Variable-to-variable length (VV) codes are a class of lossless source coding. As their name implies, VV codes encode a variable-length sequence of source symbols into a variable-length codeword. This paper will give a complete proof of an important theorem for variable-to-variable length codes.

翻译：变长到变长（VV）码是一类无损信源编码技术。顾名思义，VV码将可变长度的信源符号序列编码为可变长度的码字。本文将给出变长到变长编码的一个重要定理的完整证明。