vorbis.c

ffmpeg源码分析

    (get_bits(gb, 8)!='r') || (get_bits(gb, 8)!='b') ||
    (get_bits(gb, 8)!='i') || (get_bits(gb, 8)!='s')) {
        av_log(vc->avccontext, AV_LOG_ERROR, " Vorbis id header packet corrupt (no vorbis signature). \n");
        return 1;
    }

    vc->version=get_bits_long_le(gb, 32);    //FIXME check 0
    vc->audio_channels=get_bits(gb, 8);   //FIXME check >0
    vc->audio_samplerate=get_bits_long_le(gb, 32);   //FIXME check >0
    vc->bitrate_maximum=get_bits_long_le(gb, 32);
    vc->bitrate_nominal=get_bits_long_le(gb, 32);
    vc->bitrate_minimum=get_bits_long_le(gb, 32);
    bl0=get_bits(gb, 4);
    bl1=get_bits(gb, 4);
    vc->blocksize_0=(1<<bl0);
    vc->blocksize_1=(1<<bl1);
    if (bl0>13 || bl0<6 || bl1>13 || bl1<6) {
        av_log(vc->avccontext, AV_LOG_ERROR, " Vorbis id header packet corrupt (illegal blocksize). \n");
        return 3;
    }
    vc->swin=vwin[bl0-6];
    vc->lwin=vwin[bl1-6];

    if ((get_bits1(gb)) == 0) {
        av_log(vc->avccontext, AV_LOG_ERROR, " Vorbis id header packet corrupt (framing flag not set). \n");
        return 2;
    }

    vc->channel_residues=(float *)av_malloc((vc->blocksize_1/2)*vc->audio_channels * sizeof(float));
    vc->channel_floors=(float *)av_malloc((vc->blocksize_1/2)*vc->audio_channels * sizeof(float));
    vc->saved=(float *)av_malloc((vc->blocksize_1/2)*vc->audio_channels * sizeof(float));
    vc->ret=(float *)av_malloc((vc->blocksize_1/2)*vc->audio_channels * sizeof(float));
    vc->buf=(float *)av_malloc(vc->blocksize_1 * sizeof(float));
    vc->buf_tmp=(float *)av_malloc(vc->blocksize_1 * sizeof(float));
    vc->saved_start=0;

    ff_mdct_init(&vc->mdct0, bl0, 1);
    ff_mdct_init(&vc->mdct1, bl1, 1);

    AV_DEBUG(" vorbis version %d \n audio_channels %d \n audio_samplerate %d \n bitrate_max %d \n bitrate_nom %d \n bitrate_min %d \n blk_0 %d blk_1 %d \n ",
            vc->version, vc->audio_channels, vc->audio_samplerate, vc->bitrate_maximum, vc->bitrate_nominal, vc->bitrate_minimum, vc->blocksize_0, vc->blocksize_1);

/*
    BLK=vc->blocksize_0;
    for(i=0;i<BLK/2;++i) {
        vc->swin[i]=sin(0.5*3.14159265358*(sin(((float)i+0.5)/(float)BLK*3.14159265358))*(sin(((float)i+0.5)/(float)BLK*3.14159265358)));
    }
*/

    return 0;
}

// Process the extradata using the functions above (identification header, setup header)

static int vorbis_decode_init(AVCodecContext *avccontext) {
    vorbis_context *vc = avccontext->priv_data ;
    uint8_t *headers = avccontext->extradata;
    int headers_len=avccontext->extradata_size;
    uint8_t *header_start[3];
    int header_len[3];
    GetBitContext *gb = &(vc->gb);
    int i, j, hdr_type;

    vc->avccontext = avccontext;

    if (!headers_len) {
        av_log(avccontext, AV_LOG_ERROR, "Extradata corrupt.\n");
        return -1;
    }

