subs 1 frame off

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subs 1 frame off

Post by jaddax on Wed Aug 10, 2016 1:50 pm

Occasionally subtitles are 1 frame off when using K-Lite. I've checked the video+subtitle file in Aegisub and the bleeds weren't there. Sometimes it happens and sometimes not. If it helps, it seemed to happen at keyframes/scene-changes. Other than that, I haven't seen any real pattern. Just figured I'd let you guys know

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Re: subs 1 frame off

Post by Admin on Thu Aug 11, 2016 1:41 am

Subtitles are shown at specific timestamps. They are not coupled to specific frames. If a timestamp falls in between two frames, then it is rounded. Maybe Aegisub uses a different rounding method.

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Re: subs 1 frame off

Post by jaddax on Mon Aug 15, 2016 10:16 pm

Aegisub doesn't use rounding, nor does KCP seem to (I was mostly using K-Lite for HEVC viewing).

The "beginning frame" of a subtitle is the closest frame whose start time is after that of the subtitle's start time. Frames are approx. 42 milliseconds long in most anime. If the subtitle timestamp is even 1 millisecond after the start of a frame, it won't appear until the next frame (41 milliseconds later than the timestamp).

Same goes for the end; if the subtitle is set to end at let's say  00:05.040, and a frame begins at 00:05.039, the subtitle will be displayed for the entire duration of that frame (the actual end-time being rounded up to about 00:05.081)

Considering its tendency to round up/delay, the fact that K-Lite is showing additional 1-frame delays can't be attributed to that, I would think. The only possible way that could be the case is maybe if it were 1/10- or 1/100-of-a-millisecond-rounding. This was not the case, however, as I tested it by changing the end time to be much closer (more likely to be rounded down) to the previous frame in Aegisub, and it still appeared for the full last frame+the first frame of the next scene in K-Lite.


Last edited by jaddax on Mon Aug 15, 2016 10:18 pm; edited 1 time in total (Reason for editing : what is proofreading)

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Re: subs 1 frame off

Post by Admin on Tue Aug 16, 2016 12:05 am

Difference compared to KCP is:
1) K-Lite uses a newer version of madVR (I assume you are using madVR again, instead of default EVR-CP)
2) K-Lite uses internal subtitle renderer of MPC-HC instead of XySubFilter (which is based on code from MPC-HC).

Do you have a sample file that clearly shows the problem? If there is a bug I can get it fixed.

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Re: subs 1 frame off

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