What improvements can I make to my FFMPEG script?

Question

I am trying to create an FFMPEG script for some of my emulated game captures. I normally use Virtualdub2 (formerly Virtualdubmod) to upscale and trim my game captures for YouTube. With my laptop gone and the nearest area where can I use Virtualdub2 is at my library. My Chromebook does not use Windows programs anyway and my old XP computer is too slow (I need more memory, an SSD drive and a new Pentium 4 processor). I was hoping to create an FFMPEG script that I can use to automate my process. I want to know what I can do to improve the script as I mostly upscale the emulated game captures from Genesis, Super Nintendo, Nintendo games for YouTube. I could try AVISynth but I am still trying to learnt he process. Here is the script in question:

ffmpeg -i input -vf "scale=iwX:ihX" -sws_flags neighbor -pix_fmt yuv420p -c:v libx264 -preset slower -crf 16 -c:a libopus -b:a 128k

I am mostly aiming for lossless with a Slower compression, HD 720 (4x upscaling) and nearest neighbor (pointresize). I want to put it in an mp4 container with aac or libopus for audio sound. I also wanted to have aspect ratio correction as well. What do you think of my script? Or can it use some improvements? I mostly got my ideas from these sites right here.

Answer 1

you can add -vf "scale=iwX:ihX:force_original_aspect_ratio=decrease,pad=max(iw\,ih*(16/9)):ow/(16/9):(ow-iw)/2:(oh-ih)/2" to your script to correct aspect ratio and pad the video.

You can also add -filter_complex "[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]" to speed up your video and audio2.