Other information must also be included, such as sound and the synchronization of sound and picture. This information is carried in lines and pixels that are not visible on screen.
This gives us two auxiliary data regions (or ancillary data regions), arranged horizontally and vertically: HANC and VANC (for horizontal and vertical ancillary data). Audio tracks are generally placed in HANC. Each image must also be delimited by start and end markers. Several 10-bit “words” are thus used to encode the transition from an active image to an ancillary region, as well as the transition to the next image, as shown below.
