http://www.vso-software.fr/guides/cxd/cxd-cut.php
For older versions of ConvertXtoDVD keep on reading:
Recommended For Experienced Users
To remove a part of the video file (intro to film, unwanted scenes or commercial) is not easy, if your video file is already encoded (divx, xvid, mpeg2, wmv). If you remove a part of a video file, you'll necessary break the timestamp continuity in the file. If we keep the timestamp discontinuity, it may cause an out of sync on Convertxtodvd, when encoding the modified file, in particular if the audiostream is AC3.
In order to avoid timestamp discontinuity on the audio & video stream, the best solution will be to rebuild a new file completely. Yes, a new compression could be needed. But it could alter the quality of your source video.
The following procedure shows how to remove a part of a video.
To cut or remove parts of your video file (intro to film, undesired scenes or commercials) you can first remove those parts with the free software VirtualDub and then convert that your new file with ConvertXtoDVD. Note: This will only work for AVI (divx/xvid encoded), MPEG2, and some WMV files. If you know of other software that cuts other file formats please feel free to share them in this thread.
1) Download latest stable version of VirtualDub. Open the Zip file, and double click on VirtualDub.exe file.
If you want to work with MPEG2 files, you'll need also to download the VirtualDub MPEG2 Plugin. Open the zip file and check readme.txt for installation instructions.
If you want to work with WMV files, you'll need also to download the VirtualDub WMV Plugin. Open the zip file and check readme.txt for installation instructions.
If you want to work with AC3 audio streams, you'll need also to download the VirtualDub AC3 Plugin. Open the zip file and check readme.txt for installation instructions.
2) In VirtualDub go to File / Open video file. . .. Select the file you want to edit.
3) To remove just the beginning of a file, move the cursor on the bottom of the window to the place where you want the new beginning of your video file to be. Now click on the icon boxed in red in Figure 1. Now you will see a blue line appear on the time line of the section you want to remove. Now go to Edit and select Delete. Now notice the time line, your new beginning is now located at "0" and the section that was once there has been removed. Skip to section 5.
Figure 1
4) If you want to remove a section in the middle of the video file. Move the cursor on the bottom of the window to the starting section of what you want to remove (for example: beginning of commercial) and click on the icon boxed in red in Figure 2. You will notice a small blue line appear in the cursor to "mark" this spot.
Figure 2
Now move the cursor to the to end of the section you want to remove (for example: the end of the commercial) and click on the icon in Figure 3 . Notice now the section you would like to remove is highlighted in blue. Now go to Edit / and select Delete. Now notice your new beginning is now located at "0" and me line, the section that was once there has been removed.
Figure 3
5) Once you have removed the sections you wanted, go to Video / Compression. Then you'll have to choose the compression format for output, according to the codecs installed on your computer.
The best result would be by selecting "(Uncompressed RGB/YCbCr)", but the file generated will be very huge (about 6 Gbytes for 3 minutes, if the source video is 720x576 25fps). You'll need a big harddisk (at least, 250 Gbytes) for that.
If you've the chance to have any video lossless codecs like DV codecs, you can use it for compression. Select it on the list and change the video mode to "full processing mode"
Now go to File / Save as AVI select a location to save your new file (and perhaps rename it) and click on save. Now the new file will be made by VirtualDub this can take some time the new file is processed to create new headers for the file so it can be properly read afterwards. Then, you will add this file to ConvertXtoDVD to be converted.