContext *avctx)
{
    int freq = avctx->sample_rate;
    int channels = avctx->channels;
    FlacEncodeContext *s = avctx->priv_data;
    int i, level;
    uint8_t *streaminfo;

    s->avctx = avctx;

    dsputil_init(&s->dsp, avctx);

    if(avctx->sample_fmt != SAMPLE_FMT_S16) {
        return -1;
    }

    if(channels < 1 || channels > FLAC_MAX_CH) {
        return -1;
    }
    s->channels = channels;
    s->ch_code = s->channels-1;

    /* find samplerate in table */
    if(freq < 1)
        return -1;
    for(i=4; i<12; i++) {
        if(freq == flac_samplerates[i]) {
            s->samplerate = flac_samplerates[i];
            s->sr_code[0] = i;
            s->sr_code[1] = 0;
            break;
        }
    }
    /* if not in table, samplerate is non-standard */
    if(i == 12) {
        if(freq % 1000 == 0 && freq < 255000) {
            s->sr_code[0] = 12;
            s->sr_code[1] = freq / 1000;
        } else if(freq % 10 == 0 && freq < 655350) {
            s->sr_code[0] = 14;
            s->sr_code[1] = freq / 10;
        } else if(freq < 65535) {
            s->sr_code[0] = 13;
            s->sr_code[1] = freq;
        } else {
            return -1;
        }
        s->samplerate = freq;
    }

    /* set compression option defaults based on avctx->compression_level */
    if(avctx->compression_level < 0) {
        s->options.compression_level = 5;
    } else {
        s->options.compression_level = avctx->compression_level;
    }
    av_log(avctx, AV_LOG_DEBUG, " compression: %d\n", s->options.compression_level);

    level= s->options.compression_level;
    if(level > 12) {
        av_log(avctx, AV_LOG_ERROR, "invalid compression level: %d\n",
               s->options.compression_level);
        return -1;
    }

    s->options.block_time_ms       = ((int[]){ 27, 27, 27,105,105,105,105,105,105,105,105,105,105})[level];
    s->options.use_lpc             = ((int[]){  0,  0,  0,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1})[level];
    s->options.min_prediction_order= ((int[]){  2,  0,  0,  1,  1,  1,  1,  1,  1,  1,  1,  1,  1})[level];
    s->options.max_prediction_order= ((int[]){  3,  4,  4,  6,  8,  8,  8,  8, 12, 12, 12, 32, 32})[level];
    s->options.prediction_order_method = ((int[]){ ORDER_METHOD_EST,    ORDER_METHOD_EST,    ORDER_METHOD_EST,
                                                   ORDER_METHOD_EST,    ORDER_METHOD_EST,    ORDER_METHOD_EST,
                                                   ORDER_METHOD_4LEVEL, ORDER_METHOD_LOG,    ORDER_METHOD_4LEVEL,
                                                   ORDER_METHOD_LOG,    ORDER_METHOD_SEARCH, ORDER_METHOD_LOG,
                                                   ORDER_METHOD_SEARCH})[level];
    s->options.min_partition_order = ((int[]){  2,  2,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0})[level];
    s->options.max_partition_order = ((int[]){  2,  2,  3,  3,  3,  8,  8,  8,  8,  8,  8,  8,  8})[level];

    /* set compression option overrides from AVCodecContext */
    if(avctx->use_lpc >= 0) {
        s->options.use_lpc = av_clip(avctx->use_lpc, 0, 11);
    }
    if(s->options.use_lpc == 1)
        av_log(avctx, AV_LOG_DEBUG, " use lpc: Levinson-Durbin recursion with Welch window\n");
    else if(s->options.use_lpc > 1)
        av_log(avctx, AV_LOG_DEBUG, " use lpc: Cholesky factorization\n");

