vorbis_enc.c

ffmpeg的完整源代码和作者自己写的文档。不但有在Linux的工程哦

    venc->nmappings = 1;
    venc->mappings = av_malloc(sizeof(mapping_t) * venc->nmappings);

    // single mapping
    mc = &venc->mappings[0];
    mc->submaps = 1;
    mc->mux = av_malloc(sizeof(int) * venc->channels);
    for (i = 0; i < venc->channels; i++)
        mc->mux[i] = 0;
    mc->floor = av_malloc(sizeof(int) * mc->submaps);
    mc->residue = av_malloc(sizeof(int) * mc->submaps);
    for (i = 0; i < mc->submaps; i++) {
        mc->floor[i] = 0;
        mc->residue[i] = 0;
    }
    mc->coupling_steps = venc->channels == 2 ? 1 : 0;
    mc->magnitude = av_malloc(sizeof(int) * mc->coupling_steps);
    mc->angle = av_malloc(sizeof(int) * mc->coupling_steps);
    if (mc->coupling_steps) {
        mc->magnitude[0] = 0;
        mc->angle[0] = 1;
    }

    venc->nmodes = 1;
    venc->modes = av_malloc(sizeof(vorbis_mode_t) * venc->nmodes);

    // single mode
    venc->modes[0].blockflag = 0;
    venc->modes[0].mapping = 0;

    venc->have_saved = 0;
    venc->saved = av_malloc(sizeof(float) * venc->channels * (1 << venc->log2_blocksize[1]) / 2);
    venc->samples = av_malloc(sizeof(float) * venc->channels * (1 << venc->log2_blocksize[1]));
    venc->floor = av_malloc(sizeof(float) * venc->channels * (1 << venc->log2_blocksize[1]) / 2);
    venc->coeffs = av_malloc(sizeof(float) * venc->channels * (1 << venc->log2_blocksize[1]) / 2);

    venc->win[0] = ff_vorbis_vwin[venc->log2_blocksize[0] - 6];
    venc->win[1] = ff_vorbis_vwin[venc->log2_blocksize[1] - 6];

    ff_mdct_init(&venc->mdct[0], venc->log2_blocksize[0], 0);
    ff_mdct_init(&venc->mdct[1], venc->log2_blocksize[1], 0);
}

static void put_float(PutBitContext * pb, float f) {
    int exp, mant;
    uint32_t res = 0;
    mant = (int)ldexp(frexp(f, &exp), 20);
    exp += 788 - 20;
    if (mant < 0) { res |= (1 << 31); mant = -mant; }
    res |= mant | (exp << 21);
    put_bits(pb, 32, res);
}

static void put_codebook_header(PutBitContext * pb, codebook_t * cb) {
    int i;
    int ordered = 0;

    put_bits(pb, 24, 0x564342); //magic
    put_bits(pb, 16, cb->ndimentions);
    put_bits(pb, 24, cb->nentries);

    for (i = 1; i < cb->nentries; i++)
        if (cb->lens[i] < cb->lens[i-1]) break;
    if (i == cb->nentries)
        ordered = 1;

    put_bits(pb, 1, ordered);
    if (ordered) {
        int len = cb->lens[0];
        put_bits(pb, 5, len - 1);
        i = 0;
        while (i < cb->nentries) {
            int j;
            for (j = 0; j+i < cb->nentries; j++)
                if (cb->lens[j+i] != len) break;
            put_bits(pb, ilog(cb->nentries - i), j);
            i += j;
            len++;
        }
    } else {
        int sparse = 0;
        for (i = 0; i < cb->nentries; i++)
            if (!cb->lens[i]) break;
        if (i != cb->nentries)
            sparse = 1;
        put_bits(pb, 1, sparse);

        for (i = 0; i < cb->nentries; i++) {
            if (sparse) put_bits(pb, 1, !!cb->lens[i]);
            if (cb->lens[i]) put_bits(pb, 5, cb->lens[i] - 1);
        }
    }

    put_bits(pb, 4, cb->lookup);
    if (cb->lookup) {
        int tmp = cb_lookup_vals(cb->lookup, cb->ndimentions, cb->nentries);
        int bits = ilog(cb->quantlist[0]);

        for (i = 1; i < tmp; i++)
            bits = FFMAX(bits, ilog(cb->quantlist[i]));

        put_float(pb, cb->min);
        put_float(pb, cb->delta);

        put_bits(pb, 4, bits - 1);
        put_bits(pb, 1, cb->seq_p);

        for (i = 0; i < tmp; i++)
            put_bits(pb, bits, cb->quantlist[i]);
    }
}

static void put_floor_header(PutBitContext * pb, floor_t * fc) {
    int i;

