Lossless Compression of Audio

• Tests of Shorten, MUSICompress/WaveZIP, Waveform Archiver, Pegasus SPS (ELS-Ultra), Sonarc and LTAC / LPAC lossless audio compression software.

Links to material concerning the lossless compression (data reduction) of digital audio signals, including some other programs (such as RAR) which I did not test as fully as those listed above, because initial tests indicated their compression ratios were not as good.

My particular interest is in delivery of music via the Net - with compression which does not affect the sound quality at all.  I am primarily interested in compression ratios, not speed of the programs.  I think this is the first web site devoted to listing all known lossless audio compression algorithms and software - please email your suggestions and I will try to keep it up-to-date.

Copyright Robin Whittle 1998 rw@firstpr.com.au  Originally written 8 December 1998  (Links added to on various dates.  Latest update 2 November 2000.  )

Back to the First Principles main page - for material on telecommunications, music marketing via Internet delivery, stick insects . . .

To the /audiocomp/ directory, which leads to material on lossy audio compression, in particular, comparing AAC, MP3 and TwinVQ.
 
 

Note:  I will soon be conducting a new series of tests of the updated versions of the programs tested previously, and of several new programs as listed below. I will try to keep links to lossless sites up to date, since I don't know of any other web site which attempts to maintain a comprehensive list of lossless audio links.

Tests: what can be achieved with lossless compression?

On 2 December 1998, I ran some tests to see what compression ratios could be achieved with Shorten, and MUSICompress (WaveZip), Wave Archiver and Pegasus SPS.  In the days which followed I also tested Sonarc and LPAC (and it's predecessor LTAC).  See the links section below for details on where to obtain this software and which versions I tested. My main interest is in the maximum attainable compression - rather than encode speed. Some of the compressors were very fast - faster than the music's playing time - and not much slower on a 180 MHz K6 than the limitations imposed by reading and writing the large files involved.  Generally the higher compression programs ran slower.
 
 

I have not tested the speed of these programs! A number of people - including the authors of the programs - are interested in this.  Its not my primary concern at present which of these is the fastest.  Generally the lower compression programs were faster - for instance WaveZIP was damn fast.  Since there is just a few percentage points between the various compression ratios, and a larger variation in compression speed, many users will select a program based on its speed and ease of use rather than it providing the best attainable compression ratio.  (A friend who does a lot of hard-disk recording is very happy with WinZip.) I can't anticipate what someone else will find easiest to use.  For some it will be a GUI program for X Windows (Unix) or MS Windows.  For others a command-line driven program is ideal since it can be easily driven from a script or .bat file.  Compression size, for the music I have chosen, I can reliably report - user interface and compression speed, I can't.  The actual speed of the program depends on many things, including: CPU type and clock speed.  I could measure compression times on my K6 machine, but the same programs could run at quite different speeds, relative to each other, on a Pentium II - due to their differing use of floating point instructions and interaction with the cache. (None of these programs seem to use MMX instructions.)  Motherboad, cache and RAM.  Hard disk and hard disk controller.  Other programs running on the computer.  Operating system.  Nature of the file to be compressed.  All these programs are available for free, or on a trial basis, so please test the speeds on your system with your music.  If anyone wants to do a proper speed test, I could include it here - but be sure to specify all the above factors and give details of the music you are using.  I nominate Kylie Minogue's "I should be so lucky" as a severe and an easy to find test of a lossless algorithm.

All tracks were .WAV files read directly from audio CD and are either electronic productions or microphone based recordings - except for my Spare Luxury piece which was generated entirely with software.  The music constituted 775 Megabytes of data - 73 minutes of music.  The tabulation of these figures has involved quite a lot of manual and pocket calculator work, so it is possible that there are some errors.

My original test of Shorten was without options, but Tony Robinson pointed out that I neglected to use the "-p 8" option to get the best compression from Shorten.  I tried this, and while some resulting files were shorter, others were longer and in total the files were longer.  I tried again with "-p 3" and the sum total of all file sizes was still bigger than without options.  The results shown are from my initial tests with no options, but I suggest you experiment with the -p option to find which suits your music best.

