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Lossy Marvels

JPEG and MP3 are very popular formats for storing photographs and music respectively. They are both lossy formats and yet achieve amazing compression ratios without a loss of quality that is easily perceptible by normal people. I have always wondered how this is achieved.

The respective technical specifications are unfortunately too complicated to follow for a layman. Purportedly "explanatory" articles elsewhere gloss too much over the important points leaving me quite unsatisfied. I have fortunately come across two articles recently that seem to strike the perfect balance between these extremes.

"The Audiofile: Understanding MP3 Compression" was published in Ars Technica some time back and very nicely explains the compression algorithm behind MP3 as well as shedding some light over some of the apparent idiosyncrasies of this format. "Image Compression: Seeing What's Not There" was published by the American Mathematical Society and does a similar service for JPEG, including its successor JPEG 2000. (Come to think of it, these articles are "lossy" marvels in their own right.)

Now let us see if I can find an article with a similar depth that explains the MPEG video formats.


  1. Hey JPEG is simple - take a frequency transform of the image ( divide the image up into blocks , and each block is like a matrix of numbers which you can transform). Most images have little high frequency information , so when encoding that can be ignored, thus enabling compression.

  2. rmathew,
    I just wanted to thank you for your blog. I'm an old guy living in the USA, and recently started back to college to finish my business degree. I'm taking a business math class and needed to figure out how to calculate interest compounded monthly. Your explanation helped tremendously. You gotta love the globalization of the world.

  3. hi ranjit
    this is your cousin Lisa form NY
    and your other Lino
    nice site- too bad i don't know anything about computers to find this helpful :)


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