Apple Vision Pro will be the first home entertainment device offering Disney’s HFR versions of James Cameron’s movies at home. In the future, Pixelworks intends to establish a logo certification program for TVs and other consumer devices featuring TrueCut Motion, ensuring that devices like TVs play the HFR version of the movie exactly as intended, natively, without motion smoothing or altering cadence. Pixelworks has reached out to all the top TV brands, but as of yet, there are no certified televisions. The UHD Blu-ray specification currently does not support 48Hz, making streaming the sole delivery method for now. Source: FlatpanelsHD
What is judder, anyway?
To understand judder, we must first understand the Nyquist sampling theorem.
“The Nyquist–Shannon sampling theorem is an essential principle for digital signal processing linking the frequency range of a signal and the sample rate required to avoid a type of distortion called aliasing. The theorem states that the sample rate must be at least twice the bandwidth of the signal to avoid aliasing.” – wiki
What is aliasing?
“Aliasing is the overlapping of frequency components resulting from a sample rate below the Nyquist rate.
This overlap results in distortion or artifacts when the signal is reconstructed from samples which causes the reconstructed signal to differ from the original continuous signal.” –wiki
What is spatial aliasing?
Aliasing in spatially sampled signals (e.g., moiré patterns in digital images) is referred to as spatial aliasing. Oversampling is a technique used in video to reduce artifacts like moire. The drawback of oversampling is that we end up with a greater amount of data. Cinema cameras frequently use an optical low pass filter, or OLPF, to minimize false color and aliasing.
Temporal aliasing
Aliasing that occurs in signals sampled in time, for instance in digital video, is referred to as temporal aliasing. Temporal aliasing is what causes judder in motion imaging.
What is noise?
Noise refers to unwanted modifications to the signal, such as graininess. Aliasing can also be considered a type of noise because it is an incorrect signal.
“Nearly 50% of the signal acquired by a camera with a 180-degree shutter can be aliasing noise, regardless of the frame rate at which it is acquired.” – Tessive
Why 24p looks bad on HDR TV
“While high dynamic range (HDR) enhances the viewing experience by rendering a more life-like image, it amplifies motion artifacts due to the higher temporal contrast sensitivity of the human visual system at higher luminance levels and higher contrast ratios typical for HDR images. These motion artifacts are known as strobing or judder.”
“Motion artifacts like judder were already present in the earliest motion pictures. They actually contribute to the “cinematic look,” which is an integral part of the movie-going experience. However, with HDR, judder artifacts are often perceived as disturbing, as they are stressful to the human eye. This calls for methods to reduce said artifacts.”
Can high frame rate (HFR) alone solve the problem of temporal aliasing?
In cinema, anything faster than 24 frames per second is considered HFR. High frame rate makes action look smoother, but also less cinematic.
“The MTF for a given shutter angle is unaffected by frame rate, so the relative ratios of signal to aliasing don’t change regardless of frame rate. Second, increasing the sample rate never pushes the aliasing band into a region where there is no signal to alias. In audio, this isn’t true. In audio systems, we can increase the sample rate to the point that the air and microphones no longer have any frequency content that could alias and cause noise in the recording. In the optical situation, however, the real-world frequency content is nearly infinite, so there always exists frequencies to cause aliasing.”
“High frame rate imaging will yield more realistic imagery because of the increased bandwidth, but in that bandwidth the aliasing ratio will remain unchanged. While audiences have become used to aliasing at 24fps, the new judder frequencies introduced by 48 or 60fps acquisition and playback may be very unfamiliar.” – Tessive
48 fps along with synthetic shutter was found to reduce judder to acceptable levels for most participants in study
“Judder cannot be significantly reduced by rendering softer synthetic shutter shapes at a traditional 24 fps frame rate. Even using a very long shutter still only results in a very slight reduction of judder but renders an extremely soft and, therefore, a non-cinematic motion feel. The computational effort and the increase of data rates to implement such a shutter do not justify the marginal benefit. Increasing the frame rate to 48 fps eliminates judder artifacts for almost all participants. Hence, to effectively reduce judder artifacts, a frame rate increase cannot be avoided.”
The HFR footage for the study was shot on an ARRI AMIRA at 192 fps
A while back, we shared a story where James Cameron said that 48 fps only works in 3D.
The Daejeon Chronicles 
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