WaveZIP had no options regarding compression speed.  I tested Waveform Archiver (WaveArc) at its two highest compression settings, since the highest was very slow.  More on Waveform Archiver times below.  As noted below, I used the highest compression setting for Pegasus-SPS.  With Sonarc I used the "-X" option.

When I tested it, on 4 December, LPAC was a new program from Tilman Liebchen, still at the beta state - a replacement for LTAC which I had begun testing.  I used LPAC with the "JS / AP 30 / AQ 7" settings which Tilman advised me were best for high compression.  This is joint stereo, and provided higher compression than LTAC in joint stereo mode for those files I tested before I he told me of LPAC, except for the software synthesis track for which LTAC produced a remarkably good compression to 36.50 %.
 

Audio files contain a certain amount of information - "entropy" - so they cannot be compressed losslessly to any size smaller than that.  So it is not realistic to expect an ever-increasing improvement in lossless compression algorithm performance.  The performance can only approach more closely whatever the basic entropy of the file is.  No-one quite knows what that entropy is of course . . . I think that would require understanding the datastream in a way which is exactly in tune with it's true nature.  For instance a .jpg image of handwriting would appear to contain a lot of data, unless you could see and recognise the handwriting and record its characters in a suitably compressed format.  The true nature of sound varies with its source, physical environment and recording method, and a lossless compression program cannot adapt itself entirely to the "true" nature of the sound in each piece of music.  Therefore it is not surprising that different algorithms work best on different kinds of music.

* Prior to 22 March 2000, I had this figure as 1.845 which must have been a clerical error on my part from working things out with a calculator and on paper.  Thanks to Lin Xiao for pointing this out!
 

The pattern of compressed file sizes is:

• MUSICompress / WaveZIP files were the largest in each case.
• The next largest files were generally from Shorten or Sonarc.
• The runner up in compression ratio for each file was either Waveform Archiver,  Pegasus-SPS or LPAC.
• 7 of the 11 shortest files were from Wave Archiver at compression level 5 (which is too slow for many applications). 3 of the shortest were from the beta version of LPAC and one was from its predecessor, LTAC.

There is a factor of two difference between resultant file sizes between the easiest and hardest cases - Hildegard von Bingen and Kylie Minogue!  So the "average final file size" shown above is entirely dependent on the choice of music for this test.  As it happens, I like both Hildergard and Kylie - and Bach, techno and Indian classical music - so it is a realistic mix for me.  Death Metal buffs will probably find their music harder to compress than Kylie.

One experiment I tried was filtering the inaudible frequencies from a file.  I took the Kylie track - which according to graphic frequency analysis had high frequencies ending at about 20.5 kHz - and filtered it with an 18 kHz low-pass 20 order filter.  Visibly, this made the limit of high frequencies at 18.5 kHz.  Then I compressed the resulting .WAV file with Waveform Archiver at compression levels 4 and 5.  The results are as follows:
 
 

File sizes as % of original --> Compression ratio	WavArc,  comp. level 4	WavArc,  comp. level 5	Notes
Pop - Kylie Minogue, I Should be so Lucky (35.9)	71.38% 1.401:1	70.41% 1.420:1	Level 5 gives 1.36% improvement over level 4.
As above, but frequencies above 18 kHz removed	71.11% 1.406:1	69.00% 1.449:1	Filtering makes 2% improvement on level 5 results, but only 0.36% improvement on level 4 results.

I tried using WinZip to compress an output file of each algorithm.  The Shorten file could be compressed to 0.9999746 of its original size, and the MUSICompress/WaveZIP file could be compressed to 0.9890647 of its original size. WinZip could not compress the Wave Archiver, Pegasus-SPS, Sonarc, LTAC or LTAC files which I tried.
 

While there is a 2:1 range in the final file percentages attainable in the range of music I chose, the average difference between the file sizes, for each file between the worst and best compressor, was 1.17:1.  So it seems that all algorithms are doing a reasonable job of reaching towards the fundamental information content of each file.

