ffmpeg - Multiple side-to-side video streams in one file without transcoding

Question

I am investigating a possibility to store video streams which are coming from few sources already coded in h264 without video transcoding as the device I would like to use for this project won't be capable of transcoding combined video on the fly.

What I am looking for is two or more pictures side to side (not video concatenation) packed into mp4/avi/mkv.

I believe mkv container supports such kind of packaging but I've not been able to find appropriate options for ffmpeg or other tool to store it this way. What it does is very slow video transcoding into one big h264 stream.

Answer 1

If your player can handle it just make it perform the side-by-side view. No encoding or muxing required.

mpv video player

Example using mpv:

mpv --lavfi-complex="[vid1][vid2]hstack[vo];[aid1][aid2]amix[ao]" input1.mp4 --external-file=input2.mp4

The above example assumes each input has the same height. Otherwise you will have to add the scale, scale2ref, pad, and/or crop filters. Simple example using the crop filter to remove 20 pixels from the height:

mpv --lavfi-complex="[vid1]crop=iw:ih-20[c];[c][vid2]hstack[vo];[aid1][aid2]amix[ao]" input1.mp4 --external-file=input2.mp4

See the mpv documentation and FFmpeg Filters for more info.