Just following up on my post: Found a reference to the 1024px multiples advice I gave....
https://developers.google.com/cardboard/vrview#supported_formats Note, this is advice for maximum compatibility on web browsers etc. and might not be an issue for your applications but its worth recording here.
Quote:
Image Specifications
VR view images can be stored as png, jpeg, or gif. We recommend you use jpeg for improved compression.
For maximum compatibility and performance, image dimensions should be powers of two (e.g. 2048 or 4096).
Mono images should be 2:1 aspect ratio (e.g. 4096 x 2048).
Stereo images should be 1:1 aspect ratio (e.g. 4096 x 4096). <<<Note again for web and you'll want to go higher for 8196x8196 say....>>>
Video Specifications
VR view videos should be stored as mp4s encoded with h264. <<<note Vray guide suggests that h264 compression (and other high-compression formats) introduce too much artifact which exposes seams. Less of an issue for equirectangular image format that cubemap but still something to think about. Anyone else want to offer some animation/video advice?>>>
Mono videos should be 2:1 aspect ratio.
Stereo videos should be 1:1 aspect ratio.
Some older devices cannot decode video larger than 1080p (1920x1080). If maximum compatibility and quality is a priority, we recommend that users provide both a monoscopic 1920x1080 video and a stereo video at 2048x2048 or higher.