Waveform Archiver (v1.1) has a compression level parameter, from 0 to 5, with a default of 1.  At level 1, the compression was fast - probably limited by disk access speed.  The file sizes were rarely larger than those of Shorten, and sometimes a lot smaller.  At level 5, the program descends into deep thought!  On my K6 180 MHz machine it took 6.5 hours to compress the 775 Megabytes of music at compression level 5 whereas it took 34 minutes at level 4.  The resulting total file sizes were 49.098% and 51.322% respectively.  (Note that these figures the total size of all compressed files.  These differ from the average file size, because some pieces of music in my test selection which were easier to compress were much longer.)

This table shows Waveform Archiver's encode times and resultant file sizes for the compression levels 1 to 5, using the ElBeano trance techno track.
 

Compression level	Time, seconds	File size
1	52	67.915%
2	74	67.736%
3	78	67.093%
4	98	66.949%
5	868	66.621%

Remember that the results depicted here are entirely dependent on my choice of music.  All these programs are available freely - on a trial or unrestricted basis - so please experiment with them yourself.  The programmers may improve their software after I write this review, so please check the current versions with those that I used, as noted below.

At the time of writing - 5 December 1998 - there is a new version 2.0 of Waveform Archiver in the works, and LPAC is moving beyond the beta stage.  Be sure to check the developer's site for the latest information.

Thanks to the programmers for tackling this field of lossless audio compression and for making their software available!

Al Wegener: MUSICompress.Tony Robinson: Shorten.Dennis Lee: Waveform Archiver.The Pegasus team and Krishna Software : Pegasus-SPS.Richard P. Sprague: Sonarc.Tilman Liebchen: LTAC and LPAC.

Thanks also to Mat Hans for his thesis: Optimisation of Audio for Internet Transmission.

Links

Here is a set of links to lossless audio compression sites.  On 1 Dec 1998 AltaVista found about 488 pages in response to the boolean query string:

lossless near (sound or audio) and (compression or "data reduction")

To perform this search yourself, click here.

Links specific to lossless audio compression

Shorten

Tony Robinson's Shorten is a program for lossless and near-lossless audio compression. http://www.softsound.com/Shorten.html  The Windows (95/98 and 3.1) GUI versions can be purchased for USD$68.95, but the source code and the executables for Linux, MS-DOS and command-line under Windows are available for free, subject to certain licensing conditions.  Demo copies of the Windows GUI programs are free too. Technical background to the program is at: http://svr-www.eng.cam.ac.uk/~ajr/GroupPubs/Robinson94-tr156/index.html  The help text for the command-line Windows version I used for these tests is here.  I tested version 2.3.
 

MUSICompress

Soundspace Audio of Sunnyvale, California has a lossless audio compression MUSICompress algorithm: http://members.aol.com/_ht_a/sndspace/index.html .   The information sheet at: http://members.aol.com/sndspace/download/musi_txt.txt indicates it is capable of reducing rock recordings to between 60 and 70% of their original size. A highly informative paper from the developer, Al Wegener, is available in Word 6 format from the Soundspace site.  MUSICompress is written in ANSI C using integer math only.  It has been ported to at least two DSPs and is used in the WaveZIP program (see below). According to Al Wegener, like other commercial lossless audio compression algorithms, MUSICompress uses a predictor to approximate the audio signal - encoding the prediction data in the output stream - and then computes a set of difference values between the prediction and the actual signal.  These difference values are relatively small integers (in general) and these are compressed using Huffman coding and sent to the output stream.  The compress and decompress functions can apparently be implemented in hardware with 4,700 gates and 20,500 bits of RAM (compress) and 3,800 gates and 1,500 bits of RAM (decompress) - which sounds pretty snappy to me.
 

