On 3/6/2011 9:47 AM, Kevin McMurtrie wrote:

I'm all for digital radio but Ibiquity will screw it up. According to
their specification, the removal of analog bandwidth does not increase
the bandwidth for audio. It goes to some other unspecified use that I
can only imagine isn't for free radio. The current encoding, which is
barely good enough for interim use, remains.

As I understand the HD-FM spec, the maximum bitrate for stereo audio is
around 98kbps. Upper and Lower secondary channels replace the analog in
all-digital, and it's about the same bps, but at lower power for the
secondary channels.

So all-digital does allow for more "virtual CD" quality audio channels,
but no, you cannot combine multiple audio channels for even higher
quality audio.

The big advantage of all-digital is that raising power levels no longer
will interfere with analog, presuming all stations do a complete digital
switchover. This is many years in the future of course.