Some video players will allow playing video from an archive. This depends on a number of factors. The cpu must be fast enough to decompress the video and play it at the same time. Depending on the video resolution, a video could be playing fine and the other could skip frames.
And it's not every video player that has the ability to play a video while it is being extracted from the archive. The majority of the video players on the market don't have this feature while other video players will even have the capabilities to play a video, even if the video is splitted over several zip files.
Using Zip for .NET, you would have to know the filename to stream/extract (filename.avi), make a stream of the video, and have a player able to read the file while it's being extracted. This is perfectly feasible, as long as you have a good player.
This being said, unless you want to group the videos together, in the same archive, you are not going to save a lot of space. 2%-3%, not more than this. MP3, JPG, MPG, etc, are already very compressed.
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