FFmpeg/libavcodec/adpcmenc.c

/*
 * Copyright (c) 2001-2003 The ffmpeg Project
 *
 * This file is part of Libav.
 *
 * Libav is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * Libav is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with Libav; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "avcodec.h"
#include "get_bits.h"
#include "put_bits.h"
#include "bytestream.h"
#include "adpcm.h"
#include "adpcm_data.h"

/**
 * @file
 * ADPCM encoders
 * First version by Francois Revol (revol@free.fr)
 * Fringe ADPCM codecs (e.g., DK3, DK4, Westwood)
 *   by Mike Melanson (melanson@pcisys.net)
 *
 * Reference documents:
 * http://www.pcisys.net/~melanson/codecs/simpleaudio.html
 * http://www.geocities.com/SiliconValley/8682/aud3.txt
 * http://openquicktime.sourceforge.net/plugins.htm
 * XAnim sources (xa_codec.c) http://www.rasnaimaging.com/people/lapus/download.html
 * http://www.cs.ucla.edu/~leec/mediabench/applications.html
 * SoX source code http://home.sprynet.com/~cbagwell/sox.html
 */

typedef struct TrellisPath {
    int nibble;
    int prev;
} TrellisPath;

typedef struct TrellisNode {
    uint32_t ssd;
    int path;
    int sample1;
    int sample2;
    int step;
} TrellisNode;

typedef struct ADPCMEncodeContext {
    ADPCMChannelStatus status[6];
    TrellisPath *paths;
    TrellisNode *node_buf;
    TrellisNode **nodep_buf;
    uint8_t *trellis_hash;
} ADPCMEncodeContext;

#define FREEZE_INTERVAL 128

static av_cold int adpcm_encode_init(AVCodecContext *avctx)
{
    ADPCMEncodeContext *s = avctx->priv_data;
    uint8_t *extradata;
    int i;
    if (avctx->channels > 2)
        return -1; /* only stereo or mono =) */

    if(avctx->trellis && (unsigned)avctx->trellis > 16U){
        av_log(avctx, AV_LOG_ERROR, "invalid trellis size\n");
        return -1;
    }

    if (avctx->trellis) {
        int frontier = 1 << avctx->trellis;
        int max_paths =  frontier * FREEZE_INTERVAL;
        FF_ALLOC_OR_GOTO(avctx, s->paths,     max_paths * sizeof(*s->paths), error);
        FF_ALLOC_OR_GOTO(avctx, s->node_buf,  2 * frontier * sizeof(*s->node_buf), error);
        FF_ALLOC_OR_GOTO(avctx, s->nodep_buf, 2 * frontier * sizeof(*s->nodep_buf), error);
        FF_ALLOC_OR_GOTO(avctx, s->trellis_hash, 65536 * sizeof(*s->trellis_hash), error);
    }

    switch(avctx->codec->id) {
    case CODEC_ID_ADPCM_IMA_WAV:
        avctx->frame_size = (BLKSIZE - 4 * avctx->channels) * 8 / (4 * avctx->channels) + 1; /* each 16 bits sample gives one nibble */
                                                             /* and we have 4 bytes per channel overhead */
        avctx->block_align = BLKSIZE;
        /* seems frame_size isn't taken into account... have to buffer the samples :-( */
        break;
    case CODEC_ID_ADPCM_IMA_QT:
        avctx->frame_size = 64;
        avctx->block_align = 34 * avctx->channels;
        break;
    case CODEC_ID_ADPCM_MS:
        avctx->frame_size = (BLKSIZE - 7 * avctx->channels) * 2 / avctx->channels + 2; /* each 16 bits sample gives one nibble */
                                                             /* and we have 7 bytes per channel overhead */
        avctx->block_align = BLKSIZE;
        avctx->extradata_size = 32;
        extradata = avctx->extradata = av_malloc(avctx->extradata_size);
        if (!extradata)
            return AVERROR(ENOMEM);
        bytestream_put_le16(&extradata, avctx->frame_size);
        bytestream_put_le16(&extradata, 7); /* wNumCoef */
        for (i = 0; i < 7; i++) {
            bytestream_put_le16(&extradata, ff_adpcm_AdaptCoeff1[i] * 4);
            bytestream_put_le16(&extradata, ff_adpcm_AdaptCoeff2[i] * 4);
        }
        break;
    case CODEC_ID_ADPCM_YAMAHA:
        avctx->frame_size = BLKSIZE * avctx->channels;
        avctx->block_align = BLKSIZE;
        break;
    case CODEC_ID_ADPCM_SWF:
        if (avctx->sample_rate != 11025 &&
            avctx->sample_rate != 22050 &&
            avctx->sample_rate != 44100) {
            av_log(avctx, AV_LOG_ERROR, "Sample rate must be 11025, 22050 or 44100\n");
            goto error;
        }
        avctx->frame_size = 512 * (avctx->sample_rate / 11025);
        break;
    default:
        goto error;
    }

