The effects of compression


In class the other day, we were talking about the effects of file compression on – even – HD TV pictures. Basicially, bandwidth is limited and higher quality means FAT files. Everything is compressed, especially on the “minor” Freeview TV channels. The government needs to switch off the analogue signals to create more bandwidth for HD-on-Freeview, which couldn’t happen, otherwise. (Personally, there are any number of FreeView channels I would do without for a higher-quality picture on the ones I watch.)

MPEG compression is similar to JPEG compression in that it removes information from files to make them smaller. This is called “lossy” compression. Once lost, it cannot be recovered. You can convert an MP3 to an AIFF or WAV file, but it won’t contain more information than the MP3. You can convert from JPEG to TIFF – same story. We talked about the “analogue” sky with its infinite shades of blue, compared to the “4-step” sky you might see on TV or DVD.

This video (on Vimeo, but linked to from BoingBoing) shows the effect of JPEG compression 600 times over – Boing Boing.