static int adpcm_decode_frame(AVCodecContext *avctx,

                            void *data, int *data_size,

                            uint8_t *buf, int buf_size)

{

    ADPCMContext *c = avctx->priv_data;

    ADPCMChannelStatus *cs;

    int n, m, channel, i;

    int block_predictor[2];

    short *samples;

    short *samples_end;

    uint8_t *src;

    int st; /* stereo */



    /* DK3 ADPCM accounting variables */

    unsigned char last_byte = 0;

    unsigned char nibble;

    int decode_top_nibble_next = 0;

    int diff_channel;



    /* EA ADPCM state variables */

    uint32_t samples_in_chunk;

    int32_t previous_left_sample, previous_right_sample;

    int32_t current_left_sample, current_right_sample;

    int32_t next_left_sample, next_right_sample;

    int32_t coeff1l, coeff2l, coeff1r, coeff2r;

    uint8_t shift_left, shift_right;

    int count1, count2;



    if (!buf_size)

        return 0;



    //should protect all 4bit ADPCM variants

    //8 is needed for CODEC_ID_ADPCM_IMA_WAV with 2 channels

    //

    if(*data_size/4 < buf_size + 8)

        return -1;



    samples = data;

    samples_end= samples + *data_size/2;

    *data_size= 0;

    src = buf;



    st = avctx->channels == 2 ? 1 : 0;



    switch(avctx->codec->id) {

    case CODEC_ID_ADPCM_IMA_QT:

        n = (buf_size - 2);/* >> 2*avctx->channels;*/

        channel = c->channel;

        cs = &(c->status[channel]);

        /* (pppppp) (piiiiiii) */



        /* Bits 15-7 are the _top_ 9 bits of the 16-bit initial predictor value */

        cs->predictor = (*src++) << 8;

        cs->predictor |= (*src & 0x80);

        cs->predictor &= 0xFF80;



        /* sign extension */

        if(cs->predictor & 0x8000)

            cs->predictor -= 0x10000;



        CLAMP_TO_SHORT(cs->predictor);



        cs->step_index = (*src++) & 0x7F;



        if (cs->step_index > 88){

            av_log(avctx, AV_LOG_ERROR, "ERROR: step_index = %i\n", cs->step_index);

            cs->step_index = 88;

        }



        cs->step = step_table[cs->step_index];



        if (st && channel)

            samples++;



        for(m=32; n>0 && m>0; n--, m--) { /* in QuickTime, IMA is encoded by chuncks of 34 bytes (=64 samples) */

            *samples = adpcm_ima_expand_nibble(cs, src[0] & 0x0F, 3);

            samples += avctx->channels;

            *samples = adpcm_ima_expand_nibble(cs, (src[0] >> 4) & 0x0F, 3);

            samples += avctx->channels;

            src ++;

        }



        if(st) { /* handle stereo interlacing */

            c->channel = (channel + 1) % 2; /* we get one packet for left, then one for right data */

            if(channel == 1) { /* wait for the other packet before outputing anything */

                return src - buf;

            }

        }

        break;

    case CODEC_ID_ADPCM_IMA_WAV:

        if (avctx->block_align != 0 && buf_size > avctx->block_align)

            buf_size = avctx->block_align;



//        samples_per_block= (block_align-4*chanels)*8 / (bits_per_sample * chanels) + 1;



        for(i=0; i<avctx->channels; i++){

            cs = &(c->status[i]);

            cs->predictor = (int16_t)(src[0] + (src[1]<<8));

            src+=2;



        // XXX: is this correct ??: *samples++ = cs->predictor;



            cs->step_index = *src++;

            if (cs->step_index > 88){

                av_log(avctx, AV_LOG_ERROR, "ERROR: step_index = %i\n", cs->step_index);

                cs->step_index = 88;

            }

            if (*src++) av_log(avctx, AV_LOG_ERROR, "unused byte should be null but is %d!!\n", src[-1]); /* unused */

        }



        while(src < buf + buf_size){

            for(m=0; m<4; m++){

                for(i=0; i<=st; i++)

                    *samples++ = adpcm_ima_expand_nibble(&c->status[i], src[4*i] & 0x0F, 3);

                for(i=0; i<=st; i++)

                    *samples++ = adpcm_ima_expand_nibble(&c->status[i], src[4*i] >> 4  , 3);

                src++;

            }

            src += 4*st;

