Assessing digital audio quality for the world

Leading-edge research and development (R&D) carried out by Canadian researchers is helping to assess digital audio quality.

This world-class R&D is performed by the Communications Research Centre Canada (CRC) in Ottawa. An agency of Industry Canada, CRC is the country's leading laboratory specializing in collaborative R&D in advanced telecommunications.

A decade of active participation in the International Telecommunication Union-Radiocommunication (ITU-R) sector, including major contributions to standards for subjective and objective audio quality testing, has earned Canada and the CRC an international reputation in the field of sound perception and audio quality evaluation.

World-class facilities

CRC's Audio Perception Laboratory has a control room and two calibrated listening rooms which provide controlled listening environments for performing sensitive listening tests. These facilities, which are unique in North America, have been used to host significant international tests of audio source coding technologies for the ITU-R and to develop and validate innovative test methodologies.

In the early 1990s, Louis Thibault of CRC's Advanced Audio Systems group identified a need for scientifically proven methods to accurately measure perceived audio quality. Throughout the decade, the team developed and tested both subjective and objective methodologies and tools for the evaluation of audio technologies. The methodologies they developed formed a large part of three international standards (ITU-R Recommendations).

"CRC-SEAQ [System for the Evaluation of Audio Quality] is the embodiment of our decade of work on audio quality testing," says Thibault.

CRC-SEAQ

This unique, high-powered software package became commercially available in 2000. Operating on the Windows™ 95/98/NT/2000 platform, it offers a Subjective Test Module, which allows human subjects to compare the quality of the original audio (usually from a CD) with an impaired version in listening tests and generate opinion scores; and an Objective Test Module where a sophisticated and computerised model of the human ear performs this comparison and measurement automatically.

Although the Objective Test Module has a good degree of accuracy in comparison to the Subjective Test Module, it is unlikely that testing with the electronic ear would ever completely replace subjective testing with humans.

"CRC-SEAQ is very popular," says Thibault. "We haven't even formally marketed it. The quality of the product and our clients' positive endorsements are our best advertisements."

Licensing success

To date, 20 companies have licences for CRC-SEAQ, including industry giants Dolby, Philips, NEC, NTT, Matsushita, Panasonic, Deutsche Telekom and France Telecom, and public broadcasters like the CBC and BBC. The licence fees have brought in about US$100,000 in two years. The majority of this money is reinvested in Advanced Audio Systems research at CRC.

CRC has recently released an update to CRC-SEAQ. The new multichannel version of the Subjective Test Module will allow testing of surround sound systems.

For more information, please visit the CRC-SEAQ Web site or contact Louis Thibault.