Originally Posted by RogerDH
To make a time-lapse with VirtualDub, you need to set both the frame rate and the "Decimate by" in the box below the frame rate setting. Decimate will throw out the frames you no longer need. If you want to speed the video up by 10, set the frame rate to the original rate x10 (= 300 in the #11), then set the "Decimate by" to 10 so it will only take every 10th frame. (That is, the output file will still have 30 frames per second, but they will be every 10th frame from the original.)
I tried your method, but it comes out very jerky compared to the method I gave. It looks to me like the toggles in the frame Rate Conversion box are all mutually exclusive (Radio Buttons!). If I set the frame rate to 300 fps there and then select decimate by 10, only the decimate by 10 toggle takes effect. The video plays back every 10th frame at what ever frame rate the source frame rate is toggle to. If I set the frame rate to 300 fps setting last in that block, I get a video that plays back at 300 fps, but with each frame duplicated 10 times, so it still looks like the original playing back at 30 fps. The only way I can get a video to play back all frames smoothly at an accelerated rate is to just set the Source Frame rate to 300 fps and leave the other toggle set to "process all frames".