cook.c

ffmpeg源码分析

/*
 * COOK compatible decoder
 * Copyright (c) 2003 Sascha Sommer
 * Copyright (c) 2005 Benjamin Larsson
 *
 * This library 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 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 *
 */

/**
 * @file cook.c
 * Cook compatible decoder.
 * This decoder handles RealNetworks, RealAudio G2 data.
 * Cook is identified by the codec name cook in RM files.
 *
 * To use this decoder, a calling application must supply the extradata
 * bytes provided from the RM container; 8+ bytes for mono streams and
 * 16+ for stereo streams (maybe more).
 *
 * Codec technicalities (all this assume a buffer length of 1024):
 * Cook works with several different techniques to achieve its compression.
 * In the timedomain the buffer is divided into 8 pieces and quantized. If
 * two neighboring pieces have different quantization index a smooth
 * quantization curve is used to get a smooth overlap between the different
 * pieces.
 * To get to the transformdomain Cook uses a modulated lapped transform.
 * The transform domain has 50 subbands with 20 elements each. This
 * means only a maximum of 50*20=1000 coefficients are used out of the 1024
 * available.
 */

#include <math.h>
#include <stddef.h>
#include <stdio.h>

#define ALT_BITSTREAM_READER
#include "avcodec.h"
#include "bitstream.h"
#include "dsputil.h"

#include "cookdata.h"

/* the different Cook versions */
#define MONO_COOK1      0x1000001
#define MONO_COOK2      0x1000002
#define JOINT_STEREO    0x1000003
#define MC_COOK         0x2000000   //multichannel Cook, not supported

#define SUBBAND_SIZE    20
//#define COOKDEBUG

typedef struct {
    int     size;
    int     qidx_table1[8];
    int     qidx_table2[8];
} COOKgain;

typedef struct __attribute__((__packed__)){
    /* codec data start */
    uint32_t cookversion;               //in network order, bigendian
    uint16_t samples_per_frame;         //amount of samples per frame per channel, bigendian
    uint16_t subbands;                  //amount of bands used in the frequency domain, bigendian
    /* Mono extradata ends here. */
    uint32_t unused;
    uint16_t js_subband_start;          //bigendian
    uint16_t js_vlc_bits;               //bigendian
    /* Stereo extradata ends here. */
} COOKextradata;


typedef struct {
    GetBitContext       gb;
    /* stream data */
    int                 nb_channels;
    int                 joint_stereo;
    int                 bit_rate;
    int                 sample_rate;
    int                 samples_per_channel;
    int                 samples_per_frame;
    int                 subbands;
    int                 log2_numvector_size;
    int                 numvector_size;                //1 << log2_numvector_size;
    int                 js_subband_start;
    int                 total_subbands;
    int                 num_vectors;
    int                 bits_per_subpacket;
    /* states */
    int                 random_state;

    /* transform data */
    FFTContext          fft_ctx;
    FFTSample           mlt_tmp[1024] __attribute__((aligned(16))); /* temporary storage for imlt */
    float*              mlt_window;
    float*              mlt_precos;
    float*              mlt_presin;
    float*              mlt_postcos;
    int                 fft_size;
    int                 fft_order;
    int                 mlt_size;       //modulated lapped transform size

    /* gain buffers */
    COOKgain*           gain_now_ptr;
    COOKgain*           gain_previous_ptr;
    COOKgain            gain_current;
    COOKgain            gain_now;
    COOKgain            gain_previous;
    COOKgain            gain_channel1[2];
    COOKgain            gain_channel2[2];

    /* VLC data */
    int                 js_vlc_bits;
    VLC                 envelope_quant_index[13];
    VLC                 sqvh[7];          //scalar quantization
    VLC                 ccpl;             //channel coupling

    /* generatable tables and related variables */
    int                 gain_size_factor;
    float               gain_table[23];
    float               pow2tab[127];
    float               rootpow2tab[127];

    /* data buffers */

    uint8_t*            decoded_bytes_buffer;
    float               mono_mdct_output[2048] __attribute__((aligned(16)));
    float*              previous_buffer_ptr[2];
    float               mono_previous_buffer1[1024];
    float               mono_previous_buffer2[1024];
    float*              decode_buf_ptr[4];
    float*              decode_buf_ptr2[2];
    float               decode_buffer_1[1024];
    float               decode_buffer_2[1024];
    float               decode_buffer_3[1024];
    float               decode_buffer_4[1024];
} COOKContext;