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

    return 0;
error:
    av_freep(&s->paths);
    av_freep(&s->node_buf);
    av_freep(&s->nodep_buf);
    av_freep(&s->trellis_hash);
    return -1;
}

static av_cold int adpcm_encode_close(AVCodecContext *avctx)
{
    ADPCMEncodeContext *s = avctx->priv_data;
    av_freep(&avctx->coded_frame);
    av_freep(&s->paths);
    av_freep(&s->node_buf);
    av_freep(&s->nodep_buf);
    av_freep(&s->trellis_hash);

    return 0;
}


static inline unsigned char adpcm_ima_compress_sample(ADPCMChannelStatus *c, short sample)
{
    int delta = sample - c->prev_sample;
    int nibble = FFMIN(7, abs(delta)*4/ff_adpcm_step_table[c->step_index]) + (delta<0)*8;
    c->prev_sample += ((ff_adpcm_step_table[c->step_index] * ff_adpcm_yamaha_difflookup[nibble]) / 8);
    c->prev_sample = av_clip_int16(c->prev_sample);
    c->step_index = av_clip(c->step_index + ff_adpcm_index_table[nibble], 0, 88);
    return nibble;
}

static inline unsigned char adpcm_ms_compress_sample(ADPCMChannelStatus *c, short sample)
{
    int predictor, nibble, bias;

    predictor = (((c->sample1) * (c->coeff1)) + ((c->sample2) * (c->coeff2))) / 64;

    nibble= sample - predictor;
    if(nibble>=0) bias= c->idelta/2;
    else          bias=-c->idelta/2;

    nibble= (nibble + bias) / c->idelta;
    nibble= av_clip(nibble, -8, 7)&0x0F;

    predictor += (signed)((nibble & 0x08)?(nibble - 0x10):(nibble)) * c->idelta;

    c->sample2 = c->sample1;
    c->sample1 = av_clip_int16(predictor);

    c->idelta = (ff_adpcm_AdaptationTable[(int)nibble] * c->idelta) >> 8;
    if (c->idelta < 16) c->idelta = 16;

    return nibble;
}

static inline unsigned char adpcm_yamaha_compress_sample(ADPCMChannelStatus *c, short sample)
{
    int nibble, delta;

    if(!c->step) {
        c->predictor = 0;
        c->step = 127;
    }

    delta = sample - c->predictor;

    nibble = FFMIN(7, abs(delta)*4/c->step) + (delta<0)*8;

    c->predictor += ((c->step * ff_adpcm_yamaha_difflookup[nibble]) / 8);
    c->predictor = av_clip_int16(c->predictor);
    c->step = (c->step * ff_adpcm_yamaha_indexscale[nibble]) >> 8;
    c->step = av_clip(c->step, 127, 24567);

    return nibble;
}

static void adpcm_compress_trellis(AVCodecContext *avctx, const short *samples,
                                   uint8_t *dst, ADPCMChannelStatus *c, int n)
{
    //FIXME 6% faster if frontier is a compile-time constant
    ADPCMEncodeContext *s = avctx->priv_data;
    const int frontier = 1 << avctx->trellis;
    const int stride = avctx->channels;
    const int version = avctx->codec->id;
    TrellisPath *paths = s->paths, *p;
    TrellisNode *node_buf = s->node_buf;
    TrellisNode **nodep_buf = s->nodep_buf;
    TrellisNode **nodes = nodep_buf; // nodes[] is always sorted by .ssd
    TrellisNode **nodes_next = nodep_buf + frontier;
    int pathn = 0, froze = -1, i, j, k, generation = 0;
    uint8_t *hash = s->trellis_hash;
    memset(hash, 0xff, 65536 * sizeof(*hash));

