[LAD] mudita24 summing pct outs

Niels Mayer nielsmayer at gmail.com
Tue Sep 14 00:50:30 UTC 2010

Since the envy24 hardware metering doesn't actually have an "over"
indicator, the best i can do is indicate when it's at 0.0dB. Note that once
the 0.0dBFS indication lights up,  if you were to push your signal a little
farther than 0.0dBFS then you'd see an over in the output stream.  Also, the
0.0dBFS indication is just the top 9 bits of the signal, which means you
still have up to 15 LSB's (in the 24 bit sound)  more before you actually
hit full-scale, and only after that, would you be over. To get actual over
indication along w/ a dB reading,  you need use something that's actually
listening to the digital stream, e.g. jkmeter.

W/r/t the mixer, you can sum the individual inputs and PCM's into the mixer.
If all the signals are equally quiet, you may never see an over and just
hear the "mix". However, let's say you have two incoming signals that are at
-1dBFS. In that case, mixing them in the digital summer of the ice1712 will
result in an over.

To understand the digital mixer and the fact that the mixer controls in
mudita24 are just 24 bit attenuators into a 20-way 36 bit wide stereo
digital summer,  consult the architecture diagram:

Also, from
///// ///// ///// /////
The peak metering data is displayed as 0 to -48dBFS in envy24control's
meters. This data is derived from the envy24's hardware peak metering:

> MT3F: Peak Meter Data Register
> [...]
> Peak data derived from the absolute value of 9 msb.  00h min - FFh max
> volume. Reading the register resets the meter to 00h.
///// ///// ///// /////

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