IEI Technology iSignager LCD 26, User Manual, Page: 54 / 73

iSignager LCD Series
Page 42
B.2 Overview of Audio Formats
B.2.1 Dolby® Digital
Dolby® Digital, or AC-3, is the common version containing 6 total channels of sound, with
5 channels for normal-range speakers (right front, center, left front, right rear and left rear)
and one channel for the LFE, or subwoofer. The Dolby Digital format supports Mono and
Stereo usages as well.
B.2.2 MP3
MPEG-1 Audio Layer 3, more commonly referred to as MP3, is a popular digital audio
encoding and lossy compression format. MP3 is compression format. It provides a
representation of pulse-code modulation-encoded (PCM) audio data in a much smaller
size by discarding portions that are considered less important to human hearing.
B.2.3 AAC
AAC (Advanced Audio Coding) is one of the audio compression formats defined by the
MPEG-2 standard. AAC is a higher quality codec than the MP3, therefore requiring less
data for the same audio reproduction. As a result, an AAC file encoded at 96kbps bit rate
may actually sound better than an MP3 encoded at 128kbps bit rate.
B.2.4 WAV or WAVE
WAV (or WAVE), short for Waveform audio format, is a Microsoft® and IBM audio file
format standard for storing audio on PCs. It is a variant of the RIFF bitstream format
method for storing data in "chunks", and thus also close to the IFF and the AIFF format
used on Macintosh computers. WAV files store digital music data in a lossless format,
meaning the file is digitally identical to its source. However, the result is a very large,
uncompressed file.
B.2.5 WMA
WMA, or Windows Media Audio, is proprietary audio codec of Microsoft®. WMA offers
the same quality as MP3 for half the bit rate (i.e., half the file size). WMA is now
positioning itself as the main competitor to AAC (Advanced Audio Codec), MP3's
successor.