        }

        break;

    case CODEC_ID_ADPCM_4XM:

        cs = &(c->status[0]);

        c->status[0].predictor= (int16_t)(src[0] + (src[1]<<8)); src+=2;

        if(st){

            c->status[1].predictor= (int16_t)(src[0] + (src[1]<<8)); src+=2;

        }

        c->status[0].step_index= (int16_t)(src[0] + (src[1]<<8)); src+=2;

        if(st){

            c->status[1].step_index= (int16_t)(src[0] + (src[1]<<8)); src+=2;

        }

        if (cs->step_index < 0) cs->step_index = 0;

        if (cs->step_index > 88) cs->step_index = 88;



        m= (buf_size - (src - buf))>>st;

        for(i=0; i<m; i++) {

            *samples++ = adpcm_ima_expand_nibble(&c->status[0], src[i] & 0x0F, 4);

            if (st)

                *samples++ = adpcm_ima_expand_nibble(&c->status[1], src[i+m] & 0x0F, 4);

            *samples++ = adpcm_ima_expand_nibble(&c->status[0], src[i] >> 4, 4);

            if (st)

                *samples++ = adpcm_ima_expand_nibble(&c->status[1], src[i+m] >> 4, 4);

        }



        src += m<<st;



        break;

    case CODEC_ID_ADPCM_MS:

        if (avctx->block_align != 0 && buf_size > avctx->block_align)

            buf_size = avctx->block_align;

        n = buf_size - 7 * avctx->channels;

        if (n < 0)

            return -1;

        block_predictor[0] = av_clip(*src++, 0, 7);

        block_predictor[1] = 0;

        if (st)

            block_predictor[1] = av_clip(*src++, 0, 7);

        c->status[0].idelta = (int16_t)((*src & 0xFF) | ((src[1] << 8) & 0xFF00));

        src+=2;

        if (st){

            c->status[1].idelta = (int16_t)((*src & 0xFF) | ((src[1] << 8) & 0xFF00));

            src+=2;

        }

        c->status[0].coeff1 = AdaptCoeff1[block_predictor[0]];

        c->status[0].coeff2 = AdaptCoeff2[block_predictor[0]];

        c->status[1].coeff1 = AdaptCoeff1[block_predictor[1]];

        c->status[1].coeff2 = AdaptCoeff2[block_predictor[1]];



        c->status[0].sample1 = ((*src & 0xFF) | ((src[1] << 8) & 0xFF00));

        src+=2;

        if (st) c->status[1].sample1 = ((*src & 0xFF) | ((src[1] << 8) & 0xFF00));

        if (st) src+=2;

        c->status[0].sample2 = ((*src & 0xFF) | ((src[1] << 8) & 0xFF00));

        src+=2;

        if (st) c->status[1].sample2 = ((*src & 0xFF) | ((src[1] << 8) & 0xFF00));

        if (st) src+=2;



        *samples++ = c->status[0].sample1;

        if (st) *samples++ = c->status[1].sample1;

        *samples++ = c->status[0].sample2;

        if (st) *samples++ = c->status[1].sample2;

        for(;n>0;n--) {

            *samples++ = adpcm_ms_expand_nibble(&c->status[0], (src[0] >> 4) & 0x0F);

            *samples++ = adpcm_ms_expand_nibble(&c->status[st], src[0] & 0x0F);

            src ++;

        }

        break;

    case CODEC_ID_ADPCM_IMA_DK4:

        if (avctx->block_align != 0 && buf_size > avctx->block_align)

            buf_size = avctx->block_align;



        c->status[0].predictor = (int16_t)(src[0] | (src[1] << 8));

        c->status[0].step_index = src[2];

        src += 4;

        *samples++ = c->status[0].predictor;

        if (st) {

            c->status[1].predictor = (int16_t)(src[0] | (src[1] << 8));

            c->status[1].step_index = src[2];

            src += 4;

            *samples++ = c->status[1].predictor;

        }

        while (src < buf + buf_size) {



            /* take care of the top nibble (always left or mono channel) */

            *samples++ = adpcm_ima_expand_nibble(&c->status[0],

                (src[0] >> 4) & 0x0F, 3);



            /* take care of the bottom nibble, which is right sample for

             * stereo, or another mono sample */

            if (st)

