Appnr

diagnosis tool for JACK audio software

As its name might suggest, the bitmeter operates at the bare metal
of JACK's I/O layer, looking at the 32 binary digits in each individual
sample.

There are three main areas to the bitmeter display:

* Statistics, at the top, including the range of sample values and keeping
a count of irregular and illegal sample values such as NaN. The statistics
on the right are cumulative, and should ordinarily read zero.
* Sign & Mantissa, a row of 24 coloured indicators showing the sign
(positive or negative) and mantissa of the samples.
* Adjusted scale, 40 smaller coloured indicators.

The sign and mantissa statistics are show as coloured indicators which
map to bits in the samples processed by the bitmeter, with the left
most indicator representing the sign bit, and then the mantissa left to
right from most significant to least significant. The colour is based
on the percentage of samples in which the associated bit was 1 over a
period of 100ms or so. Blue indicates that all samples were 0, a light
green-blue for up to 33%, green for 33-66% (i.e. about half), and orange
for more than 66%, then finally red if all samples are 1, a possible
"stuck bit". Gray is used when no samples touched the associated bit.

The "adjusted scale" shows each sample bit on a absolute scale,
adjusted for the exponent of the sample, so that internally the
bitmeter records a 280-bit binary real. For simplicity only 40 bits are
displayed, the 8 left-most bits are the integer part, and the remaining
32 bits after the marker are fractional bits.

The audio range of the adjusted scale is from about 200dB below FS to
40dB above, which would be excessive for audio work but proves useful
in diagnosing problems at a lower level.

The sample rate reported by bitmeter is directly from JACK. It's not
used to perform any calculations and is purely informative.