One of the biggest problems of the video assist is the inability to playback smooth off-speed. Reason is obvious: cameras usually output 24fps, even though internally they are recording 48fps or more.
So, instead of 48 frames per second, video recording device gets only 24. Now in order to "simulate" how the shot would look like, you set the playback speed to 50% and play it back. Most devices will playback 12 frames per second, which is correctly stretching recorded time, but it's definitely not smooth. The best way to solve this is to record playback from the camera, but often there is no time to do it.
For past few years, we have been looking into this problem. First thing we did was frame blending. This means one frame dissolves into another to generate "missing" frames. We have achieved this in real-time, without rendering. But the result was nice only if there was no big difference between two frames. Not good.
Last year we have worked hard on the true frame interpolation that could produce missing frames closely matching real ones. This is much more complicated than the frame-blending. It requires a lot of computing power to calculate motion vectors and then warp one frame into another. Result was way better, but this approach needed rendering even on the fastest Mac. And it produced some artifacts when there was a parallax motion in the image. Not good.
QTAKE 1.3 introduces the best way to handle off-speed with video assist - REVERSE PULLDOWN. Most of you know what PULLDOWN is: it's basically a method of converting 24fps film into 60i video by repeating frames in a certain cadence (usually 2-3-2-3). REVERSE PULLDOWN (or pulldown removal) is the process of getting back to original frame rate.
There is a button in QTAKE Project Window with this weird name, but powerful functionality. It detects and discards repeated frames and records only "unique" ones. Now imagine your camera is recording 48fps and outputting 60fps over 3G-SDI. QTAKE can detect those 48 original frames and record it into 24fps timebase clip. Playing back such a clip will result in a SMOOTH 50% PLAYBACK, just as if it was played back from the camera.
So, what do you need to do to utilize this awesome QTAKE feature? Just make sure you have a video card that supports 3G-SDI signal and make sure the output of the camera is set to 1080p60. In addition to smooth off-speed playback you will also get lower signal processing latency, because each frame lasts 16.6ms instead of 41.6ms.
The only downside of this method is the 60fps limit. Recording higher camera speed will result in a "simulated" off-speed playback, but still way better than if you were recording only 24fps.