Easy way to set MP4 aspect ratio flag?

[unknownsoldierX]

With AVI files, I always used MPEG4Modifier to set the DAR to 16:9. It was great for the many files that didn't look right on my TVs. On old 4:3 CRT TVs, certain widescreen videos would look squeezed, and with MPEG4Modifier I could make them stretched out to fill more of the screen. With 16:10 flatscreen TV, it made it so I didn't have to manually zoom to have them fill the screen.

With MP4s, everything I've found so far makes it sound more complicated. Talk about calculating PAR = DAR ÷ SAR and whatnot. Isn't there a simple way to do it without thinking about it? I'd like to be able to just have a program do it, preferably something command line like ffmpeg, where I can just point a batch file to a folder and have it process a bunch of files, without doing any re-encoding.

[Baldrick]

I use mymp4boxgui, open mp4, right click on video track and choose PAR. Save as and Mux.

[hello_hello]

AnotherGUI is often handy for that sort of thing. It'll batch convert and it comes with a few presets for remuxing with ffmpeg. For setting the container aspect ratio:
https://ffmpeg.org/ffmpeg.html#Video-Options

To get you started, try creating this as a ffmpeg preset for AnotherGUI. The type of source file shouldn't matter as long as the video and audio are MP4 compatible. Or change the file type to MKV if that's okay.

-i "<SourceFileName>" -y -threads 1 -vcodec copy -aspect 1.7777 -acodec copy "<OutputPath><OutputFileName>.mp4"

If your player ignores the container aspect ratio and looks for the stream aspect ratio instead, which it probably won't, but if it does and there's h264 within.... Tool to change SAR in H264 bitstream
I'm pretty sure you've got to play with pixel aspect ratios there though.

[unknownsoldierX]

Thanks to both of you.

That -aspect flag with ffmpeg does the trick.

MyMP4BoxGUI looks useful for other things. I'll be keeping that around.