Re: [LAD] new lossless/lossy audio compressor

Hello again. I discovered a disappointing, to me, bug in j2kaudio/libjasper today while I was
working on 32-bit audio support.

My previous holy-grail-looking lossless audio compression test results were incorrect. I was
passing rate=1 to the JasPer JPEG 2000 encoder, which was not performing lossless compression, but
slightly lossy compression. I actually do not know what it was doing because the behavior I was
getting is somewhat undocumented. I could not differentiate the quality by ear; everything sounded
perfect to me. I only discovered this when I had to do sample by sample checks for accuracy and I
found that they were very close, but not exactly the same. The results matched exactly when I left
rate= out of the encoder options entirely, but the resulting file size increased. I will post a
question to the jasper email list to find out what rate=1 should be doing and why it does not
match omitting the rate.

The new lossless results from my test song are:
la - 65.5%
ofr - 66.3%
ma - 66.9%
lpac - 69%
flac - 70.2%
shorten - 75.2%
j2kaudio - 76.6% (dead last)
bzip2 - 96.7%
gzip - 97.1%

Thank you again for all of your feedback and input. I apologize for getting anyone's hopes up and
for not performing a sample-by-sample check at the integer level sooner.

For now, I think I have proved and improved the concept, but I conclude that even though it
outperforms file compressors, other lossless and lossy audio compressors are superior for audio
data.

Updated tables and information:
http://geocities.com/hildstrom/projects/j2kaudio

Thanks. -Greg

Gregory Alan Hildstrom
Secure Systems Engineer - Trusted Computer Solutions
trustedcs.com
ghildstrom@email-addr-hidden
Software Engineer - Hildstrom Engineering
geocities.com/hildstrom
hildstrom@email-addr-hidden
Mobile:(210)413-6082
Fax:(210)599-0469
Office:(210)340-3151x117
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Received on Wed Aug 1 00:15:01 2007