Stands for Supplemental Enhancement Information message.
The second version of HEVC (High Efficiency Video Codling) adds several supplemental enhancement information (SEI) messages which can be standardized or specific to a company with proprietary messages that only certain terminal equipment can understand. Some significant SEI standards include:
- Color remapping information (CRI) SEI message, provides information on remapping from one color space to a different color space.
- Knee function information SEI message, provides information on how to convert from one dynamic range to a different dynamic range. An example would be to compress the upper range of High Dynamic Range (HDR) video that has a luminance level of 800 cd/m2 for output on a 100 cd/m2 display. Multiple knee function processes can be supported for different display scenarios.
- Mastering display color volume SEI message, provides information on the color primaries and dynamic range of the display that was used to author the video. Standardized as SMPTE 2086.
- Time code SEI message, provides information on the time of origin when the video was recorded. The SEI Timecode likely refers to the master timeline timecode and not so much the video content and when it was recorded.