WM8946 Datasheet, PDF (35/175 Pages) Wolfson Microelectronics plc – Stereo Low-Power CODEC with Video Buffer

Production Data
3D SURROUND
WM8946
The 3D-stereo surround effect is part of the SE1 block. This function uses time delays and controlled
cross-talk mechanisms to adjust the depth or width of the stereo audio. The 3D-stereo surround effect
includes programmable high-pass or low-pass filtering to limit the 3D effect to specific frequency
bands if required. The structure of the 3D surround processing is illustrated in Figure 15.
forward_l
+
L
HPF
z^-n
LPF
bypass
cross_r
cross_l
R
HPF
z^-n
LPF
bypass
+
forward_r
Figure 15 3D Surround Processing
The 3D surround depth is programmable; the default setting is OFF. The 3D surround processing can
also be configured to create a mono mix of the Left and Right channels.
The 3D effect is enabled on the left and right channels using the SE1_3D_L_ENA and
SE1_3D_R_ENA register bits defined in Table 13. These bits can be set independently of each other.
For the derivation of the other associated registers, refer to the configuration tools supplied with the
WM8946 Evaluation Kit.
5-NOTCH FILTER
The 5-notch filter is part of the SE1 block. This function allows up to 5 programmable frequency
bands to be attenuated. The frequency and width of each notch is configurable; the depth of the
attenuation may also be adjusted. The default setting is bypass (OFF).
The notch filters may be enabled on the left and right channels using the SE1_NOTCH_L_ENA and
SE1_NOTCH_R_ENA register bits defined in Table 13. Note that, although the 5-notch filter can be
enabled on the left/right channels independently, the parameters that define the notch filters apply
equally to the left and right channels, when enabled.
The notch filter coefficients are programmed in registers R72 to R91. For the derivation of these
registers, refer to the configuration tools supplied with the WM8946 Evaluation Kit.
Note that the notch filters should not be configured for centre-frequencies below 120Hz. To apply
filtering at low frequencies, the SE1 High Pass Filter should be used.
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PD, July 2012, Rev 4.3
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