Hi,
experimented a bit with the demorecord function and how to add motion blur to recorded video. I have come up with two options, both are time and space consuming, one is free, one is not. You should be aware, that this does not do perform miracles. But the following guide gives you the means to add an effect that goes beyond what the engine is capable.
First of all record your video at 192fps. That can be achieved, by slowing down the playback rate. I personally set my recording software to 6fps and the demo player to 0.03125 with the lossless Lagarith codec (free).
Then you can go two ways to get motion blured 24p:
- VirtualDub
- A professional video editor
VirtualDub
VirtualDub comes with a built in motion blur filter. Select it via "Video" -> "Filters" -> "Add...". Make sure "Full processing Mode" is active in the "Video" menu (otherwise, the filter is not applied). Then in "Video" -> "Framerate" change the framerate to 192fps. Choose your compression codec in "Video" -> "Compression" save the video to a new file.
Then open the newly encoded video, remove the filter and set "Decimate by:" to 8 in the "Frame Rate..." Dialog (do not change the framerate from 192p). If you have compressed your video with Lagarith you can select "Direct Stream Copy" in the "Video" menu for a huge speed-up during rendering.
The resulting video should be 24p and have some sort of mock-up motion blur. Due to the nature of the VirtualDub processing pipeline, the blur will always "trail behind". If you can live with that, thats a zero cost solution.
Professional Program
"Real" video processors offer mathematical correct motion blur approximations. I did a speed-up using a gauss distribution over four frames and then extracted every other frame via VirtualDub. I did not blend all eight images, because then the blur becomes unrealistic. A camera does not blur that much because each frame has only a limited time of exposure. In between frames a black shutter blocks out the light. So I only blend four frames together, discard four and so on to simulate a physical camera.
Conclusion
This kind of post-processing does require a lot of storage (ca. 10GB per minute at 720p and 192fps) and quite some time. That effort pays of with a slightly more polished look of your demo. This is definitely not a must have, but will pay of in fast paced scenes.
You can take a look at a demo comparison, I uploaded to YouTube. Remember it is a subtle effect. It is most visible, when the camera sweeps across the Borg alcoves.
Regards,
Rachel