What is AAC?
AAC
stands for either MPEG2 Advanced Audio Coding or MPEG4 Advanced
Audio Coding.
The MPEG2 audio-encoding standard of the format is not backward-compatible
with MPEG1 audio. MPEG2 AAC can produce better audio quality than
MP3 using less physical space for the files. MPEG4 AAC can produce
better quality and smaller files than MPEG2 AAC. AAC is the audio
file format used by Apple in their popular iTunes Music Store. Files
may appear on your system with the ".M4A" filename extension.
AAC is conceptually
similar to the ubiquitous MP3 format. it takes advantage of deficiencies
in human hearing to discard digital bits corresponding to sounds
unlikely to be heard. The human hearing system cannot hear quiet
sounds in the presence of loud sounds of a similar frequency; for
example, a voice conversation cannot be heard while a jumbo jet
flies low overhead. Known as auditory masking, this phenomenon allows
the discarding of data with minimal loss of fidelity.
AAC also like MP3,
AAC is a lossy algorithm, meaning the original digital audio cannot
be recreated from the compressed bits alone. In terms of audio fidelity,
however, there is no loss of data if the compressed audio is properly
encoded. AAC claims an advantage over MP3 in this regard: while
MP3 requires a bit rate of approximately 256 kilobits per second
(kbps) to achieve transparency, AAC can achieve the same quality
at 128 kbps. This allows AAC files to be roughly half the size of
MP3 files of the same quality, and one-tenth the size of CD digital
data.
AAC
provides several other advantages over MP3. It is capable of handling
much higher and lower frequencies of sound, provides up to 48 channels
of audio, and allows the creation of low-latency audio necessary
for two-way communication. For example, AAC can be used for compressing
telephone conversations on the fly, whereas using MP3 would introduce
delays in the audio. AAC also allows for Digital Rights Management,
or DRM, which can be used to control how the audio file is used.
An area where AAC excels is in low bit-rate compression. Audio books,
for example, don't have the dynamic range of music since they consist
of little more than spoken word. Potentially, this allows for much
higher levels of compression. Using MP3 at such levels of compression
produces scratchy, hissy compressed audio not unlike low-quality
cassette tape recordings. AAC was specifically designed to handle
such applications properly.
Unlike MP3, there is no public, free version of the encoding/decoding
algorithms of AAC. All AAC users must license the technology from
the VIA Licensing Corporation. AAC is most widely used in Apple
Computer's line of iPod portable music players and is part of the
next-generation DVD specifications.
AAC Software Review:
- ImTOO
MP3 WAV Converter is a MP3 WAV conversion utility
which can convert MP3 to WAV, convert WAV and OGG to MP3 file.
It's not only a MP3 WAV converter but supports converting video
or audio file format, such as convert WAV to MP3, convert MP3
to WAV and convert WMV, AVI, MPEG, ASF, WMA, AAC, M4A, MP4,
OGG to MP3 or WAV file.
- ImTOO
WMA MP3 Converter is a MP3 to WMA converter software
which can convert WMA to MP3, AAC to MP3 and MP3 to WMA. This
conversion tool is not only a WMA MP3 converter but supports
converting video or audio file format, such as convert WMA to
MP3, MP3 to WMA and WMV, AVI, MPEG, ASF, WAV, AAC, OGG, M4A,
MP4, AAC to MP3 and WMA.
- Xilisoft
Audio Converter - Perfect convert MP4 MP3 M4A WAV
WMA VQF APE OGG AAC FLAC Audio Converter, provides an easy and
completed way to convert between all of the popular audio formats,
such as MP3, WAV, WMA, MP4, M4A, MP2, VQF, APE, OGG, AAC and
FLAC.
- Xilisoft
MP3 WAV Converter is an excellent MP3 converter
with friendly interface and lots of useful features. The MP3
WAV converter can convert mp3 to wav, mp3 to ogg, it also can
convert wav to mp3, ogg to mp3, etc. The MP3 WAV converter supports
WAV, MP3, WMA, OGG, AAC, FLAC, APE, VQF etc.
- Xilisoft
WMA MP3 Converter is an excellent MP3 converter
with friendly interface and lots of useful features. The WMA
MP3 converter can convert WMA to MP3, AAC to MP3, it also can
convert MP3 to WMA, convert OGG to MP3, etc. The WMA MP3 converter
supports WAV, MP3, WMA, OGG, AAC, FLAC, APE, VQF etc.
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