Section 7 AUDIO CODING PRINCIPLES
108
80
60
40
20
0
dB
-60
0
50
100 150
0
50
100 150 200
t (in ms
Pre-
Simultaneous-
Post- Masking
Masking effects in the time domain. Masking occurs both
before and after the masking signal.
ISO/MPEG LAYER III
MPEG Layer III is the most powerful coding method available in the Zephyr, and we
particularly like it because it is perfectly matched to the bitrates available on ISDN BRI
lines.
It offers:
•
15 or 20kHz mono or stereo audio bandwidth.
•
Full- fidelity mono on a single 56/64kbps channel.
•
CD- quality stereo on a single ISDN Telco circuit.
•
Affordable, transparent, audio transmission for AM/FM radio or television audio.
After extensive testing by broadcasting organizations around the world under the
direction of the CCIR, it has been designated as the most powerful of the three audio
coding systems standardized in ISO/MPEG IS- 11172. It is specifically recommended for
56 and 64 kbps channels.
IMPORTANT!
Due to a perceptual coder’s reliance on precise principles of
human perception, audio to be coded should not be processed
with any non-linear dynamics-processing such as clipping,
multi-band compression or limiting. Wideband compression or
AGC is acceptable and may be desirable if a consistent level
cannot otherwise be achieved.
The same is true to audio which has been decoded after
passing through a perceptual coding cycle, but to much lesser
degree.
For more information contact Telos Systems customer support
for a copy of a paper delivered at the AES by Frank Foti on
this topic.
Summary of Contents for Zephyr
Page 13: ...Table of Contents 13 SECTION 1 QUICK RESULTS ...
Page 26: ...Section 2 INTRODUCTION 26 This page intentially left blank ...
Page 27: ...Section 2 INTRODUCTION 27 SECTION 2 INTRODUCTION ...
Page 38: ...Section 2 INTRODUCTION 38 This page intentionally left blank ...
Page 39: ...39 SECTION 3 ZEPHYR AT A GLANCE ...
Page 52: ...Section 4 INSTALLATION BASIC OPERATION 52 This page intentionally left blank ...
Page 53: ...Section 4 INSTALLATION BASIC OP 53 SECTION 4 INSTALLATION BASIC OPERATION ...
Page 84: ...Section 4 INSTALLATION BASIC OPERATION 84 ...
Page 85: ...Section 5 ISDN 85 SECTION 5 ISDN ...
Page 105: ...Section 6 NON ISDN NETWORKS 105 SECTION 7 AUDIO CODING ...
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Page 119: ...Section 8 DETAILED MENU REFERENCE 119 SECTION 8 DETAILED MENU REFERENCE ...
Page 157: ...Section 9 REMOTE CONTROL 157 SECTION 9 REMOTE CONTROL ...
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Page 177: ...Section 10 ADVANCED PROBLEM SOLVING 177 SECTION 10 ADVANCED PROBLEM SOLVING ...
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Page 197: ...Section 11 TECHNICAL INFORMATION 197 SECTION 11 DETAILED TECHNICAL INFORMATION ...
Page 219: ...Section 12 SCHEMATICS 219 SECTION 12 SCHEMATICS ...
Page 221: ...Section 13 MANUFACTURER S DATA SHEETS 221 SECTION 13 MANUFACTURER S DATA SHEETS ...
Page 223: ...Section 14 SPECIFICATIONS WARRANTY 223 SECTION 14 SPECIFICATIONS AND WARRANTY ...
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Page 229: ...Section 15 APPENDICES 229 SECTION 15 APPENDICES ...