                *samples++ = adpcm_ima_expand_nibble(&c->status[1],

                    src[0] & 0x0F, 3);

            else

                *samples++ = adpcm_ima_expand_nibble(&c->status[0],

                    src[0] & 0x0F, 3);



            src++;

        }

        break;

    case CODEC_ID_ADPCM_IMA_DK3:

        if (avctx->block_align != 0 && buf_size > avctx->block_align)

            buf_size = avctx->block_align;



        if(buf_size + 16 > (samples_end - samples)*3/8)

            return -1;



        c->status[0].predictor = (int16_t)(src[10] | (src[11] << 8));

        c->status[1].predictor = (int16_t)(src[12] | (src[13] << 8));

        c->status[0].step_index = src[14];

        c->status[1].step_index = src[15];

        /* sign extend the predictors */

        src += 16;

        diff_channel = c->status[1].predictor;



        /* the DK3_GET_NEXT_NIBBLE macro issues the break statement when

         * the buffer is consumed */

        while (1) {



            /* for this algorithm, c->status[0] is the sum channel and

             * c->status[1] is the diff channel */



            /* process the first predictor of the sum channel */

            DK3_GET_NEXT_NIBBLE();

            adpcm_ima_expand_nibble(&c->status[0], nibble, 3);



            /* process the diff channel predictor */

            DK3_GET_NEXT_NIBBLE();

            adpcm_ima_expand_nibble(&c->status[1], nibble, 3);



            /* process the first pair of stereo PCM samples */

            diff_channel = (diff_channel + c->status[1].predictor) / 2;

            *samples++ = c->status[0].predictor + c->status[1].predictor;

            *samples++ = c->status[0].predictor - c->status[1].predictor;



            /* process the second predictor of the sum channel */

            DK3_GET_NEXT_NIBBLE();

            adpcm_ima_expand_nibble(&c->status[0], nibble, 3);



            /* process the second pair of stereo PCM samples */

            diff_channel = (diff_channel + c->status[1].predictor) / 2;

            *samples++ = c->status[0].predictor + c->status[1].predictor;

            *samples++ = c->status[0].predictor - c->status[1].predictor;

        }

        break;

    case CODEC_ID_ADPCM_IMA_WS:

        /* no per-block initialization; just start decoding the data */

        while (src < buf + buf_size) {



            if (st) {

                *samples++ = adpcm_ima_expand_nibble(&c->status[0],

                    (src[0] >> 4) & 0x0F, 3);

                *samples++ = adpcm_ima_expand_nibble(&c->status[1],

                    src[0] & 0x0F, 3);

            } else {

                *samples++ = adpcm_ima_expand_nibble(&c->status[0],

                    (src[0] >> 4) & 0x0F, 3);

                *samples++ = adpcm_ima_expand_nibble(&c->status[0],

                    src[0] & 0x0F, 3);

            }



            src++;

        }

        break;

    case CODEC_ID_ADPCM_XA:

        c->status[0].sample1 = c->status[0].sample2 =

        c->status[1].sample1 = c->status[1].sample2 = 0;

        while (buf_size >= 128) {

            xa_decode(samples, src, &c->status[0], &c->status[1],

                avctx->channels);

            src += 128;

            samples += 28 * 8;

            buf_size -= 128;

        }

        break;

    case CODEC_ID_ADPCM_EA:

        samples_in_chunk = AV_RL32(src);

        if (samples_in_chunk >= ((buf_size - 12) * 2)) {

            src += buf_size;

            break;

        }

        src += 4;

        current_left_sample = (int16_t)AV_RL16(src);

        src += 2;

        previous_left_sample = (int16_t)AV_RL16(src);

        src += 2;

        current_right_sample = (int16_t)AV_RL16(src);

        src += 2;

        previous_right_sample = (int16_t)AV_RL16(src);

        src += 2;



        for (count1 = 0; count1 < samples_in_chunk/28;count1++) {

            coeff1l = ea_adpcm_table[(*src >> 4) & 0x0F];

            coeff2l = ea_adpcm_table[((*src >> 4) & 0x0F) + 4];

            coeff1r = ea_adpcm_table[*src & 0x0F];

            coeff2r = ea_adpcm_table[(*src & 0x0F) + 4];

            src++;



            shift_left = ((*src >> 4) & 0x0F) + 8;

            shift_right = (*src & 0x0F) + 8;

            src++;



            for (count2 = 0; count2 < 28; count2++) {

                next_left_sample = (((*src & 0xF0) << 24) >> shift_left);

                next_right_sample = (((*src & 0x0F) << 28) >> shift_right);

                src++;



                next_left_sample = (next_left_sample +

                    (current_left_sample * coeff1l) +

                    (previous_left_sample * coeff2l) + 0x80) >> 8;

                next_right_sample = (next_right_sample +

                    (current_right_sample * coeff1r) +

                    (previous_right_sample * coeff2r) + 0x80) >> 8;

