if(decoder->bsf)
{
    decoder->pkt.data = NULL;
    decoder->pkt.size = 0;
    if(av_bitstream_filter_filter(decoder->bsf, avctx, NULL,
                &decoder->pkt.data, &decoder->pkt.size,
                avpkt->data, avpkt->size, !!(avpkt->flags & AV_PKT_FLAG_KEY)) < 0)
{
    printf("Error in av_bitstream_filter_filter \n");
}
else
{
    //do decoding here
}