I have been working on a good way (with tCi) to convert DivX movies to VCD format (to play on a dvd/vcd player) for a while. We've come up with a pretty good way that has excellent results.
Note: Using larger AVI files is always the best choice. The bigger (and better) the original file is, the better quality your final vcd will be.
Step 1: Splitting the movie
First of all, you must know that when burning the CD, you will not be able to fit more than 70 minutes of the movie (just like when burning music). However, the difference here is that the higher the quality, the less you are able to fit. If you convert at 100% quality, you will not be able to fit more than 60minutes of the movie on a single CD (I do not know the exact time restraints, however this is fairly close).
When splitting the movie, DO NOT use Avi Chopper. This can create corrupted split files (you will not be able to join them back again). So, you use VirtualDub. This is done by selecting the first half of the movie, and deleting it. You save that half. Then select the second half of the movie, and save that remaining half. It's fairly simple and gives the best results (also allows you to cut at the beginning of a scene instead of in the middle of the scene).
Step 2: Uncompressing the audio
You must uncompress the audio of a DivX in order for the mpeg-1 to be burnable as a VCD.
To do this, use VirtualDub. Put the Video on "Direct Streaming" and the audio on "Full processing mode." In the audio section, go to "compression" and select the empty space " ".
Then save the Avi as is. This should not take very long, however will produce a much larger file (normally around 75% to 100% larger).
Step 3: Converting Avi to Mpeg-1
This is usually a very long process (depending on your cpu, RAM and the amount of changes you make, it can take anywhere between 6 and 40 hours). It also create a fairly large file (100-500mb larger than the uncompressed avi). The program to use in this is called "TMPGEnc." (The Mpg Encoder) FYI, this program is supposedly optimized for AMD processors.
The first step is to select the audio and video sources (both the same file) and then to select the output file (the file which will be created after conversion). Select the "configure" button to set up the aspects and quality.
Stream type: Mpeg-1
Size: 352x240 (must be this size!!)
Aspect Ratio: 4:3 525line (this can vary depending on the AVI and the dvd player- but 4:3 usually works best)
Frame Rate: 29.97fps
Rate Control Mode: Constant Image Quality. Then go to the settings and change the quality to 100 and the maximum bitrate to 100 000.
Motion Search Accuracy: Highest Quality (very slow)
Source aspect ratio: This can be changed depending on the AVI that you have. Try to find out the aspect of your AVI. Otherwise pick one at random as this does not seem to make THAT much of a difference usually.
Image Positioning Method: Fit to Frame (preserve aspect ratio)
In the area below, select the following boxes- Ghost Reduction, Noise Reduction, Edge Enhancement, Basic Colour Correction, Crop Video, Audio Effects
Stream type: Mpeg-1 Audio Layer II
Sampling Frequency: 44100 (must be this!!!)
Channel mode: Stereo
Stream type: Mpeg-1 Video CD
Anything I did not mention should be left at it's default setting.
Then you just Click ENCODE!!! That should be it. My advice is to cancel the conversion after a small portion is completed and check the mpeg file to make sure the size and aspect is ok and that nothing is cut out from the movie. If something is wrong, selecting a different aspect ratio (both source and final) will usually work.
This is the best method I have seen for the amount of time it takes. Very good quality depending on the original DivX.