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Comparisson of Audio Compression
I've
compiled a table containing the same audio sample compressed into
different bit rate using several common compression techniques. Namely
MP3, windows media audio, ogg vorbis, AAC and flac. My intention is that
you can use this to work out the lowest bit rate at which the audio
souds clear to you. this will depend on the equiptment you're using,
and your hearing. I firmly believe that if you can't her the difference
then there is no point wasting space.
Notation:
k
means kilo which is 1024. b means bit. B means Byte
Bandwidth
As
you can imagine this page is quite bandwidth intensive, for me as well
as you. I'd ask you to be sparing. That is to say if you've decided
that
MP3 at 192kbps sounds the same to you as the original file then there
is
probably no need to download all the higher bitrates too. Finally i
would ask that you try and only download the larger files once. Right
click 'Save As...' and save them to your desktop.
Details
of the sample and the various encoding techniques used can be found
below the table together with some
thoughts....
|
MP3 |
WMA |
AAC |
Ogg
Vorbis |
FLAC |
WAV |
| 32kbps |
150kB |
158kB |
151kB |
|
|
|
| 40kbps |
186kB |
|
187kB |
|
|
|
| 48kbps |
222kB |
235kB |
226kB |
220kB |
|
|
| 56kbps |
258kB |
|
260kB |
|
|
|
| 64kbps |
295kB |
305kB |
298kB |
297kB |
|
|
| 80kbps |
368kB |
379kB |
375kB |
370kB |
|
|
| 96kbps |
440kB |
453kB |
441kB |
437kB |
|
|
| 112kbps |
513kB |
|
510kB |
509kB |
|
|
| 128kbps |
585kB |
601kB |
589kB |
587kB |
|
|
| 160kbps |
731kB |
749kB |
734kB |
740kB |
|
|
| 192kbps |
876kB |
896kB |
888kB |
882kB |
|
|
| 224kbps |
1,021kB |
|
1,038kB |
1,013kB |
|
|
| 256kbps |
1,166kB |
|
1,185kB |
1,149kB |
|
|
| 320kbps |
1,457kB |
|
1,485kB |
1,146kB |
|
|
| 467kbps |
|
|
|
2,110kB |
|
|
| 968kbps |
|
|
|
|
4,384kB |
|
| 1.4Mbps |
|
|
|
|
|
6,389kB |
The Sample (also WAV
file):
The Sample contains three songs: Dido – My
Lover’s Gone, Daft Punk – Short
Circuit and R.E.M. – Everybody
Hurts the Tracks were ripped from cd using CDex 1.70 beta 2.
And joined using Audacity 1.2.4.
The sample is 37.086176 seconds long.
MP3
The MP3s were encoded using the Lame MP3 Encoder Version 1.32 engine
3.97 Beta 2 (MMX), constant bit rate (CBR), J-Stereo, quality factor 2
(high) this is my encoder of choice.
WMA
Microsoft's Windows Media Audio encoder
AAC
This is not a codec i know much about but many of you will be familiar
with it because it is iTunes' native format. the wav file was converted
using 7.6.0.29, AAC, CBR. I haven't included apple's lossless
format, simply because i do believe them if they say it's lossless. but
the conversion resulted in a file of 4,081kB coresponding to around
882kbps. notably better than FLAC.
Ogg Vorbis
Ogg Vorbis 20051117
The audio was encoded using the quality factor technique rather than
artificially specifying minimum maximum and nominal bit rates, as this
is recommended
for ogg vorbis. The quality factor (shown) was then adjusted so the
file size most closely matched the mp3. it is then compared to the
mp3’s bitrate. The last Ogg file is a quality factor of 10,
this is the maximum quality for an ogg file.
FLAC
The FLAC codec allows a compression level from 0 to 8. I encoded the
sample with all of these levels which resulted in files with bit rates
from 901kbps (level 8) to 968kbps (level 0). Since this represents a
variation of less than 10% i have only included the one file of
compression level 0.
Conclusion
When not really a conclusion so much as some thoughts.
It's immediately clear that at very low bitrates the MP3 codec does not
produce the clarity of WMA, AAC or Ogg Vorbis. This may lead you to
conclude
that the MP3 codec is inferior. However, the codec was not designed to
work at this level, and you would never use it so. to form a valid
comparison you need to simulate real world conditions and listen in
your usual way....
Nigel Coldwell 2008
LINKS
Nokia BB5 (3G)
6630, 6680 6681, N70 and N90 Unlocking : Nokia DCT 4
UnlockBing
My Brain training
puzzles site. Nokia
Firmware unbranding
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