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EN 102
9.
9.4.3
Audio processing (Diagrams SC13, 14 and 15)
This chapter describes the audio processing on the SCAVIO
board. The circuit enables to connect several audio sources,
selects the source on the desired input, and performs audio
Audio
inputs
VGA1
-4dB
Audio-VGA-in
VGA2
-4dB
Audio-Flex-VGA
(Enhanced only)
DVI-D
-4dB
Audio-DVI
(Enhanced only)
AV1
-4dB
Audio-CVBS
(Enhanced only)
AV2
-4dB
Audio-YC
(Enhanced only)
AV3
Audio-YPbPr
7801 : 7808
Mute
Logic
Power-ok
&
MSP-Reset
I2C-SDA
I2C-SCL
= Only for Basic configuration.
The processing part consists mainly of the following
components:
•
MSP3415G:
A DSP sound processor from Micronas. This component is
able to do all kinds of digital signal processing like volume,
bass/treble, UltraBass and balance. It has analogue inputs
and outputs, as well as an I
audio delay.
•
RAM:
With its logic to be able to store the I
audio delay.
•
Anti-plop/ mute circuit:
Which is necessary to prevent disturbances on the audio
lines during start-up or switching.
•
TEA6422:
A matrix switch of ST. This component is able to switch six
inputs to three different outputs (only used in the Enhanced
version).
MSP3415G
Ultra Bass
Because of the closed box implementation in FM24, a common
DBE solution will not give an optimal bass performance. A
closed box needs a substantial boost over a wide frequency
range, while DBE operates in a limited frequency region.
Adaptive Ultra Bass 2 (UB2) is a suitable alternative. This
feature is based on the psycho-acoustic effect of the missing
fundamental, and gives the impression of a deep bass while
FM24
Circuit Descriptions and List of Abbreviations
(Basic only)
7798
(Enhanced only)
Matrix
Switch
TEA6422
PRE-out1 (L)
In 4
Out 1
(Enhanced only)
In 5
(Enhanced only)
In 6
PRE-out2 (R)
Out 2
(Enhanced only)
In 2
(Enhanced only)
In 3
(Enhanced only)
-4dB
In 1
Out 3
(Enhanced only)
7800
2
S in/output used for digital
2
S information for
processing and audio delay. It also matches the output signals
for the Audio Amplifier panel.
The sound-related electronics for FM24 are very straight
forward, and consists of a Micronas MSP3415G sound
processor, an active highpass and lowpass filter, and separate
Class-D amplifiers for woofers and tweeters.
7880
Digital Audio
Delay Line
T1
7812
I2C
I2S
SCART1-in
SCART2-in
AUDIO DSP
MSP3415
(Basic only)
Switch
Figure 9-15 Audio Path
the loudspeakers do not reproduce these low frequencies. This
feature is implemented in the MSP3415G.
Audio delay
To compensate for 'lip sync error' (the difference in time
between the aural and visual perceptions), two different audio
delays are selectable via the customer's menu (one for the
Receiver box and one for the Monitor).
This is done at the audio processor IC7812 via an I
an additional delay circuit (IC7880 - 7882).
One can select delays of 24 ms (I2S_DATA_IN1) and 40 ms
(I2S_DATA_IN2), or no delay.
In case of a delay, the AUDIO_L/R_IN is re-routed as
I2S_DATA_OUT to the audio delay circuit and, depending on
the selected delay, returned as I2S_DATA_IN1 or
I2S_DATA_IN2, resulting in AUDIO_L/R_OUT.
Anti-plop/Mute
In several cases, it is necessary to mute the sound output. This
muting is handled by the MSP sound processor, or by the
Receiver box in case of TV-mode.
•
In Monitor mode:
–
–
–
–
•
In TV mode:
–
–
–
–
T2
2* Differential
I2S
DACM-L
+4.9dB
DACM-R
+4.9dB
SC1-OUT
+3.0dB
During switch 'on/off' of the monitor.
During source change.
During video or sync loss, or
By a user action (A/V-mute or mute).
During switch 'on/off' of the Monitor/Receiver box.
During source change in the Receiver box.
During video or sync loss, or
By a user action (mute).
0388
Amplifier
7841
L-NEG
L-POS
7851
R-NEG
L-NEG
Audio Enable
CL 26532038_012.eps
280302
2
S bus and
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