scope:

This standard establishes the requirements to be met by NITFS compliant systems when image data are decompressed using the VQ compression algorithm. This allows NITFS-compliant systems to accept and decompress data that are compressed using a VQ compression scheme. This standard describes the VQ compression in the general requirements section, but does not fully describe the steps for compression. The steps involved in decompressing images compressed with VQ are fully described by this standard.

This standard provides technical detail of the NITFS VQ decompression algorithm, designated by the code C4 or M4 in the image compression field of the image subheader in a NITF file.

This standard is applicable to the IC and the DOD. It is mandatory for all Secondary Imagery Dissemination Systems (SIDS) in accordance with the memorandum by the Assistant Secretary of Defense for Command, Control, Communications, and Intelligence ASD(C³I) Subject: National Imagery Transmission Format Standard (NITFS), 12 August 1991. This directive shall be implemented in accordance with the MIL-STD-2500, JIEO Circular 9008 and MIL-HDBK-1300. New digital imagery equipment and systems, those undergoing major modification, or those capable of rehabilitation shall conform to this standard.

The compliance requirements for implementation of this decompression algorithm are defined in JIEO Circular 9008.

This standard establishes the requirements for the communication or interchange of image data in VQ compressed form. Each type of operation defined by this standard consists of two parts:

a. The compressed data interchange format (which defines the image data field of the NITF file format).

b. The decoder.

Two types of operations are specified by the acquisition authority:

a. Type 1 - Eight-bit monochrome sample compression

b. Type 2 - 24-bit color sample compression