Windows File Compression degrades video files?

[andrew006]

Anyone knows if windows compresses a multimedia file during disk clean-up, then what happens to the multimedia's quality?

[Yong]

the compression is lossless just like zip, it wont hurt anything;)
and dont expect too much, it wont compress further on already compressed(mp3/avi) file.

[Sharktooth]

it wont compress already compressed files at all...

[Shinigami-Sama]

I noticed it actually increases file size on disk under certain circumstances...
overhead and such

but your degradation could be the overhead of unpacking the file before being sent off the renderer mayhaps

[hsoftwaremaster]

Compression programs like zip or rar won't degrade the quality and even won't really compress the file, they are not made for video files. Converting files to another more compressed format (like degrading the file size or changing the bitrate) will mostly degrade the quality