Q: C# video transcoding library I need to transcode video streams using C#.  The streams come in a variety of formats, like MP4, H264, H263, VP8.  Is there any library for c# that can transcode a MemoryStream?

A: There is a ffmpeg-sharp library

ffmpeg-sharp is a wrapper library over the FFmpeg multimedia suite
  that provides easy to use wrappers for use in CIL products under both
  Mono and .NET

Also look at SharpFFmpeg

SharpFFmpeg is a C# binding of ffmpeg. The goal of SharpFFmpeg is to
  provide the facility that allows .NET developers to easily create
  audio and video applications.

And MeWiG - MEncoder GUI for Windows

MeWiG is a Windows Frontend to the MEncoder (part of MPlayer) using
  the .NET Framework.You should be able to crop, scale, deinterlace, etc
  and finally convert almost any digital video-source, without the need
  for commandline-options.

