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

            coded[i] = 0; // must be used later as flag!
            continue;
        } else {
            if (!coded[fc->list[i].low ]) coded[fc->list[i].low ] = -1;
            if (!coded[fc->list[i].high]) coded[fc->list[i].high] = -1;
        }
        if (posts[i] > predicted) {
            if (posts[i] - predicted > room)
                coded[i] = posts[i] - predicted + lowroom;
            else
                coded[i] = (posts[i] - predicted) << 1;
        } else {
            if (predicted - posts[i] > room)
                coded[i] = predicted - posts[i] + highroom - 1;
            else
                coded[i] = ((predicted - posts[i]) << 1) - 1;
        }
    }

    counter = 2;
    for (i = 0; i < fc->partitions; i++) {
        floor_class_t * c = &fc->classes[fc->partition_to_class[i]];
        int k, cval = 0, csub = 1<<c->subclass;
        if (c->subclass) {
            codebook_t * book = &venc->codebooks[c->masterbook];
            int cshift = 0;
            for (k = 0; k < c->dim; k++) {
                int l;
                for (l = 0; l < csub; l++) {
                    int maxval = 1;
                    if (c->books[l] != -1)
                        maxval = venc->codebooks[c->books[l]].nentries;
                    // coded could be -1, but this still works, cause that is 0
                    if (coded[counter + k] < maxval) break;
                }
                assert(l != csub);
                cval |= l << cshift;
                cshift += c->subclass;
            }
            put_codeword(pb, book, cval);
        }
        for (k = 0; k < c->dim; k++) {
            int book = c->books[cval & (csub-1)];
            int entry = coded[counter++];
            cval >>= c->subclass;
            if (book == -1) continue;
            if (entry == -1) entry = 0;
            put_codeword(pb, &venc->codebooks[book], entry);
        }
    }

    ff_vorbis_floor1_render_list(fc->list, fc->values, posts, coded, fc->multiplier, floor, samples);
}

static float * put_vector(codebook_t * book, PutBitContext * pb, float * num) {
    int i, entry = -1;
    float distance = FLT_MAX;
    assert(book->dimentions);
    for (i = 0; i < book->nentries; i++) {
        float * vec = book->dimentions + i * book->ndimentions, d = book->pow2[i];
        int j;
        if (!book->lens[i]) continue;
        for (j = 0; j < book->ndimentions; j++)
            d -= vec[j] * num[j];
        if (distance > d) {
            entry = i;
            distance = d;
        }
    }
    put_codeword(pb, book, entry);
    return &book->dimentions[entry * book->ndimentions];
}

static void residue_encode(venc_context_t * venc, residue_t * rc, PutBitContext * pb, float * coeffs, int samples, int real_ch) {
    int pass, i, j, p, k;
    int psize = rc->partition_size;
    int partitions = (rc->end - rc->begin) / psize;
    int channels = (rc->type == 2) ? 1 : real_ch;
    int classes[channels][partitions];
    int classwords = venc->codebooks[rc->classbook].ndimentions;

    assert(rc->type == 2);
    assert(real_ch == 2);
    for (p = 0; p < partitions; p++) {
        float max1 = 0., max2 = 0.;
        int s = rc->begin + p * psize;
        for (k = s; k < s + psize; k += 2) {
            max1 = FFMAX(max1, fabs(coeffs[          k / real_ch]));
            max2 = FFMAX(max2, fabs(coeffs[samples + k / real_ch]));
        }

        for (i = 0; i < rc->classifications - 1; i++) {
            if (max1 < rc->maxes[i][0] && max2 < rc->maxes[i][1]) break;
        }
        classes[0][p] = i;
    }

    for (pass = 0; pass < 8; pass++) {
        p = 0;
        while (p < partitions) {
            if (pass == 0)
                for (j = 0; j < channels; j++) {
                    codebook_t * book = &venc->codebooks[rc->classbook];
                    int entry = 0;
                    for (i = 0; i < classwords; i++) {
                        entry *= rc->classifications;
                        entry += classes[j][p + i];
                    }
                    put_codeword(pb, book, entry);
                }
            for (i = 0; i < classwords && p < partitions; i++, p++) {
                for (j = 0; j < channels; j++) {
                    int nbook = rc->books[classes[j][p]][pass];
                    codebook_t * book = &venc->codebooks[nbook];
                    float * buf = coeffs + samples*j + rc->begin + p*psize;
                    if (nbook == -1) continue;

