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The MPEG Layer 3 Compression Standard
Over the last few years, new data compression technologies have made it possible to compress
digital audio and video by a factor 10 or more. One of the most popular compression standards is the MPEG standard,
which compresses video and audio data. MPEG Layer 3 is, also known as MP3, is the MPEG standard currently used for
compressing audio data and is by far the most popular format for compressed music and other audio files. The MP3
compression scheme is fairly complex and includes a number of compression algorithms, but essentially it removes
all parts of the sounds that are less likely to be percepted by human ears. For example, if there's a loud drum
you probably won't hear a person whispering in the background, and consequently the whispering person can be removed
without much difference in percepted quality. The result is similar to an oil painting where most of the pencil
strokes are used to paint the foreground objects that are likely to catch your attention.
MP3 Audio streams and buffering
Like most
popular compression technologies, MP3 is fairly
complicated in terms of the number of
calculations needed to turn your MP3 files back
into music. Unlike other many other compression
algorithms though, you usually expect to hear
the result as soon as you select a new file. To
make this possible, mp3 decoders uses a
technique known as streaming, which means that
the CPU will decode the mp3 file on the fly.
Since modern computers can usually decode mp3
audio streams much faster than you can listen to
them, this is rarely a problem. To ensure that
the song will continue to play even when mp3
software is interrupted for a brief period time
(This happens many times per second in a
multitasking OS like Windows.), the mp3 decoder
usually works a little faster than the playback
speed and buffers the audio data that will be
played within the next few seconds. Although
this buffer is long enough to remove most gaps
and jumps, it is still a possible in Windows for
some other program to use the CPU for more than
a few seconds. For example, when you start a
large and complex program like Word or plays a
game there might not be enough CPU time left for
the MP3 decoder to keep the audio buffer filled,
resulting in a buffer underrun error. This often
causes the MP3 player to skip a few kilobytes of
audio data, or to stop playing for a few
milliseconds. The result can be some very
annoying gaps and jump or loud clicks in the
music (If you skip a part of a digitally sampled
continuous sound wave, you will get a discrete
jump which sounds like a loud, high frequent
clicking noise to human ears)
Avoiding gaps and noises
Most operating
systems that support multitasking, also assigns
different priorities to different tasks, so that
you can tell the system which tasks are more
important. Windows is no exception and, even
though many users are not aware of this, you can
assign different priorities to different
processes in Windows 98 as well as Windows XP
and Windows 2000 if you have the right tools.
WinTasks 4 will not only help you change the
priority of any process, but it will also give
you valuable information on system processes and
other processes to help you decide what to
modify without crashing the system. This
information can also be very useful when
tracking down a specific problem. Sometimes you
may also have to terminate some unnecessary
processes to free up other resources like
memory, but assigning the right priorities will
usually be sufficient. If you are running
Windows NT, 2000 or XP, WinTasks will give you
detailed logs on the CPU and memory usage for
each process during the last 24 hours. This
information is often critical when you want to
optimize your system to run smoothly for longer
periods of time.
Things to consider when you are having
problems playing mp3 files:
1. If the computer has been running for a very long time, reboot
it to make sure the system is completely stable.
2. Assign a higher priority to the MP3 player process, and if
there are other processes running at a high priority that
requires a lot of CPU time, lower their priorities to normal. I
recommend using WinTasks to help you decide exactly which
processes to modify without causing stability problems. Since
WinTasks assigns user friendly names to most processes, it will
also be a lot easier to actually find the process you are
locking for.
3. Terminate all programs that aren't absolutely necessary. You
will be surprised by the number of processes running in the
backgroung on most systems, consuming valuable resources. Try
creating a WinTasks preset so that you won't have to repeat this
step every time you reboot. Or if you have
WinTasks 5 Professional you could use the WinTasks autostart
feature to permanently remove any unwanted processes.
4. Make sure you have the latest drivers installed for your
sound card. Drivers can usually be found at the manufacturers
web site.
5. Defrag your hard drive to improve access times, or if you are
playing MP3s from a CD, make sure you have the latest drivers
and the correct settings for your CD drive. (To find out how
WinTasks can improve defragmentation speeds,
click here.)
Of course, don't forget to get a good, fast MP3 player that is
optimized for the latest processors.
Recommended Software :
Acoustica MP3 CD Burner
Written by Emil Malmberg, Senior Software Developer for LIUtilities
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