imc.c.svn-base

mediastreamer2是开源的网络传输媒体流的库

        for(i = 0; i < BANDS; i++) {
            workT[i] = q->bitsBandT[i] ? (q->bitsBandT[i] * -2 + q->flcoeffs4[i] + 1.585) : 1.e20;
        }
        if (stream_format_code & 0x2) {
            workT[0] = 1.e20;
            workT[1] = 1.e20;
            workT[2] = 1.e20;
            workT[3] = 1.e20;
        }
        while (freebits < summer){
            lowest = 1.e10;
            low_indx = 0;
            for(i = 0; i < BANDS; i++) {
                if (workT[i] < lowest) {
                    lowest = workT[i];
                    low_indx = i;
                }
            }
            //if(lowest >= 1.e10) break;
            workT[low_indx] = lowest + 2.0;

            if (!(--q->bitsBandT[low_indx]))
                workT[low_indx] = 1.e20;

            for(j = band_tab[low_indx]; j < band_tab[low_indx+1] && (freebits < summer); j++){
                if(q->CWlengthT[j] > 0){
                    q->CWlengthT[j]--;
                    summer--;
                }
            }
        }
    }
    return 0;
}

static void imc_get_skip_coeff(IMCContext* q) {
    int i, j;

    memset(q->skipFlagBits, 0, sizeof(q->skipFlagBits));
    memset(q->skipFlagCount, 0, sizeof(q->skipFlagCount));
    for(i = 0; i < BANDS; i++) {
        if (!q->bandFlagsBuf[i] || !q->bandWidthT[i])
            continue;

        if (!q->skipFlagRaw[i]) {
            q->skipFlagBits[i] = band_tab[i+1] - band_tab[i];

            for(j = band_tab[i]; j < band_tab[i+1]; j++) {
                if ((q->skipFlags[j] = get_bits1(&q->gb)))
                    q->skipFlagCount[i]++;
            }
        } else {
            for(j = band_tab[i]; j < (band_tab[i+1]-1); j += 2) {
                if(!get_bits1(&q->gb)){//0
                    q->skipFlagBits[i]++;
                    q->skipFlags[j]=1;
                    q->skipFlags[j+1]=1;
                    q->skipFlagCount[i] += 2;
                }else{
                    if(get_bits1(&q->gb)){//11
                        q->skipFlagBits[i] +=2;
                        q->skipFlags[j]=0;
                        q->skipFlags[j+1]=1;
                        q->skipFlagCount[i]++;
                    }else{
                        q->skipFlagBits[i] +=3;
                        q->skipFlags[j+1]=0;
                        if(!get_bits1(&q->gb)){//100
                            q->skipFlags[j]=1;
                            q->skipFlagCount[i]++;
                        }else{//101
                            q->skipFlags[j]=0;
                        }
                    }
                }
            }

            if (j < band_tab[i+1]) {
                q->skipFlagBits[i]++;
                if ((q->skipFlags[j] = get_bits1(&q->gb)))
                    q->skipFlagCount[i]++;
            }
        }
    }
}

/**
 * Increase highest' band coefficient sizes as some bits won't be used
 */
static void imc_adjust_bit_allocation (IMCContext* q, int summer) {
    float workT[32];
    int corrected = 0;
    int i, j;
    float highest = 0;
    int found_indx=0;

    for(i = 0; i < BANDS; i++) {
        workT[i] = (q->bitsBandT[i] == 6) ? -1.e20 : (q->bitsBandT[i] * -2 + q->flcoeffs4[i] - 0.415);
    }

    while (corrected < summer) {
        if(highest <= -1.e20)
            break;

        highest = -1.e20;

        for(i = 0; i < BANDS; i++) {
            if (workT[i] > highest) {
                highest = workT[i];
                found_indx = i;
            }
        }

        if (highest > -1.e20) {
            workT[found_indx] -= 2.0;
            if (++(q->bitsBandT[found_indx]) == 6)
                workT[found_indx] = -1.e20;

            for(j = band_tab[found_indx]; j < band_tab[found_indx+1] && (corrected < summer); j++) {
                if (!q->skipFlags[j] && (q->CWlengthT[j] < 6)) {
                    q->CWlengthT[j]++;
                    corrected++;
                }
            }
        }
    }
}

static void imc_imdct256(IMCContext *q) {
    int i;
    float re, im;

    /* prerotation */
    for(i=0; i < COEFFS/2; i++){
        q->samples[i].re = -(q->pre_coef1[i] * q->CWdecoded[COEFFS-1-i*2]) -
                           (q->pre_coef2[i] * q->CWdecoded[i*2]);
        q->samples[i].im = (q->pre_coef2[i] * q->CWdecoded[COEFFS-1-i*2]) -
                           (q->pre_coef1[i] * q->CWdecoded[i*2]);
    }

    /* FFT */
    ff_fft_permute(&q->fft, q->samples);
    ff_fft_calc (&q->fft, q->samples);

