View Single Post
Old 16th July 2017, 18:32   #1359  |  Link
sneaker_ger
Registered User
 
Join Date: Dec 2002
Posts: 5,565
Quote:
Originally Posted by Scorpius666 View Post
There are two ways to time a subtitle:

1.- Absolute time: Like the SUP files have, or text SRT files have. That is from 00:00:51.128 to 00:00:55.762. That's absolute. You don't need a frame rate for that since you know exactly when to show the subtitle.

2.- Relative time: A frame rate + frame number. For example from frame #2510 to frame #2650. If your frame rate is wrong, then your subtitle will show at the wrong time.

Since SUP files have absolute time, they don't need a frame rate, and this value is simply not included since it's not necessary. Also, normal text SRT files don't include this value either: it's not needed. Now the weird thing here is that those XML files also have absolute time, and they have a frame rate value I don't know why. I would assume the players would ignore the frame rate value in the XML file. I haven't tested that (I don't use that format).

Now since SUP files from BDs and DVDs don't have a frame rate value, BDSup2Sub takes the default value you have for frame rate. If you haven't changed it, it's 25. But you can change it and press the "Store" button to set a new default. But BDSup2Sub can't possibly know the frame rate of the movie since that information is not inside the SUP file.
What I meant by "bound to frame timings" is: will subtitles only start/end if a video frame starts? That could be true even with absolute subtitle times (in e.g. seconds). If you have an absolute time of 00:00:00.040 you know it must be from 25 fps video:
1000ms/25 = 40ms
1000ms/23.976 = 42ms
1000ms/29.97 = 33ms
(may have to gather statistics over whole file to safely differ between 24 and 23.976 or 25 and 50 but you get the idea)

About why XML has both: I'm too lazy to look now but could it be because of "drop" and "non-drop" timings?
https://documentation.apple.com/en/f...6%26tasks=true

Last edited by sneaker_ger; 16th July 2017 at 18:35.
sneaker_ger is offline   Reply With Quote