Always set bt709 for VUI on BD rips?

[tppytel]

I'm aware that players routinely ignore the VUI flags set by x264/5, but is it still basically always correct to set the primaries, transfer, and matrix flags to bt709 when reencoding a bluray rip? I've read up on color spaces numerous times, but I'm still unclear on how each of those flags differ (even theoretically, assuming the player honors them). Assuming I'm working with a typical BD of movie or TV series, is there any reason not to set those flags?

Thanks.

[SeeMoreDigital]

I'm aware that players routinely ignore the VUI flags set by x264/5, but....What sort of 'players'. Hardware or software?

[tppytel]

I'm encoding for various streamers playing files off a Plex server myself. From what I've read, the VUI data isn't always used. But details are hard to come by.

I don't have a particular problem I'm encountering. It's just that I'm doing some lengthy reencodes on movies and want to do everything as correctly as possible. Some of the video streams in my BD rips have the colorimetry VUI flags set and others don't. I'm not sure if there's any meaning behind that, or if it's only that some production facilities don't bother setting those flags.

edit: And I guess I'm asking only about "main features" for movies or regular episodes for TV. I know that special features (making-of's and such) get encoded in all kinds of crazy ways by the studios. I have one making-of handy that was included on a BD but was originally made for DVD, and it's explicitly tagged bt601 in the video stream. That makes sense since it's SD material. But, for example, the BD rips of Twin Peaks have no colorimetry data set. But if that material was remastered for BD, then it's bt709, right?

[SeeMoreDigital]

I'm encoding for various streamers playing files off a Plex server myself. From what I've read, the VUI data isn't always used. But details are hard to come by.
Okay... But what device are you using to play your files?

Are you using a 'hardware' playback device, such as a Blu-ray player or a smart TV. Or are you using a 'software' playback device, such as a computer?

[tppytel]

I'm using a Shield TV and a Roku primarily.

[benwaggoner]

I can't think of any downside of setting metadata correctly. At worst, it gets ignored. At best, it gets used to improve accuracy of playback.