Crop black bars from .mkv files without recoding

[Gillie]

Is there a way to crop the black bars from an .mkv file but keep the same bitrates.

I have loads of Blu-ray "film-only" .mkv files (typically 15GB to 20GB each) and just want to crop the black "widescreen" bars at the top and bottom of each as I'm assuming they take space within the file.

TPMGenc EXpress can crop the bars but you then have to recode.

Can mencoder do this but keep all other info the same, i.e. bitrate.

[guns1inger]

You cannot change the video like this without re-encoding. If the bars are in the video, they are taking up very little space, and quality hot from re-encoding will be far more damaging. I would be surprised if there is very much in the way of black bars anyway. Anything 1.778 : 1 won't have any. Anything 1.85 : 1 will have very small bars. It is only when you get out to 2.20 or 2.35 : 1 that they start to eat real restate, but very little bitrate.

[jagabo]

Even if you could remove the black bars without reencoding you would find that your 20 GB file drops down to 19.9 GB. The black bars take almost no bitrate to encode.

[Gillie]

guns1inger
jagabo

Thanks guys. Guess when I thought about it a little more you're both absolutely right. Given that they don't change at all between frames the black bars will account for next to nothing in the overall size of the files.

One other question. If I did recode the movies from say 25GB down to 12.5GB. Would I be able to see any discernable difference on a 42-inch LCD. I know there would be a difference but would I notice it. 12.5GB is twice the filesize of most DVD's (film only) and the encoding and bit-rate is superior. Think what I'm trying to do is strike a balance between using huge amounts of disk space and keeping the quality at a really high level.

[Nelson37]

Some people could not tell the difference.

Some would notice it, but it would not bother them.

Some would call the difference totally unacceptable.

Which group are you in?

[jagabo]

If the 25 GB is MPEG 2 and the 12.5 GB is MPEG 4 you may not see much difference.