Nov
08

Do you know time Remap? You’ll freak out with this video technique!

posted on November 8th 2012 in Video with 0 Comments

Have you ever wanted to play with the time in your video edition, to manipulate time and speed as you want with an amazing result? This is the time remapping, mostly known for its use in After Effects. Einstein knew about it!

If there’s something a video editor can handle better than anyone else, that’s the time. Not only altering the perception of time with the selection, sequencing and duration of sequences, but can literally alter it by changing the duration time of each moment. However, there are limits to this capacity for handling.

The film or video recording is no more than the uptake of a certain number of images over a period of time, normally defined in one second. Thus, the film uses 24 images or frames per second (fps and above), while the video has traditionally used 25 fps. I say traditionally because, with the advent of high definition, many camcorders offer the currently available recording speeds ranging from 24 fps film to 60.

When playing a video at a speed different from the one we recorded creates the effects of fast and slow motion camera. The method for accelerating the original speed of a video is simple, you just need to skip a specified number of frames. So, if we skip every second, the playback speed will double, ie 200%, if we skip one in five, 500%, etc.

The first problems arise when we want to accelerate the video up to 110%, for example. In that case, we will need intermediate frames that do not exist in the original recording, so the editing software will need to apply some technique to solve this problem.

Using Adobe After Effects like the reference software to solve this issue, we could be able to understand the different techniques that it has to perform a slow motion.

Although when manipulating the playback speed of a video the term most commonly used is the English loan Time Remap or Time Warp.

Once applied we see that we have three options:

  • Full Frame: With this technique all you’ll do is repeat a frame many times as necessary to fill the gaps that have been created between the actual frames.
  • Frame Mix: This technique is, as its name suggests, mixing two actual frames in one or more frames in between. The problem is that when viewing two frames simultaneously, both are with 50% transparency and a halo is quite annoying sometimes moving areas.
  • Pixel motion: This technique is the most advanced of all. It makes a real optical frame and, using complex calculations, a prediction is made on the location of each pixel in the images and recreate intermediate frames that do not exist in the original recording.

During recording:

While applying techniques such as pixel motion range can vary quite playback speed of a video, the best solution is to use the highest speed we can during recording. In that sense we are limited by the speed that the camera can offer, but if your camera allows, please film with 50p or 60p if you plan to make a subsequent slow. It can also help increase the shutter speed during recording, so as frames get sharper and later interpolation is more accurate.

It is also important to note that in each interlaced video, each frame is divided into two fields, which correspond to two different instants in time. Therefore, before making speed changes should deinterlace first.

Video credits: Adrien M

It was filmed with a Canon 7D at 60fps, making it really more smooth.It was recorded as a funny pause while working on the performance “Cinematique“… but this short dance is actually not in the show.

It’s made with a custom Quartz Composer plug-in that transform a video stream in a 3D texture.
It can run at 60fps live at lower resolution (512×512)

Music from Beirut

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