By Alvin Foster & Stephen Owades
Deciding on the right compression
format to store and play back CDs led to a format investigation.
The search was limited to the most popular lossless formats
lossless. The goal: to adopt a 'transparent' (no coloration)
application to store and play back CDs on the hard drive of
my new media computer.
To insure complete transparency,
Steve Owades and I decided to conduct the ultimate test, a bit-by-bit
The CD source file chosen for the
ultimate test was a three minute and fifty-two second rap song.
The music was selected because it has an extremely limited dynamic
range and, unfortunately, represents today's most dominant,
popular recording technique. MediaMonkey
was used for all the hard drive recording tests.
The CD source file was first compressed
and stored in FLAC and WMA lossless, and also stored as an uncompressed
file. The second step uncompressed the FLAC and WMA files and
converted them into the WAV format. After the conversion, the
three WAV files were carefully trimmed to the same starting
and ending points, and Microsoft's
File Compare was used to determine if they were the same.
This program evaluates two files bit-by-bit to determine if
they are identical; i.e., a perfect match. Happily, both FLAC
and WMA lossless passed. The compressed and then uncompressed
files were no different from the original CD music file.
TABLE OF RESULTS
FLAC offers variable compression
rates. We selected three: Hi, Medium, and Low. The File Type
describes the type of file tested. The File Size in kilobytes
is the resulting size after compression. The Storage Speed in
Seconds is the amount of time required for the music to be stored
onto the computer's hard drive (including reading from the original
CD, compression, and writing to disc). The Playback CPU Usage
column gives an indication of how much the central processing
unit was utilized to return the compressed files to a playable
format. The numbers were obtained from the Windows Task Manager.
The CPU usage differences on playback were too small to cause
a modern computer to 'slow' down, or to make one prefer either
compression scheme. The original, uncompressed WAV file results
show the track's original size, and the copying speed without
|FLAC Hi Compression
|FLAC Medium Compression
|FLAC Low Compression
|WAVE (PCM Audio)
Both FLAC and WMA lossless use variable
rate compression. The compression speed and stored file size
differ with the amount of complexity and 'silence' in the music.
WMA is a proprietary file format and FLAC is 'open source';
i.e., the source code is available free to users. All the compression
results noted above will fluctuate with the speed of the computer
and the CD reader. For example, classical music is typically
more complex than a hard-hitting rap song, and an ultra-fast
CPU will compress files more rapidly.
The differences between the FLAC
and WMA formats are too small to be of much significance. Both
will save around 30% compared with the size of uncompressed
files. The results of the bit-by-bit comparison to the original
file indicate that both formats offer an inaudible difference
and vary insignificantly in playback CPU usage. FLAC's open
source availability is important to me, so it is my choice.