static int smacker_read_packet(AVFormatContext *s, AVPacket *pkt)

{

    SmackerContext *smk = s->priv_data;

    int flags;

    int ret;

    int i;

    int frame_size = 0;

    int palchange = 0;



    if (s->pb->eof_reached || smk->cur_frame >= smk->frames)

        return AVERROR_EOF;



    /* if we demuxed all streams, pass another frame */

    if(smk->curstream < 0) {

        avio_seek(s->pb, smk->nextpos, 0);

        frame_size = smk->frm_size[smk->cur_frame] & (~3);

        flags = smk->frm_flags[smk->cur_frame];

        /* handle palette change event */

        if(flags & SMACKER_PAL){

            int size, sz, t, off, j, pos;

            uint8_t *pal = smk->pal;

            uint8_t oldpal[768];



            memcpy(oldpal, pal, 768);

            size = avio_r8(s->pb);

            size = size * 4 - 1;

            frame_size -= size;

            frame_size--;

            sz = 0;

            pos = avio_tell(s->pb) + size;

            while(sz < 256){

                t = avio_r8(s->pb);

                if(t & 0x80){ /* skip palette entries */

                    sz += (t & 0x7F) + 1;

                    pal += ((t & 0x7F) + 1) * 3;

                } else if(t & 0x40){ /* copy with offset */

                    off = avio_r8(s->pb);

                    j = (t & 0x3F) + 1;

                    if (off + j > 0x100) {

                        av_log(s, AV_LOG_ERROR,

                               "Invalid palette update, offset=%d length=%d extends beyond palette size\n",

                               off, j);

                        return AVERROR_INVALIDDATA;

                    }

                    off *= 3;

                    while(j-- && sz < 256) {

                        *pal++ = oldpal[off + 0];

                        *pal++ = oldpal[off + 1];

                        *pal++ = oldpal[off + 2];

                        sz++;

                        off += 3;

                    }

                } else { /* new entries */

                    *pal++ = smk_pal[t];

                    *pal++ = smk_pal[avio_r8(s->pb) & 0x3F];

                    *pal++ = smk_pal[avio_r8(s->pb) & 0x3F];

                    sz++;

                }

            }

            avio_seek(s->pb, pos, 0);

            palchange |= 1;

        }

        flags >>= 1;

        smk->curstream = -1;

        /* if audio chunks are present, put them to stack and retrieve later */

        for(i = 0; i < 7; i++) {

            if(flags & 1) {

                uint32_t size;

                uint8_t *tmpbuf;



                size = avio_rl32(s->pb) - 4;

                if (!size || size > frame_size) {

                    av_log(s, AV_LOG_ERROR, "Invalid audio part size\n");

                    return AVERROR_INVALIDDATA;

                }

                frame_size -= size;

                frame_size -= 4;

                smk->curstream++;

                tmpbuf = av_realloc(smk->bufs[smk->curstream], size);

                if (!tmpbuf)

                    return AVERROR(ENOMEM);

                smk->bufs[smk->curstream] = tmpbuf;

                smk->buf_sizes[smk->curstream] = size;

                ret = avio_read(s->pb, smk->bufs[smk->curstream], size);

                if(ret != size)

                    return AVERROR(EIO);

                smk->stream_id[smk->curstream] = smk->indexes[i];

            }

            flags >>= 1;

        }

        if (frame_size < 0)

            return AVERROR_INVALIDDATA;

        if (av_new_packet(pkt, frame_size + 769))

            return AVERROR(ENOMEM);

        if(smk->frm_size[smk->cur_frame] & 1)

            palchange |= 2;

        pkt->data[0] = palchange;

        memcpy(pkt->data + 1, smk->pal, 768);

        ret = avio_read(s->pb, pkt->data + 769, frame_size);

        if(ret != frame_size)

            return AVERROR(EIO);

        pkt->stream_index = smk->videoindex;

        pkt->pts          = smk->cur_frame;

        pkt->size = ret + 769;

        smk->cur_frame++;

        smk->nextpos = avio_tell(s->pb);

    } else {

        if (smk->stream_id[smk->curstream] < 0)

            return AVERROR_INVALIDDATA;

        if (av_new_packet(pkt, smk->buf_sizes[smk->curstream]))

            return AVERROR(ENOMEM);

        memcpy(pkt->data, smk->bufs[smk->curstream], smk->buf_sizes[smk->curstream]);

        pkt->size = smk->buf_sizes[smk->curstream];

        pkt->stream_index = smk->stream_id[smk->curstream];

        pkt->pts = smk->aud_pts[smk->curstream];

        smk->aud_pts[smk->curstream] += AV_RL32(pkt->data);

        smk->curstream--;

    }



    return 0;

}
