basE91 is an advanced method for encoding binary data as ASCII characters. It is similar to UUencode or base64, but is more efficient. The overhead produced by basE91 depends on the input data. It amounts at most to 23% (versus 33% for base64) and can range down to 14%, which typically occurs on 0-byte blocks. This makes basE91 very useful for transferring larger files over binary unsafe connections like e-mail or terminal lines.
Opus is a totally open, royalty-free, highly versatile audio codec. Opus is unmatched for interactive speech and music transmission over the Internet, but is also intended for storage and streaming applications. It is standardized by the Internet Engineering Task Force (IETF) as RFC 6716 which incorporated technology from Skype's SILK codec and Xiph.Org's CELT codec.
Nanopb is a plain-C implementation of Google's Protocol Buffers data format. It is targeted at 32 bit microcontrollers, but is also fit for other embedded systems with tight (2-10 kB ROM, <1 kB RAM) memory constraints.