How would i add scaling to this command (-vf scale=-1:720). It's a 1920x1080 transport stream.

ffmpeg -i input.ts -i input.srt -map 0 -map 1 -acodec copy -scodec copy -c:v libx264 -preset medium -crf 23 -profile:v high -level 4.1 -deinterlace output.mkv