RB-Opt is a 3rd party program designed specifically to tweak settings for DVD Rebuilder projects. Before you open a DVD Rebuilder project with it, you need to run it once (RBOpt.exe) and click the Select MPlayer button. This will open a file browser window where you need to locate a media player for RB-Opt to use for previewing video segments. Select your media player (I use Media Player Classic and then you can either close RB-Opt or load a DVD Rebuilder project and start tweaking.

Tweaking Bitrates RB-Opt

Before you start tweaking bitrates with RB-Opt, you'll need to make sure you understand some basic terms - VTS, VOB-ID, and Cell. No doubt you've noticed by now that a DVD is made up of groups of files with similar names that start with VTS_xx, where xx is a number from 01-99. Each group of files with the same number is referred to as a Video Titleset or VTS. For example, The Matrix has 3 Video Titlesets VTS_01, VTS_02, and VTS_03. Titlesets can be further divided by VOB-ID. Every VTS will have 1 or more VOB-IDs, which are just a way to organize the information. Each VOB-ID will then have 1 or more Cells associated with it (once again an organizational unit), and each segment encoded by DVD Rebuilder is a single Cell. RB-Opt is able to set bitrates either for every cell associated with a given VOB-ID or for individual cells.

Start RB-Opt and click the Import Settings button. Browse to the REBUILDER.INF file for your project and select it. On the left side of the window, RB-Opt will show you a list of titles, including the VTS number and VOB-ID for each. Keep in mind that there isn't always an advantage to changing the default bitrates. If the size of the video you're lowering the bitrate on is negligible compared to the size of the video receiving a higher bitrate, the increase in quality will be equally negligible, but the effect on the video with the lower bitrate may be severe. Read that last sentence again if you didn't understand it the first time because you may save yourself some grief later. You can also end up with a smaller DVD than you would get without tweaking bitrates.

Tweaking By VOB-ID

The easiest way to tweak bitrates with RB-Opt is to adjust entire VOB-IDs. A title may only have 1 VOB ID or it may have many. The easiest way I've found to do this is to start by determining which VOB-IDs I want to receive the bits I'm going to free up. Select the first VOB-ID and click the View First Cell button. The video for the first cell for that VOB-ID will play. If it's set to Half D1 it will only have half the horizontal resolution. Don't worry about this as the aspect ratio will be correct once encoded to MPEG-2. If you want to reduce the bitrate (or keep it the same) uncheck the Autosized checkbox. Repeat for each VOB ID until you've looked at all of them.

Now you can go back to each one you want to reduce and adjust the slider under Reduction. The percentage of bits for that VOB-ID (compared to the original DVD) will change as you move the slider, and any parts that still have Autosized checked will increase accordingly.

I automatically reduce the bitrate of any VOB-ID that's being encoded at Half D1 resolution to no more than half what it had on the original DVD. If this doesn't make sense to you, you may want to go back and read the paragraph on Resolution And Bitrate earlier in this guide.

Finally, if you want to increase the bitrate of any titles that you previously left Autosized checked for, you can do this now.

Tweaking Individual Cells

Each chapter will start and end at cell boundaries, so if your movie (or extra) has specific chapters you want to sacrifice bitrate on (just the credits for example), RB-Opt can do that for you. Select the VOB-ID containing the cell you want to reduce and make sure Autosized is unchecked. This will enable the Tweak Cells button. Click the Tweak Cells button and another window will appear, similar to the main window, but with a list of cells in the selected VOB-ID. Select the cell you want to adjust and uncheck the Autosized checkbox. Adjusting the bitrate works just like adjusting it for an entire VOB-ID. The percentage of bits for the cell will change as you move it and Autosized parts of the DVD will be adjusted automatically.

I normally set the credits to the lowest possible bitrate whenever I tweak with RB-Opt, but I always use the View Cell button to preview first. Not all movies have credits in a separate cell so make sure to check before you make any changes.

Edit AVS Files

In addition to the tweaking CCE settings, RB-Opt has the ability to edit AVS files. Unlike Rebuilder though, changes are made by individual VOB-ID instead of all AVS files in the project. If you want to apply the same filters to every AVS file, it's normally easier to use DVD Rebuilder's built in AVS editor. To edit the AVS files for a VOB-ID, select the one you want to change on the left side and click the AVS Editing button. This will open the editor where you will see the VOB-ID listed at the top and the current script below it.

To add a filter, find the line you want to insert your filter before, and select the corresponding line number in the dropdown labeled Insert statements in line #. Type the line you want to add and click the Add Line button. To delete a line, select the line number from the Line # dropdown and click the Remove Line button.

You can add a line to your Favorites by typing it in to add it to the script and clicking the Add Line To Favorites button before the Add Line button. Once you've added it to your Favorites you can select it later instead of retyping it. To add lines from your Favorites, click the arrow button next to the text entry box you would normally type it into, and select a line from the dropdown.

When you're done with your editing, use the Test Script button to make sure it works. If you don't do this, RB-Opt won't let you go back to the main window. See the beginning of this guide for more information on AviSynth filters.

Finishing Up

Once you have all your changes made, use the Save Settings button to save them to your project. At any time during the process you can use the Reset Bitrates button to return all bitrates to their original values. If you try to save and the new size for the DVD would be higher than DVD Rebuilder's original settings would have made it, you'll get a warning but if you want you can still save. If you've made a lot of changes, but need to get the size back down to its original level, it's often easier to reset everything and start over. Once you've saved it you can encode normally using DVD Rebuilder.
Written by: Rich Fiscus
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