SAA2500H View Datasheet(PDF) - Philips Electronics
Part Name
Description
Manufacturer
SAA2500H Datasheet PDF : 47 Pages
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Philips Semiconductors
MPEG Audio Source Decoder
Preliminary specification
SAA2500
SYMBOL
TMS
TDI
FSCLK384
FSCLKM
MCLK24
PIN
DESCRIPTION
40 boundary scan test mode select input
41 boundary scan test data input
42 sample rate clock frequency indication input
43 sample rate clock source selection for the master input
44 master clock frequency indication
TYPE
I
I
I
I
I
handbook, full pagewidth
handbook, full pagewidth
RESET 1
FSCLK 2
FSCLKIN 3
MCLK 4
VDD 5
GND 6
MCLKOUT 7
MCLKIN 8
X22OUT 9
X22IN 10
STOP 11
SAA2500
(QFP44)
33 TB
32 TI
31 TO
30 WS
29 SCK
28 GND
27 TA
26 SD
25 L3MODE
24 L3DATA
23 L3CLK
MGB490
Fig.2 Pin configuration.
FUNCTIONAL DESCRIPTION
Coding system
The perceptual audio encoding/decoding scheme defined
within the “ISO/IEC 11172-3 MPEG Standard” allows for a
high reduction in the amount of data needed for digital
audio whilst maintaining a high perceived sound quality.
The coding is based upon a psycho-acoustic model of the
human auditory system. The coding scheme exploits the
fact that the human ear does not perceive weak spectral
components that are in the proximity (both in time and
frequency) of loud components. This phenomenon is
called masking.
For layers I and II of ISO/MPEG the broadband audio
signal spectrum is split into 32 sub-bands of equal
bandwidth. For each sub-band signal a masking threshold
is calculated. The sub-band samples are then
re-quantized to such an accuracy that the spectral
distribution of the re-quantization noise does not exceed
the masking threshold. It is this reduction of representation
accuracy which yields the data reduction. The
re-quantized sub-band signals are multiplexed, together
with ancillary information regarding the actual
re-quantization, into a MPEG audio bitstream.
September 1994
5
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