    put_bits(pb, 16, 1); // type, only floor1 is supported

    put_bits(pb, 5, fc->partitions);

    for (i = 0; i < fc->partitions; i++)
        put_bits(pb, 4, fc->partition_to_class[i]);

    for (i = 0; i < fc->nclasses; i++) {
        int j, books;

        put_bits(pb, 3, fc->classes[i].dim - 1);
        put_bits(pb, 2, fc->classes[i].subclass);

        if (fc->classes[i].subclass)
            put_bits(pb, 8, fc->classes[i].masterbook);

        books = (1 << fc->classes[i].subclass);

        for (j = 0; j < books; j++)
            put_bits(pb, 8, fc->classes[i].books[j] + 1);
    }

    put_bits(pb, 2, fc->multiplier - 1);
    put_bits(pb, 4, fc->rangebits);

    for (i = 2; i < fc->values; i++)
        put_bits(pb, fc->rangebits, fc->list[i].x);
}

static void put_residue_header(PutBitContext * pb, residue_t * rc) {
    int i;

    put_bits(pb, 16, rc->type);

    put_bits(pb, 24, rc->begin);
    put_bits(pb, 24, rc->end);
    put_bits(pb, 24, rc->partition_size - 1);
    put_bits(pb, 6, rc->classifications - 1);
    put_bits(pb, 8, rc->classbook);

    for (i = 0; i < rc->classifications; i++) {
        int j, tmp = 0;
        for (j = 0; j < 8; j++)
            tmp |= (rc->books[i][j] != -1) << j;

        put_bits(pb, 3, tmp & 7);
        put_bits(pb, 1, tmp > 7);

        if (tmp > 7)
            put_bits(pb, 5, tmp >> 3);
    }

    for (i = 0; i < rc->classifications; i++) {
        int j;
        for (j = 0; j < 8; j++)
            if (rc->books[i][j] != -1)
                put_bits(pb, 8, rc->books[i][j]);
    }
}

static int put_main_header(venc_context_t * venc, uint8_t ** out) {
    int i;
    PutBitContext pb;
    uint8_t buffer[50000] = {0}, * p = buffer;
    int buffer_len = sizeof buffer;
    int len, hlens[3];

    // identification header
    init_put_bits(&pb, p, buffer_len);
    put_bits(&pb, 8, 1); //magic
    for (i = 0; "vorbis"[i]; i++)
        put_bits(&pb, 8, "vorbis"[i]);
    put_bits(&pb, 32, 0); // version
    put_bits(&pb, 8, venc->channels);
    put_bits(&pb, 32, venc->sample_rate);
    put_bits(&pb, 32, 0); // bitrate
    put_bits(&pb, 32, 0); // bitrate
    put_bits(&pb, 32, 0); // bitrate
    put_bits(&pb, 4, venc->log2_blocksize[0]);
    put_bits(&pb, 4, venc->log2_blocksize[1]);
    put_bits(&pb, 1, 1); // framing

    flush_put_bits(&pb);
    hlens[0] = (put_bits_count(&pb) + 7) / 8;
    buffer_len -= hlens[0];
    p += hlens[0];

    // comment header
    init_put_bits(&pb, p, buffer_len);
    put_bits(&pb, 8, 3); //magic
    for (i = 0; "vorbis"[i]; i++)
        put_bits(&pb, 8, "vorbis"[i]);
    put_bits(&pb, 32, 0); // vendor length TODO
    put_bits(&pb, 32, 0); // amount of comments
    put_bits(&pb, 1, 1); // framing

    flush_put_bits(&pb);
    hlens[1] = (put_bits_count(&pb) + 7) / 8;
    buffer_len -= hlens[1];
    p += hlens[1];

    // setup header
    init_put_bits(&pb, p, buffer_len);
    put_bits(&pb, 8, 5); //magic
    for (i = 0; "vorbis"[i]; i++)
        put_bits(&pb, 8, "vorbis"[i]);

    // codebooks
    put_bits(&pb, 8, venc->ncodebooks - 1);
    for (i = 0; i < venc->ncodebooks; i++)
        put_codebook_header(&pb, &venc->codebooks[i]);

    // time domain, reserved, zero
    put_bits(&pb, 6, 0);
    put_bits(&pb, 16, 0);

    // floors
    put_bits(&pb, 6, venc->nfloors - 1);
    for (i = 0; i < venc->nfloors; i++)
        put_floor_header(&pb, &venc->floors[i]);

    // residues
    put_bits(&pb, 6, venc->nresidues - 1);
    for (i = 0; i < venc->nresidues; i++)
        put_residue_header(&pb, &venc->residues[i]);