    memset(nodep_buf, 0, 2 * frontier * sizeof(*nodep_buf));
    nodes[0] = node_buf + frontier;
    nodes[0]->ssd = 0;
    nodes[0]->path = 0;
    nodes[0]->step = c->step_index;
    nodes[0]->sample1 = c->sample1;
    nodes[0]->sample2 = c->sample2;
    if((version == CODEC_ID_ADPCM_IMA_WAV) || (version == CODEC_ID_ADPCM_IMA_QT) || (version == CODEC_ID_ADPCM_SWF))
        nodes[0]->sample1 = c->prev_sample;
    if(version == CODEC_ID_ADPCM_MS)
        nodes[0]->step = c->idelta;
    if(version == CODEC_ID_ADPCM_YAMAHA) {
        if(c->step == 0) {
            nodes[0]->step = 127;
            nodes[0]->sample1 = 0;
        } else {
            nodes[0]->step = c->step;
            nodes[0]->sample1 = c->predictor;
        }
    }

    for(i=0; i<n; i++) {
        TrellisNode *t = node_buf + frontier*(i&1);
        TrellisNode **u;
        int sample = samples[i*stride];
        int heap_pos = 0;
        memset(nodes_next, 0, frontier*sizeof(TrellisNode*));
        for(j=0; j<frontier && nodes[j]; j++) {
            // higher j have higher ssd already, so they're likely to yield a suboptimal next sample too
            const int range = (j < frontier/2) ? 1 : 0;
            const int step = nodes[j]->step;
            int nidx;
            if(version == CODEC_ID_ADPCM_MS) {
                const int predictor = ((nodes[j]->sample1 * c->coeff1) + (nodes[j]->sample2 * c->coeff2)) / 64;
                const int div = (sample - predictor) / step;
                const int nmin = av_clip(div-range, -8, 6);
                const int nmax = av_clip(div+range, -7, 7);
                for(nidx=nmin; nidx<=nmax; nidx++) {
                    const int nibble = nidx & 0xf;
                    int dec_sample = predictor + nidx * step;
#define STORE_NODE(NAME, STEP_INDEX)\
                    int d;\
                    uint32_t ssd;\
                    int pos;\
                    TrellisNode *u;\
                    uint8_t *h;\
                    dec_sample = av_clip_int16(dec_sample);\
                    d = sample - dec_sample;\
                    ssd = nodes[j]->ssd + d*d;\
                    /* Check for wraparound, skip such samples completely. \
                     * Note, changing ssd to a 64 bit variable would be \
                     * simpler, avoiding this check, but it's slower on \
                     * x86 32 bit at the moment. */\
                    if (ssd < nodes[j]->ssd)\
                        goto next_##NAME;\
                    /* Collapse any two states with the same previous sample value. \
                     * One could also distinguish states by step and by 2nd to last
                     * sample, but the effects of that are negligible.
                     * Since nodes in the previous generation are iterated
                     * through a heap, they're roughly ordered from better to
                     * worse, but not strictly ordered. Therefore, an earlier
                     * node with the same sample value is better in most cases
                     * (and thus the current is skipped), but not strictly
                     * in all cases. Only skipping samples where ssd >=
                     * ssd of the earlier node with the same sample gives
                     * slightly worse quality, though, for some reason. */ \
                    h = &hash[(uint16_t) dec_sample];\
                    if (*h == generation)\
                        goto next_##NAME;\
                    if (heap_pos < frontier) {\
                        pos = heap_pos++;\
                    } else {\
                        /* Try to replace one of the leaf nodes with the new \
                         * one, but try a different slot each time. */\
                        pos = (frontier >> 1) + (heap_pos & ((frontier >> 1) - 1));\
                        if (ssd > nodes_next[pos]->ssd)\
                            goto next_##NAME;\
                        heap_pos++;\
                    }\
                    *h = generation;\
                    u = nodes_next[pos];\
                    if(!u) {\
                        assert(pathn < FREEZE_INTERVAL<<avctx->trellis);\
                        u = t++;\
                        nodes_next[pos] = u;\
                        u->path = pathn++;\
                    }\
                    u->ssd = ssd;\
                    u->step = STEP_INDEX;\
                    u->sample2 = nodes[j]->sample1;\
                    u->sample1 = dec_sample;\
                    paths[u->path].nibble = nibble;\
                    paths[u->path].prev = nodes[j]->path;\
                    /* Sift the newly inserted node up in the heap to \
                     * restore the heap property. */\
                    while (pos > 0) {\
                        int parent = (pos - 1) >> 1;\
                        if (nodes_next[parent]->ssd <= ssd)\
                            break;\
                        FFSWAP(TrellisNode*, nodes_next[parent], nodes_next[pos]);\
                        pos = parent;\
                    }\
                    next_##NAME:;
                    STORE_NODE(ms, FFMAX(16, (ff_adpcm_AdaptationTable[nibble] * step) >> 8));
                }
            } else if((version == CODEC_ID_ADPCM_IMA_WAV)|| (version == CODEC_ID_ADPCM_IMA_QT)|| (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 * ff_adpcm_yamaha_difflookup[nibble]) / 8;\
                    STORE_NODE(NAME, STEP_INDEX);\
                }
                LOOP_NODES(ima, ff_adpcm_step_table[step], av_clip(step + ff_adpcm_index_table[nibble], 0, 88));
            } else { //CODEC_ID_ADPCM_YAMAHA
                LOOP_NODES(yamaha, step, av_clip((step * ff_adpcm_yamaha_indexscale[nibble]) >> 8, 127, 24567));
#undef LOOP_NODES
#undef STORE_NODE
            }
        }

