Video Compression

and the Internet

Need for Compression

• Important to advancement of internet• Video prevalent all over the net• Compression has improved greatly over the

past 10 years• Helped revolutionize the way internet delivers

content

How it works

• Exploits flaw in human perception• Algorithms written to do this• Areas of similar color averaged out• Image is the same over period of time• All works to make files smaller, with better

quality• Allowing faster transmission online• Able to fit onto ipods, phones, etc

What is a codec?

• Allows for the compression (co), and decompression (dec) of a video file

• Represents analog information in a digital way• Bitrate – amount of data per second required– Lower is better

List of codecs through the years• MPEG1• MPEG2• Sorenson• Realplayer• Quicktime• DivX• XviD• H.264/x264• VC-1

Importance of flash

• Allowed sites like Youtube to flourish• Unified the standard of how to deliver video• Prior to flash video, different standards,

confusing• Including Windows Media player, Quicktime,

Realplayer and more• Everybody already has flash, so no ambiguity

The flash video format

• Flv files embedded in websites– Contain video files

• H.264, VP6, Sorenson H.263• Previous flash versions starting at 6 supported

different formats

Why encode video• Too large to upload to YouTube– 1gb file limit

• Most digital cameras use poor codecs with little to no compression, wasting hard drive space, also making sending over internet unfeasible

• Rip your dvds to your computer• Digitalize old home movies on analog sources for

preservation and sharing online• To put on your portable media player (ipod)• Use of filters to improve video quality from bad

sources

What does it take to encode video?

• Choose a codec– h.264/x264 and xvid are common

• A video file• An encoder– FFMpeg, MeGUI, Handbrake

What’s next

• GPU based encoding• Badaboom– Uses Nvidia graphics cards

• Faster than CPU• Quality an issue currently

Further Information

• www.doom9.org

• www.videohelp.com

Sources• http://www.doom9.org/index.html?/gknot-main6.htm• http://www.animemusicvideos.org/guides/avtech/

video4_2.htm#Interesting• http://www.adobe.com/devnet/flv/pdf/

video_file_format_spec_v10.pdf• http://www.kaourantin.net/2007/08/what-just-

happened-to-video-on-web_20.html• http://www.maximumpc.com/article/features/

is_era_gpubased_computing_really_upon_us• http://www.anandtech.com/video/showdoc.aspx?

i=3339&p=2