Recap: Make It Small
July 9, 2010 Emily Lewis
For our July 7 event, Jack Moffitt discussed clever algorithms to make MP3s and video files tiny without altering their quality much. If you were unable to attend or need a refresher, we've got you covered:
Some takeaways from Jack's presentation:
- Any time you make digital copies of light or sound, you are already using compression.
- Compression is used to make everything (the Internet, your iPod, YouTube etc.) faster.
- Lossless compression means that none of the information is lost. Also, it is "reversable."
- Lossless compression isn't great for binary stuff (images, audio) but great for text data.
- Lossy compression is great for audio-visual media that humans consume. Codecs can remove the data that humans don't perceive, so that you get smaller files without a perceived loss in quality.
- Lossy compression relies on the brain's ability to insert info that isn't actually there. We don't notice what was removed.
- Audio demo of Led Zeppelin's "Stairway to Heaven" backwards. If you hear "satan" it's your brain just trying to make sense of the words in reverse.
- How to take advantage of these brain nuances when it comes to audio compression? Get rid of hi-frequency stuff; 20 MHz and higher, which can't be perceived by most humans.
- Can also use lossy compression for images/pictures. JPEG, for example, converts RGB to YCbCr.
- There is also lossy video, which ranges from the same codecs used for JPEG to more complex codecs for MPEG-4
- Some techniques for lossy video compression: motion estimation and prediction.
- Support royalty free and open standards! Check out Google's WebM Project for one.
Jack also provided the audio demos he used in his presentation:
Video of the presentation is available on Vimeo:
The slide deck for this presentation is available online:
Photos are available on Flickr:
Stay Tuned for Our Next Event!
For our August 4 event, Mark Casias will discuss the main features of jQuery, as well as some of it's advantages:
- jQuery UI
- Third-party plug-ins
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