Datasheet

3−40
The transfer curve remains a constant 24 dB above the 1:1 transfer curve for input levels above and below T2 until
the computed DRC gain coefficient falls within the dynamic range of a 5.23-format number. For input levels above
T2, k2 implements a 5:1 compression. At an input level 7.5 dB above T2 (−62.5 dB), the DRC transfer curve has risen
7.5/5 = 1.5 dB. The boost at this point is 30 dB – (7.5 dB – 1.5 dB) = 24 dB. The DRC has come out of gain saturation.
For input levels above −62.5 dB, the transfer curve exhibits 5:1 compression.
Table 3−5. DRC Example 2 Parameters
DRC
PARAMETER
REQUIRED (SPECIFIED) VALUE
(NET GAIN
SAP Input-DRC
= 0 dB)
I
2
C COEFFICIENT VALUE
T1 and T2 −148.7 dB
Input
≥ −172.7 dB
DRC
−172.7/−6.0206= 28.684849
= 0x0000 0E57 A91F
25.23 format
O2 −20 dB (−20 + 24.0824)/6.0206= 0.678072
= 0x0000 0056 CB0F
25.23 format
O1 10 dB (10 + 24.0824)/6.0206 = 5.660964
= 0x0000 02D4 9A78
25.23 format
k2 ∞:1 compression (1/∞) − 1 = −1 = 0xF800 000
5.23 format
k1 1:1 transfer (1/1) − 1 = 0 = 0x0000 000
5.23 format
k0 2:1 compression (1/2) − 1 = −0.5 = 0xFC00 000
5.23 format
For input levels below T2, k1 implements a 1:2 expansion. With a 1:2 expansion in effect, the transfer curve has
dropped 12 dB at an input level 6 dB below T2. The boost at this level is 30 dB − (12 dB − 6 dB) = 24 dB. The DRC
gain coefficient has again come out of saturation. For input levels below −76 dB and above −150 dB, the transfer curve
exhibits a 1:2 expansion.
At T1 (–150 dB), the transfer curve is 50 dB below the 1:1 transfer curve. Because O1 = 50 dB, there is no discontinuity
in the transfer function. For inputs below −150 dB, k0 implements a 2:1 compression. The change from a 2:1
compression to a 1:1 transfer at −192 dB is due to 32-bit dynamic range saturation at the DRC input.
3.7.3.3 Example 3—1:1 Transfer/Infinite Compression With Minimum Gain Saturation, 32-Bit
Dynamic Range Saturation, and Equal Threshold Settings (T1 = T2)
The DRC transfer function parameters for this example are given in Table 3−6. In addition to illustrating minimum gain
saturation, this example also illustrates the operation of the DRC when T1 and T2 are set equal.