    if(headers[0] == 0 && headers[1] == 30) {
        for(i = 0; i < 3; i++){
            header_len[i] = *headers++ << 8;
            header_len[i] += *headers++;
            header_start[i] = headers;
            headers += header_len[i];
        }
    } else if(headers[0] == 2) {
        for(j=1,i=0;i<2;++i, ++j) {
            header_len[i]=0;
            while(j<headers_len && headers[j]==0xff) {
                header_len[i]+=0xff;
                ++j;
            }
            if (j>=headers_len) {
                av_log(avccontext, AV_LOG_ERROR, "Extradata corrupt.\n");
                return -1;
            }
            header_len[i]+=headers[j];
        }
        header_len[2]=headers_len-header_len[0]-header_len[1]-j;
        headers+=j;
        header_start[0] = headers;
        header_start[1] = header_start[0] + header_len[0];
        header_start[2] = header_start[1] + header_len[1];
    } else {
        av_log(avccontext, AV_LOG_ERROR, "Extradata corrupt.\n");
        return -1;
    }

    init_get_bits(gb, header_start[0], header_len[0]*8);
    hdr_type=get_bits(gb, 8);
    if (hdr_type!=1) {
        av_log(avccontext, AV_LOG_ERROR, "First header is not the id header.\n");
        return -1;
    }
    if (vorbis_parse_id_hdr(vc)) {
        av_log(avccontext, AV_LOG_ERROR, "Id header corrupt.\n");
        vorbis_free(vc);
        return -1;
    }

    init_get_bits(gb, header_start[2], header_len[2]*8);
    hdr_type=get_bits(gb, 8);
    if (hdr_type!=5) {
        av_log(avccontext, AV_LOG_ERROR, "Third header is not the setup header.\n");
        return -1;
    }
    if (vorbis_parse_setup_hdr(vc)) {
        av_log(avccontext, AV_LOG_ERROR, "Setup header corrupt.\n");
        vorbis_free(vc);
        return -1;
    }

    avccontext->channels = vc->audio_channels;
    avccontext->sample_rate = vc->audio_samplerate;

    return 0 ;
}

// Decode audiopackets -------------------------------------------------

// Read and decode floor

static uint_fast8_t vorbis_floor0_decode(vorbis_context *vc,
                                         vorbis_floor_data *vfu, float *vec) {
    vorbis_floor0 * vf=&vfu->t0;
    float * lsp=vf->lsp;
    uint_fast32_t amplitude;
    uint_fast32_t book_idx;
    uint_fast8_t blockflag=vc->modes[vc->mode_number].blockflag;

    amplitude=get_bits(&vc->gb, vf->amplitude_bits);
    if (amplitude>0) {
        float last = 0;
        uint_fast16_t lsp_len = 0;
        uint_fast16_t idx;
        vorbis_codebook codebook;

        book_idx=get_bits(&vc->gb, ilog(vf->num_books));
        if ( book_idx >= vf->num_books ) {
            av_log( vc->avccontext, AV_LOG_ERROR,
                    "floor0 dec: booknumber too high!\n" );
            //FIXME: look above
        }
        AV_DEBUG( "floor0 dec: booknumber: %u\n", book_idx );
        codebook=vc->codebooks[vf->book_list[book_idx]];

        while (lsp_len<vf->order) {
            int vec_off;

            AV_DEBUG( "floor0 dec: book dimension: %d\n", codebook.dimensions );
            AV_DEBUG( "floor0 dec: maximum depth: %d\n", codebook.maxdepth );
            /* read temp vector */
            vec_off=get_vlc2(&vc->gb,
                             codebook.vlc.table,
                             codebook.nb_bits,
                             codebook.maxdepth ) *
                             codebook.dimensions;
            AV_DEBUG( "floor0 dec: vector offset: %d\n", vec_off );
            /* copy each vector component and add last to it */
            for (idx=0; idx<codebook.dimensions; ++idx) {
                lsp[lsp_len+idx]=codebook.codevectors[vec_off+idx]+last;
            }
            last=lsp[lsp_len+idx-1]; /* set last to last vector component */

            lsp_len += codebook.dimensions;
        }
#ifdef V_DEBUG
        /* DEBUG: output lsp coeffs */
        {
            int idx;
            for ( idx = 0; idx < lsp_len; ++idx )
                AV_DEBUG("floor0 dec: coeff at %d is %f\n", idx, lsp[idx] );
        }
#endif