    /* postrotation, window and reorder */
    for(i = 0; i < COEFFS/2; i++){
        re = (q->samples[i].re * q->post_cos[i]) + (-q->samples[i].im * q->post_sin[i]);
        im = (-q->samples[i].im * q->post_cos[i]) - (q->samples[i].re * q->post_sin[i]);
        q->out_samples[i*2] = (q->mdct_sine_window[COEFFS-1-i*2] * q->last_fft_im[i]) + (q->mdct_sine_window[i*2] * re);
        q->out_samples[COEFFS-1-i*2] = (q->mdct_sine_window[i*2] * q->last_fft_im[i]) - (q->mdct_sine_window[COEFFS-1-i*2] * re);
        q->last_fft_im[i] = im;
    }
}

static int inverse_quant_coeff (IMCContext* q, int stream_format_code) {
    int i, j;
    int middle_value, cw_len, max_size;
    const float* quantizer;

    for(i = 0; i < BANDS; i++) {
        for(j = band_tab[i]; j < band_tab[i+1]; j++) {
            q->CWdecoded[j] = 0;
            cw_len = q->CWlengthT[j];

            if (cw_len <= 0 || q->skipFlags[j])
                continue;

            max_size = 1 << cw_len;
            middle_value = max_size >> 1;

            if (q->codewords[j] >= max_size || q->codewords[j] < 0)
                return -1;

            if (cw_len >= 4){
                quantizer = imc_quantizer2[(stream_format_code & 2) >> 1];
                if (q->codewords[j] >= middle_value)
                    q->CWdecoded[j] = quantizer[q->codewords[j] - 8] * q->flcoeffs6[i];
                else
                    q->CWdecoded[j] = -quantizer[max_size - q->codewords[j] - 8 - 1] * q->flcoeffs6[i];
            }else{
                quantizer = imc_quantizer1[((stream_format_code & 2) >> 1) | (q->bandFlagsBuf[i] << 1)];
                if (q->codewords[j] >= middle_value)
                    q->CWdecoded[j] = quantizer[q->codewords[j] - 1] * q->flcoeffs6[i];
                else
                    q->CWdecoded[j] = -quantizer[max_size - 2 - q->codewords[j]] * q->flcoeffs6[i];
            }
        }
    }
    return 0;
}


static int imc_get_coeffs (IMCContext* q) {
    int i, j, cw_len, cw;

    for(i = 0; i < BANDS; i++) {
        if(!q->sumLenArr[i]) continue;
        if (q->bandFlagsBuf[i] || q->bandWidthT[i]) {
            for(j = band_tab[i]; j < band_tab[i+1]; j++) {
                cw_len = q->CWlengthT[j];
                cw = 0;

                if (get_bits_count(&q->gb) + cw_len > 512){
//av_log(NULL,0,"Band %i coeff %i cw_len %i\n",i,j,cw_len);
                    return -1;
                }

                if(cw_len && (!q->bandFlagsBuf[i] || !q->skipFlags[j]))
                    cw = get_bits(&q->gb, cw_len);

                q->codewords[j] = cw;
            }
        }
    }
    return 0;
}

static int imc_decode_frame(AVCodecContext * avctx,
                            void *data, int *data_size,
                            const uint8_t * buf, int buf_size)
{

    IMCContext *q = avctx->priv_data;

    int stream_format_code;
    int imc_hdr, i, j;
    int flag;
    int bits, summer;
    int counter, bitscount;
    uint16_t buf16[IMC_BLOCK_SIZE / 2];

    if (buf_size < IMC_BLOCK_SIZE) {
        av_log(avctx, AV_LOG_ERROR, "imc frame too small!\n");
        return -1;
    }
    for(i = 0; i < IMC_BLOCK_SIZE / 2; i++)
        buf16[i] = bswap_16(((const uint16_t*)buf)[i]);

    init_get_bits(&q->gb, (const uint8_t*)buf16, IMC_BLOCK_SIZE * 8);

    /* Check the frame header */
    imc_hdr = get_bits(&q->gb, 9);
    if (imc_hdr != IMC_FRAME_ID) {
        av_log(avctx, AV_LOG_ERROR, "imc frame header check failed!\n");
        av_log(avctx, AV_LOG_ERROR, "got %x instead of 0x21.\n", imc_hdr);
        return -1;
    }
    stream_format_code = get_bits(&q->gb, 3);

    if(stream_format_code & 1){
        av_log(avctx, AV_LOG_ERROR, "Stream code format %X is not supported\n", stream_format_code);
        return -1;
    }

