ac3dec.c

ffmpeg移植到symbian的全部源代码

typedef struct {
    int b1_mant[3];
    int b2_mant[3];
    int b4_mant[2];
    int b1ptr;
    int b2ptr;
    int b4ptr;
} mant_groups;

/**
 * Get the transform coefficients for a particular channel
 * reference: Section 7.3 Quantization and Decoding of Mantissas
 */
static void get_transform_coeffs_ch(AC3DecodeContext *s, int ch_index, mant_groups *m)
{
    GetBitContext *gbc = &s->gbc;
    int i, gcode, tbap, start, end;
    uint8_t *exps;
    uint8_t *bap;
    int *coeffs;

#ifndef __CW32__
    exps = s->dexps[ch_index];
#else
    exps = (uint8_t*)s->dexps[ch_index];
#endif
    bap = s->bap[ch_index];
    coeffs = s->fixed_coeffs[ch_index];
    start = s->start_freq[ch_index];
    end = s->end_freq[ch_index];

    for (i = start; i < end; i++) {
        tbap = bap[i];
        switch (tbap) {
            case 0:
                coeffs[i] = (av_random(&s->dith_state) & 0x7FFFFF) - 4194304;
                break;

            case 1:
                if(m->b1ptr > 2) {
                    gcode = get_bits(gbc, 5);
                    m->b1_mant[0] = b1_mantissas[gcode][0];
                    m->b1_mant[1] = b1_mantissas[gcode][1];
                    m->b1_mant[2] = b1_mantissas[gcode][2];
                    m->b1ptr = 0;
                }
                coeffs[i] = m->b1_mant[m->b1ptr++];
                break;

            case 2:
                if(m->b2ptr > 2) {
                    gcode = get_bits(gbc, 7);
                    m->b2_mant[0] = b2_mantissas[gcode][0];
                    m->b2_mant[1] = b2_mantissas[gcode][1];
                    m->b2_mant[2] = b2_mantissas[gcode][2];
                    m->b2ptr = 0;
                }
                coeffs[i] = m->b2_mant[m->b2ptr++];
                break;

            case 3:
                coeffs[i] = b3_mantissas[get_bits(gbc, 3)];
                break;

            case 4:
                if(m->b4ptr > 1) {
                    gcode = get_bits(gbc, 7);
                    m->b4_mant[0] = b4_mantissas[gcode][0];
                    m->b4_mant[1] = b4_mantissas[gcode][1];
                    m->b4ptr = 0;
                }
                coeffs[i] = m->b4_mant[m->b4ptr++];
                break;

            case 5:
                coeffs[i] = b5_mantissas[get_bits(gbc, 4)];
                break;

            default: {
                /* asymmetric dequantization */
                int qlevel = quantization_tab[tbap];
                coeffs[i] = get_sbits(gbc, qlevel) << (24 - qlevel);
                break;
            }
        }
        coeffs[i] >>= exps[i];
    }
}

/**
 * Remove random dithering from coefficients with zero-bit mantissas
 * reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0)
 */
static void remove_dithering(AC3DecodeContext *s) {
    int ch, i;
    int end=0;
    int *coeffs;
    uint8_t *bap;

    for(ch=1; ch<=s->fbw_channels; ch++) {
        if(!s->dither_flag[ch]) {
            coeffs = s->fixed_coeffs[ch];
            bap = s->bap[ch];
            if(s->channel_in_cpl[ch])
                end = s->start_freq[CPL_CH];
            else
                end = s->end_freq[ch];
            for(i=0; i<end; i++) {
                if(!bap[i])
                    coeffs[i] = 0;
            }
            if(s->channel_in_cpl[ch]) {
                bap = s->bap[CPL_CH];
                for(; i<s->end_freq[CPL_CH]; i++) {
                    if(!bap[i])
                        coeffs[i] = 0;
                }
            }
        }
    }
}

/**
 * Get the transform coefficients.
 */
static void get_transform_coeffs(AC3DecodeContext *s)
{
    int ch, end;
    int got_cplchan = 0;
    mant_groups m;

    m.b1ptr = m.b2ptr = m.b4ptr = 3;

    for (ch = 1; ch <= s->channels; ch++) {
        /* transform coefficients for full-bandwidth channel */
        get_transform_coeffs_ch(s, ch, &m);
        /* tranform coefficients for coupling channel come right after the
           coefficients for the first coupled channel*/
        if (s->channel_in_cpl[ch])  {
            if (!got_cplchan) {
                get_transform_coeffs_ch(s, CPL_CH, &m);
                uncouple_channels(s);
                got_cplchan = 1;
            }
            end = s->end_freq[CPL_CH];
        } else {
            end = s->end_freq[ch];
        }
        do
            s->fixed_coeffs[ch][end] = 0;
        while(++end < 256);
    }

    /* if any channel doesn't use dithering, zero appropriate coefficients */
    if(!s->dither_all)
        remove_dithering(s);
}

