Can an AVI be cropped?

[benafk]

I have received a number of nice AVI's from a friend but he told me that he never uses cropping. I am certain it would save me around 100 mb per hour of movie, encoded at a bitrate of 1300.

My problem is that I have not been able to figure out how to crop a movie that has already been encoded using Gknot > Divx 4/5

Can anyone lend advice?

Much appreciated.

[manono]

Hi-

You can't crop without reencoding and degrading quality. Anyway, as I understand it, even if cropped correctly to begin with, the file size saving would be less than 5%, or around 30 MB/Hour on a 2 hour, 2 CD movie, partly depending on how large the Audio File Size was.

I'd suggest leaving them as they are and teaching your friend to crop properly.

[benafk]

I based my estimated space savings on an actual test of an encoding job using the movie Saving Private Ryan (approx 3 hrs). My settings were bitrate of 1300, resolution of 640 x 352, Audio - just mux 2 Ch AC3 file. I set up 2 Gknot jobs with these same settings, the only difference was on the second job I used smart crop.

The size difference was slightly less than 300 mb using Divx 5.02. I did not realize that the cropping could result in such a huge space savings (approx 20%). I am a novice at this so I could be missing something but those were my results.

I would be happy to post the log files if anyone is interested.

Thanks for the feedback concerning cropping the resulting AVI. I have always cropped by default, but am now a big proponant of it considering how much space is saved.

[manono]

Hi-

I got my figures from this thread here (http://forums.divx.com/viewtopic.php?topic=33531&forum=16) . He kept the picture at the same resolution both times, and added back the black bars to one of them. If I understand you correctly, you did them both at 640x352, and the one with the black bars would have a seriously squashed picture. And of course you'll get a much higher file size savings doing it that way, but unless you let your player give you correct AR, it's not something you'd want to keep. In addition, using a constant quality, or constant quant would give you a more accurate comparison than doing it by bitrate. My guess is, that by using a high bit rate, with so much of the picture being black, that you couldn't use all of the bit rate for at least some of the movie, even if it is SPR. But correct me if I'm wrong somewhere.

[benafk]

You raise an intersting point concerning the size of the picture. I must double check to see if the second encode (cropped) was at the exact same resolution. I know I didn't change the resolution in Gknot, but it may be automatically adjusted when I used smart crop. This could explain the drastic change in my file size.

I will follow up once I have had a chance to review my logs.

Thanks for the link

[smiller667]

Did you have a chance to review your logs and follow up on this? I'd be very much interested ... Thanks!