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Guide to Defining Video Quality Requirements

Revised May 29, 2012
Section 8 of 11 of step 3 -- Understand System Tasks and System Functions -- in the bar chart highlighing the 4-step process for definfing video quality requirements.

Processing

Processing refers to any compression, enhancement, restoration, or other operation that is performed on a video signal. This could also refer to any processing done automatically as part of a system, such as the processing done inside a digital camera from RAW to TIFF or JPEG.

Equipment: CODEC

The CODEC performs compression or coding by reducing the amount of space that a video file occupies on its media. Most methods for compression result in a loss of fidelity that is not recoverable. Compression is also used to reduce the amount of bandwidth needed to transmit the video.

If a video has been compressed (or encoded), a decoder must be used to view the video. There are many open-source video encoders/decoders, but there are also many proprietary systems. If a proprietary system is used, and a decoder (player) is not provided, the video cannot be viewed. Features:

  • Type of encoding used — as in, H.264, MPEG-2, M-JPEG.

  • Output bitrate — how much compression is done.

  • Delay — if video is being used for real-time decisions, the encoding and decoding processing can delay the delivery of the video to the decision maker.

Equipment: Analog to Digital Converter

Performs digitization, which is the conversion of an analog video source to a digital format by sampling the analog signal. Features:

  • Sampling rate — how many horizontal and vertical samples per frame.

  • Bits/sample — how many bits are used for each sample.

Equipment: Editing Software

Performs enhancement for analysis. There are many methods available to increase clarity to certain parts of the video. Examples are frame averaging, edge enhancement, and color balancing. Features:

  • Proprietary

  • Irreversible data loss

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