Problems with Chapters which are cut inaccuratly

[abel413]

Hi,

Sometimes, after remuxing a movie (to mkv) from a Bluray, it seems chapters are inaccurate : actually, when I play the video (on Media Player Classic for example) and try to switch from a chapter to another, it occurs, sometimes, that a chapter has been unproperly cut. Then one can see a few mili seconds from previous scene of the video before new scene starts. It is like that chapter starts too quickly. I encountered that many times and that's why I'm there. Is there something to do against that ? Like loading a chapter file to use or not muxing chapters with MakeMKV ?

At that time, The only thing I can do against this is use ChapterGrabber, a tool that allows me to get chapters from the BluRay and save them to a .xml file. After that I remux previous mkv with these chapters (and removing unproper muxed chapters) and it works well. But I waste time as I have to mux twice then. Anyway, it is clear the issue is in MakeMKV : would it be possible it somehow rounds some chapters timestamp instead of letting them untouched (which, to my mind, could explain some chapters don't start 'exactly' at the timestamp intended). Then, how could one control that on MakeMKV ?

[Woodstock]

USUALLY, this is a case of the disk authoring. The chapter track is a set of time stamps, and not necessarily the location of KEY FRAMES within the video track.

A key frame is a "complete" video frame, while many (most?) other frames are "difference from last frame" to save space. Playback software tries to find the most recent key frame to start their display, which may or may not be the frame that the chapter actually begins.

[abel413]

USUALLY, this is a case of the disk authoring. The chapter track is a set of time stamps, and not necessarily the location of KEY FRAMES within the video track.

A key frame is a "complete" video frame, while many (most?) other frames are "difference from last frame" to save space. Playback software tries to find the most recent key frame to start their display, which may or may not be the frame that the chapter actually begins.

Thanks, then do you have a solution (different from using ChapterGrabber and remuxing) ?

[Woodstock]

Not really - I live with it on the shows where it happens.

About the only way you could really "fix" it is using a video editor that can export exactly what you want, inserting a manufactured key frame at the start of the chapter.

[abel413]

I opened that new topic : http://www.makemkv.com/forum2/viewtopic ... 10&t=15500 ; actually, I think issue is related to the fact extra decimals of the chapter position are not kept or rounded.

[Woodstock]

That difference in fractions between the chapter track in the BD data and the one in the MKV data will have to be explained by someone more knowledgeable than me.