bmp2DivX - Optimizing quality and size

[Snippit]

Hello, new here...enough with the chit chat.....

I have been outputting huge amounts of .tga's from QuakeIIIArena, converted them to .bmp's and then used the little prog bmp2avi to stitch them together into an avi, and then loaded the avi into Virtualdub and encoded it using the DivX5.02Pro codec using 2-pass encoding. Now, compared to encoding a DVD, it seems like I need to set the bitrate unreasonably high in order to get even decent quality. At a resolution of 640*480 a bitrate of 4000 kbps doesn't seem insane. Well, it does actually, and that's why I'm here. =)

I'm not asking anybody to tell me how to go about optimizing quality and size, but I would greatly appreciate if somebody could provide me with pointers, suggestions and tips so I can learn about it myself. Should I use a different codec? What applications are useful? That sorta things.

=)
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[jggimi]

Welcome!

I have a few thoughts....

Try a lower resolution. 640x480 doesn't seem like that large a resolution for computers...but for video, it may be overkill. NTSC DVDs are 720x480, for example. There are many resizers that can provide very sharp edges, such as sharp bicubic, or Lanczos.

4:3 aspect ratios make for high bitrates, in general. There's a lot of pixels in every frame. If you're not already using it, turn on bi-directional encoding (B-frames). You can see significant improvements in compressibility using it. It's probably THE most significant feature in the DivX Pro package.

You might find Gordian Knot a very helpful tool. The latest release (0.27) now accepts .avi files as input, which may make it easier to use. It's a bitrate calculator and AviSynth script creator, and it will allow you to preview different filtering options (such as resizers) prior to encoding, allowing you to make many tests wihtout taking a lot of time. It has a little viewing window primarily used for cropping and resizing, but it is the "preview" function that runs your AviSynth script (with resizing, noise reduction, and the like) through an .avi player that I think is a terrific feature. In addition, Doom9 has an excellent guide for it.

[manono]

Hello, new here...enough with the chit chat.....

Don't you just hate all that idle chit-chat? :)

I agree with jggimi. You might try resizing down to 512x384 or so, and with a sharp resizer and a bit rate of 1500-1800 or so you should get similar quality. If these things are noisy, a filter or 2 might help. If you're repeating a lot of frames, then you should find neuron2's Dup Filter (http://shelob.mordor.net/dgraft/dup/duplegacy.html) very useful in cutting down the file size.

[Snippit]

jggimi:
Thanks for your reply. Lowering the resolution isn't a bad idea, and, I'm a bit ashamed to admit, I hadn't really done the math when comparing the amount of pixels/frame in a cropped DVD rip with a 4:3 fragmovie. The difference is indeed significant.

The preview option granted by GordianKnot is indeed a nice feature, and one that I will be using plenty. I can't believe I've made all those DVD backups without noticing that particular feature. Slave to the guides I guess. ;)
Loading the .avi-file using GKnot provides the nice feature of being able to control the file size a little bit better. Question: Are the results I get back from running the compressibility check comparable to the ones when doing the same thing with a DVD backup-in-progress?

I'll go read up on the different filters and AviSynth in general. Thank you for your suggestions.

=)
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manono:
Duplicate frame detection seems like a very nice idea, and I'll be sure to check it out. I wonder though if it will have an impact on fast motion sequences like those in a "game movie".

Thank you for the compass.

=)
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