Mixed Mpeg4 (MMA) Guide

Recently a new sort of DivX rips has appeared. They're called MMA because they combine parts of different DivX encoding session, at different bitrates or even using the two types of the DivX codec. 

The method on how to join high and low motion DivX files has been know for a while know and was first published on this site. Since then a bunch of tools to facilitate the task have been developed, among other FourCC changers which allow to "make" high motion files like low motion ones and then to join them in VirtualDub, which only allows you to join files that use the same codec. But since both DivX variants are in fact the same codec, only different builds, it's possible to join in this case. More advanced tools allow you to select directly from the video which scenes should be taken of high or low motion video. Among others there is MakeFilm, CompressAvi and Project DivX. I've never tried MakeFilm since the procedure outlined at DivX Digest sounds so complicated, and CompressAvi would try to create several hundred parts of my encoded movies and which would takes days ( I suspect somewhere along the way it recompresses the video, otherwise it wouldn't take so long).

In this guide we're going to talk about Project DivX, which use seems pretty straightforward to me. In order to get started you need two DivX encodes of the same movie, using the same encoder (for synch reasons). You are free to use whichever DivX codec you use and which bitrate you set. You can even have more than 2 files.. but the procedure gets more complicated there since you'll have to compare the files 2 by 2. To be able to make a more precise choice it's suggested that you set keyframes each couple of seconds - remember that for 1 CD a keyframe every one or two seconds degrades quality.

It's not also possible to use somebody else's settings to recreate their perfect rip. You will no longer have to encode and reencode for days to create the perfect 1/2 CD rip.. you can use profiles that you'll soon be able to download of the internet, then set up a frameserver and let Project DivX handle the rest.

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ENCODING DIRECTLY OFF THE VOBS
USING PROFILES

Start up Project DivX, and load your low and high movie. Low and high does not mean you'll have to encode one in DivX low-motion and the other in high motion. I used 2 low-motion encodes for my test, one at 910kbit/s and one at 1500kbit/s. I took chapters 28 and 29 of "The Matrix", 28 is pretty much Morpheus' interrogation and 29 the lobby fight. The 910kbit/s file was 47MB, the 1500kbit/s file 66MB. I chose to load the low bitrate as the "low" movie and the high bitrate movie as the "high" movie.

As you can see Project DivX shows both movies at the same time, which is highly useful to make a direct comparison. If you click on one of the movies it will be shown in full size, and you can move it around on the screen. This is the ideal way to make a frame by frame comparison of your two movies.

The controls are also pretty straightforward. All the small buttons refer to individual frames: First jumps to the first frame, last to the last frame. Prev will go backwards one frame, next will go to the next frame. Prev Key will go to the previous keyframe and Next Key will go to the next Keyframe. Set Start will set the start frame of a clip, and Set End will set the end frame of the current clip. Use the position slider, the keyframe and frame buttons to locate the first high motion position. As you can see in the screenshot above hell is about to break loose so it's a good time to switch to the high bitrate clip. Note that the lowest 2 buttons are only active at a keyframe, due to the structure of compressed video. The currently shown keyframe is the last before the fight begins. So press the Set End button, and now press Add as "low" part. This will add a clip from frames 1320 to 1896 to the encoding list. When pressing the button the start frame will be set to the current end frame, which spares you to select the start point of the next clip. Now locate the end of the action scene.

In this case this is frame 9504, so press set end again, and then press Add as "fast" part since we want to use the high bitrate movie.

Repeat this procedure for every high action scene in your movie. Clearly that will take you quite a while. In the end you'll end up with a huge encoding list.

Now it's time to create the final movie. Press the Merge AVIs button. Since it's all direct stream copy that will only take a couple of minutes. Then check the result and enjoy. If you have more than 2 different movie files you may compare the mixed movie to the one with an even higher bitrate and repeat the whole procedure until you're satisfied with the final product. That's pretty much how DVDs are being encoded.. first make a relatively low bitrate encode and then use high bitrate parts where needed. It may be interesting to know that the 29th chapter of "The Matrix" consists of 10 cells - the smallest unit of a DVD - so 10 different clips have been used for that chapter.

And now for the statistics: The source files were 47 respectively 66MB large. The final file was 56MB. So we shaved off 10MB off the high bitrate encode and the movie really looks pretty much the same. Can you see where this is going?

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AUTO CREATING ENCODING LIST