Description
This article is from the MPEG FAQ, by
Frank Gadegast phade@cs.tu-berlin.de with numerous contributions
by others.
17 Which Layer should I use for my application? (MPEG-Audio)
Good Question. Of course, it depends on all your requirements.
But as a first approach, you should consider the available
bitrate of your application as the Layers have been
designed to support certain areas of bitrates most
efficiently, i.e. with a minimum drop of sound quality.
Let us look a little closer at the strong domains of each
Layer.
Layer-1: Its ISO target bitrate is 192 kbps per audio
channel.
Layer-1 is a simplified version of Layer-2. It is most useful
for bitrates around the "high" bitrates around or above
192 kbps. A version of Layer-1 is used as "PASC" with the
DCC recorder.
Layer-2: Its ISO target bitrate is 128 kbps per audio
channel.
Layer-2 is identical with MUSICAM. It has been designed as
trade-off between sound quality per bitrate and encoder
complexity. It is most useful for bitrates around the
"medium" bitrates of 128 or even 96 kbps per audio
channel. The DAB (EU 147) proponents have decided to use
Layer-2 in the future Digital Audio Broadcasting network.
Layer-3: Its ISO target bitrate is 64 kbps per audio channel.
Layer-3 merges the best ideas of MUSICAM and ASPEC. It has
been designed for best performance at "low" bitrates
around 64 kbps or even below. The Layer-3 format specifies
a set of advanced features that all address one goal: to
preserve as much sound quality as possible even at rather
low bitrates. Today, Layer-3 is already in use in various
telecommunication networks (ISDN, satellite links, and so
on) and speech announcement systems.
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