                    assert(rc->type == 0 || rc->type == 2);
                    assert(!(psize % book->ndimentions));

                    if (rc->type == 0) {
                        for (k = 0; k < psize; k += book->ndimentions) {
                            float * a = put_vector(book, pb, &buf[k]);
                            int l;
                            for (l = 0; l < book->ndimentions; l++)
                                buf[k + l] -= a[l];
                        }
                    } else {
                        int s = rc->begin + p * psize, a1, b1;
                        a1 = (s % real_ch) * samples;
                        b1 =  s / real_ch;
                        s = real_ch * samples;
                        for (k = 0; k < psize; k += book->ndimentions) {
                            int dim, a2 = a1, b2 = b1;
                            float vec[book->ndimentions], * pv = vec;
                            for (dim = book->ndimentions; dim--; ) {
                                *pv++ = coeffs[a2 + b2];
                                if ((a2 += samples) == s) {
                                    a2=0;
                                    b2++;
                                }
                            }
                            pv = put_vector(book, pb, vec);
                            for (dim = book->ndimentions; dim--; ) {
                                coeffs[a1 + b1] -= *pv++;
                                if ((a1 += samples) == s) {
                                    a1=0;
                                    b1++;
                                }
                            }
                        }
                    }
                }
            }
        }
    }
}

static int apply_window_and_mdct(venc_context_t * venc, signed short * audio, int samples) {
    int i, j, channel;
    const float * win = venc->win[0];
    int window_len = 1 << (venc->log2_blocksize[0] - 1);
    float n = (float)(1 << venc->log2_blocksize[0]) / 4.;
    // FIXME use dsp

    if (!venc->have_saved && !samples) return 0;

    if (venc->have_saved) {
        for (channel = 0; channel < venc->channels; channel++) {
            memcpy(venc->samples + channel*window_len*2, venc->saved + channel*window_len, sizeof(float)*window_len);
        }
    } else {
        for (channel = 0; channel < venc->channels; channel++) {
            memset(venc->samples + channel*window_len*2, 0, sizeof(float)*window_len);
        }
    }

    if (samples) {
        for (channel = 0; channel < venc->channels; channel++) {
            float * offset = venc->samples + channel*window_len*2 + window_len;
            j = channel;
            for (i = 0; i < samples; i++, j += venc->channels)
                offset[i] = -audio[j] / 32768. / n * win[window_len - i - 1]; //FIXME find out why the sign has to be fliped
        }
    } else {
        for (channel = 0; channel < venc->channels; channel++) {
            memset(venc->samples + channel*window_len*2 + window_len, 0, sizeof(float)*window_len);
        }
    }

    for (channel = 0; channel < venc->channels; channel++) {
        ff_mdct_calc(&venc->mdct[0], venc->coeffs + channel*window_len, venc->samples + channel*window_len*2, venc->floor/*tmp*/);
    }

    if (samples) {
        for (channel = 0; channel < venc->channels; channel++) {
            float * offset = venc->saved + channel*window_len;
            j = channel;
            for (i = 0; i < samples; i++, j += venc->channels)
                offset[i] = -audio[j] / 32768. / n * win[i]; //FIXME find out why the sign has to be fliped
        }
        venc->have_saved = 1;
    } else {
        venc->have_saved = 0;
    }
    return 1;
}

static int vorbis_encode_init(AVCodecContext * avccontext)
{
    venc_context_t * venc = avccontext->priv_data;

    if (avccontext->channels != 2) {
        av_log(avccontext, AV_LOG_ERROR, "Current FFmpeg Vorbis encoder only supports 2 channels.\n");
        return -1;
    }

    create_vorbis_context(venc, avccontext);

    if (avccontext->flags & CODEC_FLAG_QSCALE)
        venc->quality = avccontext->global_quality / (float)FF_QP2LAMBDA / 10.;
    else
        venc->quality = 1.;
    venc->quality *= venc->quality;

    avccontext->extradata_size = put_main_header(venc, (uint8_t**)&avccontext->extradata);

    avccontext->frame_size = 1 << (venc->log2_blocksize[0] - 1);

    avccontext->coded_frame = avcodec_alloc_frame();
    avccontext->coded_frame->key_frame = 1;