    if(avctx->min_prediction_order >= 0) {
        if(s->options.use_lpc) {
            if(avctx->min_prediction_order < MIN_LPC_ORDER ||
                    avctx->min_prediction_order > MAX_LPC_ORDER) {
                av_log(avctx, AV_LOG_ERROR, "invalid min prediction order: %d\n",
                       avctx->min_prediction_order);
                return -1;
            }
        } else {
            if(avctx->min_prediction_order > MAX_FIXED_ORDER) {
                av_log(avctx, AV_LOG_ERROR, "invalid min prediction order: %d\n",
                       avctx->min_prediction_order);
                return -1;
            }
        }
        s->options.min_prediction_order = avctx->min_prediction_order;
    }
    if(avctx->max_prediction_order >= 0) {
        if(s->options.use_lpc) {
            if(avctx->max_prediction_order < MIN_LPC_ORDER ||
                    avctx->max_prediction_order > MAX_LPC_ORDER) {
                av_log(avctx, AV_LOG_ERROR, "invalid max prediction order: %d\n",
                       avctx->max_prediction_order);
                return -1;
            }
        } else {
            if(avctx->max_prediction_order > MAX_FIXED_ORDER) {
                av_log(avctx, AV_LOG_ERROR, "invalid max prediction order: %d\n",
                       avctx->max_prediction_order);
                return -1;
            }
        }
        s->options.max_prediction_order = avctx->max_prediction_order;
    }
    if(s->options.max_prediction_order < s->options.min_prediction_order) {
        av_log(avctx, AV_LOG_ERROR, "invalid prediction orders: min=%d max=%d\n",
               s->options.min_prediction_order, s->options.max_prediction_order);
        return -1;
    }
    av_log(avctx, AV_LOG_DEBUG, " prediction order: %d, %d\n",
           s->options.min_prediction_order, s->options.max_prediction_order);

    if(avctx->prediction_order_method >= 0) {
        if(avctx->prediction_order_method > ORDER_METHOD_LOG) {
            av_log(avctx, AV_LOG_ERROR, "invalid prediction order method: %d\n",
                   avctx->prediction_order_method);
            return -1;
        }
        s->options.prediction_order_method = avctx->prediction_order_method;
    }
    switch(s->options.prediction_order_method) {
        case ORDER_METHOD_EST:    av_log(avctx, AV_LOG_DEBUG, " order method: %s\n",
                                         "estimate"); break;
        case ORDER_METHOD_2LEVEL: av_log(avctx, AV_LOG_DEBUG, " order method: %s\n",
                                         "2-level"); break;
        case ORDER_METHOD_4LEVEL: av_log(avctx, AV_LOG_DEBUG, " order method: %s\n",
                                         "4-level"); break;
        case ORDER_METHOD_8LEVEL: av_log(avctx, AV_LOG_DEBUG, " order method: %s\n",
                                         "8-level"); break;
        case ORDER_METHOD_SEARCH: av_log(avctx, AV_LOG_DEBUG, " order method: %s\n",
                                         "full search"); break;
        case ORDER_METHOD_LOG:    av_log(avctx, AV_LOG_DEBUG, " order method: %s\n",
                                         "log search"); break;
    }

    if(avctx->min_partition_order >= 0) {
        if(avctx->min_partition_order > MAX_PARTITION_ORDER) {
            av_log(avctx, AV_LOG_ERROR, "invalid min partition order: %d\n",
                   avctx->min_partition_order);
            return -1;
        }
        s->options.min_partition_order = avctx->min_partition_order;
    }
    if(avctx->max_partition_order >= 0) {
        if(avctx->max_partition_order > MAX_PARTITION_ORDER) {
            av_log(avctx, AV_LOG_ERROR, "invalid max partition order: %d\n",
                   avctx->max_partition_order);
            return -1;
        }
        s->options.max_partition_order = avctx->max_partition_order;
    }
    if(s->options.max_partition_order < s->options.min_partition_order) {
        av_log(avctx, AV_LOG_ERROR, "invalid partition orders: min=%d max=%d\n",
               s->options.min_partition_order, s->options.max_partition_order);
        return -1;
    }
    av_log(avctx, AV_LOG_DEBUG, " partition order: %d, %d\n",
           s->options.min_partition_order, s->options.max_partition_order);

    if(avctx->frame_size > 0) {
        if(avctx->frame_size < FLAC_MIN_BLOCKSIZE ||
                avctx->frame_size > FLAC_MAX_BLOCKSIZE) {
            av_log(avctx, AV_LOG_ERROR, "invalid block size: %d\n",
                   avctx->frame_size);
            return -1;
        }
        s->blocksize = avctx->frame_size;
    } else {
        s->blocksize = select_blocksize(s->samplerate, s->options.block_time_ms);
        avctx->frame_size = s->blocksize;
    }
    av_log(avctx, AV_LOG_DEBUG, " block size: %d\n", s->blocksize);