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

        generation++;
        if (generation == 255) {
            memset(hash, 0xff, 65536 * sizeof(*hash));
            generation = 0;
        }

        // 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;
    ADPCMEncodeContext *c = avctx->priv_data;
    uint8_t *buf;

    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_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[0];
/*                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) {
                FF_ALLOC_OR_GOTO(avctx, buf, 2*n*8, error);
                adpcm_compress_trellis(avctx, samples, buf, &c->status[0], n*8);
                if(avctx->channels == 2)
                    adpcm_compress_trellis(avctx, samples+1, buf + n*8, &c->status[1], n*8);
                for(i=0; i<n; i++) {
                    *dst++ = buf[8*i+0] | (buf[8*i+1] << 4);
                    *dst++ = buf[8*i+2] | (buf[8*i+3] << 4);
                    *dst++ = buf[8*i+4] | (buf[8*i+5] << 4);
                    *dst++ = buf[8*i+6] | (buf[8*i+7] << 4);
                    if (avctx->channels == 2) {
                        uint8_t *buf1 = buf + n*8;
                        *dst++ = buf1[8*i+0] | (buf1[8*i+1] << 4);
                        *dst++ = buf1[8*i+2] | (buf1[8*i+3] << 4);
                        *dst++ = buf1[8*i+4] | (buf1[8*i+5] << 4);
                        *dst++ = buf1[8*i+6] | (buf1[8*i+7] << 4);
                    }
                }
                av_free(buf);
            } else
            for (; n>0; n--) {
                *dst = adpcm_ima_compress_sample(&c->status[0], samples[0]);
                *dst |= adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels]) << 4;
                dst++;
                *dst = adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels * 2]);
                *dst |= adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels * 3]) << 4;
                dst++;
                *dst = adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels * 4]);
                *dst |= adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels * 5]) << 4;
                dst++;
                *dst = adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels * 6]);
                *dst |= adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels * 7]) << 4;
                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_IMA_QT:
    {
        int ch, i;
        PutBitContext pb;
        init_put_bits(&pb, dst, buf_size*8);

        for(ch=0; ch<avctx->channels; ch++){
            put_bits(&pb, 9, (c->status[ch].prev_sample + 0x10000) >> 7);
            put_bits(&pb, 7, c->status[ch].step_index);
            if(avctx->trellis > 0) {
                uint8_t buf[64];
                adpcm_compress_trellis(avctx, samples+ch, buf, &c->status[ch], 64);
                for(i=0; i<64; i++)
                    put_bits(&pb, 4, buf[i^1]);
                c->status[ch].prev_sample = c->status[ch].predictor & ~0x7F;
            } else {
                for (i=0; i<64; i+=2){
                    int t1, t2;
                    t1 = adpcm_ima_compress_sample(&c->status[ch], samples[avctx->channels*(i+0)+ch]);
                    t2 = adpcm_ima_compress_sample(&c->status[ch], samples[avctx->channels*(i+1)+ch]);
                    put_bits(&pb, 4, t2);
                    put_bits(&pb, 4, t1);
                }
                c->status[ch].prev_sample &= ~0x7F;
            }
        }

