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APPENDIX
Audio information
Audio and video synchronization (lip sync)
Lip sync, an abbreviation for lip synchronization, is a technical term that
involves both a problem, and the capability of maintaining audio and video
signals synchronized during post-production and transmission.
Whereas the audio and video latency requires complex end-user
adjustment, HDMI version 1.3 incorporates an automatic audio and video
syncing capability that allows devices to perform this synchronization
automatically and accurately without user interaction.
Dolby Digital
Dolby Digital is a digital surround sound system that gives you completely
independent multi-channel audio. With 3 front channels (front L/R and
center), and 2 surround stereo channels, Dolby Digital provides 5 full-range
audio channels. With an additional channel especially for bass effects,
referred to as LFE (Low-Frequency Effect), the system has a total of 5.1-
channels (LFE is counted as 0.1 channel). By using 2-channel stereo for the
surround speakers, more accurate moving sound effects and surround sound
environments are possible than with Dolby Surround. The wide dynamic
range from maximum to minimum volumes that are reproduced by the 5
full-range channels, and the precise sound orientation generated using
digital sound processing provides listeners with unprecedented excitement
and realism. With this unit, any sound environment from monaural up to a
5.1-channel configuration can be freely selected for your enjoyment.
Dolby Pro Logic II
Dolby Pro Logic II is an improved technique used to decode vast numbers
of existing Dolby Surround sources. This new technology enables a discrete
5-channel playback with 2 front left and right channels, 1 center channel,
and 2 surround left and right channels, instead of only 1 surround channel
for conventional Pro Logic technology. There are three modes available:
“Music mode” for music sources, “Movie mode” for movie sources, and
“Game mode” for game sources.
Dolby Surround
Dolby Surround uses a 4-channel analog recording system to reproduce
realistic and dynamic sound effects: 2 front left and right channels (stereo),
a center channel for dialog (monaural), and a surround channel for special
sound effects (monaural). The surround channel reproduces sound within a
narrow frequency range. Dolby Surround is widely used with nearly all
video tapes and laser discs, as well as in many TV and cable broadcasts.
The Dolby Pro Logic decoder built into this unit employs a digital signal
processing system that automatically stabilizes the volume on each channel
to enhance moving sound effects and directionality.
DTS Digital Surround
DTS Digital Surround was developed to replace the analog soundtracks of
movies with a 5.1-channel digital sound track, and is now rapidly gaining
popularity in movie theaters around the world. DTS, Inc. has developed a
home theater system so that you can enjoy the depth of sound and natural
spatial representation of DTS Digital Surround in your home. This system
produces practically distortion-free 5.1-channel sound (technically, left,
right and center channels, 2 surround channels, plus an LFE 0.1 channel as
a subwoofer, for a total of 5.1-channels).
DSD
Direct Stream Digital (DSD) technology stores audio signals on digital
storage media, such as Super Audio CDs. Using DSD, signals are stored as
single bit values at a high-frequency sampling rate of 2.8224 MHz, while
noise shaping and oversampling are used to reduce distortion, a common
occurrence with very high quantization of audio signals. Due to the high
sampling rate, better audio quality can be achieved than that offered by the
PCM format used for normal audio CDs. The frequency is equal to or
higher than 100 kHz, with a dynamic range of 120 dB. This unit can
transmit or receive DSD signals via the HDMI jack.
LFE 0.1 channel
This channel reproduces low-frequency bass signals, and has a frequency
range from 20 Hz to 120 Hz. This channel is counted as 0.1, because it only
enforces a low-frequency range compared to the full-range reproduced by
the other 5 channels in Dolby Digital or DTS 5.1-channel systems.
PCM (Linear PCM)
Linear PCM is a signal format under which an analog audio signal is
digitized, recorded and transmitted without using any compression. This is
used as a method of recording BD, DVD or CD audio. The PCM system
uses a technique for sampling the size of the analog signal per very small
unit of time. Standing for “Pulse Code Modulation,” the analog signal is
encoded as pulses and then modulated for recording.
Sampling frequency and number of quantized bits
When digitizing an analog audio signal, the number of times the signal is
sampled per second is called the sampling frequency, while the degree of
accuracy when converting the sound level into a numeric value is called the
number of quantized bits. The range of rates that can be played back is
determined based on the sampling rate, whereas the dynamic range
representing the sound level difference is determined by the number of
quantized bits. In principle, the higher the sampling frequency, the wider
the range of frequencies that can be played back, and the higher the number
of quantized bits, the more accurately the sound level can be reproduced.
Glossary
