Notes on photo sphere/panoramic EXIF metadata

• Google's EXIF/XMP metadata tag specification for panoramic images
• Panorama images with sky are to have a negative value for the CroppedAreaTopPixels tag. (The panoramic viewer of Facebook ignores the value altogether, though, and assumes the horizon in the middle of the picture.)
• If a camera or software normally produces panoramic images with cylindrical projection, then doing a vertical capture actually produces a transverse cylindrical image. There is no standardized value for the EXIF ProjectionType field to cover this. (One option is to reproject them to equirectangular — which, again, is not very well supported.)
• Facebook's document on what tags to set
• The Facebook web interface insists that FullPanoHeightPixels be half the size of FullPanoWidthPixels. Else you get “no new photos were uploaded”.

/ Tags: Photo.

Filesystems, Kernel, Linux.

Current XFS status.

• Dave Chinner reports that “It's well known that XFS uses more CPU per metadata operation than either ext4 or btrfs, so it won't be any surprise that they are faster than XFS on this particular test.”; still, his 2012 presentation on XFS coming out better on scalability is still up to date.
• Darrick J. Wong posted support for reflink/deduplication. (Merge 35a891be)
• [2017-01-27] Darrick J. Wong posted support for online scrub/repair.

It does indeed seem like btrfs features are being retrofitted to XFS like I've heard.