    return 0;
}

static int vorbis_encode_frame(AVCodecContext * avccontext, unsigned char * packets, int buf_size, void *data)
{
    venc_context_t * venc = avccontext->priv_data;
    signed short * audio = data;
    int samples = data ? avccontext->frame_size : 0;
    vorbis_mode_t * mode;
    mapping_t * mapping;
    PutBitContext pb;
    int i;

    if (!apply_window_and_mdct(venc, audio, samples)) return 0;
    samples = 1 << (venc->log2_blocksize[0] - 1);

    init_put_bits(&pb, packets, buf_size);

    put_bits(&pb, 1, 0); // magic bit

    put_bits(&pb, ilog(venc->nmodes - 1), 0); // 0 bits, the mode

    mode = &venc->modes[0];
    mapping = &venc->mappings[mode->mapping];
    if (mode->blockflag) {
        put_bits(&pb, 1, 0);
        put_bits(&pb, 1, 0);
    }

    for (i = 0; i < venc->channels; i++) {
        floor_t * fc = &venc->floors[mapping->floor[mapping->mux[i]]];
        uint_fast16_t posts[fc->values];
        floor_fit(venc, fc, &venc->coeffs[i * samples], posts, samples);
        floor_encode(venc, fc, &pb, posts, &venc->floor[i * samples], samples);
    }

    for (i = 0; i < venc->channels * samples; i++) {
        venc->coeffs[i] /= venc->floor[i];
    }

    for (i = 0; i < mapping->coupling_steps; i++) {
        float * mag = venc->coeffs + mapping->magnitude[i] * samples;
        float * ang = venc->coeffs + mapping->angle[i] * samples;
        int j;
        for (j = 0; j < samples; j++) {
            float a = ang[j];
            ang[j] -= mag[j];
            if (mag[j] > 0) ang[j] = -ang[j];
            if (ang[j] < 0) mag[j] = a;
        }
    }

    residue_encode(venc, &venc->residues[mapping->residue[mapping->mux[0]]], &pb, venc->coeffs, samples, venc->channels);

    flush_put_bits(&pb);
    return (put_bits_count(&pb) + 7) / 8;
}


static int vorbis_encode_close(AVCodecContext * avccontext)
{
    venc_context_t * venc = avccontext->priv_data;
    int i;

    if (venc->codebooks)
        for (i = 0; i < venc->ncodebooks; i++) {
            av_freep(&venc->codebooks[i].lens);
            av_freep(&venc->codebooks[i].codewords);
            av_freep(&venc->codebooks[i].quantlist);
            av_freep(&venc->codebooks[i].dimentions);
            av_freep(&venc->codebooks[i].pow2);
        }
    av_freep(&venc->codebooks);

    if (venc->floors)
        for (i = 0; i < venc->nfloors; i++) {
            int j;
            if (venc->floors[i].classes)
                for (j = 0; j < venc->floors[i].nclasses; j++)
                    av_freep(&venc->floors[i].classes[j].books);
            av_freep(&venc->floors[i].classes);
            av_freep(&venc->floors[i].partition_to_class);
            av_freep(&venc->floors[i].list);
        }
    av_freep(&venc->floors);

    if (venc->residues)
        for (i = 0; i < venc->nresidues; i++) {
            av_freep(&venc->residues[i].books);
            av_freep(&venc->residues[i].maxes);
        }
    av_freep(&venc->residues);

    if (venc->mappings)
        for (i = 0; i < venc->nmappings; i++) {
            av_freep(&venc->mappings[i].mux);
            av_freep(&venc->mappings[i].floor);
            av_freep(&venc->mappings[i].residue);
            av_freep(&venc->mappings[i].magnitude);
            av_freep(&venc->mappings[i].angle);
        }
    av_freep(&venc->mappings);

    av_freep(&venc->modes);

    av_freep(&venc->saved);
    av_freep(&venc->samples);
    av_freep(&venc->floor);
    av_freep(&venc->coeffs);

    ff_mdct_end(&venc->mdct[0]);
    ff_mdct_end(&venc->mdct[1]);

    av_freep(&avccontext->coded_frame);
    av_freep(&avccontext->extradata);

    return 0 ;
}

AVCodec vorbis_encoder = {
    "vorbis",
    CODEC_TYPE_AUDIO,
    CODEC_ID_VORBIS,
    sizeof(venc_context_t),
    vorbis_encode_init,
    vorbis_encode_frame,
    vorbis_encode_close,
    .capabilities= CODEC_CAP_DELAY,
};