cook.c

ffmpeg源码分析

    if(bits_left > q->samples_per_channel) {
        bits_left = q->samples_per_channel +
                    ((bits_left - q->samples_per_channel)*5)/8;
        //av_log(NULL, AV_LOG_ERROR, "bits_left = %d\n",bits_left);
    }

    memset(&exp_index1,0,102*sizeof(int));
    memset(&exp_index2,0,102*sizeof(int));
    memset(&tmp_categorize_array1,0,128*sizeof(int));
    memset(&tmp_categorize_array2,0,128*sizeof(int));

    bias=-32;

    /* Estimate bias. */
    for (i=32 ; i>0 ; i=i/2){
        num_bits = 0;
        index = 0;
        for (j=q->total_subbands ; j>0 ; j--){
            exp_idx = (i - quant_index_table[index] + bias) / 2;
            if (exp_idx<0){
                exp_idx=0;
            } else if(exp_idx >7) {
                exp_idx=7;
            }
            index++;
            num_bits+=expbits_tab[exp_idx];
        }
        if(num_bits >= bits_left - 32){
            bias+=i;
        }
    }

    /* Calculate total number of bits. */
    num_bits=0;
    for (i=0 ; i<q->total_subbands ; i++) {
        exp_idx = (bias - quant_index_table[i]) / 2;
        if (exp_idx<0) {
            exp_idx=0;
        } else if(exp_idx >7) {
            exp_idx=7;
        }
        num_bits += expbits_tab[exp_idx];
        exp_index1[i] = exp_idx;
        exp_index2[i] = exp_idx;
    }
    tmpbias = bias = num_bits;

    for (j = 1 ; j < q->numvector_size ; j++) {
        if (tmpbias + bias > 2*bits_left) {  /* ---> */
            int max = -999999;
            index=-1;
            for (i=0 ; i<q->total_subbands ; i++){
                if (exp_index1[i] < 7) {
                    v = (-2*exp_index1[i]) - quant_index_table[i] - 32;
                    if ( v >= max) {
                        max = v;
                        index = i;
                    }
                }
            }
            if(index==-1)break;
            tmp_categorize_array1[tmp_categorize_array1_idx++] = index;
            tmpbias -= expbits_tab[exp_index1[index]] -
                       expbits_tab[exp_index1[index]+1];
            ++exp_index1[index];
        } else {  /* <--- */
            int min = 999999;
            index=-1;
            for (i=0 ; i<q->total_subbands ; i++){
                if(exp_index2[i] > 0){
                    v = (-2*exp_index2[i])-quant_index_table[i];
                    if ( v < min) {
                        min = v;
                        index = i;
                    }
                }
            }
            if(index == -1)break;
            tmp_categorize_array2[tmp_categorize_array2_idx++] = index;
            tmpbias -= expbits_tab[exp_index2[index]] -
                       expbits_tab[exp_index2[index]-1];
            --exp_index2[index];
        }
    }

    for(i=0 ; i<q->total_subbands ; i++)
        category[i] = exp_index2[i];

    /* Concatenate the two arrays. */
    for(i=tmp_categorize_array2_idx-1 ; i >= 0; i--)
        category_index[category_index_size++] =  tmp_categorize_array2[i];

    for(i=0;i<tmp_categorize_array1_idx;i++)
        category_index[category_index_size++ ] =  tmp_categorize_array1[i];

    /* FIXME: mc_sich_ra8_20.rm triggers this, not sure with what we
       should fill the remaining bytes. */
    for(i=category_index_size;i<q->numvector_size;i++)
        category_index[i]=0;

}


/**
 * Expand the category vector.
 *
 * @param q                     pointer to the COOKContext
 * @param category              pointer to the category array
 * @param category_index        pointer to the category_index array
 */

static void inline expand_category(COOKContext *q, int* category,
                                   int* category_index){
    int i;
    for(i=0 ; i<q->num_vectors ; i++){
        ++category[category_index[i]];
    }
}

/**
 * The real requantization of the mltcoefs
 *
 * @param q                     pointer to the COOKContext
 * @param index                 index
 * @param band                  current subband
 * @param quant_value_table     pointer to the array
 * @param subband_coef_index    array of indexes to quant_centroid_tab
 * @param subband_coef_noise    use random noise instead of predetermined value
 * @param mlt_buffer            pointer to the mlt buffer
 */


static void scalar_dequant(COOKContext *q, int index, int band,
                           float* quant_value_table, int* subband_coef_index,
                           int* subband_coef_noise, float* mlt_buffer){
    int i;
    float f1;

    for(i=0 ; i<SUBBAND_SIZE ; i++) {
        if (subband_coef_index[i]) {
            if (subband_coef_noise[i]) {
                f1 = -quant_centroid_tab[index][subband_coef_index[i]];
            } else {
                f1 = quant_centroid_tab[index][subband_coef_index[i]];
            }
        } else {
            /* noise coding if subband_coef_noise[i] == 0 */
            q->random_state = q->random_state * 214013 + 2531011;    //typical RNG numbers
            f1 = randsign[(q->random_state/0x1000000)&1] * dither_tab[index]; //>>31
        }
        mlt_buffer[band*20+ i] = f1 * quant_value_table[band];
    }
}
/**
 * Unpack the subband_coef_index and subband_coef_noise vectors.
 *
 * @param q                     pointer to the COOKContext
 * @param category              pointer to the category array
 * @param subband_coef_index    array of indexes to quant_centroid_tab
 * @param subband_coef_noise    use random noise instead of predetermined value
 */