                CLAMP_TO_SHORT(next_left_sample);

                CLAMP_TO_SHORT(next_right_sample);



                previous_left_sample = current_left_sample;

                current_left_sample = next_left_sample;

                previous_right_sample = current_right_sample;

                current_right_sample = next_right_sample;

                *samples++ = (unsigned short)current_left_sample;

                *samples++ = (unsigned short)current_right_sample;

            }

        }

        break;

    case CODEC_ID_ADPCM_IMA_SMJPEG:

        c->status[0].predictor = *src;

        src += 2;

        c->status[0].step_index = *src++;

        src++;  /* skip another byte before getting to the meat */

        while (src < buf + buf_size) {

            *samples++ = adpcm_ima_expand_nibble(&c->status[0],

                *src & 0x0F, 3);

            *samples++ = adpcm_ima_expand_nibble(&c->status[0],

                (*src >> 4) & 0x0F, 3);

            src++;

        }

        break;

    case CODEC_ID_ADPCM_CT:

        while (src < buf + buf_size) {

            if (st) {

                *samples++ = adpcm_ct_expand_nibble(&c->status[0],

                    (src[0] >> 4) & 0x0F);

                *samples++ = adpcm_ct_expand_nibble(&c->status[1],

                    src[0] & 0x0F);

            } else {

                *samples++ = adpcm_ct_expand_nibble(&c->status[0],

                    (src[0] >> 4) & 0x0F);

                *samples++ = adpcm_ct_expand_nibble(&c->status[0],

                    src[0] & 0x0F);

            }

            src++;

        }

        break;

    case CODEC_ID_ADPCM_SBPRO_4:

    case CODEC_ID_ADPCM_SBPRO_3:

    case CODEC_ID_ADPCM_SBPRO_2:

        if (!c->status[0].step_index) {

            /* the first byte is a raw sample */

            *samples++ = 128 * (*src++ - 0x80);

            if (st)

              *samples++ = 128 * (*src++ - 0x80);

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

        }

        if (avctx->codec->id == CODEC_ID_ADPCM_SBPRO_4) {

            while (src < buf + buf_size) {

                *samples++ = adpcm_sbpro_expand_nibble(&c->status[0],

                    (src[0] >> 4) & 0x0F, 4, 0);

                *samples++ = adpcm_sbpro_expand_nibble(&c->status[st],

                    src[0] & 0x0F, 4, 0);

                src++;

            }

        } else if (avctx->codec->id == CODEC_ID_ADPCM_SBPRO_3) {

            while (src < buf + buf_size && samples + 2 < samples_end) {

                *samples++ = adpcm_sbpro_expand_nibble(&c->status[0],

                    (src[0] >> 5) & 0x07, 3, 0);

                *samples++ = adpcm_sbpro_expand_nibble(&c->status[0],

                    (src[0] >> 2) & 0x07, 3, 0);

                *samples++ = adpcm_sbpro_expand_nibble(&c->status[0],

                    src[0] & 0x03, 2, 0);

                src++;

            }

        } else {

            while (src < buf + buf_size && samples + 3 < samples_end) {

                *samples++ = adpcm_sbpro_expand_nibble(&c->status[0],

                    (src[0] >> 6) & 0x03, 2, 2);

                *samples++ = adpcm_sbpro_expand_nibble(&c->status[st],

                    (src[0] >> 4) & 0x03, 2, 2);

                *samples++ = adpcm_sbpro_expand_nibble(&c->status[0],

                    (src[0] >> 2) & 0x03, 2, 2);

                *samples++ = adpcm_sbpro_expand_nibble(&c->status[st],

                    src[0] & 0x03, 2, 2);

                src++;

            }

        }

        break;

    case CODEC_ID_ADPCM_SWF:

    {

        GetBitContext gb;

        const int *table;

        int k0, signmask, nb_bits;

        int size = buf_size*8;



        init_get_bits(&gb, buf, size);