//    av_log(avctx, AV_LOG_DEBUG, "stream_format_code = %d\n", stream_format_code);

    if (stream_format_code & 0x04)
        q->decoder_reset = 1;

    if(q->decoder_reset) {
        memset(q->out_samples, 0, sizeof(q->out_samples));
        for(i = 0; i < BANDS; i++)q->old_floor[i] = 1.0;
        for(i = 0; i < COEFFS; i++)q->CWdecoded[i] = 0;
        q->decoder_reset = 0;
    }

    flag = get_bits1(&q->gb);
    imc_read_level_coeffs(q, stream_format_code, q->levlCoeffBuf);

    if (stream_format_code & 0x4)
        imc_decode_level_coefficients(q, q->levlCoeffBuf, q->flcoeffs1, q->flcoeffs2);
    else
        imc_decode_level_coefficients2(q, q->levlCoeffBuf, q->old_floor, q->flcoeffs1, q->flcoeffs2);

    memcpy(q->old_floor, q->flcoeffs1, 32 * sizeof(float));

    counter = 0;
    for (i=0 ; i<BANDS ; i++) {
        if (q->levlCoeffBuf[i] == 16) {
            q->bandWidthT[i] = 0;
            counter++;
        } else
            q->bandWidthT[i] = band_tab[i+1] - band_tab[i];
    }
    memset(q->bandFlagsBuf, 0, BANDS * sizeof(int));
    for(i = 0; i < BANDS-1; i++) {
        if (q->bandWidthT[i])
            q->bandFlagsBuf[i] = get_bits1(&q->gb);
    }

    imc_calculate_coeffs(q, q->flcoeffs1, q->flcoeffs2, q->bandWidthT, q->flcoeffs3, q->flcoeffs5);

    bitscount = 0;
    /* first 4 bands will be assigned 5 bits per coefficient */
    if (stream_format_code & 0x2) {
        bitscount += 15;

        q->bitsBandT[0] = 5;
        q->CWlengthT[0] = 5;
        q->CWlengthT[1] = 5;
        q->CWlengthT[2] = 5;
        for(i = 1; i < 4; i++){
            bits = (q->levlCoeffBuf[i] == 16) ? 0 : 5;
            q->bitsBandT[i] = bits;
            for(j = band_tab[i]; j < band_tab[i+1]; j++) {
                q->CWlengthT[j] = bits;
                bitscount += bits;
            }
        }
    }

    if(bit_allocation (q, stream_format_code, 512 - bitscount - get_bits_count(&q->gb), flag) < 0) {
        av_log(avctx, AV_LOG_ERROR, "Bit allocations failed\n");
        q->decoder_reset = 1;
        return -1;
    }

    for(i = 0; i < BANDS; i++) {
        q->sumLenArr[i] = 0;
        q->skipFlagRaw[i] = 0;
        for(j = band_tab[i]; j < band_tab[i+1]; j++)
            q->sumLenArr[i] += q->CWlengthT[j];
        if (q->bandFlagsBuf[i])
            if( (((band_tab[i+1] - band_tab[i]) * 1.5) > q->sumLenArr[i]) && (q->sumLenArr[i] > 0))
                q->skipFlagRaw[i] = 1;
    }

    imc_get_skip_coeff(q);

    for(i = 0; i < BANDS; i++) {
        q->flcoeffs6[i] = q->flcoeffs1[i];
        /* band has flag set and at least one coded coefficient */
        if (q->bandFlagsBuf[i] && (band_tab[i+1] - band_tab[i]) != q->skipFlagCount[i]){
                q->flcoeffs6[i] *= q->sqrt_tab[band_tab[i+1] - band_tab[i]] /
                                   q->sqrt_tab[(band_tab[i+1] - band_tab[i] - q->skipFlagCount[i])];
        }
    }

    /* calculate bits left, bits needed and adjust bit allocation */
    bits = summer = 0;

    for(i = 0; i < BANDS; i++) {
        if (q->bandFlagsBuf[i]) {
            for(j = band_tab[i]; j < band_tab[i+1]; j++) {
                if(q->skipFlags[j]) {
                    summer += q->CWlengthT[j];
                    q->CWlengthT[j] = 0;
                }
            }
            bits += q->skipFlagBits[i];
            summer -= q->skipFlagBits[i];
        }
    }
    imc_adjust_bit_allocation(q, summer);

    for(i = 0; i < BANDS; i++) {
        q->sumLenArr[i] = 0;

        for(j = band_tab[i]; j < band_tab[i+1]; j++)
            if (!q->skipFlags[j])
                q->sumLenArr[i] += q->CWlengthT[j];
    }

    memset(q->codewords, 0, sizeof(q->codewords));

    if(imc_get_coeffs(q) < 0) {
        av_log(avctx, AV_LOG_ERROR, "Read coefficients failed\n");
        q->decoder_reset = 1;
        return 0;
    }

    if(inverse_quant_coeff(q, stream_format_code) < 0) {
        av_log(avctx, AV_LOG_ERROR, "Inverse quantization of coefficients failed\n");
        q->decoder_reset = 1;
        return 0;
    }

    memset(q->skipFlags, 0, sizeof(q->skipFlags));

    imc_imdct256(q);

    q->dsp.float_to_int16(data, q->out_samples, COEFFS);

    *data_size = COEFFS * sizeof(int16_t);

    return IMC_BLOCK_SIZE;
}


static int imc_decode_close(AVCodecContext * avctx)
{
    IMCContext *q = avctx->priv_data;

    ff_fft_end(&q->fft);
    return 0;
}


AVCodec imc_decoder = {
    .name = "imc",
    .type = CODEC_TYPE_AUDIO,
    .id = CODEC_ID_IMC,
    .priv_data_size = sizeof(IMCContext),
    .init = imc_decode_init,
    .close = imc_decode_close,
    .decode = imc_decode_frame,
};