croping really worth it

[kamachi923]

i was just wondering if croping is really worth it. i mean does it help with size, quality, speed. if it does how much should be croped off of each side. also i use avisynth and if i add borders to the sides to bring back the original size does this change the size, quality, and speed. would it be better to let tmpg add borders or something like that. if tmpg would be better then how would i go about doing that. thanks for all your help.

[uxbridge]

Yes, cropping is always the best choice.
Mpeg2 and whatever reduction algorithm, work better with frames who are as small as possible. One might argue that black borders captured from TV will compress very well, and this is true, however the border area between the actual video and the border can be extremely sharp (think of a sky vision) and would demand high bit allocation to the algorithm.
That is why you want to crop keeping only the part of the frame you actually see.

You can crop using TMPGenc, it is easy in ADVANCED SETTINGS, just input the amount of pixels/line you want to crop and control the preview.
Cropping will slow your process of making and Mpeg file but will be worth.

You can crop in VDub as well, the way is similar to TMPGenc.

You do not need to add any black borders, those you see on 4:3 TV when you watch, say a 16/9 video, are not added by TMPGenc, but by your DVD player.

Ciao

[kamachi923]

thanks uxbridge for the reply. i was just wondering if you knew the correct way to crop with avisynth. because i would like to crop the file before i resize it and when its in tmpg its already resized. they only way i found to do this is to crop the edges then add blackborders to get it back to its original size. but im assuming by doing this im losing some quality, is that a correct assumption. So my question is if i crop, then how much, then what size would i resize it to, and lastly how would i set up tmpg so its centered and not sized like a 480x480 box. just to remind you my original was going from 640x480. well ill keep trying, and thanks for the reply.

[uxbridge]

I do not use Avisynth, so I do not know how to help you on this.

The reason I do not crop before encoding is simply because I noticed it is difficult to preview TMPGenc output if your input is not really a 4:3 or 16:9 size frame. In the end I succeeeded but I do not really know why.
Anyway, how much quality you loose using cropping is a good question. I think you loose zero but somebody can have diffrent opinion.

Once you crop, you do not want to add borders to the cropped frames because this last action will make cropping unuseful. Your DVD player wil add the borders while playing.

In TMPGEnc Usually you have to use FULL SCREEN (KEEP ASPECT RATIO). if you have a 16:9 or 4:3 input not cropped, such as DVD or a TV capture.
In doing this TMPGenc will maximize your window.
You also need to set the right aspect ratio, 4:3 or 16:9, sometimes TMPGenc cannot detect it right and you'll get wrong aspect ration in this case.

If you have cropped before, I've seen it working using CENTER feature in TMPGenc.

TMPGenc has a "preview" option, that is NOT the picture shown during encoding. You need to click: FILE-PREVIEW to get this, and it will temporarily stop your encoding.
This will give you a good idea of how the result will be before you spend time on an encoding with wrong Aspet Ratio.
Consider that this PREVIEW does not rescale horizontally in a proper way, that means if you are encoding an SVCD at 480x480 it will show a picture fitting perfectly in a square. But what you need to watch is just if it fits all of the horizontal space and if the letterboxing (black bars) is correct.

You DVD player will rescale horizontally.
Have also a look at this:

http://www.doom9.org/index.html?/aspectratios.htm

Ciao