Video Compression: What Producers Need To Know


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This presentation describes what video producers need to know about video compression and how it affects video quality.

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Video Compression: What Producers Need To Know

  1. 1. Prepared by Larry Kless Kaiser Permanente January 22, 2008 What Producers Need to Know About VIDEO COMPRESSION
  2. 2. Producers need to know about <ul><ul><li>Video compression </li></ul></ul><ul><ul><li>Data rates </li></ul></ul><ul><ul><li>Video codecs vs. container formats </li></ul></ul><ul><ul><li>Format considerations </li></ul></ul><ul><ul><li>Progressive download vs. Streaming </li></ul></ul><ul><ul><li>Optimal quality settings </li></ul></ul><ul><ul><li>Shooting tips for web video </li></ul></ul>
  3. 3. What is Video compression? <ul><ul><li>Video compression is the process of reducing the quantity of data used to represent video images </li></ul></ul><ul><ul><li>It’s a straight forward combination of image compression and motion compensation </li></ul></ul><ul><ul><li>It gets rid of redundant information of the video file which dramatically reduces the storage and bandwidth requirements </li></ul></ul><ul><ul><li>Video quality is reduced as the file is more compressed </li></ul></ul><ul><ul><li>Compressed video is encoded using a codec (coder-decoder) and is saved in container format (.mov, .flv, .wmv, .m4v, mp4) </li></ul></ul>
  4. 4. What is Data Rate? <ul><ul><li>Data rate (also known as bit rate) is the amount data that is transferred per second </li></ul></ul><ul><ul><li>Described in Kilobits per seconds (Kbps) or Megabits per second (Mbps) </li></ul></ul><ul><ul><li>For smooth video playback, data rate must conform to the the amount of available bandwidth e.g. size of the pipe or stored on physical media (CD or DVD) </li></ul></ul><ul><ul><li>Higher data rate = less video compression </li></ul></ul><ul><ul><ul><ul><li>Results in higher quality video resolution </li></ul></ul></ul></ul><ul><ul><li>Lower data rate = more video compression </li></ul></ul><ul><ul><ul><ul><li>Results in lower quality video resolution, especially with motion </li></ul></ul></ul></ul>
  5. 5. Compression Basics Why Should Producers Care? <ul><ul><li>The most important point to remember when producing video for the web is that any motion degrades video quality </li></ul></ul><ul><ul><li>For web video, keep in mind amount of bandwidth (or connection speed) that’s available to your viewers controls their ability to retrieve and play video smoothly </li></ul></ul><ul><ul><li>You may need to create a high and low quality version to accommodate your audience </li></ul></ul>
  6. 6. Codecs vs. Containers <ul><li>Codecs (compression) </li></ul><ul><ul><li>DV/DVCPRO </li></ul></ul><ul><ul><li>Sorenson Spark </li></ul></ul><ul><ul><li>On2 VP6-S </li></ul></ul><ul><ul><li>H.264 </li></ul></ul><ul><ul><li>MP3, AAC (audio) </li></ul></ul><ul><li>Container (file format) </li></ul><ul><li>MOV </li></ul><ul><li>FLV </li></ul><ul><li>MP4V, M4V </li></ul><ul><li>3GP, 3G2 (mobile) </li></ul><ul><li>MP3, M4A, MP4 (audio) </li></ul>Example “I’m creating a FLV file using the Sorenson Spark codec compressed at 448 Kbps for my client’s web site”
