STV8247 Datasheet, PDF (34/149 Pages) STMicroelectronics – Digital Audio Decoder/Processor for A2 and NICAM Television/Video Recorders

Dedicated Digital Signal Processor (DSP)
STV82x7
is processed by an identical HRTF curve but mixed in at a much lower amount. This HRTF
processing of equal (L/R) signals was again used to virtualize information to the rear of the listener.
The SRS® TruSurround® is certified by Dolby Laboratories to be a Virtual Dolby® Digital and
Virtual Dolby® Surround.
4.7.2
SRS WOW
The SRS® WOW™ is an a sound processing system including:
● SRS® 3D Mono/Stereo™
● SRS® Dialog Clarity™
● SRS® TruBass™
4.7.2.1 SRS 3D Mono/Stereo
This system is used to create a pseudo-stereo signal for mono inputs or a three-dimensional spatial
signal for stereo inputs.
4.7.2.2 SRS Dialog Clarity
This system is used to enhance dialog perception.
4.7.2.3 SRS TruBass
The SRS® TruBass™ audio enhancement technology provides deep, rich bass to small speaker
systems without the need for a subwoofer or additional extra physical components. For systems
with a subwoofer, TruBass™ complements and enhances bass performance. Psycho-acoustically,
when the human ear is presented with a low frequency sound signal that is missing the fundamental
harmonic, it will fill in the fundamental frequency based on the higher harmonics that are present.
By accentuating the second and higher frequency harmonics of the bass portion of a signal,
TruBass™ gives the perception of greatly improved bass response.
SRS® TruBass™ is implemented on loudspeakers path, headphone path or on both in parallel.
4.8 Smart Volume Control (SVC)
The Smart Volume Control regulates the audio signal level before audio processing. This regulation
is necessary in order for the signal level to be independent from the source (terrestrial channels, I2S
or SCART), its modulation (AM, FM or NICAM) and annoying volume changes (advertising, etc.).
The Smart Volume Control works as an audio compressor/expander; i.e. when the input signal
exceeds the threshold level, a very rapid attenuation (-2 dB/ms) is applied to rescale the signal
down to the threshold value. When the input signal is below the threshold level, the previous
attenuation is reduced slowly in order to retrieve the original input level (0dB gain). If the input signal
is too low, an addition gain of 6 dB can be provided.
To personalize the action of the SVC, five parameters are available:
1. Threshold: Maximum quasi-peak level that can be expected on output
2. Peak measurement mode: Select the channel on which the peak measurement must be
performed (Left, Right, Center...)
3. Release time: Gain slope applied to the amplification phase
4. Expander switch: To allow a +6dB amplification of small signals in order to reduce the output
dynamic range
5. Make up gain: Allows compensation of the signal amplitude limitation thanks to a 0 to 24 dB
adjustable gain.
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