
Audio Processor Block
STV82x6
18/97
Note:
The audio signals available on the I2S and SCART outputs are not affected by any digital or analog
matrix processing.
3.2
Smart Volume Control (SVC)
The Smart Volume Control (SVC) feature is designed to process sound level variations caused by
changes in signal sources (e.g. when switching channels) or in volume (e.g. when advertisements
are broadcast). The SVC is controlled by the SVC_ON bit in the
SVC_CTRL
register.
When the SVC_ON bit is set, the Smart Volume Control prevents annoying volume changes by
automatically adjusting the selected sound source (demodulator or SCART) to a programmable
reference level before audio processing. The regulation ranges from +6 dB to -30 dB with a fast
attenuation and a programmable slow amplification. The fast attenuation reduces audio peak (and
potential clipping) and slow amplification is a compromise between regulation recovery and limited
audio amplification during audio silence. The programmable output reference level must be defined
to prevent internal clipping depending on the selected audio processing boosting functions such as
Surround (up to +9 dB), Equalizer or Bass/Treble (up to +12 dB) and Loudness (up to +6 dB). When
the SVC is enabled, recommended reference values are -18 dB for the Loudspeaker path and -9 dB
for the Headphone path.
When the SVC is disabled, it acts as a wide-range prescaler (between -30 dB and +15.5 dB) before
audio-processing to prevent internal clipping depending on the selected functions (see above). If
Figure 9: Audio Processor Block Diagram
E
L
Spatial
Effects
B
V
L
V
Lowpass
Beeper
B
Woofer
B
Volume
SRS
1
0
(L+R)/2
(L+R)/2
T
5
(
Loudspeaker Processing
L
SW_ON
S
H
Headphone Processing
G
H
(
Low
Noise
Audio
Mute
Audio Mute
Smart
Volume
Control
BEEPER_CTRL (79h)
BEEPER_TONE (7Ah)
SVC_SEL (59h)
SVC_CTRL (5Ah)
LS_EQ_CTRL (60h)
LS_EQ_BAND1 (61h)
LS_EQ_BAND2 (62h)
LS_EQ_BAND3 (63h)
LS_EQ_BAND4 (64h)
LS_EQ_BAND5 (65h)
LS_BAL(69h)
SW_BAND (6Bh) SW_GAIN (6Ah)
ANA_LS_HP (07h)
HPD
LS_VOL_CTRL(67h)
LS_CVOL(68h)
LS_SRD_CTRL (5Bh)
LS_STS_GAIN (5Ch)
LS_STS_FREQ (5Dh)
LS_SRS_SPACE (5Eh)
LS_SRS_CENTER (5Fh)
ANA_LS_HP (07h)
HP_VOL_CTRL (75h)
HP_CVOL (76h)
HP_BAL (77h)
HP_BT_CTRL (71h)
HP_BASS_GAIN (72h)
HP_TREB_GAIN (73h)
SVC_SEL (59h)
SVC_CTRL (5Ah)
CUT_ID (00h)
ANA_LS_HP (07h)
Low Noise
LS_LOUD(66h)_
Smart
Volume
Control