static int smka_decode_frame(AVCodecContext *avctx, void *data,
                             int *got_frame_ptr, AVPacket *avpkt)
{
    SmackerAudioContext *s = avctx->priv_data;
    const uint8_t *buf = avpkt->data;
    int buf_size = avpkt->size;
    GetBitContext gb;
    HuffContext h[4] = { { 0 } };
    VLC vlc[4]       = { { 0 } };
    int16_t *samples;
    uint8_t *samples8;
    int val;
    int i, res, ret;
    int unp_size;
    int bits, stereo;
    int pred[2] = {0, 0};
    if (buf_size <= 4) {
        av_log(avctx, AV_LOG_ERROR, "packet is too small\n");
        return AVERROR(EINVAL);
    unp_size = AV_RL32(buf);
    init_get_bits(&gb, buf + 4, (buf_size - 4) * 8);
    if(!get_bits1(&gb)){
        av_log(avctx, AV_LOG_INFO, "Sound: no data\n");
        *got_frame_ptr = 0;
        return 1;
    stereo = get_bits1(&gb);
    bits = get_bits1(&gb);
    if (stereo ^ (avctx->channels != 1)) {
        av_log(avctx, AV_LOG_ERROR, "channels mismatch\n");
        return AVERROR(EINVAL);
    if (bits && avctx->sample_fmt == AV_SAMPLE_FMT_U8) {
        av_log(avctx, AV_LOG_ERROR, "sample format mismatch\n");
        return AVERROR(EINVAL);
    /* get output buffer */
    s->frame.nb_samples = unp_size / (avctx->channels * (bits + 1));
    if ((ret = avctx->get_buffer(avctx, &s->frame)) < 0) {
        av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
        return ret;
    samples  = (int16_t *)s->frame.data[0];
    samples8 =            s->frame.data[0];
    // Initialize
    for(i = 0; i < (1 << (bits + stereo)); i++) {
        h[i].length = 256;
        h[i].maxlength = 0;
        h[i].current = 0;
        h[i].bits = av_mallocz(256 * 4);
        h[i].lengths = av_mallocz(256 * sizeof(int));
        h[i].values = av_mallocz(256 * sizeof(int));
        skip_bits1(&gb);
        smacker_decode_tree(&gb, &h[i], 0, 0);
        skip_bits1(&gb);
        if(h[i].current > 1) {
            res = init_vlc(&vlc[i], SMKTREE_BITS, h[i].length,
                    h[i].lengths, sizeof(int), sizeof(int),
                    h[i].bits, sizeof(uint32_t), sizeof(uint32_t), INIT_VLC_LE);
            if(res < 0) {
                av_log(avctx, AV_LOG_ERROR, "Cannot build VLC table\n");
    if(bits) { //decode 16-bit data
        for(i = stereo; i >= 0; i--)
            pred[i] = sign_extend(av_bswap16(get_bits(&gb, 16)), 16);
        for(i = 0; i <= stereo; i++)
            *samples++ = pred[i];
        for(; i < unp_size / 2; i++) {
            if(get_bits_left(&gb)<0)
            if(i & stereo) {
                if(vlc[2].table)
                    res = get_vlc2(&gb, vlc[2].table, SMKTREE_BITS, 3);
                else
                    res = 0;
                if (res < 0) {
                    av_log(avctx, AV_LOG_ERROR, "invalid vlc\n");
                val  = h[2].values[res];
                if(vlc[3].table)
                    res = get_vlc2(&gb, vlc[3].table, SMKTREE_BITS, 3);
                else
                    res = 0;
                if (res < 0) {
                    av_log(avctx, AV_LOG_ERROR, "invalid vlc\n");
                val |= h[3].values[res] << 8;
                pred[1] += sign_extend(val, 16);
                *samples++ = av_clip_int16(pred[1]);
            } else {
                if(vlc[0].table)
                    res = get_vlc2(&gb, vlc[0].table, SMKTREE_BITS, 3);
                else
                    res = 0;
                if (res < 0) {
                    av_log(avctx, AV_LOG_ERROR, "invalid vlc\n");
                val  = h[0].values[res];
                if(vlc[1].table)
                    res = get_vlc2(&gb, vlc[1].table, SMKTREE_BITS, 3);
                else
                    res = 0;
                if (res < 0) {
                    av_log(avctx, AV_LOG_ERROR, "invalid vlc\n");
                val |= h[1].values[res] << 8;
                pred[0] += sign_extend(val, 16);
                *samples++ = av_clip_int16(pred[0]);
    } else { //8-bit data
        for(i = stereo; i >= 0; i--)
            pred[i] = get_bits(&gb, 8);
        for(i = 0; i <= stereo; i++)
            *samples8++ = pred[i];
        for(; i < unp_size; i++) {
            if(get_bits_left(&gb)<0)
            if(i & stereo){
                if(vlc[1].table)
                    res = get_vlc2(&gb, vlc[1].table, SMKTREE_BITS, 3);
                else
                    res = 0;
                if (res < 0) {
                    av_log(avctx, AV_LOG_ERROR, "invalid vlc\n");
                pred[1] += sign_extend(h[1].values[res], 8);
                *samples8++ = av_clip_uint8(pred[1]);
            } else {
                if(vlc[0].table)
                    res = get_vlc2(&gb, vlc[0].table, SMKTREE_BITS, 3);
                else
                    res = 0;
                if (res < 0) {
                    av_log(avctx, AV_LOG_ERROR, "invalid vlc\n");
                pred[0] += sign_extend(h[0].values[res], 8);
                *samples8++ = av_clip_uint8(pred[0]);
    for(i = 0; i < 4; i++) {
        if(vlc[i].table)
            ff_free_vlc(&vlc[i]);
        av_free(h[i].bits);
        av_free(h[i].lengths);
        av_free(h[i].values);
    *got_frame_ptr   = 1;
    *(AVFrame *)data = s->frame;
    return buf_size;