header = AV_RL32(buf);
    version = header & 0xff;
    if (version !=s->version && s->version > -1) {
        av_log(avctx, AV_LOG_INFO, "Multiple versions encountered in file\n");
        if (s->frame.data[0])
            avctx->release_buffer(avctx, &s->frame);
    }
    s->version = version;
    header_size = (header & (1<<30))? 8 : 4; /* bit 30 means pad to 8 bytes */