Summary - H Suppl. 21 (01/2025) - Film grain synthesis technology for video applications

Supplement 21 to ITU-T H-series Recommendations provides information on the use of film grain synthesis technology for video applications. Film grain synthesis technology offers subjective quality benefits for certain video applications and can effectively improve video compression. The use of such technology can involve pre-processing to reduce film grain and sensor noise present in a video or image signal prior to compression. Metadata can then be conveyed to a decoder and used to synthesize noise with similar characteristics, as in the original content as a post-processing stage that follows the compression decoding process. This metadata may be signalled using appropriate mechanisms, such as the supplemental enhancement information messages that are supported by several video coding standards.
This Supplement provides a referenceable overview of the end-to-end processing steps for film grain and sensor noise removal, estimation, parameterization, synthesis, and blending for consumer distribution applications. The Supplement includes examples of encoder-side and post-decoding processing steps for grain blending with some of the currently defined technologies.
This H-series Supplement was developed collaboratively with ISO/IEC JTC 1, Information technology, Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information, and corresponds with ISO/IEC TR 23002-9:2024 as technically aligned twin text.