High-speed and DV video

Compression/recompression CoDecs

Most video capture applications save their input to AVI files which are "container" objects for various file formats (compression algorithms).
Codecs (compressor/decompressor) are used to encode and decode the compressed data.

You will have to install the corresponding codec when you want to play a compressed clip. Some codecs are shipped with Windows or DirectX (including the codec to view DV-videos).
It is highly recommended not to recompress DV video streams because they are already compressed. Recompression will add artefacts and the resulting quality will not be suitable for image processing any more.
If you still want to reduce the data rate you can use DivX ( www.divx.com) or MPEG-2 or MPEG-4 codecs to do so.
The resulting data rate can be 1/10 or even better.

Since ENCODING is quite costly some codecs use special hardware to compress the video. Most of them have free DECODERs which can easily be installed on several machines.
Other encoders are "software only" but require usually one CPU per video stream for live processing.
It might be a good idea to capture the video in best quality and recompress it later for archiving.