  7. 7. Choosing a Format <ul><li>Makes no difference if you don’t know * </li></ul><ul><ul><li>Who your audience is </li></ul></ul><ul><ul><li>What do they want to see </li></ul></ul><ul><ul><li>How do they want to see it </li></ul></ul><ul><ul><li>What’s the business application </li></ul></ul><ul><li>Other considerations include </li></ul><ul><ul><li>Complexity of the content (motion, background lighting) </li></ul></ul><ul><ul><li>Desired reach (internal or external) </li></ul></ul><ul><ul><li>Ability to archive (high quality master) </li></ul></ul><ul><ul><li>Licensing considerations (Talent licensing? Broadcast licensing? Streaming server? Digital rights management?) </li></ul></ul>* Acknowledgement to Dan Rayburn
  8. 8. Progressive Download vs. Streaming <ul><li>Progressive Download </li></ul><ul><ul><li>Available within KP </li></ul></ul><ul><ul><li>Uses a regular web server </li></ul></ul><ul><ul><li>No hosting costs since files are on KP servers </li></ul></ul><ul><ul><li>On-demand only </li></ul></ul><ul><ul><li>Content can be compressed to any data rate </li></ul></ul><ul><ul><li>Can be easily upload to any web server </li></ul></ul><ul><ul><li>Video data must load before you can skip to the end of clip </li></ul></ul><ul><ul><li>Very difficult to capture any viewing metrics (page clicks at most) </li></ul></ul><ul><li>Streaming </li></ul><ul><ul><li>Not available within KP </li></ul></ul><ul><ul><li>Uses a special streaming server </li></ul></ul><ul><ul><li>Cost varies based on hosting service (approx. $300/mo.) </li></ul></ul><ul><ul><li>Both live and on-demand </li></ul></ul><ul><ul><li>Content must conform to available bandwidth </li></ul></ul><ul><ul><li>Outsourced to streaming service provider </li></ul></ul><ul><ul><li>You can skip around to any point of the video </li></ul></ul><ul><ul><li>Can capture robust viewing metrics </li></ul></ul>
  9. 9. Optimal Quality Settings Flash Video <ul><li>Medium quality (current standard) </li></ul><ul><ul><li>Encode video for Flash 7 player </li></ul></ul><ul><ul><li>Video codec: On2 VP6 </li></ul></ul><ul><ul><li>Video data rate: 300 Kbps </li></ul></ul><ul><ul><li>Audio codec: MPEG Layer III </li></ul></ul><ul><ul><li>Audio data rate: 64 Kbps </li></ul></ul><ul><ul><li>Advanced settings: 30 Fps, Aspect ratio: 320x240 pixels, Key frame placement: Automatic </li></ul></ul><ul><li>High quality </li></ul><ul><ul><li>Encode video for Flash 7 player </li></ul></ul><ul><ul><li>Video codec: On2 VP6 </li></ul></ul><ul><ul><li>Video data rate: 448 Kbps (For higher motion video use 700 Kbps) </li></ul></ul><ul><ul><li>Audio codec: MPEG Layer III </li></ul></ul><ul><ul><li>Audio data rate: 64 Kbps </li></ul></ul><ul><ul><li>Advanced settings: 30 Fps, Aspect ratio: 480x360 pixels, Key frame placement: Automatic </li></ul></ul>
  10. 10. Shooting for Web Video Four Need to Knows <ul><ul><li>Watch the amount of motion as it degrades the quality of the compressed video. Limit camera motion. Multiple cuts from shot to shot compress at much higher quality than panning, zooming or dissolves. </li></ul></ul><ul><ul><li>Manage your backgrounds carefully. Codecs respond differently to different backgrounds. The best backgrounds have no motion and low detail. Don’t use high contrast colors or wide open spaces, break up the background with some texture. </li></ul></ul><ul><ul><li>Lighting is key. Compression decreases overall contrast, so use soft lights to reduce artifacts and noise during compression. You have to avoid gain noise in the camera, and create adequate contrast between the subject and the background. Both 3-point and flat lighting work well for web video. </li></ul></ul><ul><ul><li>When possible, shoot in progressive mode vs. interlaced. </li></ul></ul>
  11. 11. For More Information <ul><ul><li>[email_address] Production Manager, Videoconferencing Multimedia Communications Kaiser Foundation Health Plan, Inc. 1950 Franklin, 3rd Floor Oakland, CA 94612 Tel: (510) 987-3956 Cell: (510) 847-4286 </li></ul></ul>