static int unpack_SQVH(COOKContext *q, int category, int* subband_coef_index,
                       int* subband_coef_noise) {
    int i,j;
    int vlc, vd ,tmp, result;
    int ub;
    int cb;

    vd = vd_tab[category];
    result = 0;
    for(i=0 ; i<vpr_tab[category] ; i++){
        ub = get_bits_count(&q->gb);
        vlc = get_vlc2(&q->gb, q->sqvh[category].table, q->sqvh[category].bits, 3);
        cb = get_bits_count(&q->gb);
        if (q->bits_per_subpacket < get_bits_count(&q->gb)){
            vlc = 0;
            result = 1;
        }
        for(j=vd-1 ; j>=0 ; j--){
            tmp = (vlc * invradix_tab[category])/0x100000;
            subband_coef_index[vd*i+j] = vlc - tmp * (kmax_tab[category]+1);
            vlc = tmp;
        }
        for(j=0 ; j<vd ; j++){
            if (subband_coef_index[i*vd + j]) {
                if(get_bits_count(&q->gb) < q->bits_per_subpacket){
                    subband_coef_noise[i*vd+j] = get_bits1(&q->gb);
                } else {
                    result=1;
                    subband_coef_noise[i*vd+j]=0;
                }
            } else {
                subband_coef_noise[i*vd+j]=0;
            }
        }
    }
    return result;
}


/**
 * Fill the mlt_buffer with mlt coefficients.
 *
 * @param q                 pointer to the COOKContext
 * @param category          pointer to the category array
 * @param quant_value_table pointer to the array
 * @param mlt_buffer        pointer to mlt coefficients
 */


static void decode_vectors(COOKContext* q, int* category,
                           float* quant_value_table, float* mlt_buffer){
    /* A zero in this table means that the subband coefficient is
       random noise coded. */
    int subband_coef_noise[SUBBAND_SIZE];
    /* A zero in this table means that the subband coefficient is a
       positive multiplicator. */
    int subband_coef_index[SUBBAND_SIZE];
    int band, j;
    int index=0;

    for(band=0 ; band<q->total_subbands ; band++){
        index = category[band];
        if(category[band] < 7){
            if(unpack_SQVH(q, category[band], subband_coef_index, subband_coef_noise)){
                index=7;
                for(j=0 ; j<q->total_subbands ; j++) category[band+j]=7;
            }
        }
        if(index==7) {
            memset(subband_coef_index, 0, sizeof(subband_coef_index));
            memset(subband_coef_noise, 0, sizeof(subband_coef_noise));
        }
        scalar_dequant(q, index, band, quant_value_table, subband_coef_index,
                       subband_coef_noise, mlt_buffer);
    }

    if(q->total_subbands*SUBBAND_SIZE >= q->samples_per_channel){
        return;
    }
}


/**
 * function for decoding mono data
 *
 * @param q                 pointer to the COOKContext
 * @param mlt_buffer1       pointer to left channel mlt coefficients
 * @param mlt_buffer2       pointer to right channel mlt coefficients
 */

static void mono_decode(COOKContext *q, float* mlt_buffer) {

    int category_index[128];
    float quant_value_table[102];
    int quant_index_table[102];
    int category[128];

    memset(&category, 0, 128*sizeof(int));
    memset(&quant_value_table, 0, 102*sizeof(int));
    memset(&category_index, 0, 128*sizeof(int));

    decode_envelope(q, quant_index_table);
    q->num_vectors = get_bits(&q->gb,q->log2_numvector_size);
    dequant_envelope(q, quant_index_table, quant_value_table);
    categorize(q, quant_index_table, category, category_index);
    expand_category(q, category, category_index);
    decode_vectors(q, category, quant_value_table, mlt_buffer);
}


/**
 * The modulated lapped transform, this takes transform coefficients
 * and transforms them into timedomain samples. This is done through
 * an FFT-based algorithm with pre- and postrotation steps.
 * A window and reorder step is also included.
 *
 * @param q                 pointer to the COOKContext
 * @param inbuffer          pointer to the mltcoefficients
 * @param outbuffer         pointer to the timedomain buffer
 * @param mlt_tmp           pointer to temporary storage space
 */

static void cook_imlt(COOKContext *q, float* inbuffer, float* outbuffer,
                      float* mlt_tmp){
    int i;

    /* prerotation */
    for(i=0 ; i<q->mlt_size ; i+=2){
        outbuffer[i] = (q->mlt_presin[i/2] * inbuffer[q->mlt_size-1-i]) +
                       (q->mlt_precos[i/2] * inbuffer[i]);
        outbuffer[i+1] = (q->mlt_precos[i/2] * inbuffer[q->mlt_size-1-i]) -
                         (q->mlt_presin[i/2] * inbuffer[i]);
    }

