Cropping video files causes an increase in file size?

[colt4523]

I had to fix the aspect ratio of a file that looked like it was recorded wrong when it was put on a vhs tape. It had black boxes on the left and right of the video. So I converted the vhs tape with my dvd recorded then decided the best way to fix this problem was to crop the left and right side using Mpeg video wizard. This caused the file size to almost double its original size. Is there a better way to fix my video without doubling its size? thanks

[redwudz]

I don't use that program, but my guess is that it reencoded at a higher bitrate or different audio format from the original and that's where your size increase came from.

[colt4523]

The bitrate for audio and video are the same on the reencode, so I do not know where the extra file size is coming from. Is anyone familiar with mgeg video wizard?

[presto]

When you captured the video with the black bars the file size was probably smaller than usual because the black bars contain no information. When you crop off the black bars you have a full screen of info and that causes the bitrate to go up to a value that is normal.

(Take this with a grain of salt because I'm just guessing based on hanging around here for a while. I could be way off. Maybe someone with some technical knowledge will confirm or shoot down my idea)

[Nelson37]

Actually, presto, I think you are probably right.

The bigger problem, however, is that such a crop and resize would really whack the aspect ratio, does it look correct after this operation? Hard to imagine a commercial video would be done that badly.

[mats.hogberg]

The bitrate for audio and video are the same on the reencode

If that is a fact, and the video length hasn't changed, the file size can't change. There are only 2 variables determining the size of a video file, and those are the bitrate used, and how long (in time) the video is. Nothing else.

/Mats

[Nelson37]

I am assuming that he gave the Specified bitrate, as opposed to the actual bitrate given in a viewer. Or it was just Good, better, etc.

Agree it cannot be identical, unless the file was doubled or duplicated somehow?

[presto]

What if he is using variable bit rate?

[colt4523]

Thanks for the input...

It was encoded at a varible bit rate. It is not a commercial tape but a tape made with several wrestling matches thrown to make a compilation. So whoever originally made the tape screwed up the aspect ration. Mpeg Video Wizard automatically chooses the bit rate which in this case was variable (most common). Some of the matches have proper aspect ratios and when I encode them, they turn out fine.

So should I just encode the file at a constant bitrate?

[Nelson37]

You stated that the bitrates on both files were the same. Are you assuming that two files which have variable bit rates are using the same numbers? What are the actual, numbered bitrates?

Many progs will not adhere precisely to the bitrates specified. Variation should be fairly small.

CBR may solve the problem, but should not be necessary.

[colt4523]

I tried to encode at a constant bitrate and I got the same results (file with cropping is bigger). I encoded both files at 9496 VBR then at a constant rate of 9496. When I do this without cropping, I get around 700 megs. When I encode with cropping only, changing nothing else, I get around 1.1gigs. Mpeg Wizard must be doing something I dont want on the reencode. Back to the drawing board