STV8247 Datasheet, PDF (36/149 Pages) STMicroelectronics – Digital Audio Decoder/Processor for A2 and NICAM Television/Video Recorders

Dedicated Digital Signal Processor (DSP)
STV82x7
4.12 Automatic Loudness Control
As the human ear does not hear the audio frequency range the same way depending on the power
of the audio source, the Loudness Control corrects this effect by sensing the volume level and then
boosting bass and treble frequencies proportionally to middle frequencies at lower volume.
While maintaining the amplitude of the 1 kHz components at an approximately constant value, the
gain values of lower and higher frequencies are automatically progressively amplified up to +18 dB
when the audio volume level decreases.The maximum treble amplification can be adjusted from
0 dB (first order loudness) to +18 dB (second order loudness) in steps of 0.125 dB. As the volume is
proportional to the external audio amplification power, the loudness amplification threshold is
programmable in order to tune the absolute level. The Loudspeakers Loudness function is enabled
by setting the LS_LOUD_ON bit in register LS_LOUDNESS. The Loudspeakers Loudness
Threshold and Maximum Treble Gain values are also programmed in this register. The Headphone
Loudness function is enabled by setting the HP_LOUD_ON bit in register HP_LOUDNESS. The
Headphone Loudness Threshold and Maximum Treble Gain values are also programmed in this
register.
The loudness cut-off frequency is 100 Hz.
4.13 Volume/Balance Control
The STV82x7 provides a Volume/Balance Control for all output channels configuration (except for
S/PDIF) with different volume level per channel (L, R, C, L_S, R_S, SubW, SCART). Its wide range
(from +11.875 to -116 dB, in a dB linear scale with a 0.125 dB step) largely covers typical home
applications (approx. 60 dB) while maintaining a good S/N ratio.
Figure 19: Volume Control
+11.875 dB
-116 dB
Mute
00h
I²C Control
3FFh
An extra Master Volume Control can apply an extra gain/attenuation on L, R, C, L_S, R_S and SubW
channels.
The Volume/Balance Control can operate in one of two different modes:
● In Differential mode (default value), the volume control is a common volume value for both the
Left and Right Loudspeakers or Headphone channels (see Figure 19) and complimentary
balance control is used (see Figure 20).
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