Media Technology Systems ION8.8 - Manual (Page 10)

Page 10 of 26 Jul‐09
Although 6.3 is an intimidating list of possible parameters, much of the information will
be irrelevant to the needs of a particular application and can be ignored.
There are 830 possible read/write control parameters and 450 possible read only
monitoring parameters, but only a small number will be used for configuration and a
much smaller number (~20‐30) used for day to day control and monitoring.
3.4 Crunch Values
All OID’s are 32‐bit values. How the value is interpreted depends on the parameter. The
way values are interpreted can be discerned by examining the Crunch Functions section
in the element's implementation XML file. For details on the implementation XML file
refer to Cirrus application note AN277, “Creating DSP Conductor Primitives”.
Note: A doubling of level is 6dB. 1 bit in the digital domain doubles a value (ie shifting a
number 1 bit to the left is the same as multiplying by 2). Thus having (for example) a
signed 29 bit fractional value, allows the use of the 32 nd bit for sign, the 31 st and 30 th
bits for +12dB of gain and the 29 th to 0 th bits for greater than ‐100dB of attenuation.
An example of how this interprets to Mixer gain is given in Figure 3-1 below.
Mixer NxM Non‐inverted Inverted
Input gain (dB) OID value 2^29 OID value 2^29
24 8508830537 ‐8508830537
12 2137321597 ‐2137321597
0 536870912 ‐536870912
‐12 134855876 ‐134855876
‐24 33874264 ‐33874264
‐36 8508831 ‐8508831
‐48 2137322 ‐2137322
‐64 338743 ‐338743
‐100 5369 ‐5369
Mute 0 0
Figure 3-1: Example of Mixer Gain OID values
The algorithm used above is POWER ( 10, ( Target dB value) /20 ) *2^29. This will give the
needed OID value.
Integer values (eg Bypass and Router) are usually defined as fractional bits = 0. These
values are simple, as they are represented by a conventional integer, as shown in
Figure
3-2 and Figure 3-3 below.
Bypass OID value
OFF 0
ON 1