Audio routing for scalable conferencing using AAC-ELD and bit stream domain energy estimation

There is an increasing interest in multipoint conferencing but service providers face the challenge of complexity when scaling to thousands of users. This problem can be resolved by a scalable architecture based on central media routers, which allows for low complexity server components and therefore low operational cost. In this paper we describe an audio routing approach using advantages offered by the AAC-ELD bit stream structure. By estimating the signal energy in the bit stream domain, we can detect active speakers at low complexity, which results in substantial bitrate and complexity reduction. Subjective tests with mediated conversations among four participants are conducted to compare the perceived audio quality of the audio router to conventional mixing in a conference bridge. The results show a reduction of complexity by one order of magnitude while maintaining the same subjective audio quality when forwarding the two most active speakers on a 10 ms framing.