Sunday, February 01, 2015

experiences with google cardboard

Got an assembled Google cardboard from K - had ordered via for around $2. This reddit thread helped in getting to know some basic apps. My USP was two-fold. Try out immersive planetarium-style experience with VR Player, and to get a large screen experience for movie watching, normal flat screen movies. Phone used was the Xiaomi Mi3.

The magnet on the cardboard viewer was not fixed properly. This dodocase thread gave the pointer of testing with the app called Sensors for testing. Also, how to correctly assemble, from this video. But the magnet is not used in the apps I needed, below.

Planetarium show experience:
The only app I found which supported fulldome rendering was VR Player. It needs the video to be in mp4 AVC (H264) format with baseline profile in order to display without dropping frames! Have to re-encode with Handbrake for this - ensure zero cropping in the first screen - Picture tab, and choose H.264 Profile as baseline in the Video tab. With those settings, and choosing constant framerate and specifying an average bitrate of 6000 kbps, good results for me, and a 1.5 GB file for a half-hour planetarium show in 2K.

In the VR Player app, the default 110 degree FOV setting gives reasonably good results with the full dome projection. But the default number of slices - 32 - leads to somewhat wavy straight lines etc - distortions in the warping. Number of slices 100 gave much cleaner results. The Coverage setting was at 180, and Tilt at 0. Using this, by hitting the calibrate button at the bottom of the screen when onscreen controls are on (toggle on and off by touching the screen) an appropriate tilt of 30-40 degrees could be set.

I also needed to disable the Gestures in the settings - before that, the screen was getting tapped by the cardboard, and was calibrating again and again during the movie, causing the viewport to shift. Removing the magnet may also be necessary to prevent drift - I removed it, just to be safe.

The experience is somewhat like viewing the show in the dome through blinkers or through binoculars. Somewhat restricted field of view, somewhat distorted at the edges. Suggestions for settings tweaks are welcome.

For flat movie viewing, found that VR Cinema Pro was the best choice for me. It has an option to not track based on sensors, then the movie is shown on the centre of the screen. Choosing the + - buttons so that the movie is largest without being truncated, and choosing the pincushion/barrel distortion button to choose no distortion, side-by-side viewing gives a widescreen experience on Cardboard. Unfortunately the current version has a bug - every time a file is opened, it becomes thinner and thinner - squashed vertically.

After 3-4 times of open file, display becomes just a single line.

Rebooting the phone fixes it. Also, this app does not show up on the registered apps for viewing videos, so have to go through its own interface to open files, and then put on Cardboard.

Other apps with the same functionality, but more bells and whistles, have the unfortunate problem of needing mp4 video with baseline encoding for smooth playback, with other codecs causing dropped frames. Examples: Cmoar VR Cinema Pro, Fibrum VR CinemaVR Player, Side-by-side video player.

There are many other things which can be done with google cardboard, of course. Viewing photospheres with Orbulus, games, the official cardboard app, SBS (side-by-side) 3D youtube videos with VRTube and more.

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