/**
 * Stereo rematrixing.
 * reference: Section 7.5.4 Rematrixing : Decoding Technique
 */
static void do_rematrixing(AC3DecodeContext *s)
{
    int bnd, i;
    int end, bndend;
    int tmp0, tmp1;

    end = FFMIN(s->end_freq[1], s->end_freq[2]);

    for(bnd=0; bnd<s->num_rematrixing_bands; bnd++) {
        if(s->rematrixing_flags[bnd]) {
            bndend = FFMIN(end, ff_ac3_rematrix_band_tab[bnd+1]);
            for(i=ff_ac3_rematrix_band_tab[bnd]; i<bndend; i++) {
                tmp0 = s->fixed_coeffs[1][i];
                tmp1 = s->fixed_coeffs[2][i];
                s->fixed_coeffs[1][i] = tmp0 + tmp1;
                s->fixed_coeffs[2][i] = tmp0 - tmp1;
            }
        }
    }
}

/**
 * Perform the 256-point IMDCT
 */
static void do_imdct_256(AC3DecodeContext *s, int chindex)
{
    int i, k;
    DECLARE_ALIGNED_16(float, x[128]);
    FFTComplex z[2][64];
    float *o_ptr = s->tmp_output;

    for(i=0; i<2; i++) {
        /* de-interleave coefficients */
        for(k=0; k<128; k++) {
            x[k] = s->transform_coeffs[chindex][2*k+i];
        }

        /* run standard IMDCT */
        s->imdct_256.fft.imdct_calc(&s->imdct_256, o_ptr, x, s->tmp_imdct);

        /* reverse the post-rotation & reordering from standard IMDCT */
        for(k=0; k<32; k++) {
            z[i][32+k].re = -o_ptr[128+2*k];
            z[i][32+k].im = -o_ptr[2*k];
            z[i][31-k].re =  o_ptr[2*k+1];
            z[i][31-k].im =  o_ptr[128+2*k+1];
        }
    }

    /* apply AC-3 post-rotation & reordering */
    for(k=0; k<64; k++) {
        o_ptr[    2*k  ] = -z[0][   k].im;
        o_ptr[    2*k+1] =  z[0][63-k].re;
        o_ptr[128+2*k  ] = -z[0][   k].re;
        o_ptr[128+2*k+1] =  z[0][63-k].im;
        o_ptr[256+2*k  ] = -z[1][   k].re;
        o_ptr[256+2*k+1] =  z[1][63-k].im;
        o_ptr[384+2*k  ] =  z[1][   k].im;
        o_ptr[384+2*k+1] = -z[1][63-k].re;
    }
}

/**
 * Inverse MDCT Transform.
 * Convert frequency domain coefficients to time-domain audio samples.
 * reference: Section 7.9.4 Transformation Equations
 */
static inline void do_imdct(AC3DecodeContext *s, int channels)
{
    int ch;

    for (ch=1; ch<=channels; ch++) {
        if (s->block_switch[ch]) {
            do_imdct_256(s, ch);
        } else {
            s->imdct_512.fft.imdct_calc(&s->imdct_512, s->tmp_output,
                                        s->transform_coeffs[ch], s->tmp_imdct);
        }
        /* For the first half of the block, apply the window, add the delay
           from the previous block, and send to output */
        s->dsp.vector_fmul_add_add(s->output[ch-1], s->tmp_output,
                                     s->window, s->delay[ch-1], 0, 256, 1);
        /* For the second half of the block, apply the window and store the
           samples to delay, to be combined with the next block */
        s->dsp.vector_fmul_reverse(s->delay[ch-1], s->tmp_output+256,
                                   s->window, 256);
    }
}

/**
 * Downmix the output to mono or stereo.
 */
static void ac3_downmix(AC3DecodeContext *s,
                        float samples[AC3_MAX_CHANNELS][256], int ch_offset)
{
    int i, j;
    float v0, v1;

    for(i=0; i<256; i++) {
        v0 = v1 = 0.0f;
        for(j=0; j<s->fbw_channels; j++) {
            v0 += samples[j+ch_offset][i] * s->downmix_coeffs[j][0];
            v1 += samples[j+ch_offset][i] * s->downmix_coeffs[j][1];
        }
        v0 *= s->downmix_coeff_adjust[0];
        v1 *= s->downmix_coeff_adjust[1];
        if(s->output_mode == AC3_CHMODE_MONO) {
            samples[ch_offset][i] = (v0 + v1) * LEVEL_MINUS_3DB;
        } else if(s->output_mode == AC3_CHMODE_STEREO) {
            samples[  ch_offset][i] = v0;
            samples[1+ch_offset][i] = v1;
        }
    }
}

