adpcm.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

                    STORE_NODE(ms, FFMAX(16, (AdaptationTable[nibble] * step) >> 8));
                }
            } else if((version == CODEC_ID_ADPCM_IMA_WAV)|| (version == CODEC_ID_ADPCM_SWF)) {
#define LOOP_NODES(NAME, STEP_TABLE, STEP_INDEX)\
                const int predictor = nodes[j]->sample1;\
                const int div = (sample - predictor) * 4 / STEP_TABLE;\
                int nmin = av_clip(div-range, -7, 6);\
                int nmax = av_clip(div+range, -6, 7);\
                if(nmin<=0) nmin--; /* distinguish -0 from +0 */\
                if(nmax<0) nmax--;\
                for(nidx=nmin; nidx<=nmax; nidx++) {\
                    const int nibble = nidx<0 ? 7-nidx : nidx;\
                    int dec_sample = predictor + (STEP_TABLE * yamaha_difflookup[nibble]) / 8;\
                    STORE_NODE(NAME, STEP_INDEX);\
                }
                LOOP_NODES(ima, step_table[step], av_clip(step + index_table[nibble], 0, 88));
            } else { //CODEC_ID_ADPCM_YAMAHA
                LOOP_NODES(yamaha, step, av_clip((step * yamaha_indexscale[nibble]) >> 8, 127, 24567));
#undef LOOP_NODES
#undef STORE_NODE
            }
        }

        u = nodes;
        nodes = nodes_next;
        nodes_next = u;

        // prevent overflow
        if(nodes[0]->ssd > (1<<28)) {
            for(j=1; j<frontier && nodes[j]; j++)
                nodes[j]->ssd -= nodes[0]->ssd;
            nodes[0]->ssd = 0;
        }

        // merge old paths to save memory
        if(i == froze + FREEZE_INTERVAL) {
            p = &paths[nodes[0]->path];
            for(k=i; k>froze; k--) {
                dst[k] = p->nibble;
                p = &paths[p->prev];
            }
            froze = i;
            pathn = 0;
            // other nodes might use paths that don't coincide with the frozen one.
            // checking which nodes do so is too slow, so just kill them all.
            // this also slightly improves quality, but I don't know why.
            memset(nodes+1, 0, (frontier-1)*sizeof(TrellisNode*));
        }
    }

    p = &paths[nodes[0]->path];
    for(i=n-1; i>froze; i--) {
        dst[i] = p->nibble;
        p = &paths[p->prev];
    }

    c->predictor = nodes[0]->sample1;
    c->sample1 = nodes[0]->sample1;
    c->sample2 = nodes[0]->sample2;
    c->step_index = nodes[0]->step;
    c->step = nodes[0]->step;
    c->idelta = nodes[0]->step;
}

static int adpcm_encode_frame(AVCodecContext *avctx,
                            unsigned char *frame, int buf_size, void *data)
{
    int n, i, st;
    short *samples;
    unsigned char *dst;
    ADPCMContext *c = avctx->priv_data;

    dst = frame;
    samples = (short *)data;
    st= avctx->channels == 2;
/*    n = (BLKSIZE - 4 * avctx->channels) / (2 * 8 * avctx->channels); */

    switch(avctx->codec->id) {
    case CODEC_ID_ADPCM_IMA_QT: /* XXX: can't test until we get .mov writer */
        break;
    case CODEC_ID_ADPCM_IMA_WAV:
        n = avctx->frame_size / 8;
            c->status[0].prev_sample = (signed short)samples[0]; /* XXX */
/*            c->status[0].step_index = 0; *//* XXX: not sure how to init the state machine */
            bytestream_put_le16(&dst, c->status[0].prev_sample);
            *dst++ = (unsigned char)c->status[0].step_index;
            *dst++ = 0; /* unknown */
            samples++;
            if (avctx->channels == 2) {
                c->status[1].prev_sample = (signed short)samples[1];
/*                c->status[1].step_index = 0; */
                bytestream_put_le16(&dst, c->status[1].prev_sample);
                *dst++ = (unsigned char)c->status[1].step_index;
                *dst++ = 0;
                samples++;
            }

