You are previewing HTML5: Up and Running.

HTML5: Up and Running

Cover of HTML5: Up and Running by Mark Pilgrim Published by O'Reilly Media, Inc.
  1. HTML5: Up and Running
    1. SPECIAL OFFER: Upgrade this ebook with O’Reilly
    2. Preface
      1. Diving In
      2. Conventions Used in This Book
      3. Using Code Examples
      4. A Note on the Editions of This Book
      5. Safari® Books Online
      6. How to Contact Us
    3. 1. How Did We Get Here?
      1. Diving In
      2. MIME Types
      3. A Long Digression into How Standards Are Made
      4. An Unbroken Line
      5. A Timeline of HTML Development from 1997 to 2004
      6. Everything You Know About XHTML Is Wrong
      7. A Competing Vision
      8. What Working Group?
      9. Back to the W3C
      10. Postscript
      11. Further Reading
    4. 2. Detecting HTML5 Features
      1. Diving In
      2. Detection Techniques
      3. Modernizr: An HTML5 Detection Library
      4. Canvas
      5. Canvas Text
      6. Video
      7. Video Formats
      8. Local Storage
      9. Web Workers
      10. Offline Web Applications
      11. Geolocation
      12. Input Types
      13. Placeholder Text
      14. Form Autofocus
      15. Microdata
      16. Further Reading
    5. 3. What Does It All Mean?
      1. Diving In
      2. The Doctype
      3. The Root Element
      4. The <head> Element
      5. New Semantic Elements in HTML5
      6. A Long Digression into How Browsers Handle Unknown Elements
      7. Headers
      8. Articles
      9. Dates and Times
      10. Navigation
      11. Footers
      12. Further Reading
    6. 4. Let’s Call It a Draw(ing Surface)
      1. Diving In
      2. Simple Shapes
      3. Canvas Coordinates
      4. Paths
      5. Text
      6. Gradients
      7. Images
      8. What About IE?
      9. A Complete Example
      10. Further Reading
    7. 5. Video on the Web
      1. Diving In
      2. Video Containers
      3. Video Codecs
      4. Audio Codecs
      5. What Works on the Web
      6. Licensing Issues with H.264 Video
      7. Encoding Ogg Video with Firefogg
      8. Batch Encoding Ogg Video with ffmpeg2theora
      9. Encoding H.264 Video with HandBrake
      10. Batch Encoding H.264 Video with HandBrake
      11. Encoding WebM Video with ffmpeg
      12. At Last, the Markup
      13. What About IE?
      14. A Complete Example
      15. Further Reading
    8. 6. You Are Here (And So Is Everybody Else)
      1. Diving In
      2. The Geolocation API
      3. Show Me the Code
      4. Handling Errors
      5. Choices! I Demand Choices!
      6. What About IE?
      7. geo.js to the Rescue
      8. A Complete Example
      9. Further Reading
    9. 7. The Past, Present, and Future of Local Storage for Web Applications
      1. Diving In
      2. A Brief History of Local Storage Hacks Before HTML5
      3. Introducing HTML5 Storage
      4. Using HTML5 Storage
      5. HTML5 Storage in Action
      6. Beyond Named Key/Value Pairs: Competing Visions
      7. Further Reading
    10. 8. Let’s Take This Offline
      1. Diving In
      2. The Cache Manifest
      3. The Flow of Events
      4. The Fine Art of Debugging, a.k.a. “Kill Me! Kill Me Now!”
      5. Let’s Build One!
      6. Further Reading
    11. 9. A Form of Madness
      1. Diving In
      2. Placeholder Text
      3. Autofocus Fields
      4. Email Addresses
      5. Web Addresses
      6. Numbers As Spinboxes
      7. Numbers As Sliders
      8. Date Pickers
      9. Search Boxes
      10. Color Pickers
      11. And One More Thing...
      12. Further Reading
    12. 10. “Distributed,” “Extensibility,” and Other Fancy Words
      1. Diving In
      2. What Is Microdata?
      3. The Microdata Data Model
      4. Marking Up People
      5. Marking Up Organizations
      6. Marking Up Events
      7. Marking Up Reviews
      8. Further Reading
    13. A. The All-in-One Almost-Alphabetical Guide to Detecting Everything
      1. List of Elements
      2. Further Reading
    14. Index
    15. About the Author
    16. Colophon
    17. SPECIAL OFFER: Upgrade this ebook with O’Reilly
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Video Codecs

When you talk about “watching a video,” you’re probably talking about a combination of one video stream and one audio stream. But you don’t have two different files; you just have “the video.” Maybe it’s an AVI file, or an MP4 file. As described in the preceding section, these are just container formats, like a ZIP file that contains multiple kinds of files within it. The container format defines how to store the video and audio streams in a single file.

When you “watch a video,” your video player is doing several things at once:

  • Interpreting the container format to find out which video and audio tracks are available, and how they are stored within the file so that it can find the data it needs to decode next

  • Decoding the video stream and displaying a series of images on the screen

  • Decoding the audio stream and sending the sound to your speakers

A video codec is an algorithm by which a video stream is encoded. That is, it specifies how to do #2 above. (The word “codec” is a portmanteau, a combination of the words “coder” and “decoder.”) Your video player decodes the video stream according to the video codec, then displays a series of images, or “frames,” on the screen. Most modern video codecs use all sorts of tricks to minimize the amount of information required to display one frame after the next. For example, instead of storing each individual frame (like screenshots), they only store the differences between frames. Most videos don’t actually change all that much from ...

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