/**
 * Upmix delay samples from stereo to original channel layout.
 */
static void ac3_upmix_delay(AC3DecodeContext *s)
{
    int channel_data_size = sizeof(s->delay[0]);
    switch(s->channel_mode) {
        case AC3_CHMODE_DUALMONO:
        case AC3_CHMODE_STEREO:
            /* upmix mono to stereo */
            memcpy(s->delay[1], s->delay[0], channel_data_size);
            break;
        case AC3_CHMODE_2F2R:
            memset(s->delay[3], 0, channel_data_size);
        case AC3_CHMODE_2F1R:
            memset(s->delay[2], 0, channel_data_size);
            break;
        case AC3_CHMODE_3F2R:
            memset(s->delay[4], 0, channel_data_size);
        case AC3_CHMODE_3F1R:
            memset(s->delay[3], 0, channel_data_size);
        case AC3_CHMODE_3F:
            memcpy(s->delay[2], s->delay[1], channel_data_size);
            memset(s->delay[1], 0, channel_data_size);
            break;
    }
}

/**
 * Parse an audio block from AC-3 bitstream.
 */
static int ac3_parse_audio_block(AC3DecodeContext *s, int blk)
{
    int fbw_channels = s->fbw_channels;
    int channel_mode = s->channel_mode;
    int i, bnd, seg, ch;
    int different_transforms;
    int downmix_output;
    int cpl_in_use;
    GetBitContext *gbc = &s->gbc;
    uint8_t bit_alloc_stages[AC3_MAX_CHANNELS];

    memset(bit_alloc_stages, 0, AC3_MAX_CHANNELS);

    /* block switch flags */
    different_transforms = 0;
    for (ch = 1; ch <= fbw_channels; ch++) {
        s->block_switch[ch] = get_bits1(gbc);
        if(ch > 1 && s->block_switch[ch] != s->block_switch[1])
            different_transforms = 1;
    }

    /* dithering flags */
    s->dither_all = 1;
    for (ch = 1; ch <= fbw_channels; ch++) {
        s->dither_flag[ch] = get_bits1(gbc);
        if(!s->dither_flag[ch])
            s->dither_all = 0;
    }

    /* dynamic range */
    i = !(s->channel_mode);
    do {
        if(get_bits1(gbc)) {
            s->dynamic_range[i] = ((dynamic_range_tab[get_bits(gbc, 8)]-1.0) *
                                  s->avctx->drc_scale)+1.0;
        } else if(blk == 0) {
            s->dynamic_range[i] = 1.0f;
        }
    } while(i--);

    /* coupling strategy */
    if (get_bits1(gbc)) {
        memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
        cpl_in_use = get_bits1(gbc);
        if (cpl_in_use) {
            /* coupling in use */
            int cpl_begin_freq, cpl_end_freq;

            if (channel_mode < AC3_CHMODE_STEREO) {
                av_log(s->avctx, AV_LOG_ERROR, "coupling not allowed in mono or dual-mono\n");
                return -1;
            }

            /* determine which channels are coupled */
            for (ch = 1; ch <= fbw_channels; ch++)
                s->channel_in_cpl[ch] = get_bits1(gbc);

            /* phase flags in use */
            if (channel_mode == AC3_CHMODE_STEREO)
                s->phase_flags_in_use = get_bits1(gbc);

            /* coupling frequency range and band structure */
            cpl_begin_freq = get_bits(gbc, 4);
            cpl_end_freq = get_bits(gbc, 4);
            if (3 + cpl_end_freq - cpl_begin_freq < 0) {
                av_log(s->avctx, AV_LOG_ERROR, "3+cplendf = %d < cplbegf = %d\n", 3+cpl_end_freq, cpl_begin_freq);
                return -1;
            }
            s->num_cpl_bands = s->num_cpl_subbands = 3 + cpl_end_freq - cpl_begin_freq;
            s->start_freq[CPL_CH] = cpl_begin_freq * 12 + 37;
            s->end_freq[CPL_CH] = cpl_end_freq * 12 + 73;
            for (bnd = 0; bnd < s->num_cpl_subbands - 1; bnd++) {
                if (get_bits1(gbc)) {
                    s->cpl_band_struct[bnd] = 1;
                    s->num_cpl_bands--;
                }
            }
            s->cpl_band_struct[s->num_cpl_subbands-1] = 0;
        } else {
            /* coupling not in use */
            for (ch = 1; ch <= fbw_channels; ch++)
                s->channel_in_cpl[ch] = 0;
        }
    } else if (!blk) {
        av_log(s->avctx, AV_LOG_ERROR, "new coupling strategy must be present in block 0\n");
        return -1;
    } else {
        cpl_in_use = s->cpl_in_use[blk-1];
    }
    s->cpl_in_use[blk] = cpl_in_use;

    /* coupling coordinates */
    if (cpl_in_use) {
        int cpl_coords_exist = 0;

        for (ch = 1; ch <= fbw_channels; ch++) {
            if (s->channel_in_cpl[ch]) {
                if (get_bits1(gbc)) {
                    int master_cpl_coord, cpl_coord_exp, cpl_coord_mant;
                    cpl_coords_exist = 1;