        /* synthesize floor output vector */
        {
            int i;
            int order=vf->order;
            float wstep=M_PI/vf->bark_map_size;

            for(i=0;i<order;i++) { lsp[i]=2.0f*cos(lsp[i]); }

            AV_DEBUG("floor0 synth: map_size=%d; m=%d; wstep=%f\n",
                     vf->map_size, order, wstep);

            i=0;
            while(i<vf->map_size[blockflag]) {
                int j, iter_cond=vf->map[blockflag][i];
                float p=0.5f;
                float q=0.5f;
                float two_cos_w=2.0f*cos(wstep*iter_cond); // needed all times

                /* similar part for the q and p products */
                for(j=0;j<order;j+=2) {
                    q *= lsp[j]  -two_cos_w;
                    p *= lsp[j+1]-two_cos_w;
                }
                if(j==order) { // even order
                    p *= p*(2.0f-two_cos_w);
                    q *= q*(2.0f+two_cos_w);
                }
                else { // odd order
                    q *= two_cos_w-lsp[j]; // one more time for q

                    /* final step and square */
                    p *= p*(4.f-two_cos_w*two_cos_w);
                    q *= q;
                }

                /* calculate linear floor value */
                {
                    q=exp( (
                             ( (amplitude*vf->amplitude_offset)/
                               (((1<<vf->amplitude_bits)-1) * sqrt(p+q)) )
                             - vf->amplitude_offset ) * .11512925f
                         );
                }

                /* fill vector */
                do { vec[i]=q; ++i; }while(vf->map[blockflag][i]==iter_cond);
            }
        }
    }
    else {
        /* this channel is unused */
        return 1;
    }

    AV_DEBUG(" Floor0 decoded\n");

    return 0;
}
static uint_fast8_t vorbis_floor1_decode(vorbis_context *vc, vorbis_floor_data *vfu, float *vec) {
    vorbis_floor1 * vf=&vfu->t1;
    GetBitContext *gb=&vc->gb;
    uint_fast16_t range_v[4]={ 256, 128, 86, 64 };
    uint_fast16_t range=range_v[vf->multiplier-1];
    uint_fast16_t floor1_Y[vf->x_list_dim];
    uint_fast16_t floor1_Y_final[vf->x_list_dim];
    uint_fast8_t floor1_flag[vf->x_list_dim];
    uint_fast8_t class_;
    uint_fast8_t cdim;
    uint_fast8_t cbits;
    uint_fast8_t csub;
    uint_fast8_t cval;
    int_fast16_t book;
    uint_fast16_t offset;
    uint_fast16_t i,j;
    uint_fast16_t *floor_x_sort=vf->x_list_order;
    /*u*/int_fast16_t adx, ady, off, predicted; // WTF ? dy/adx= (unsigned)dy/adx ?
    int_fast16_t dy, err;
    uint_fast16_t lx,hx, ly, hy=0;


    if (!get_bits1(gb)) return 1; // silence

// Read values (or differences) for the floor's points

    floor1_Y[0]=get_bits(gb, ilog(range-1));
    floor1_Y[1]=get_bits(gb, ilog(range-1));

    AV_DEBUG("floor 0 Y %d floor 1 Y %d \n", floor1_Y[0], floor1_Y[1]);

    offset=2;
    for(i=0;i<vf->partitions;++i) {
        class_=vf->partition_class[i];
        cdim=vf->class_dimensions[class_];
        cbits=vf->class_subclasses[class_];
        csub=(1<<cbits)-1;
        cval=0;

        AV_DEBUG("Cbits %d \n", cbits);

        if (cbits) { // this reads all subclasses for this partition's class
            cval=get_vlc2(gb, vc->codebooks[vf->class_masterbook[class_]].vlc.table,
            vc->codebooks[vf->class_masterbook[class_]].nb_bits, 3);
        }

        for(j=0;j<cdim;++j) {
            book=vf->subclass_books[class_][cval & csub];

            AV_DEBUG("book %d Cbits %d cval %d  bits:%d \n", book, cbits, cval, get_bits_count(gb));

            cval=cval>>cbits;
            if (book>0) {
                floor1_Y[offset+j]=get_vlc2(gb, vc->codebooks[book].vlc.table,
                vc->codebooks[book].nb_bits, 3);
            } else {
                floor1_Y[offset+j]=0;
            }

            AV_DEBUG(" floor(%d) = %d \n", vf->x_list[offset+j], floor1_Y[offset+j]);
        }
        offset+=cdim;
    }

