cx25840 Conexant Systems, Inc., cx25840 Datasheet - Page 133

• Manufacturer Part Number: cx25840
• Description: Video Decoder And Broadcast Audio
• Manufacturer: Conexant Systems, Inc.

CX25840/1/2/3 Data Sheet
3.25.7
Table 3-44. Available Soft Clip Parameters
102284B
8/3/05
RMS Time Constant
Threshold
Compression Ratio
Attack Time
Release Time
Compressor Gain
Parameter
Soft Clip
Pathway
Path 1
Path 1
Path 1
Path 2
Path 2
Path 2
Soft clip is essentially the same thing as an AVC, but the purpose, and therefore the
parameter settings, are different. Soft clip is not used to simply normalize the audio
volume of commercial and regular programming, but rather is used to prevent over-
modulation of the audio signal. Thus, the compression ratio is much higher, and the
attack times RMS time constant and the attack and release times need to be smaller.
Additionally, there is no gain or required signal level associated with the soft clip
algorithm.
There are two modes of operation: independent and stereo. A mode selection bit in the
Path1 Soft Clip Control1 (0x8DC) and Path2 Soft Clip Control2 (0x8EC) selects
between stereo and independent modes. In independent mode, left and right audio
signals are operated on separately; the value of the left signal has no effect on the soft
clip function of the right signal and vice versa. This may be appropriate for soft clip,
even in stereo modes.
Table 3-44
function. Below are the available register parameters defined by pathway:
100 ms
0x0400
8:1
100 ms
100 ms
1
Default Value
shows the user configurable parameters for setting up the soft clip
Soft Clip Threshold Low/High
Soft Clip Threshold Low/High
Soft Clip Control1
Soft Clip Control2
Soft Clip Control1
Soft Clip Control2
Conexant
0, 10 ms, 20 ms, 100 ms, 500 ms, 1 s, 2 s, 4 s, 8 s
User Configurable
2:1, 4:1, 8:1, 16:1, 32:1
0, 10 ms, 20 ms, 100 ms, 500 ms, 1 s, 2 s, 4 s, 8 s
1
0, 10 ms, 20 ms, 100 ms, 500 ms, 1 s, 2 s, 4 s, 8 s
Variable
Available Values
0x8DE, 0x8DF
0x8EE, 0x8EF
Register
0x8DD
0x8DC
0x8EC
0x8ED
Detailed Functional Description
3-107