            /* stereo: 4 bytes (8 samples) for left, 4 bytes for right, 4 bytes left, ... */
            if(avctx->trellis > 0) {
                uint8_t buf[2][n*8];
                adpcm_compress_trellis(avctx, samples, buf[0], &c->status[0], n*8);
                if(avctx->channels == 2)
                    adpcm_compress_trellis(avctx, samples+1, buf[1], &c->status[1], n*8);
                for(i=0; i<n; i++) {
                    *dst++ = buf[0][8*i+0] | (buf[0][8*i+1] << 4);
                    *dst++ = buf[0][8*i+2] | (buf[0][8*i+3] << 4);
                    *dst++ = buf[0][8*i+4] | (buf[0][8*i+5] << 4);
                    *dst++ = buf[0][8*i+6] | (buf[0][8*i+7] << 4);
                    if (avctx->channels == 2) {
                        *dst++ = buf[1][8*i+0] | (buf[1][8*i+1] << 4);
                        *dst++ = buf[1][8*i+2] | (buf[1][8*i+3] << 4);
                        *dst++ = buf[1][8*i+4] | (buf[1][8*i+5] << 4);
                        *dst++ = buf[1][8*i+6] | (buf[1][8*i+7] << 4);
                    }
                }
            } else
            for (; n>0; n--) {
                *dst = adpcm_ima_compress_sample(&c->status[0], samples[0]) & 0x0F;
                *dst |= (adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels]) << 4) & 0xF0;
                dst++;
                *dst = adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels * 2]) & 0x0F;
                *dst |= (adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels * 3]) << 4) & 0xF0;
                dst++;
                *dst = adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels * 4]) & 0x0F;
                *dst |= (adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels * 5]) << 4) & 0xF0;
                dst++;
                *dst = adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels * 6]) & 0x0F;
                *dst |= (adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels * 7]) << 4) & 0xF0;
                dst++;
                /* right channel */
                if (avctx->channels == 2) {
                    *dst = adpcm_ima_compress_sample(&c->status[1], samples[1]);
                    *dst |= adpcm_ima_compress_sample(&c->status[1], samples[3]) << 4;
                    dst++;
                    *dst = adpcm_ima_compress_sample(&c->status[1], samples[5]);
                    *dst |= adpcm_ima_compress_sample(&c->status[1], samples[7]) << 4;
                    dst++;
                    *dst = adpcm_ima_compress_sample(&c->status[1], samples[9]);
                    *dst |= adpcm_ima_compress_sample(&c->status[1], samples[11]) << 4;
                    dst++;
                    *dst = adpcm_ima_compress_sample(&c->status[1], samples[13]);
                    *dst |= adpcm_ima_compress_sample(&c->status[1], samples[15]) << 4;
                    dst++;
                }
                samples += 8 * avctx->channels;
            }
        break;
    case CODEC_ID_ADPCM_SWF:
    {
        int i;
        PutBitContext pb;
        init_put_bits(&pb, dst, buf_size*8);

        n = avctx->frame_size-1;

        //Store AdpcmCodeSize
        put_bits(&pb, 2, 2);                //Set 4bits flash adpcm format

        //Init the encoder state
        for(i=0; i<avctx->channels; i++){
            c->status[i].step_index = av_clip(c->status[i].step_index, 0, 63); // clip step so it fits 6 bits
            put_bits(&pb, 16, samples[i] & 0xFFFF);
            put_bits(&pb, 6, c->status[i].step_index);
            c->status[i].prev_sample = (signed short)samples[i];
        }

        if(avctx->trellis > 0) {
            uint8_t buf[2][n];
            adpcm_compress_trellis(avctx, samples+2, buf[0], &c->status[0], n);
            if (avctx->channels == 2)
                adpcm_compress_trellis(avctx, samples+3, buf[1], &c->status[1], n);
            for(i=0; i<n; i++) {
                put_bits(&pb, 4, buf[0][i]);
                if (avctx->channels == 2)
                    put_bits(&pb, 4, buf[1][i]);
            }
        } else {
            for (i=1; i<avctx->frame_size; i++) {
                put_bits(&pb, 4, adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels*i]) & 0xF);
                if (avctx->channels == 2)
                    put_bits(&pb, 4, adpcm_ima_compress_sample(&c->status[1], samples[2*i+1]) & 0xF);
            }
        }
        flush_put_bits(&pb);
        dst += put_bits_count(&pb)>>3;
        break;
    }
    case CODEC_ID_ADPCM_MS:
        for(i=0; i<avctx->channels; i++){
            int predictor=0;

            *dst++ = predictor;
            c->status[i].coeff1 = AdaptCoeff1[predictor];
            c->status[i].coeff2 = AdaptCoeff2[predictor];
        }
        for(i=0; i<avctx->channels; i++){
            if (c->status[i].idelta < 16)
                c->status[i].idelta = 16;

            bytestream_put_le16(&dst, c->status[i].idelta);
        }
        for(i=0; i<avctx->channels; i++){
            c->status[i].sample1= *samples++;

            bytestream_put_le16(&dst, c->status[i].sample1);
        }
        for(i=0; i<avctx->channels; i++){
            c->status[i].sample2= *samples++;

