ffdshow is an open source decoder and encoder mainly used for the fast and high-quality decoding of video in the MPEG-4 ASP (e.g. encoded with DivX, Xvid or FFmpeg MPEG-4) and AVC (H.264) formats, but supporting numerous other video and audio formats as well. It runs on Windows and is implemented as a DirectShow decoding filter.

ffdshow can be configured to display subtitles, to enable or disable various built-in codecs, to grab screenshots, to enable keyboard control, and to enhance movies with increased resolution, sharpness, and many other post-processing filters. It has the ability to manipulate audio with effects like an equalizer, a Dolby decoder, Reverb, Winamp DSP plugins, and more. Some of the postprocessing is borrowed from the MPlayer project and AviSynth filters.

ffdshow uses the libavcodec library and several other free, open source software packages to decode video in most common formats, such as MPEG-4 (including video encoded with Xvid, 3ivx, and all versions of DivX), H.263 and VP6 (used by sites such as YouTube), H.264/AVC, WMV, as well as numerous others. ffdshow also decodes audio in the MP3, AAC, Dolby AC3, WMA, and Vorbis formats, among others.

The post-processing video filters of ffdshow can be used in video editors such as VirtualDub or AviSynth, by configuring the VFW settings. In these editors, ffdshow can also be used to encode MPEG-4 video compatible with Xvid, DivX, or x264 codecs, as well as lossless video and a few other formats supported by libavcodec.