        //read bits & inital values

        nb_bits = get_bits(&gb, 2)+2;

        //av_log(NULL,AV_LOG_INFO,"nb_bits: %d\n", nb_bits);

        table = swf_index_tables[nb_bits-2];

        k0 = 1 << (nb_bits-2);

        signmask = 1 << (nb_bits-1);



        for (i = 0; i < avctx->channels; i++) {

            *samples++ = c->status[i].predictor = get_sbits(&gb, 16);

            c->status[i].step_index = get_bits(&gb, 6);

        }



        while (get_bits_count(&gb) < size)

        {

            int i;



            for (i = 0; i < avctx->channels; i++) {

                // similar to IMA adpcm

                int delta = get_bits(&gb, nb_bits);

                int step = step_table[c->status[i].step_index];

                long vpdiff = 0; // vpdiff = (delta+0.5)*step/4

                int k = k0;



                do {

                    if (delta & k)

                        vpdiff += step;

                    step >>= 1;

                    k >>= 1;

                } while(k);

                vpdiff += step;



                if (delta & signmask)

                    c->status[i].predictor -= vpdiff;

                else

                    c->status[i].predictor += vpdiff;



                c->status[i].step_index += table[delta & (~signmask)];



                c->status[i].step_index = av_clip(c->status[i].step_index, 0, 88);

                c->status[i].predictor = av_clip(c->status[i].predictor, -32768, 32767);



                *samples++ = c->status[i].predictor;

                if (samples >= samples_end) {

                    av_log(avctx, AV_LOG_ERROR, "allocated output buffer is too small\n");

                    return -1;

                }

            }

        }

        src += buf_size;

        break;

    }

    case CODEC_ID_ADPCM_YAMAHA:

        while (src < buf + buf_size) {

            if (st) {

                *samples++ = adpcm_yamaha_expand_nibble(&c->status[0],

                        src[0] & 0x0F);

                *samples++ = adpcm_yamaha_expand_nibble(&c->status[1],

                        (src[0] >> 4) & 0x0F);

            } else {

                *samples++ = adpcm_yamaha_expand_nibble(&c->status[0],

                        src[0] & 0x0F);

                *samples++ = adpcm_yamaha_expand_nibble(&c->status[0],

                        (src[0] >> 4) & 0x0F);

            }

            src++;

        }

        break;

    case CODEC_ID_ADPCM_THP:

    {

        int table[2][16];

        unsigned int samplecnt;

        int prev[2][2];

        int ch;



        if (buf_size < 80) {

            av_log(avctx, AV_LOG_ERROR, "frame too small\n");

            return -1;

        }



        src+=4;

        samplecnt = bytestream_get_be32(&src);



        for (i = 0; i < 32; i++)

            table[0][i] = (int16_t)bytestream_get_be16(&src);



        /* Initialize the previous sample.  */

        for (i = 0; i < 4; i++)

            prev[0][i] = (int16_t)bytestream_get_be16(&src);



        if (samplecnt >= (samples_end - samples) /  (st + 1)) {

            av_log(avctx, AV_LOG_ERROR, "allocated output buffer is too small\n");

            return -1;

        }



        for (ch = 0; ch <= st; ch++) {

            samples = (unsigned short *) data + ch;



            /* Read in every sample for this channel.  */

            for (i = 0; i < samplecnt / 14; i++) {

                int index = (*src >> 4) & 7;

                unsigned int exp = 28 - (*src++ & 15);

                int factor1 = table[ch][index * 2];

                int factor2 = table[ch][index * 2 + 1];



                /* Decode 14 samples.  */

                for (n = 0; n < 14; n++) {

                    int32_t sampledat;

                    if(n&1) sampledat=  *src++    <<28;

                    else    sampledat= (*src&0xF0)<<24;



                    *samples = ((prev[ch][0]*factor1

                                + prev[ch][1]*factor2) >> 11) + (sampledat>>exp);

                    prev[ch][1] = prev[ch][0];

                    prev[ch][0] = *samples++;



                    /* In case of stereo, skip one sample, this sample

                       is for the other channel.  */

                    samples += st;

                }

            }

        }



        /* In the previous loop, in case stereo is used, samples is

           increased exactly one time too often.  */

        samples -= st;

        break;

    }



    default:

        return -1;

    }

    *data_size = (uint8_t *)samples - (uint8_t *)data;

    return src - buf;

}