        flush_put_bits(&pb);
        dst += put_bits_count(&pb)>>3;
        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_sbits(&pb, 16, samples[i]);
            put_bits(&pb, 6, c->status[i].step_index);
            c->status[i].prev_sample = (signed short)samples[i];
        }

        if(avctx->trellis > 0) {
            FF_ALLOC_OR_GOTO(avctx, buf, 2*n, error);
            adpcm_compress_trellis(avctx, samples+2, buf, &c->status[0], n);
            if (avctx->channels == 2)
                adpcm_compress_trellis(avctx, samples+3, buf+n, &c->status[1], n);
            for(i=0; i<n; i++) {
                put_bits(&pb, 4, buf[i]);
                if (avctx->channels == 2)
                    put_bits(&pb, 4, buf[n+i]);
            }
            av_free(buf);
        } else {
            for (i=1; i<avctx->frame_size; i++) {
                put_bits(&pb, 4, adpcm_ima_compress_sample(&c->status[0], samples[avctx->channels*i]));
                if (avctx->channels == 2)
                    put_bits(&pb, 4, adpcm_ima_compress_sample(&c->status[1], samples[2*i+1]));
            }
        }
        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 = ff_adpcm_AdaptCoeff1[predictor];
            c->status[i].coeff2 = ff_adpcm_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].sample2= *samples++;
        }
        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++)
            bytestream_put_le16(&dst, c->status[i].sample2);

        if(avctx->trellis > 0) {
            int n = avctx->block_align - 7*avctx->channels;
            FF_ALLOC_OR_GOTO(avctx, buf, 2*n, error);
            if(avctx->channels == 1) {
                adpcm_compress_trellis(avctx, samples, buf, &c->status[0], n);
                for(i=0; i<n; i+=2)
                    *dst++ = (buf[i] << 4) | buf[i+1];
            } else {
                adpcm_compress_trellis(avctx, samples, buf, &c->status[0], n);
                adpcm_compress_trellis(avctx, samples+1, buf+n, &c->status[1], n);
                for(i=0; i<n; i++)
                    *dst++ = (buf[i] << 4) | buf[n+i];
            }
            av_free(buf);
        } 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) {
            FF_ALLOC_OR_GOTO(avctx, buf, 2*n*2, error);
            n *= 2;
            if(avctx->channels == 1) {
                adpcm_compress_trellis(avctx, samples, buf, &c->status[0], n);
                for(i=0; i<n; i+=2)
                    *dst++ = buf[i] | (buf[i+1] << 4);
            } else {
                adpcm_compress_trellis(avctx, samples, buf, &c->status[0], n);
                adpcm_compress_trellis(avctx, samples+1, buf+n, &c->status[1], n);
                for(i=0; i<n; i++)
                    *dst++ = buf[i] | (buf[n+i] << 4);
            }
            av_free(buf);
        } else
            for (n *= avctx->channels; n>0; n--) {
                int nibble;
                nibble  = adpcm_yamaha_compress_sample(&c->status[ 0], *samples++);
                nibble |= adpcm_yamaha_compress_sample(&c->status[st], *samples++) << 4;
                *dst++ = nibble;
            }
        break;
    default:
    error:
        return -1;
    }
    return dst - frame;
}


#define ADPCM_ENCODER(id,name,long_name_)       \
AVCodec ff_ ## name ## _encoder = {             \
    #name,                                      \
    AVMEDIA_TYPE_AUDIO,                         \
    id,                                         \
    sizeof(ADPCMEncodeContext),                 \
    adpcm_encode_init,                          \
    adpcm_encode_frame,                         \
    adpcm_encode_close,                         \
    NULL,                                       \
    .sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_S16,AV_SAMPLE_FMT_NONE}, \
    .long_name = NULL_IF_CONFIG_SMALL(long_name_), \
}

ADPCM_ENCODER(CODEC_ID_ADPCM_IMA_QT, adpcm_ima_qt, "ADPCM IMA QuickTime");
ADPCM_ENCODER(CODEC_ID_ADPCM_IMA_WAV, adpcm_ima_wav, "ADPCM IMA WAV");
ADPCM_ENCODER(CODEC_ID_ADPCM_MS, adpcm_ms, "ADPCM Microsoft");
ADPCM_ENCODER(CODEC_ID_ADPCM_SWF, adpcm_swf, "ADPCM Shockwave Flash");
ADPCM_ENCODER(CODEC_ID_ADPCM_YAMAHA, adpcm_yamaha, "ADPCM Yamaha");