            bytestream_put_le16(&dst, c->status[i].sample2);
        }

        if(avctx->trellis > 0) {
            int n = avctx->block_align - 7*avctx->channels;
            uint8_t buf[2][n];
            if(avctx->channels == 1) {
                n *= 2;
                adpcm_compress_trellis(avctx, samples, buf[0], &c->status[0], n);
                for(i=0; i<n; i+=2)
                    *dst++ = (buf[0][i] << 4) | buf[0][i+1];
            } else {
                adpcm_compress_trellis(avctx, samples, buf[0], &c->status[0], n);
                adpcm_compress_trellis(avctx, samples+1, buf[1], &c->status[1], n);
                for(i=0; i<n; i++)
                    *dst++ = (buf[0][i] << 4) | buf[1][i];
            }
        } else
        for(i=7*avctx->channels; i<avctx->block_align; i++) {
            int nibble;
            nibble = adpcm_ms_compress_sample(&c->status[ 0], *samples++)<<4;
            nibble|= adpcm_ms_compress_sample(&c->status[st], *samples++);
            *dst++ = nibble;
        }
        break;
    case CODEC_ID_ADPCM_YAMAHA:
        n = avctx->frame_size / 2;
        if(avctx->trellis > 0) {
            uint8_t buf[2][n*2];
            n *= 2;
            if(avctx->channels == 1) {
                adpcm_compress_trellis(avctx, samples, buf[0], &c->status[0], n);
                for(i=0; i<n; i+=2)
                    *dst++ = buf[0][i] | (buf[0][i+1] << 4);
            } else {
                adpcm_compress_trellis(avctx, samples, buf[0], &c->status[0], n);
                adpcm_compress_trellis(avctx, samples+1, buf[1], &c->status[1], n);
                for(i=0; i<n; i++)
                    *dst++ = buf[0][i] | (buf[1][i] << 4);
            }
        } else
        for (; n>0; n--) {
            for(i = 0; i < avctx->channels; i++) {
                int nibble;
                nibble  = adpcm_yamaha_compress_sample(&c->status[i], samples[i]);
                nibble |= adpcm_yamaha_compress_sample(&c->status[i], samples[i+avctx->channels]) << 4;
                *dst++ = nibble;
            }
            samples += 2 * avctx->channels;
        }
        break;
    default:
        return -1;
    }
    return dst - frame;
}
#endif //CONFIG_ENCODERS

static int adpcm_decode_init(AVCodecContext * avctx)
{
    ADPCMContext *c = avctx->priv_data;

    if(avctx->channels > 2U){
        return -1;
    }

    c->channel = 0;
    c->status[0].predictor = c->status[1].predictor = 0;
    c->status[0].step_index = c->status[1].step_index = 0;
    c->status[0].step = c->status[1].step = 0;

    switch(avctx->codec->id) {
    case CODEC_ID_ADPCM_CT:
        c->status[0].step = c->status[1].step = 511;
        break;
    case CODEC_ID_ADPCM_IMA_WS:
        if (avctx->extradata && avctx->extradata_size == 2 * 4) {
            c->status[0].predictor = AV_RL32(avctx->extradata);
            c->status[1].predictor = AV_RL32(avctx->extradata + 4);
        }
        break;
    default:
        break;
    }
    return 0;
}

static inline short adpcm_ima_expand_nibble(ADPCMChannelStatus *c, char nibble, int shift)
{
    int step_index;
    int predictor;
    int sign, delta, diff, step;

    step = step_table[c->step_index];
    step_index = c->step_index + index_table[(unsigned)nibble];
    if (step_index < 0) step_index = 0;
    else if (step_index > 88) step_index = 88;

    sign = nibble & 8;
    delta = nibble & 7;
    /* perform direct multiplication instead of series of jumps proposed by
     * the reference ADPCM implementation since modern CPUs can do the mults
     * quickly enough */
    diff = ((2 * delta + 1) * step) >> shift;
    predictor = c->predictor;
    if (sign) predictor -= diff;
    else predictor += diff;

    c->predictor = av_clip_int16(predictor);
    c->step_index = step_index;

    return (short)c->predictor;
}

static inline short adpcm_ms_expand_nibble(ADPCMChannelStatus *c, char nibble)
{
    int predictor;

    predictor = (((c->sample1) * (c->coeff1)) + ((c->sample2) * (c->coeff2))) / 256;
    predictor += (signed)((nibble & 0x08)?(nibble - 0x10):(nibble)) * c->idelta;

    c->sample2 = c->sample1;
    c->sample1 = av_clip_int16(predictor);
    c->idelta = (AdaptationTable[(int)nibble] * c->idelta) >> 8;
    if (c->idelta < 16) c->idelta = 16;

    return c->sample1;
}

static inline short adpcm_ct_expand_nibble(ADPCMChannelStatus *c, char nibble)
{
    int sign, delta, diff;
    int new_step;

    sign = nibble & 8;
    delta = nibble & 7;
    /* perform direct multiplication instead of series of jumps proposed by
     * the reference ADPCM implementation since modern CPUs can do the mults
     * quickly enough */
    diff = ((2 * delta + 1) * c->step) >> 3;
    /* predictor update is not so trivial: predictor is multiplied on 254/256 before updating */
    c->predictor = ((c->predictor * 254) >> 8) + (sign ? -diff : diff);
    c->predictor = av_clip_int16(c->predictor);
    /* calculate new step and clamp it to range 511..32767 */
    new_step = (ct_adpcm_table[nibble & 7] * c->step) >> 8;
    c->step = av_clip(new_step, 511, 32767);

    return (short)c->predictor;
}

static inline short adpcm_sbpro_expand_nibble(ADPCMChannelStatus *c, char nibble, int size, int shift)
{
    int sign, delta, diff;

    sign = nibble & (1<<(size-1));
    delta = nibble & ((1<<(size-1))-1);
    diff = delta << (7 + c->step + shift);

    /* clamp result */