    // mappings
    put_bits(&pb, 6, venc->nmappings - 1);
    for (i = 0; i < venc->nmappings; i++) {
        mapping_t * mc = &venc->mappings[i];
        int j;
        put_bits(&pb, 16, 0); // mapping type

        put_bits(&pb, 1, mc->submaps > 1);
        if (mc->submaps > 1)
            put_bits(&pb, 4, mc->submaps - 1);

        put_bits(&pb, 1, !!mc->coupling_steps);
        if (mc->coupling_steps) {
            put_bits(&pb, 8, mc->coupling_steps - 1);
            for (j = 0; j < mc->coupling_steps; j++) {
                put_bits(&pb, ilog(venc->channels - 1), mc->magnitude[j]);
                put_bits(&pb, ilog(venc->channels - 1), mc->angle[j]);
            }
        }

        put_bits(&pb, 2, 0); // reserved

        if (mc->submaps > 1)
            for (j = 0; j < venc->channels; j++)
                put_bits(&pb, 4, mc->mux[j]);

        for (j = 0; j < mc->submaps; j++) {
            put_bits(&pb, 8, 0); // reserved time configuration
            put_bits(&pb, 8, mc->floor[j]);
            put_bits(&pb, 8, mc->residue[j]);
        }
    }

    // modes
    put_bits(&pb, 6, venc->nmodes - 1);
    for (i = 0; i < venc->nmodes; i++) {
        put_bits(&pb, 1, venc->modes[i].blockflag);
        put_bits(&pb, 16, 0); // reserved window type
        put_bits(&pb, 16, 0); // reserved transform type
        put_bits(&pb, 8, venc->modes[i].mapping);
    }

    put_bits(&pb, 1, 1); // framing

    flush_put_bits(&pb);
    hlens[2] = (put_bits_count(&pb) + 7) / 8;

    len = hlens[0] + hlens[1] + hlens[2];
    p = *out = av_mallocz(64 + len + len/255);

    *p++ = 2;
    p += av_xiphlacing(p, hlens[0]);
    p += av_xiphlacing(p, hlens[1]);
    buffer_len = 0;
    for (i = 0; i < 3; i++) {
        memcpy(p, buffer + buffer_len, hlens[i]);
        p += hlens[i];
        buffer_len += hlens[i];
    }

    return p - *out;
}

static float get_floor_average(floor_t * fc, float * coeffs, int i) {
    int begin = fc->list[fc->list[FFMAX(i-1, 0)].sort].x;
    int end   = fc->list[fc->list[FFMIN(i+1, fc->values - 1)].sort].x;
    int j;
    float average = 0;

    for (j = begin; j < end; j++)
        average += fabs(coeffs[j]);
    return average / (end - begin);
}

static void floor_fit(venc_context_t * venc, floor_t * fc, float * coeffs, uint_fast16_t * posts, int samples) {
    int range = 255 / fc->multiplier + 1;
    int i;
    float tot_average = 0.;
    float averages[fc->values];
    for (i = 0; i < fc->values; i++){
        averages[i] = get_floor_average(fc, coeffs, i);
        tot_average += averages[i];
    }
    tot_average /= fc->values;
    tot_average /= venc->quality;

    for (i = 0; i < fc->values; i++) {
        int position = fc->list[fc->list[i].sort].x;
        float average = averages[i];
        int j;

        average *= pow(tot_average / average, 0.5) * pow(1.25, position/200.); // MAGIC!
        for (j = 0; j < range - 1; j++)
            if (ff_vorbis_floor1_inverse_db_table[j * fc->multiplier] > average) break;
        posts[fc->list[i].sort] = j;
    }
}

static int render_point(int x0, int y0, int x1, int y1, int x) {
    return y0 +  (x - x0) * (y1 - y0) / (x1 - x0);
}

static void floor_encode(venc_context_t * venc, floor_t * fc, PutBitContext * pb, uint_fast16_t * posts, float * floor, int samples) {
    int range = 255 / fc->multiplier + 1;
    int coded[fc->values]; // first 2 values are unused
    int i, counter;

    put_bits(pb, 1, 1); // non zero
    put_bits(pb, ilog(range - 1), posts[0]);
    put_bits(pb, ilog(range - 1), posts[1]);
    coded[0] = coded[1] = 1;

    for (i = 2; i < fc->values; i++) {
        int predicted = render_point(fc->list[fc->list[i].low].x,
                                     posts[fc->list[i].low],
                                     fc->list[fc->list[i].high].x,
                                     posts[fc->list[i].high],
                                     fc->list[i].x);
        int highroom = range - predicted;
        int lowroom = predicted;
        int room = FFMIN(highroom, lowroom);
        if (predicted == posts[i]) {