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Part 2 defines various extensions to Part 1, including:

• more flexible forms of wavelet decomposition and coefficient quantization
• an alternative way of encoding regions of particular interest (ROIs)
• a new file format, JPX, based on JP2 but supporting multiple compositing layers, animation, extended colour spaces and more
• a rich metadata set for photographic imagery (based on the DIG35 specification)

Most of the extensions in Part 2 operate independently of each other. To assist interoperability, mechanisms are provided at both the codestream and the JPX file format level for signalling the use of extensions.

Part 2 became an International Standard (ISO/IEC 15444-2) in November 2001.

It is currently available for download from ITU-T as their Recommendation T.801