The new ‘Smart Ambisonics’ decoder takes an incoming Ambisonics signal and analyzes it, before applying the optimal multi channel rendering.
Generally, the assessment of audio rendering quality involves the comparison of the chosen renderer to some known, quality reference. However, when evaluating spatial audio renderers, unique challenges arise. How can one assess which spatial audio decoder best represents the real sound scene, if that original scene is not immediately available for comparison?
Hence, the client’s priority was to develop a rigorous test methodology for the comparison of newly designed Ambisonics decoders. The principal challenges were to define the most important attributes to be evaluated and their relationship to the chosen methodology/reference material. Other attributes like spatial accuracy, diffuse sound directionality, locatedness, etc. were also to be considered.
The ADAPT Solution
The project began with the client supplying a re-configured copy of their newly developed Ambisonics Decoder as a software plugin for a Digital Audio Workstation. This was used to determine a test methodology that comprised perceptual attributes to be evaluated. The methodology also provided technical details on the procedure of creating a synthesised high-quality signal to which the spatial audio decoders would be compared.
Thus, the solution was to use pseudo-real high-quality recordings of real scenes as references. Even though this posed logistical challenges, it was the only accurate way to evaluate the performance of spatial audio decoders. The experience of these signals was brought closer to “reality” via high-quality loudspeakers in controlled acoustic environments.
All measures were taken to drastically reduce any difference between the reference and test signals, thus enhancing the accuracy of the decoding process and standardising the evaluation of decoders. This innovation is particularly noteworthy because such standardisation was previously lacking, even as it was increasingly needed due to the emergence of Ambisonics as an audio standard in AR, VR and 3600 video.