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VQiPS: Processing

Guide to Defining Video Quality Requirements

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PSCR System Functions

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 an unprocessed image format (RAW) to a Tagged Image File Format (TIFF) or Joint Photographic Experts Group (JPEG).

Equipment: CODEC
The coding/decoding (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 - such as MPEG-4 Motion Picture Expert Group AVC Advanced Video Coding (H.264), Motion Picture Expert Group video and audio compression specification part 2 (MPEG-2), Motion-JPEG - Joint Photographic Experts Group (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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Created October 4, 2016, Updated October 19, 2016