crop without recompress?

[previn]

Is it possible or is there any software that will enable me to crop from top and bottom of avi file without having to recompress video? I have a file which is about 20 mb too big for cd, I don't want to lose quality and there is nowhere to cut video. As aspect ratio is 4:3 and I have wide tv I could cut top/bottom off to view on my divx player. Is it possible?.

Ta

[The Edge]

Welcome to forum ;)
Not possible. :(

PS:
Wrong forum too.


Edge

[Wilbert]

Just use ffdshow to watch your divx movies. There you can adjust the aspect ratio.

[The Edge]

Still won't help him fit it onto cd though.


Edge

[Atamido]

While it is theoretically possible to remove the picture data for certain macroblocks in MPEG-4, while preserving motion data, I have never seen such a tool, and doubt that one would exist. It would be difficult to make and I can't think of a commercially viable reason to make such a tool.

Possible you could overburn, reencode, or buy a 99min CD.

[previn]

I thought this would be the case but thanks for the help

[Kedirekin]

Out of curiosity, is it even theoretically possible?

What if one of the motion vectors for the current frame results in a reference to a removed block from the prior frame? Wouldn't that cause a portion of the current frame to be totally messed up?

[sh0dan]

Originally posted by Kedirekin
What if one of the motion vectors for the current frame results in a reference to a removed block from the prior frame? Wouldn't that cause a portion of the current frame to be totally messed up?

I cannot see it done without recoding these out-of-frame predicted MB's as INTRA. It would be fast and probably accurate - but there is a big risk of the file actually getting bigger.

[Tom|420]

How could the file getting larger by removing data, without modifying anything in the remaining data?

Also I must agree than while it could possibly be possible to crop the top/bottom by removing some macro block (and adjusting the hearders I suppose) there could be a reference to blocks just removed from the previous frame. Just think of how motion works, when the camera pans up, then the blocks are simply scrolled down a bit from frame to frame. This is particularly visible in the scores for movies encoded at low bitrate where artifact are left behind the text as it scrolls up.

I believe it would be too complex to get such a tool to work correctly. Better reencode. In theory, if you reencode with the same code at about the same quality there shouldn't be too much quality lost (in theory). If you reencode with a different codec it's a know fact that data lost in encoding is added to data lost in the previous encoding.


Tom :)

[ammer]

it seems maybe possible if you had a decoder possible of decoding a constant error in a bit stream had bits missing. or perhaps placing it in a container in which the blank areas were compressed as zeros or cut-off. maybe a non-video type compression etc. doesn't sound too impossible.

[fellaw]

What kind of video is that? Is it a backup from a DVD or captured from TV/VHS? With DVD video, cropping wouldn't help you to fit that AVI on CD-R. In my experience cropping those borders in a DVD backup would give you at most 10 MB, depending on the length of the AVI. I've encoded some DVD backups with and without cropping quite some time ago. They all differed about <=10 MB. DVD borders are usually very crisp and pure black, thus it doesn't take many macroblocks to save them. An analog source might give you 20+ MB because of the higher datarate needed for noisy borders, but I doubt this.
Anyway, I agree with my previous writers. I'm not aware of a software which could crop AVIs or any kind of compressed video without recompressing.
Btw, which capacity are you talking about? Have you considered using a 90/99min CD-R?

[Mtz]

I think is better to cut the credits from the end of movie and if is not enough and from the start, using VirtualDub.
If you have an subtitle and cutting the movie at the start you'll have to resync the subtitle.

[callmeace]

Damn :( that is the question I had, I have a video file which I left the black borders on top and bottom (it is in widescreen format). I wanted to remove these black areas without having to encode the video again, but there's no know tool to do this then? :(

Oh well, I am learning more every day, and with storage space getting cheaper it is not such an issue anyway, it's more of an annoyance.

[Doobie]

Originally posted by previn
Is it possible or is there any software that will enable me to crop from top and bottom of avi file without having to recompress video?

That's a common question. I'd think someone would be tackling the problem. But, as you now know, there is not yet any such tool.

You'll have to do it another way. Burn it as a mode-2 CD (thus the CD can hold 800MB). Overburn, but you probably can't overburn 20MB, probably just 10 or 15MB. Cut off the last 20MB (part of the credits). Recompress the audio (a good option of the audio bitrate is high). Buy a DVD burner. Forget about saving the movie, I usually don't watch things more than once.