static int ape_decode_frame(AVCodecContext * avctx,

                            void *data, int *data_size,

                            AVPacket *avpkt)

{

    const uint8_t *buf = avpkt->data;

    int buf_size = avpkt->size;

    APEContext *s = avctx->priv_data;

    int16_t *samples = data;

    int nblocks;

    int i, n;

    int blockstodecode;

    int bytes_used;



    if (buf_size == 0 && !s->samples) {

        *data_size = 0;

        return 0;

    }



    /* should not happen but who knows */

    if (BLOCKS_PER_LOOP * 2 * avctx->channels > *data_size) {

        av_log (avctx, AV_LOG_ERROR, "Packet size is too big to be handled in lavc! (max is %d where you have %d)\n", *data_size, s->samples * 2 * avctx->channels);

        return -1;

    }



    if(!s->samples){

        s->data = av_realloc(s->data, (buf_size + 3) & ~3);

        s->dsp.bswap_buf((uint32_t*)s->data, (const uint32_t*)buf, buf_size >> 2);

        s->ptr = s->last_ptr = s->data;

        s->data_end = s->data + buf_size;



        nblocks = s->samples = bytestream_get_be32(&s->ptr);

        n =  bytestream_get_be32(&s->ptr);

        if(n < 0 || n > 3){

            av_log(avctx, AV_LOG_ERROR, "Incorrect offset passed\n");

            s->data = NULL;

            return -1;

        }

        s->ptr += n;



        s->currentframeblocks = nblocks;

        buf += 4;

        if (s->samples <= 0) {

            *data_size = 0;

            return buf_size;

        }



        memset(s->decoded0,  0, sizeof(s->decoded0));

        memset(s->decoded1,  0, sizeof(s->decoded1));



        /* Initialize the frame decoder */

        init_frame_decoder(s);

    }



    if (!s->data) {

        *data_size = 0;

        return buf_size;

    }



    nblocks = s->samples;

    blockstodecode = FFMIN(BLOCKS_PER_LOOP, nblocks);



    s->error=0;



    if ((s->channels == 1) || (s->frameflags & APE_FRAMECODE_PSEUDO_STEREO))

        ape_unpack_mono(s, blockstodecode);

    else

        ape_unpack_stereo(s, blockstodecode);

    emms_c();



    if(s->error || s->ptr > s->data_end){

        s->samples=0;

        av_log(avctx, AV_LOG_ERROR, "Error decoding frame\n");

        return -1;

    }



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

        *samples++ = s->decoded0[i];

        if(s->channels == 2)

            *samples++ = s->decoded1[i];

    }



    s->samples -= blockstodecode;



    *data_size = blockstodecode * 2 * s->channels;

    bytes_used = s->samples ? s->ptr - s->last_ptr : buf_size;

    s->last_ptr = s->ptr;

    return bytes_used;

}
