This is how 2.1 works in JRiver, the other three channels are empty and harmless (there's no upmixing to 5.1 going on). Given the general naming convention the 2.1 output option is effectively like "2.1 in a 5.1 container".
When this has come up previously the consensus from Matt and Hendrik was (as I recall) was that there are no output devices that support only a three channel output so 2.1 needs to be padded up to either four channels or six channels. The four channel mixing target is quadrophonic without a sub channel, so that could create confusion, and 5.1 output devices are more common anyway so 5.1 was the next logical step.
The only channel mixing that's actually going on is downmixing or upmixing to 2.1 if the source has more or fewer channels than that, JRiver isn't using 5.1 as a mixing target. That is to say, all that's happening is that JRiver is opening the output device in six-channel mode and sending the content from the Left, Right, and Sub channels, but sending no content on the Center SL and SR channels.
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Topic: Audio path converts 2.0 stereo to 5.1 when I set dsp to 2.1 (Read 857 times)