Can 8K Make A Difference in 360 VR Video Experiences?
Introducing a benchmark tool for comparing playback quality
Written by: Changyin Zhou from Visbit
Last Updated: 06/08/18
Abstract
Many discussions have come up recently regarding the comparison of 4K versus 8K, traditional rendering versus foveated rendering, and so on. You may wonder if producing and playback in 8K premium quality make any difference for 360 VR video user experience? What is the optimal resolution that yields the highest clarity in VR360 today?
The final clarity in VR360 is impacted by a number of factors from the quality of source video, compression, rendering pipeline, screen resolution, screen pixel structure, VR lens quality, and even the acuity of eyes. What makes this even more complicated is that these factors do not simply add up. It involves a lot of re-sampling, aliasing, and interpolation. It may take hours to talk (or even argue) about the tricks of this long pipeline. At last, even without all of these complexity, it’s still difficult to easily tell the differences when everyone is using their own video for comparison, which can vary in quality and resolution.
Why don’t we straight these out via real tests with one proper testing video and see with our own eyes? With us introducing a benchmark video (VB2018VR), one may easily test on various players and see the quality differences. In particular, our comparison between Visbit 8K Player and Oculus Video shows that 8K video carries a lot more visible details than 4K video, on Gear VR headset with Galaxy S9.
Introducing Visbit Benchmark 360 VR Video
Included below, is a snapshot of the Visbit Benchmark 360 VR Video (VB2018VR). You may use it for different purposes. For example, as a content creator you can use this to test, evaluate, and pick the best playback solution for your project. You can also use it to check your post-production flow to see if any quality is lost within the pipeline.
The benchmark video is about 10 seconds long, made in 7680 x 7680 resolution (stereoscopic top-bottom), with color space YUV444p, at 30 FPS and encoded by H.264 (please contact us if you need HEVC version). The video includes three visual sections specifically to test for detail and readability, dynamic range, and frame rate.
How to Use VB2018VR
Testing is straightforward. You can simply upload the 8K benchmark video to whatever video platform or player you like and compare:
- Test with your naked eyes;
- Take screenshots to compare;
Notes on color correction
- Advanced players (e.g., Visbit 8K VR Player) will correct colors to compensate the color distortion of VR lenses. The color correction will improve viewing experience in VR. But on screenshots, you may see color bleeding over sharp edges, which make details blurry.
- Make sure you ask for a non-color-correction version for benchmarking if needed.
- Otherwise, you should only compare the center of the field of view where color correction is minimized.
Here are the hardware recommendations as of June 2018, if you are aiming for the highest clarity:
- HTC Vive Focus
- Gear VR with Samsung Galaxy S9.
There are three types of quality tests you may use while watching the benchmark video.
Section 1: Field of View Test
Section 2: Detail and Readability Test
Section 3: Dynamic Range Test and Frame Rate Test
If you want to read details of how to run these quality tests, please read further on Visbit Blog.
VB2018VR File List
Here is a list of the same testing videos, but at different resolutions. Feel free to download and use them to test any video player as you want, and share comparison results.
- visbit-8k-stereo.mp4: YUV444P, 7680 x 7680 @ 30fps
- visbit-6k-stereo.mp4: YUV444P, 5760 x 5760 @ 30fps
- visbit-6k-stereo-yuv420.mp4: YUV420P, 5760 x 5760 @ 30fps
- visbit-4k-stereo.mp4: YUV444P, 3840 x 3840 @ 30fps
- visbit-4k-stereo-yuv420.mp4: YUV420P, 3840 x 3840 @ 30fps
- visbit-4k-squeeze-stereo.mp4: YUV444P, 3840 x 1920 @ 30fps
- visbit-4k-squeeze-stereo-yuv420.mp4: YUV420P, 3840 x 1920 @ 30fps
Example of Use: A/B Comparison Between Visbit 8K Player and Oculus Video
Below is an example of using VB2018VR to compare the playback quality between Oculus Video and Visbit 8K Player.
A/B Setup
We found that the Oculus Video Player can only play up to 4K x 4K, Yuv420p on Samsung Galaxy S9 (Snapdragon 845 Soc). Below are the results of A/B comparison screenshots:
A: Oculus Video
- Device: Gear VR + Samsung Galaxy S9 with Snapdragon 845 Soc
- Player: Oculus Video
- Video: visbit-4k-stereo-yuv420.mp4
- How: mp4 sideloaded
B: Visbit 8K Player
- Device: Gear VR + Samsung Galaxy S9 with Snapdragon 845 Soc
- Player: Visbit 8K Player (with color correction turned off)
- Video: visbit-8k-stereo.mp4
- How: Uploaded to Visbit Portal, transcoded, downloaded to Visbit 8K Player, and played
Note: Viewers can find the benchmark video in Visbit Public Demo App. And make sure the version is v1.5.2 or later. Note that this App has color correction enabled. So your screenshot will have color bleedings as explained above.
Results
You can find all files at full resolution here. When you compare, make sure you zoom into details and that the photos occupy about 70° of your field of view.
Below are the details of the close-ups. It is obvious to see that Visbit 8K carries a lot more details than Oculus Video 4K.
Please send any questions to info@visbit.co
Copyright © 2018, Visbit Inc. All rights reserved.