/* debug functions */

#ifdef COOKDEBUG
static void dump_float_table(float* table, int size, int delimiter) {
    int i=0;
    av_log(NULL,AV_LOG_ERROR,"\n[%d]: ",i);
    for (i=0 ; i<size ; i++) {
        av_log(NULL, AV_LOG_ERROR, "%5.1f, ", table[i]);
        if ((i+1)%delimiter == 0) av_log(NULL,AV_LOG_ERROR,"\n[%d]: ",i+1);
    }
}

static void dump_int_table(int* table, int size, int delimiter) {
    int i=0;
    av_log(NULL,AV_LOG_ERROR,"\n[%d]: ",i);
    for (i=0 ; i<size ; i++) {
        av_log(NULL, AV_LOG_ERROR, "%d, ", table[i]);
        if ((i+1)%delimiter == 0) av_log(NULL,AV_LOG_ERROR,"\n[%d]: ",i+1);
    }
}

static void dump_short_table(short* table, int size, int delimiter) {
    int i=0;
    av_log(NULL,AV_LOG_ERROR,"\n[%d]: ",i);
    for (i=0 ; i<size ; i++) {
        av_log(NULL, AV_LOG_ERROR, "%d, ", table[i]);
        if ((i+1)%delimiter == 0) av_log(NULL,AV_LOG_ERROR,"\n[%d]: ",i+1);
    }
}

#endif

/*************** init functions ***************/

/* table generator */
static void init_pow2table(COOKContext *q){
    int i;
    q->pow2tab[63] = 1.0;
    for (i=1 ; i<64 ; i++){
        q->pow2tab[63+i]=(float)((uint64_t)1<<i);
        q->pow2tab[63-i]=1.0/(float)((uint64_t)1<<i);
    }
}

/* table generator */
static void init_rootpow2table(COOKContext *q){
    int i;
    q->rootpow2tab[63] = 1.0;
    for (i=1 ; i<64 ; i++){
        q->rootpow2tab[63+i]=sqrt((float)((uint64_t)1<<i));
        q->rootpow2tab[63-i]=sqrt(1.0/(float)((uint64_t)1<<i));
    }
}

/* table generator */
static void init_gain_table(COOKContext *q) {
    int i;
    q->gain_size_factor = q->samples_per_channel/8;
    for (i=0 ; i<23 ; i++) {
        q->gain_table[i] = pow((double)q->pow2tab[i+52] ,
                               (1.0/(double)q->gain_size_factor));
    }
}


static int init_cook_vlc_tables(COOKContext *q) {
    int i, result;

    result = 0;
    for (i=0 ; i<13 ; i++) {
        result &= init_vlc (&q->envelope_quant_index[i], 9, 24,
            envelope_quant_index_huffbits[i], 1, 1,
            envelope_quant_index_huffcodes[i], 2, 2, 0);
    }
    av_log(NULL,AV_LOG_DEBUG,"sqvh VLC init\n");
    for (i=0 ; i<7 ; i++) {
        result &= init_vlc (&q->sqvh[i], vhvlcsize_tab[i], vhsize_tab[i],
            cvh_huffbits[i], 1, 1,
            cvh_huffcodes[i], 2, 2, 0);
    }

    if (q->nb_channels==2 && q->joint_stereo==1){
        result &= init_vlc (&q->ccpl, 6, (1<<q->js_vlc_bits)-1,
            ccpl_huffbits[q->js_vlc_bits-2], 1, 1,
            ccpl_huffcodes[q->js_vlc_bits-2], 2, 2, 0);
        av_log(NULL,AV_LOG_DEBUG,"Joint-stereo VLC used.\n");
    }

    av_log(NULL,AV_LOG_DEBUG,"VLC tables initialized.\n");
    return result;
}

static int init_cook_mlt(COOKContext *q) {
    int j;
    float alpha;

    /* Allocate the buffers, could be replaced with a static [512]
       array if needed. */
    q->mlt_size = q->samples_per_channel;
    q->mlt_window = av_malloc(sizeof(float)*q->mlt_size);
    q->mlt_precos = av_malloc(sizeof(float)*q->mlt_size/2);
    q->mlt_presin = av_malloc(sizeof(float)*q->mlt_size/2);
    q->mlt_postcos = av_malloc(sizeof(float)*q->mlt_size/2);

    /* Initialize the MLT window: simple sine window. */
    alpha = M_PI / (2.0 * (float)q->mlt_size);
    for(j=0 ; j<q->mlt_size ; j++) {
        q->mlt_window[j] = sin((j + 512.0/(float)q->mlt_size) * alpha);
    }

    /* pre/post twiddle factors */
    for (j=0 ; j<q->mlt_size/2 ; j++){
        q->mlt_precos[j] = cos( ((j+0.25)*M_PI)/q->mlt_size);
        q->mlt_presin[j] = sin( ((j+0.25)*M_PI)/q->mlt_size);
        q->mlt_postcos[j] = (float)sqrt(2.0/(float)q->mlt_size)*cos( ((float)j*M_PI) /q->mlt_size); //sqrt(2/MLT_size) = scalefactor
    }

    /* Initialize the FFT. */
    ff_fft_init(&q->fft_ctx, av_log2(q->mlt_size)-1, 0);
    av_log(NULL,AV_LOG_DEBUG,"FFT initialized, order = %d.\n",
           av_log2(q->samples_per_channel)-1);

    return (int)(q->mlt_window && q->mlt_precos && q->mlt_presin && q->mlt_postcos);
}

