PurplePaste

These notes are part of my presentation "PEG Access Centers and New Technology" at the Northeast Alliance for Community Media Conference on November 17.

Video Compression Formats

MPEG-1

• Older audio and video compression standard; used in Video CD (VCD) format
  • Constant bitrate of around 1 megabit/second
  • ~10MB per minute of video
  • Roughly equivalent to VHS in quality
• File extensions: .mpg .mpeg

MPEG-2

• Standard format used with DVD; much higher quality than MPEG-1
• Adjustable bitrates allow for a range of picture quality and file sizes; higher bitrates = higher quality video = larger file sizes
  • DVD bitrates can range from 300 Kbit/s to 9.8 Mbit/s
  • Example: at 4 megabit/second, 1 hour of video is approximately 2 Gigabytes
• Support for interlaced video
• Lots more reading material at http://en.wikipedia.org/wiki/MPEG-2

MPEG-4

• Improved compression algorithms allows for higher quality at lower bitrates
  • Results in significantly smaller file sizes
  • Fit an entire DVD on a CD
• Ideal compression format for web-based media
• Digital playback benefits:
  • Greater storage/archival ability
  • Fewer compatibility issues
  • More universal format

Media Container Formats

QuickTime

• Video format devised by Apple
• Can be used at varying quality and file sizes (container format)
• File extensions: .mov .qt

MPEG-2 Transport Stream / Program Stream

• Transport stream: standard for transmission over less reliable media (e.g. broadcast streams)
• Program stream: standard for media that can assumed to be reliable (e.g. disk access, DVD, SVCD)

AVI

• Developed by Microsoft
• Popular, but outdated container format
  • MPEG-4 is supported, but implementation is buggy and inconsistent
• Compatible with many different compression schemes

MP4

• Container standard for MPEG-4 content
• File extensions: .mp4
  • .m4a and .m4v extensions have been popularized by Apple to differentiate audio- and video-only content

3GP

• Container format for video on 3G mobile phones
• A version of the MPEG-4 standard
• File extensions: .3gp or .3g2