22.214.171.124 NSCodec Capability Set
The NSCodec Capability Set (section 2.2.1) structure is sent by both the client and server, and advertises properties of the NSCodec Bitmap Codec. This capability set is encapsulated in a Bitmap Codec ([MS-RDPBCGR] section 126.96.36.199.10.1.1) structure, which is ultimately encapsulated in the Bitmap Codecs Capability Set ([MS-RDPBCGR] section 188.8.131.52.10), which is encapsulated in a server-to-client Demand Active PDU ([MS-RDPBCGR] section 184.108.40.206.1) or client-to-server Confirm Active PDU ([MS-RDPBCGR] section 220.127.116.11.2).
The sender of the NSCodec Capability Set MUST populate the fAllowDynamicFidelity, fAllowSubsampling, and colorLossLevel fields to advertise support for lossy bitmap compression (section 18.104.22.168), chroma subsampling (section 22.214.171.124), and the maximum supported color loss level (section 126.96.36.199). The recipient of the NSCodec Capability Set MUST use the contents of the NSCodec Capability Set to initialize an NSCodec compressor so as to ensure that the peer protocol entity that receives compressed bitmap data will be able to perform decompression as outlined in section 188.8.131.52.
If the data encapsulation is invalid or errors are encountered while processing the NSCodec Capability Set, the connection SHOULD be dropped.