I would like to extract streams from WebM video files without converting them (re-compression), can somebody recommend any software that can allow this?
Since WebM is a Matroska subset, mkvtoolnix should let you demux the files. It's open source, cross platform, and the author provides binaries for Windows.
Video files have a container format and codec formats.
Its hard to 'extract' the video bits easily, but it is possible to change the container format to something you can consume whilst not altering the video bits:
To extract audio from a WebM file, using the ffmpeg tool (https://www.ffmpeg.org/download.html) :
NB : Use quotes "" around filenames that contain spaces.
The output file extension has to match with the format of the audio stream contained in the source webm file.
I use ".oga" as output file extension because most webm files I handle contain Vorbis audio.
This command line based on ffmpeg should give you the audio format from the source file :
In my case, this is the output :
Reading this wikipedia page might give you some insight on which file extensions should be used with which audio formats : http://en.wikipedia.org/wiki/Audio_file_format