I have a tech question. I muxed a few of the 720p SUP files (e.g. English, English SDH) into the 720p despecialized editions. When I play the resulting MKVs on my PC, the subtitles look like they are the correct size in relation to the image.
However, when I play the same MKVs on my Oppo UDP-203, the subtitles appear quite a bit smaller. I tried changing the Oppo from its usual 2160p output to 720p and 1080p, and the results were the same.
Has anyone else encountered this? Is this a quirk of the Oppo? If I want proper size subtitles on the Oppo, maybe I need to mux in the 1080p SUP files instead?
I’ve got that exact player, so I could give it a whirl (might not have time for a while, though). I do know that when you mux the 720p subs into an M2TS/Blu-ray folder structure (and burn it to disc), everything looks fine on the 203.
One quirk of hardware players that I know about is that while 720p/24 is a valid resolution for Blu-rays and a valid resolution for displays, it is NOT a valid resolution for the HDMI spec. So players either have to telecine the stream to 720i/30 or upscale it to 1080p/2160p/24 before they can send it over the cable – and the latter is the better choice. I also know that while the M2TS behavior of hardware players is generally very solid in order for it to work properly with discs, the MKV behavior is often a little quirky. It’s possible the 720p upscale is working well for the image, but not the subtitle stream. You could certainly try the 1080p subs and see if that improves things.
In general, resolution-matching isn’t required for anything but Blu-ray disc compatible streams. For non-disc formats, or even software playback of Blu-ray folder structures, you can mix 1080p subs with 720p video, without any issues.