Ancillary data is data that has been added to given data and uses the same form of transport. Common examples are cover art images for media files or streams, or digital data added to radio or television broadcasts. Television Ancillary data (commonly abbreviated as ANC data), in the context of television systems, refers to a means which by non-video information (such as audio, other forms of essence, and metadata) may be embedded within the serial digital interface. Ancillary data is standardized by SMPTE as SMPTE 291M: Ancillary Data Packet and Space Formatting. Ancillary data can be located in non-picture portions of horizontal scan lines. This is known as horizontal ancillary data (HANC). Ancillary data can also be located in non-picture regions of the frame, This is known as vertical ancillary data (VANC). Technical details Location Ancillary data packets may be located anywhere within a serial digital data stream, with the following exceptions: They should not be located in the lines identified as a switch point (which may be lost when switching sources). They should not be located in the active picture area. They may not cross the TRS (timing reference signal) packets. Ancillary data packets are commonly divided into two types, depending on where they are located—specific packet types are often constrained to be in one location or another. Ancillary packets located in the horizontal blanking region (after EAV but before SAV), regardless of line, are known as horizontal ancillary data, or HANC. HANC is commonly used for higher-bandwidth data, and/or for things that need to be synchronized to a particular line; the most common type of HANC is embedded audio. Ancillary packets located in the vertical blanking region, and after SAV but before EAV, are known as vertical ancillary data, or VANC. VANC is commonly used for low-bandwidth data, or for things that only need be updated on a per-field or per-frame rate. Closed caption data and VPID are generally stored as VANC. Note that ANC packets which lie in the dataspace which is in both the horizontal and vertical intervals, is considered to be HANC and not VANC. VANC packets should be inserted in this manner: (SMPTE 334M section 3): VANC data packets can appear anywhere between the SAV and EAV TRS packets in any line from the second line after the line specified for switching to the last line preceding active video, inclusive. Given the spec for