static int decode_frame(AVCodecContext *avctx,
                        void *data, int *data_size,
                        AVPacket *avpkt)
{
    const uint8_t *buf = avpkt->data;
    int buf_size = avpkt->size;
    ASV1Context * const a = avctx->priv_data;
    AVFrame *picture = data;
    AVFrame * const p= &a->picture;
    int mb_x, mb_y;

    if(p->data[0])
        avctx->release_buffer(avctx, p);

    p->reference= 0;
    if(avctx->get_buffer(avctx, p) < 0){
        av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
        return -1;
    }
    p->pict_type= AV_PICTURE_TYPE_I;
    p->key_frame= 1;

    av_fast_malloc(&a->bitstream_buffer, &a->bitstream_buffer_size, buf_size + FF_INPUT_BUFFER_PADDING_SIZE);
    if (!a->bitstream_buffer)
        return AVERROR(ENOMEM);
    memset(a->bitstream_buffer + buf_size, 0, FF_INPUT_BUFFER_PADDING_SIZE);

    if(avctx->codec_id == CODEC_ID_ASV1)
        a->dsp.bswap_buf((uint32_t*)a->bitstream_buffer, (const uint32_t*)buf, buf_size/4);
    else{
        int i;
        for(i=0; i<buf_size; i++)
            a->bitstream_buffer[i]= av_reverse[ buf[i] ];
    }

    init_get_bits(&a->gb, a->bitstream_buffer, buf_size*8);

    for(mb_y=0; mb_y<a->mb_height2; mb_y++){
        for(mb_x=0; mb_x<a->mb_width2; mb_x++){
            if( decode_mb(a, a->block) <0)
                return -1;

            idct_put(a, mb_x, mb_y);
        }
    }

    if(a->mb_width2 != a->mb_width){
        mb_x= a->mb_width2;
        for(mb_y=0; mb_y<a->mb_height2; mb_y++){
            if( decode_mb(a, a->block) <0)
                return -1;

            idct_put(a, mb_x, mb_y);
        }
    }

    if(a->mb_height2 != a->mb_height){
        mb_y= a->mb_height2;
        for(mb_x=0; mb_x<a->mb_width; mb_x++){
            if( decode_mb(a, a->block) <0)
                return -1;

            idct_put(a, mb_x, mb_y);
        }
    }

    *picture= *(AVFrame*)&a->picture;
    *data_size = sizeof(AVPicture);

    emms_c();

    return (get_bits_count(&a->gb)+31)/32*4;
}