STA328 datasheet(46/57 Pages) STMICROELECTRONICS

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User programmable processing

STA328

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7.4

Mix/bass management

The STA328 provides a post-EQ mixing block per channel. Each channel has 2 mixing

coefficients, which are each 24-bit signed fractional multipliers, that correspond to the 2

channels of input to the mixing block. These coefficients are accessible via the user

controlled coefficient RAM described below. The mix coefficients are expressed as 24-bit

signed; fractional numbers in the range +1.0 (8388607) to -1.0 (-8388608) are used to

provide three channels of output from two channels of filtered input.

Figure 19.

Mix/bass management block diagram

After a mix is achieved, STA328 also provides the capability to implement crossover filters

on all channels corresponding to 2.1 bass management solution. Channels 1 and 2 use a

first-order high-pass filter and channel 3 uses a second-order low-pass filter corresponding

to the setting of the XO bits of I2C register 0x0C. If XO = 000, user specified crossover filters

are used.

By default these coefficients correspond to pass-through. However, the user can write these

coefficients in a similar way as the EQ biquads. When user-defined setting is selected, the

user can only write 2nd order crossover filters. This output is then passed on to the

volume/limiter block.

C1MX1

C1MX2

C2MX1

C2MX2

C3MX1

C3MX2

High-Pass

Filter

High-Pass

Filter

Low-Pass

Filter

User-defined Mix Coefficients

Crossover Frequency determined

by XO setting.

User-defined when XO = 000

Channel #1

from EQ

Channel #2

from EQ

Channel#1

to GC/Vol

Channel#2

to GC/Vol

Channel#3

to GC/Vol

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