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Choosing a Format

Download vs Streaming

After you download a file to your computer, an entire copy of the audio or video file will be on your computer. You "own" that copy. When you stream a file to your computer, only the part that you are currently playing is on your computer; anything before or after that section is no longer (or not yet) on your computer. You do not "own" anything.

Downloads are useful when:

  • the file is shorter in duration than the time needed to buffer it for streaming
  • the user's connection speed is slow or of poor quality. Downloads may take a while but they will get through, whereas streaming will playback poorly.
  • the user needs to rewind and fast-forward (scrub) to either locate segments, or to replay segments easily (streaming needs to rebuffer whenever scrubbing occurs)
  • very high quality or large window sizes are needed. When the bandwidth needed for the desired media quality is not available, downloads can get the file to the user. It probably will take quite a while, but once it's there, the quality will not vary with network conditions.

Streaming is useful when:

  • the user shouldn't have a copy of the media, either for reasons of copyright or intellectual property. Note that streaming is not foolproof, and some users will be able to make copies, but it is considered a reasonable obstacle to copying.
  • live events are to be shown
  • very long files are involved, and the download time would be too great

In the past, the whole file had to be downloaded before it would start to play, so in the case of large files and low bandwidth, the wait was excessive. (With a 56K modem, a 1 MB file requires about 3 minutes to transfer.) Now, progressive downloads or fast-start movies blur the line between streaming and downloading. A progressive download will start to play before the entire file is downloaded. The amount that needs to be downloaded before playback starts is determined by the bandwidth available. However the main distinction remains--the user will own a copy of the file after the download is completed.

Streaming Formats

Choosing a streaming format has more to do with the features it offers rather than the inherent quality that is produced. To most people, the quality of the formats is comparable.

RealNetworks

  • works most reliably with SMIL (synchronized multimedia integration language), a way of synchronizing media like slides and video
  • media can be password -protected on the streaming server which helps with protecting copyright
  • has SureStream, a feature that allows one file to be delivered at several bandwidths. The server and the user's computer negotiate the best bandwidth when the file is requested, so the quality will always be as good as the bandwidth available.
  • requires a free player (www.real.com/player) that the student may need to install.
  • encoding software has a free as well as a premium version, but it only runs on Windows

Quicktime

  • comes installed on all Macintosh computers, and is available for Windows at no charge. Macintosh computers only make up a small percentage of the computers owned by Cornell students.
  • supports synchronization of other media using different tracks in the file
  • plays .mp4 files
  • media can be password-protected on the streaming server which helps with protecting copyright
  • for authoring streaming files, the Pro version (about $30) is extremely useful. Viewing files only requires the free version.

Windows Media

  • comes installed on Windows computers, which are the majority of Cornell student computers. The Macintosh version of Windows Media Player is nearly as fully functional as the Windows version.
  • cannot be password-protected

Location and Hours

  • Computing and Communications Center Room 124 Garden Ave.
  • Open Monday-Friday 9:00AM - 5:00PM during the academic year
  • Closed on university holidays

Maintenance Schedule

Any regular system maintenance and server restarts for any of our services will be scheduled weekdays between 5:00 am and 7:00 am. All users should be aware that a system may become unavailable during this maintenance time.

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