Vqm

Video Quality Metric (VQM) Software

1. Input Scene Dependencies2. Digital Transmission System Dependencies3. The Need for Technology Independence4. New Digital Video Impairments

http://www.its.bldrdoc.gov/n3/video/index.html

Repeatable Video Quality Testing

Subjective Video Quality Testing Objective Video Quality Testing

Examples of Digital Video Impairments

Tiling Edge Noise

Original Image Blurring

ANSI T1.801.03-1996 Video Quality Parameters

• Distortions are quantified using spatial and temporal gradients, or slopes, of the input and output video sequences.

• The operating characteristics of digital transmission systems (e.g., bit-rate, error rate, dropped packet rate) may change over time and this can produce quality fluctuations.

• Digital video systems produce fundamentally different kinds of impairments than analog video systems. Examples of these include tiling, error blocks, smearing, jerkiness, edge busyness, and object retention.

• Blurring: A global distortion over the entire image, characterized by reduced sharpness of edges and spatial detail.

• Block Distortion/Tiling: Distortion of the image characterized by the appearance of an underlying block encoding structure.

• Error Blocks: A form of block distortion where one or more blocks in the image bear no resemblance to the current or previous scene and often contrast greatly with adjacent blocks.

– Error blocks become more noticeable in low motion scenes than high motion scenes.

• Noise: An uncontrolled or unpredicted pattern of intensity fluctuations that is unwanted and does not contribute to the desired quality of a video image.

• Jerkiness: Motion that was originally smooth and continuous is perceived as a series of distinct snapshots.

IVQM

• The IVQM tool performs automated video capture and processing of live video signals using two PCs (a source PC and a destination PC) and an IP connection.

• Reduced reference features are communicated via the IP connection and used to perform destination video calibration and quality estimation.

Stephen Wolf, (303) 497-3771, [email protected]

In-Service VQM (IVQM) tool

iVQM

• ANSI T1.801.03 and ITU-T J.143 – This standard specifies a framework for measuring end-to-end

performance parameters that are sensitive to distortions introduced by the coder, the digital channel, or the decoder as shown in the figure.

– Features are quantities of information that are associated with individual video frames.

– Parameters are calculated using comparison functions that operate on two parallel sequences of these feature samples (one sequence from the output video frames and a corresponding sequence from the input video frames).

– Objective video quality estimation software, written in C++, processes video signals in accordance with American National Standards Institute (ANSI) T1.801.03-1996 and other more recently developed metrics, resulting in estimates of video quality that show good correlation with subjective test results.