func: static av_cold int seqvideo_decode_init(AVCodecContext *avctx)
  {
      SeqVideoContext *seq = avctx->priv_data;
      seq->avctx = avctx;
      avctx->pix_fmt = AV_PIX_FMT_PAL8;
      seq->frame = av_frame_alloc();
      if (!seq->frame)
          return AVERROR(ENOMEM);
      return 0;
  }