Week 4 Readings - Data Compression

I think the basic idea of the Wikipedia entry on “Data Compression” and the longer “Data Compression Basics” is that certain files, particularly color images, take up a lot of hard disk space and use a lot of bandwidth during transmission.  So data compression encodes the information in such a way that fewer bits are used, thus allowing more information to be stored and transferred in less time.  The compression method that recovers an exact original is referred to as “lossless” (which kind of makes sense to me, the suffix “-less” meaning “not having”; so “lossless” meaning “not having loss” or “not losing anything”).  But sometimes recovered information is not exactly identical to the original, so this is called “lossy.”  Run-length encoding (RLE) and Lempel-Ziv (LZ) are examples of lossless compression.  Now, I couldn’t really follow the theory and algorithms beyond the first basic example of “Mary had a little lamb,” but I can see the end result:  that data compression can reduce the file size significantly, amazingly to no or little detriment to the original.  The catch is that both the sender and receiver have to be on the same page as far as the encoding mechanism used for the compression process.  Regarding lossy data compression, it was interesting to me that the human eye or ear doesn’t really notice some loss of quality. 

The “Imaging Pittsburgh” project is fascinating.  Galloway’s article illustrates to me how all of these theories and algorithms are used in the real world, albeit in the background, to enable online access to visual images and photographic collections.  The Digital Library’s Image Collection is amazing.  The Historic Pittsburgh Collection alone now has 18,000 images, far exceeding the 10,000 anticipated at the time this article was written.  I also like their use of Dublin Core metadata—it’s simple and clear, easy to use and interpret.  I couldn’t help but look for my ancestors in the “Pittsburghers at Home” collection—my mom will flip when she finds out about this (she grew up in Homestead and Greenfield in the 30s and 40s). The project team had a goal to provide “consistent size and quality” of images (no doubt applying the principles of data compression).  I found the “image reproduction service” an interesting idea as a potential source of income for the project.  Why not?!  Very interesting to see how a project like this begins with a grant and a few partners, and expands way beyond the original goals, to wind up being an incredible gift to a region.  This would have been a great project to be involved in. . . .

Webb’s brief article describes the use of YouTube as a venue to promote your library.  Believe it or not, I have never gone to YouTube’s Web site directly to search for anything.  (I think I’ve always been afraid that I’ll get sucked in and won’t ever get up from the computer again.)  My experience with it is limited to the few times friends have sent me links to a video.  So I appreciated even the simple instructions of how to just sign up for an account!  I can definitely see how adding instructional or informational videos to library blogs or Web sites is a good idea—anything we can do today to get patrons and users involved in our libraries is important and all good.