    /* set LPC precision */
    if(avctx->lpc_coeff_precision > 0) {
        if(avctx->lpc_coeff_precision > MAX_LPC_PRECISION) {
            av_log(avctx, AV_LOG_ERROR, "invalid lpc coeff precision: %d\n",
                   avctx->lpc_coeff_precision);
            return -1;
        }
        s->options.lpc_coeff_precision = avctx->lpc_coeff_precision;
    } else {
        /* select LPC precision based on block size */
        if(     s->blocksize <=   192) s->options.lpc_coeff_precision =  7;
        else if(s->blocksize <=   384) s->options.lpc_coeff_precision =  8;
        else if(s->blocksize <=   576) s->options.lpc_coeff_precision =  9;
        else if(s->blocksize <=  1152) s->options.lpc_coeff_precision = 10;
        else if(s->blocksize <=  2304) s->options.lpc_coeff_precision = 11;
        else if(s->blocksize <=  4608) s->options.lpc_coeff_precision = 12;
        else if(s->blocksize <=  8192) s->options.lpc_coeff_precision = 13;
        else if(s->blocksize <= 16384) s->options.lpc_coeff_precision = 14;
        else                           s->options.lpc_coeff_precision = 15;
    }
    av_log(avctx, AV_LOG_DEBUG, " lpc precision: %d\n",
           s->options.lpc_coeff_precision);

    /* set maximum encoded frame size in verbatim mode */
    if(s->channels == 2) {
        s->max_framesize = 14 + ((s->blocksize * 33 + 7) >> 3);
    } else {
        s->max_framesize = 14 + (s->blocksize * s->channels * 2);
    }

    streaminfo = av_malloc(FLAC_STREAMINFO_SIZE);
    write_streaminfo(s, streaminfo);
    avctx->extradata = streaminfo;
    avctx->extradata_size = FLAC_STREAMINFO_SIZE;

    s->frame_count = 0;

    avctx->coded_frame = avcodec_alloc_frame();
    avctx->coded_frame->key_frame = 1;

    return 0;
}

static void init_frame(FlacEncodeContext *s)
{
    int i, ch;
    FlacFrame *frame;

    frame = &s->frame;

    for(i=0; i<16; i++) {
        if(s->blocksize == flac_blocksizes[i]) {
            frame->blocksize = flac_blocksizes[i];
            frame->bs_code[0] = i;
            frame->bs_code[1] = 0;
            break;
        }
    }
    if(i == 16) {
        frame->blocksize = s->blocksize;
        if(frame->blocksize <= 256) {
            frame->bs_code[0] = 6;
            frame->bs_code[1] = frame->blocksize-1;
        } else {
            frame->bs_code[0] = 7;
            frame->bs_code[1] = frame->blocksize-1;
        }
    }

    for(ch=0; ch<s->channels; ch++) {
        frame->subframes[ch].obits = 16;
    }
}

/**
 * Copy channel-interleaved input samples into separate subframes
 */
static void copy_samples(FlacEncodeContext *s, int16_t *samples)
{
    int i, j, ch;
    FlacFrame *frame;

    frame = &s->frame;
    for(i=0,j=0; i<frame->blocksize; i++) {
        for(ch=0; ch<s->channels; ch++,j++) {
            frame->subframes[ch].samples[i] = samples[j];
        }
    }
}


#define rice_encode_count(sum, n, k) (((n)*((k)+1))+((sum-(n>>1))>>(k)))

/**
 * Solve for d/dk(rice_encode_count) = n-((sum-(n>>1))>>(k+1)) = 0
 */
static int find_optimal_param(uint32_t sum, int n)
{
    int k;
    uint32_t sum2;

    if(sum <= n>>1)
        return 0;
    sum2 = sum-(n>>1);
    k = av_log2(n<256 ? FASTDIV(sum2,n) : sum2/n);
    return FFMIN(k, MAX_RICE_PARAM);
}

static uint32_t calc_optimal_rice_params(RiceContext *rc, int porder,
                                         uint32_t *sums, int n, int pred_order)
{
    int i;
    int k, cnt, part;
    uint32_t all_bits;

    part = (1 << porder);
    all_bits = 0;

    cnt = (n >> porder) - pred_order;
    for(i=0; i<part; i++) {
        if(i == 1) cnt = (n >> porder);
        k = find_optimal_param(sums[i], cnt);
        rc->params[i] = k;
        all_bits += rice_encode_count(sums[i], cnt, k);
    }
    all_bits += (4 * part);

    rc->porder = porder;

    return all_bits;
}

static void calc_sums(int pmin, int pmax, uint32_t *data, int n, int pred_order,
                      uint32_t sums[][MAX_PARTITIONS])
{
    int i, j;
    int parts;
    uint32_t *res, *res_end;

    /* sums for highest level */
    parts = (1 << pmax);