Institute for Telecommunication Sciences / Research / Quality of Experience / Video Quality Research / Subjective Testing / Facilities

Subjective Testing Facilities

Subjective testing is simply asking a person's opinion. This is the most accurate way to measure the perceived quality of a phone conversation or video stream.

Designing a subjective test can be tricky. The way one asks a person's opinion can influence the answer the person will give. Experts create ITU Recommendations that list "best practices." These attempt to minimize unwanted influence on a person's answer. When subjective tests are designed with care, they can be highly repeatable, that is, results are the same regardless of where or when the test takes place.

A controlled test environment can enhance repeatability. A person's attention is focused on the task at hand since the lighting is controlled, there is little or no background noise, and there are no visual distractions. A controlled room also frees the experimenter from considering environmental variables when analyzing the test results.

ITS has two identically constructed sound isolation chambers. These rooms can be connected to allow two persons to converse using audio, video, or both. This type of testing can reveal problems that are not apparent when people only listen to audio recordings or view video. An important example is audio delay-if it is too long, conversation becomes difficult.

ITS occasionally conducts video quality subjective tests in quiet rooms, such as a simulated living room. This provides flexibility, but a little less control. This sets a different context for questions about audio and video quality.