scope:

This standard covers test methodologies for multimedia transmission systems utilizing digital transport facilities. It gives a set of measurement parameters, without providing limits, to characterize the following aspects of system performance:

a) Active Video Frame inter-arrival time, which is the reciprocal of the elementary frame rate;

b) Visual channel transmission time, also called video delay;

c) Audio channel transmission time (or audio delay);

d) Data channel transmission time or delay (and frame inter-arrival time);

e) Temporal synchronization between channels.

This standard specifies methods of measurement for these parameters in the applications described in 1.3. The standard's scope is limited to cases where appropriate media input and output interfaces are present, or where these interfaces can be made available with optional test fixtures.

The following applications are beyond the scope of this standard:

a) Measuring aspects of system performance other than delay, synchronization, and frame rate. It is important to point out that delay, synchronization, and frame rate measurements do not completely characterize the quality of a multimedia transmission system. For example, the reproduction quality of Video Frames from input to output is also of obvious importance to users. Subjective test methods employing representative users yield the best available assessment of video transmission quality. The optimization of such subjective performance for all quality parameters may take precedence over the optimization of the results of parametric measurements performed according to this standard. The bibliography lists several international recommendations on subjective assessment methods for entertainment and teleconference quality video transmission systems. It also lists standards for assessment of audio and data channels.

b) Unrestricted choice of useful and representative source content. The methods of measurement specified here require restrictions on their source signals for testing. Video source sequences with high motion activity often cause increased delay, decreased frame rate, and skewed audiovisual synchronization in some multimedia applications. Therefore, measurements should use test scenes which are realistic for the application of the multimedia system under evaluation. Continuous audio tones or still video sequences will produce ambiguous delay measurements (but delay is of limited importance under these conditions). Other limitations are given in the sections for each measurement method.

c) Measuring the performance aspects of systems where the input and output interfaces are not accessible.

d) Limits for the parameters. This standard only provides methods to measure these parameters without providing values for evaluation.

Purpose

The purpose of this standard is to ensure the uniform application of, provide a framework for, and provide definitions of performance parameters for transmission systems utilizing digital transport facilities, consistent with the scope. This standard is intended to provide a common understanding among manufacturers, service providers, and their customers.