A codec is a device or computer program for encoding or decoding a digital data stream or signal. Codec is a portmanteau of coder. Preferred filter tweaker for windows about win7dsfiltertweaker. Windows 7 uses its own codecs for decoding several audio and video formats. The following is a list of compression formats and related codecs. Free download advanced codecs for windows 7. Contains nearly all known codecs that are specially optimized for windows 7, 8 and 10.