Chromium Multichannel Audio Verification Suite

Why the original test was silent / reported 2 channels:

• MediaElementAudioSourceNode.channelCount is 2 by W3C Spec: The channelCount property on an AudioNode specifies how inputs to that node are up/down-mixed. Because source nodes have 0 inputs, channelCount defaults to 2 and has no effect on output channels. The actual channel count is found via decodeAudioData() or by querying output pin connections.
• createMediaElementSource() detaches native speaker output: Calling createMediaElementSource(audio) redirects audio away from standard browser playback into the Web Audio graph. If the context is suspended (autoplay policy) or not routed to destination, the player goes silent.
• Discrete Stereo Downmixing on macOS: For channel counts > 6, the Web Audio spec mandates discrete routing. Stereo headphones/speakers only receive channels 0 & 1; channels 2+ are dropped unless mixed down to stereo.