I've changed my AAC+ internet radio stream to 48 kbps, and at this rate the encoder uses parametric stereo.
For those unfamiliar, this means a mono channel uses about 44 to 46 of the kbps, and another channel (2 - 4 kbps) tells the decoder how to "steer" the frequencies to create an approximation of the original stereo image. It works pretty well, but I'd like to make it as easy as possible on the encoder.
I've tried expanding the stereo, which made the artificial quality a lot more obvious (large chunks of a frequency band jumping to one side or another, leaving the other side sounding muted, etc. If I reduce the stereo image too much, the encoder gives up and the signal becomes basically mono.
One setting I've considered is the Matrix Mode, which should keep the L-R content about the same level all the time if I understand it properly.
I couldn't find any info in the help section about this tool. Will it help the encoder to best use those few bits to create a great stereo image? The default on "reduce stereo" is 50%... should this be higher or lower? What about L+R to L-R mix? (Default is 0%.) ...and what is "Max Not Mix?"
I keep the azimuth correction on all the time (I'm playing pop from the 1980s)... is that likely to help, or hurt? "Stereo Boost," "Stereo Image"... could any of these help?
I also might mention here, I'd love the option to "center bass" without turning on the entire stereo enhance section.
Parametric stereo certainly improves the sound quality of low bandwidth streams, but it's a challenge to process!!
