Revert "vcomp/lavc libsvtav1: do not set pred_struct=1"

This reverts commit fa8bb8c.

Actually this worsened the behavior significantly by increasing the
latency in the order of 100 frames (depending on properties). This
(currently) disallows setting the bitrate, using CRF/CQP is only possible
because the FFmpeg plugin isn't able to set CBR for now.

src/video_compress/libavcodec.cpp

@@ -1947,8 +1947,9 @@ static void configure_svt(AVCodecContext *codec_ctx, struct setparam_param *para
                 check_av_opt_set<const char *>(codec_ctx->priv_data, "preset",
                                                preset);
 #if LIBAVCODEC_VERSION_INT > AV_VERSION_INT(59, 21, 100)
+                //pred-struct=1 is low-latency mode
                 check_av_opt_set(codec_ctx->priv_data, "svtav1-params",
-                                 "fast-decode=1:tile-columns=2:tile-rows=2");
+                                 "pred_struct=1:fast-decode=1:tile-columns=2:tile-rows=2");
 #else
                 // tile_columns and tile_rows are log2 values
                 for (auto const &val : { "tile_columns", "tile_rows" }) {