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Checkpoint 9 - File optimisation

Conformance: Mandatory

Requirements

Video files must be optimised.

Benefits of conformance

  • Optimisation of files ensures smaller file sizes for faster downloading of videos.
  • Responsive web experience for all users, including those with low bandwidth, fixed or mobile internet access.

Risks of non-conformance

  • Increased download times due to larger file sizes.
  • Possible migration to other, more expensive channels due to slow response times.

Implementation advice

More information

Video and audio files can be very large. High bandwidth networks (gigabytes per second or more) are not widely available and as a result data must be compressed.

Generally speaking, there is a trade-off between file size and quality. For example, high compression of video files may reduce file size; however quality and the user's experience may be compromised. 

Too much compression can make audio sound thin. As a guide, the audio should sound comparable to an MP3 with a 128kbps - bit rate.

Most video encoders will give an indication of the output file size prior to the encoding process.

Examples

An image of a video that has been compressed whilst maintaining the quality.

Correct implementation: The video has been compressed whilst maintaining the quality.

 An image from a video that has been over-compressed resulting in loss of quality.

Incorrect implementation: The video has been over-compressed resulting in a loss of quality.

Last reviewed
01 April 2011
Last updated
17 May 2011