/*************** init functions end ***********/

/**
 * Cook indata decoding, every 32 bits are XORed with 0x37c511f2.
 * Why? No idea, some checksum/error detection method maybe.
 * Nice way to waste CPU cycles.
 *
 * @param in        pointer to 32bit array of indata
 * @param bits      amount of bits
 * @param out       pointer to 32bit array of outdata
 */

static inline void decode_bytes(uint8_t* inbuffer, uint8_t* out, int bytes){
    int i;
    uint32_t* buf = (uint32_t*) inbuffer;
    uint32_t* obuf = (uint32_t*) out;
    /* FIXME: 64 bit platforms would be able to do 64 bits at a time.
     * I'm too lazy though, should be something like
     * for(i=0 ; i<bitamount/64 ; i++)
     *     (int64_t)out[i] = 0x37c511f237c511f2^be2me_64(int64_t)in[i]);
     * Buffer alignment needs to be checked. */


    for(i=0 ; i<bytes/4 ; i++){
#ifdef WORDS_BIGENDIAN
        obuf[i] = 0x37c511f2^buf[i];
#else
        obuf[i] = 0xf211c537^buf[i];
#endif
    }
}

/**
 * Cook uninit
 */

static int cook_decode_close(AVCodecContext *avctx)
{
    int i;
    COOKContext *q = avctx->priv_data;
    av_log(NULL,AV_LOG_DEBUG, "Deallocating memory.\n");

    /* Free allocated memory buffers. */
    av_free(q->mlt_window);
    av_free(q->mlt_precos);
    av_free(q->mlt_presin);
    av_free(q->mlt_postcos);
    av_free(q->decoded_bytes_buffer);

    /* Free the transform. */
    ff_fft_end(&q->fft_ctx);

    /* Free the VLC tables. */
    for (i=0 ; i<13 ; i++) {
        free_vlc(&q->envelope_quant_index[i]);
    }
    for (i=0 ; i<7 ; i++) {
        free_vlc(&q->sqvh[i]);
    }
    if(q->nb_channels==2 && q->joint_stereo==1 ){
        free_vlc(&q->ccpl);
    }

    av_log(NULL,AV_LOG_DEBUG,"Memory deallocated.\n");

    return 0;
}

/**
 * Fill the COOKgain structure for the timedomain quantization.
 *
 * @param q                 pointer to the COOKContext
 * @param gaininfo          pointer to the COOKgain
 */

static void decode_gain_info(GetBitContext *gb, COOKgain* gaininfo) {
    int i;

    while (get_bits1(gb)) {}

    gaininfo->size = get_bits_count(gb) - 1;     //amount of elements*2 to update

    if (get_bits_count(gb) - 1 <= 0) return;

    for (i=0 ; i<gaininfo->size ; i++){
        gaininfo->qidx_table1[i] = get_bits(gb,3);
        if (get_bits1(gb)) {
            gaininfo->qidx_table2[i] = get_bits(gb,4) - 7;  //convert to signed
        } else {
            gaininfo->qidx_table2[i] = -1;
        }
    }
}

/**
 * Create the quant index table needed for the envelope.
 *
 * @param q                 pointer to the COOKContext
 * @param quant_index_table pointer to the array
 */

static void decode_envelope(COOKContext *q, int* quant_index_table) {
    int i,j, vlc_index;
    int bitbias;

    bitbias = get_bits_count(&q->gb);
    quant_index_table[0]= get_bits(&q->gb,6) - 6;       //This is used later in categorize

    for (i=1 ; i < q->total_subbands ; i++){
        vlc_index=i;
        if (i >= q->js_subband_start * 2) {
            vlc_index-=q->js_subband_start;
        } else {
            vlc_index/=2;
            if(vlc_index < 1) vlc_index = 1;
        }
        if (vlc_index>13) vlc_index = 13;           //the VLC tables >13 are identical to No. 13

        j = get_vlc2(&q->gb, q->envelope_quant_index[vlc_index-1].table,
                     q->envelope_quant_index[vlc_index-1].bits,2);
        quant_index_table[i] = quant_index_table[i-1] + j - 12;    //differential encoding
    }
}

/**
 * Create the quant value table.
 *
 * @param q                 pointer to the COOKContext
 * @param quant_value_table pointer to the array
 */

static void inline dequant_envelope(COOKContext *q, int* quant_index_table,
                                    float* quant_value_table){

    int i;
    for(i=0 ; i < q->total_subbands ; i++){
        quant_value_table[i] = q->rootpow2tab[quant_index_table[i]+63];
    }
}

/**
 * Calculate the category and category_index vector.
 *
 * @param q                     pointer to the COOKContext
 * @param quant_index_table     pointer to the array
 * @param category              pointer to the category array
 * @param category_index        pointer to the category_index array
 */

static void categorize(COOKContext *q, int* quant_index_table,
                       int* category, int* category_index){
    int exp_idx, bias, tmpbias, bits_left, num_bits, index, v, i, j;
    int exp_index2[102];
    int exp_index1[102];

    int tmp_categorize_array1[128];
    int tmp_categorize_array1_idx=0;
    int tmp_categorize_array2[128];
    int tmp_categorize_array2_idx=0;
    int category_index_size=0;

    bits_left =  q->bits_per_subpacket - get_bits_count(&q->gb);