    /* FFT */
    ff_fft_permute(&q->fft_ctx, (FFTComplex *) outbuffer);
    ff_fft_calc (&q->fft_ctx, (FFTComplex *) outbuffer);

    /* postrotation */
    for(i=0 ; i<q->mlt_size ; i+=2){
        mlt_tmp[i] =               (q->mlt_postcos[(q->mlt_size-1-i)/2] * outbuffer[i+1]) +
                                   (q->mlt_postcos[i/2] * outbuffer[i]);
        mlt_tmp[q->mlt_size-1-i] = (q->mlt_postcos[(q->mlt_size-1-i)/2] * outbuffer[i]) -
                                   (q->mlt_postcos[i/2] * outbuffer[i+1]);
    }

    /* window and reorder */
    for(i=0 ; i<q->mlt_size/2 ; i++){
        outbuffer[i] = mlt_tmp[q->mlt_size/2-1-i] * q->mlt_window[i];
        outbuffer[q->mlt_size-1-i]= mlt_tmp[q->mlt_size/2-1-i] *
                                    q->mlt_window[q->mlt_size-1-i];
        outbuffer[q->mlt_size+i]= mlt_tmp[q->mlt_size/2+i] *
                                  q->mlt_window[q->mlt_size-1-i];
        outbuffer[2*q->mlt_size-1-i]= -(mlt_tmp[q->mlt_size/2+i] *
                                      q->mlt_window[i]);
    }
}


/**
 * the actual requantization of the timedomain samples
 *
 * @param q                 pointer to the COOKContext
 * @param buffer            pointer to the timedomain buffer
 * @param gain_index        index for the block multiplier
 * @param gain_index_next   index for the next block multiplier
 */

static void interpolate(COOKContext *q, float* buffer,
                        int gain_index, int gain_index_next){
    int i;
    float fc1, fc2;
    fc1 = q->pow2tab[gain_index+63];

    if(gain_index == gain_index_next){              //static gain
        for(i=0 ; i<q->gain_size_factor ; i++){
            buffer[i]*=fc1;
        }
        return;
    } else {                                        //smooth gain
        fc2 = q->gain_table[11 + (gain_index_next-gain_index)];
        for(i=0 ; i<q->gain_size_factor ; i++){
            buffer[i]*=fc1;
            fc1*=fc2;
        }
        return;
    }
}

/**
 * timedomain requantization of the timedomain samples
 *
 * @param q                 pointer to the COOKContext
 * @param buffer            pointer to the timedomain buffer
 * @param gain_now          current gain structure
 * @param gain_previous     previous gain structure
 */

static void gain_window(COOKContext *q, float* buffer, COOKgain* gain_now,
                        COOKgain* gain_previous){
    int i, index;
    int gain_index[9];
    int tmp_gain_index;

    gain_index[8]=0;
    index = gain_previous->size;
    for (i=7 ; i>=0 ; i--) {
        if(index && gain_previous->qidx_table1[index-1]==i) {
            gain_index[i] = gain_previous->qidx_table2[index-1];
            index--;
        } else {
            gain_index[i]=gain_index[i+1];
        }
    }
    /* This is applied to the to be previous data buffer. */
    for(i=0;i<8;i++){
        interpolate(q, &buffer[q->samples_per_channel+q->gain_size_factor*i],
                    gain_index[i], gain_index[i+1]);
    }

    tmp_gain_index = gain_index[0];
    index = gain_now->size;
    for (i=7 ; i>=0 ; i--) {
        if(index && gain_now->qidx_table1[index-1]==i) {
            gain_index[i]= gain_now->qidx_table2[index-1];
            index--;
        } else {
            gain_index[i]=gain_index[i+1];
        }
    }

    /* This is applied to the to be current block. */
    for(i=0;i<8;i++){
        interpolate(q, &buffer[i*q->gain_size_factor],
                    tmp_gain_index+gain_index[i],
                    tmp_gain_index+gain_index[i+1]);
    }
}


/**
 * mlt overlapping and buffer management
 *
 * @param q                 pointer to the COOKContext
 * @param buffer            pointer to the timedomain buffer
 * @param gain_now          current gain structure
 * @param gain_previous     previous gain structure
 * @param previous_buffer   pointer to the previous buffer to be used for overlapping
 *
 */

static void gain_compensate(COOKContext *q, float* buffer, COOKgain* gain_now,
                            COOKgain* gain_previous, float* previous_buffer) {
    int i;
    if((gain_now->size  || gain_previous->size)) {
        gain_window(q, buffer, gain_now, gain_previous);
    }

    /* Overlap with the previous block. */
    for(i=0 ; i<q->samples_per_channel ; i++) buffer[i]+=previous_buffer[i];

    /* Save away the current to be previous block. */
    memcpy(previous_buffer, buffer+q->samples_per_channel,
           sizeof(float)*q->samples_per_channel);
}


/**
 * function for getting the jointstereo coupling information
 *
 * @param q                 pointer to the COOKContext
 * @param decouple_tab      decoupling array
 *
 */