// Amplitude calculation from the differences

    floor1_flag[0]=1;
    floor1_flag[1]=1;
    floor1_Y_final[0]=floor1_Y[0];
    floor1_Y_final[1]=floor1_Y[1];

    for(i=2;i<vf->x_list_dim;++i) {
        uint_fast16_t val, highroom, lowroom, room;
        uint_fast16_t high_neigh_offs;
        uint_fast16_t low_neigh_offs;

        low_neigh_offs=vf->low_neighbour[i];
        high_neigh_offs=vf->high_neighbour[i];
        dy=floor1_Y_final[high_neigh_offs]-floor1_Y_final[low_neigh_offs];  // render_point begin
        adx=vf->x_list[high_neigh_offs]-vf->x_list[low_neigh_offs];
        ady= ABS(dy);
        err=ady*(vf->x_list[i]-vf->x_list[low_neigh_offs]);
        off=err/adx;
        if (dy<0) {
            predicted=floor1_Y_final[low_neigh_offs]-off;
        } else {
            predicted=floor1_Y_final[low_neigh_offs]+off;
        } // render_point end

        val=floor1_Y[i];
        highroom=range-predicted;
        lowroom=predicted;
        if (highroom < lowroom) {
            room=highroom*2;
        } else {
            room=lowroom*2;   // SPEC mispelling
        }
        if (val) {
            floor1_flag[low_neigh_offs]=1;
            floor1_flag[high_neigh_offs]=1;
            floor1_flag[i]=1;
            if (val>=room) {
                if (highroom > lowroom) {
                    floor1_Y_final[i]=val-lowroom+predicted;
                } else {
                    floor1_Y_final[i]=predicted-val+highroom-1;
                }
            } else {
                if (val & 1) {
                    floor1_Y_final[i]=predicted-(val+1)/2;
                } else {
                    floor1_Y_final[i]=predicted+val/2;
                }
            }
        } else {
            floor1_flag[i]=0;
            floor1_Y_final[i]=predicted;
        }

        AV_DEBUG(" Decoded floor(%d) = %d / val %d \n", vf->x_list[i], floor1_Y_final[i], val);
    }

// Curve synth - connect the calculated dots and convert from dB scale FIXME optimize ?

    hx=0;
    lx=0;
    ly=floor1_Y_final[0]*vf->multiplier;  // conforms to SPEC

    vec[0]=floor1_inverse_db_table[ly];

    for(i=1;i<vf->x_list_dim;++i) {
        AV_DEBUG(" Looking at post %d \n", i);

        if (floor1_flag[floor_x_sort[i]]) {   // SPEC mispelled
            int_fast16_t x, y, dy, base, sy; // if uncommented: dy = -32 adx = 2  base = 2blablabla ?????

            hy=floor1_Y_final[floor_x_sort[i]]*vf->multiplier;
            hx=vf->x_list[floor_x_sort[i]];

            dy=hy-ly;
            adx=hx-lx;
            ady= (dy<0) ? -dy:dy;//ABS(dy);
            base=dy/adx;

            AV_DEBUG(" dy %d  adx %d base %d = %d \n", dy, adx, base, dy/adx);

            x=lx;
            y=ly;
            err=0;
            if (dy<0) {
                sy=base-1;
            } else {
                sy=base+1;
            }
            ady=ady-(base<0 ? -base : base)*adx;
            vec[x]=floor1_inverse_db_table[y];

            AV_DEBUG(" vec[ %d ] = %d \n", x, y);

            for(x=lx+1;(x<hx) && (x<vf->x_list[1]);++x) {
                err+=ady;
                if (err>=adx) {
                    err-=adx;
                    y+=sy;
                } else {
                    y+=base;
                }
                vec[x]=floor1_inverse_db_table[y];

                AV_DEBUG(" vec[ %d ] = %d \n", x, y);
            }

/*            for(j=1;j<hx-lx+1;++j) {  // iterating render_point
                dy=hy-ly;
                adx=hx-lx;
                ady= dy<0 ? -dy : dy;
                err=ady*j;
                off=err/adx;
                if (dy<0) {
                    predicted=ly-off;
                } else {
                    predicted=ly+off;
                }
                if (lx+j < vf->x_list[1]) {