Image resource block (IRB)
From The Glossary of Digital Photography
Also called legacy IPTC metadata and legacy IPTC header. Wrapper structure designed by Adobe to hold metadata for images within certain file formats such as JPEG, TIFF, and PSD. Photoshop has included this function since version 7.0. IRB is being replaced by a new system called XMP. The IRB is now commonly referred to legacy IPTC metadata. The IRB is a subset of the Information Interchange Model. See also Information Interchange Model (IIM); IPTC metadata; XMP
