Can mpv properly render two videos side by side?

[Rabcor]

I know it's possible to render two videos side by side by using this filter: --lavfi-complex="[vid1] [vid2] hstack [vo]"

However it has a problem where the rendered video's colors won't always match, because mpv's settings are only being applied to the first video, whereas the second video doesn't get the same color management, this leads to videos looking different, and unfortunately the main reason I want to be able to compare videos is to be able to confirm that the colors aren't changing between the files, so this flaw defeats the purpose of doing it this way for me.

Is there another way where the videos will both have mpv's color management applied to them individually?

[Bellavene]

I believe this is a question for ffmpeg group, as lavfi is a part of it.

[Rabcor]

there wouldn't be a way to pass mpv's settings to lavfi I don't think, this would have to be an actual feature of mpv, not something implemented over lavfi.

[Raza-0007]

unfortunately the main reason I want to be able to compare videos is to be able to confirm that the colors aren't changing between the files

I don't know which OS you are using but on Windows you can just copy your mpv directory to another location, and then run each mpv from its own directory, so now you have two instances of mpv running side-by-side. This is what I do when I am trying to compare two video files.

[avih]

There's no need to copy the mpv dir to get two instances (on any platform). Just run it twice with different videos as arguments.

The challenge here is to sync the two instances to the same frame, and make one instance follow the other if it changes.

A lua/js script can be written which does that (e.g. use some file on disk to store current timestamp, and both instances read it and seek accordingly), but the script will become complex very quickly as various edge cases and use cases handling are added to it.

An alternative might be to use https://github.com/Syncplay/ which is generally intended to sync two players over the internet, but works equally well for synching two players on the same system.

[Raza-0007]

You need a separate directory if you change a setting and want to see what effect it will have on the same video, for example, play one instance with dband on and the other with dband off to see the effect on video quality in real time. If there is a way to do this from the same mpv instance then I am not aware of it.

[Rabcor]

@Raza-0007 nah.

mpv --no-config --video-sync=display-resample video.,mp4
mpv --no-config --video-sync=audio video.mp4

I mean ify ou want to test a whole sperate config, then copying just the mpv.conf and changing it and then using that is certainly a way but I can't think of many reasons to do so, the above is the way to test 2 separate settings.

[Raza-0007]

Thanks, but this will only work if your were testing one or two settings with the default config. If you wanted to test a particular setting change with your main config, it is far more practical to launch another mpv from a different directory. Just change the setting you want to test, while keeping the rest of the config the same. At least, this is what I do. I am sure your method is suitable for certain situations.

[guidocella]

You can define a profile with all the different settings and launch the second instance with it.

[mrfragger]

apply luts and it splits screen in two but yes it's the same source.

so for sure you can apply two different settings to same video ...but yeah not sure if two different videos works or not. I was trying to do video thumbnails and do have it 2x2 for each thumb but thought to do a few seconds but it was way too much processing power.

[Rabcor]

I ended up just bailing on mpv and used ffplay instead.

ffplay -f lavfi "movie=<file1>[a];movie=<file2>,hflip[b];[a][b]hstack,zscale=min=709,format=gbrp"
#or
ffplay -f lavfi "movie=<file1>[a];movie=<file2>,vflip[b];[a][b]vstack,zscale=min=709,format=gbrp"

The mirroring helps me see more clearly if there's a color difference (without the mirroring it always looks like the colors are mismatched to me for some reason, brains are weird).

The zscale and format filters help color correct the output so it usually looks the same as mpv which I guess half answers my original question, but isn't really a good enough answer since it wouldn't actually allow me to play it according to mpv's settings.

I'm still interestedi n doing this with mpv instead btw, but I have another way for now i suppose.