MKV Problem when Spliting

[tirafesi]

I have a series, in which the Opening and Ending were removed from the episodes, and linked using ordered chapters/segment linking.

I'm trying to undo this, merging the OP and ED back into each episode.

The layout of the episodes is the following: Prologue - Opening - Episode - Ending - Preview

Here's my plan:

1. Remove chapters from episode
2. Split episode into 3 separate mkv (prologue + episode + preview)
3. Append everything in the correct order (prologue + opening + episode + ending + preview)

However, I'm stuck at #2.

I'm using MKVToolNix-GUI to split, but for some reason, prologue mkv always ends with an extra 3s of nothing.
This means that when I append everything, there's a 3s break between prologue ending and opening starting.

I've tried both split by timecodes, and split by parts based on timecodes, and the result is the same.

I try to split at 00:01:06, and for some reason, the resulting file is always 00:01:09 long.

When I try to play this file in VLC for example, as soon as the video hits the 00:01:06 timestamp, the player just closes the video. However, it does state in the timebar that the video has a duration of 00:01:09, and so does Mediainfo.

Why is this hapening, and how can I fix this?

[sneaker]

https://github.com/mbunkus/mkvtoolnix/wiki/Splitting-imprecise
Note that in addition to the video keyframe limitation mkvmerge will also avoid splitting subtitle lines in two. Since an mkv file can have several tracks they can end up having different lengths. Also with things like OpenGOP stray slices could appear that cannot be decoded correctly. Different players may react differently to these things.

Try to split a bit earlier or other software like SolveigMM Video Splitter that does "smart re-encoding".


An additional warning: you may not even be able to append them later on if the parts are encoded differently.

[tirafesi]

I think I understand the keyframe logic, but then wouldn't that make it so that the split would actually happen at the wrong time?

Take my file for example (the episode file, excluding OP and EDs)

The duration is 23:13.

And I want to split at 01:06.

If it was a keyframe problem (let's assume it would split at 01:09 instead), the result would be a file 00:00-01:09 and another file 01:09-23:13 right?

So the durations of both files would be: 01:09 and 22:04 correct?

But that's not what's happening here. In my case, what happens is that the split actually happens at 01:06, however, the first resulting file gets 3 extra seconds of nothing (no audio, no video, no subtitles, nothing - the player isn't even capable to playing those 3 seconds).

So, my resulting files are: 00:00-01:06 and 01:06-23:13.

And the durations are: 01:09 and 22:07 (notice those 3 extra seconds of nothing added to the duration of the first file)

As you can see, the durations don't add up to the total of the original episode. 01:09 + 22:07 = 23:16 > 23:13

[sneaker]

I think I understand the keyframe logic, but then wouldn't that make it so that the split would actually happen at the wrong time?

Good point. But I can't really tell without actually having the file.

[tirafesi]

Delete this comment pls

[sneaker]

Subtitles. I frame at 1:06.483, subtitles from 1:06:48 to 01:09.46. You could edit the subtitles to let them start a bit later. Or split with subtitles deactivated and manually integrate them later or something like that.

(I'm not talking about OP or the chapters. OP plays no role at this point. You are still trying to split the file 01. Since the subtitle starts a tiny bit before the I frame they don't get split. Like I said: mkvmerge will not split subtitle lines in half.)

[tirafesi]

Oh, I see.

So in order to solve this, I'd have to:

1. Extract the ass subs and delay that line to start only after the Iframe.
2. Mux the new subs into the episode.
3. Split and merge.

I'll try it out tomorrow and let you know how it went, thank you!

[tirafesi]

You were right

I just had to delay the subs by one frame and it worked.

Thank you so much!