WaveZIP

WaveZIP is a Windows program for lossless compression of audio files. http://www.gadgetlabs.com/wavezip.htm   It uses the MUSICompress algorithm mentioned above.  Cost is USD$49.95 and the program is available for a 15 day free trial.  With the trial version I tested, the "About WaveZIP" help window reports: "v1.15T".
 

Waveform Archiver

Dennis Lee's Waveform Archiver http://www.ecf.utoronto.ca/~denlee/wavarc.htm is a freeware command-line program to run under MS-DOS or in a Windows command line mode.  It can store multiple .WAV files in a single archive.  No source code is available, and there is no mention of what algorithms are used.  This program is made available on a low-key basis - but its performance in "compression level 5" mode significantly exceeds the alternatives that I am aware of.  When compressing, I found that the report it gives on screen about the percentage file size is sometimes completely wrong.  I tested version 1.1 of 1 August 1997.

Dennis told me (4 December 1998) that he has done a lot of work on version 2.0 of Waveform Archiver - but is not sure when it will be finished:

Shortly before completing WA v2.0 I became involved with another project full-time, and haven't been able to work on WA since.  WA v2.0 has some significant improvements including: 1) Faster at all compression settings. 2) -c6 codec (slightly more optimal than v1.1's -c5). 3) A new -c5 that's much faster (about half the speed of -c4).    This new codec is both backward and forward compatible with v1.1's -c5. 4) Lossless compression for non-audio files (provided by zlib). 5) Several bug fixes including the incorrect compression status on     large files. I hope to continue work on WA when I find the time.

 

Pegasus SPS

Krishna Software Inc. has a lossless audio compression program for Windows: http://www.pegasusimaging.com/sound.html .  A 10 day trial version is available for free and the full program (which supports batch compression) can be purchased for USD$39.  The compression algorithms come from Krishna Software: http://www.krishnasoft.com .  From the introduction:
 
Thank you for taking interest in the Sound Processing Software (SPS).  This software provides a very easy way to edit, record, compress, and play digitized audio files.  There is no limit to file size since all editing, recording, compressing, and playing is done directly to/from the hard disk.  The algorithms are also very efficiently done via optimized assembly language coding.

This software was gradually developed over the past few years to support multimedia projects being developed by Krishna Software Inc.  Thus, it is well tested and its results are already being used in some of the multimedia software available.


Pegasus-SPS provides four lossless compression modes and has the ability to truncate a specified number of bits for lossy compression.  I used the default and highest performance "ELS-Ultra" algorithm for my tests.  This was reasonably fast and produced results a fraction of a percent better than the next two best performing algorithms. When the compression function is working, this program seems to use virtually all the CPU cycles - at least under Windows 98 - so don't plan on doing much else with your computer!

A software developer kit is also available - which I assume means source code or a DLL which can be linked into other programs. Some information on ELS - Entropy Logarithmic Scale - encoding is at: http://www.pegasusimaging.com/imagetech_els.htm this leads to a .PDF file which has a scanned version of a 47 page 1996 paper explaining the algorithm: "A Rapid Entropy-Coding Algorithm" by Wm. Douglas Withers.

I tested version 1.00 of Pegasus-SPS.
 

Sonarc

A MSDOS x86 shareware program called Sonarc specialises in compression of audio signals.  There is no web site for it, as far as I can tell, and it has not been developed since 1994.  The author is Richard P. Sprague. His email address was "76635.652@compuserve.com" but in December 1998, this address was no longer valid. There is an entry for it in the speech compression FAQ http://www.itl.atr.co.jp/comp.speech/ at: http://www.itl.atr.co.jp/comp.speech/Section3/Software/sonarc.html . Sonarc is also listed in Jeff Gilchrist's magnificent MS-DOS/Windows "Archive Comparison Test" site http://web.act.by.net/~act/ at: http://web.act.by.net/~act/act-indx.html which gives an FTP site for the program:     ftp://ftp.elf.stuba.sk/pub/pc/pack/snrc21i.zip .  This is the program I tested: version 2.1i.  The programs are MS-DOS executables, dated 27 June 1994.  The documentation file, with the shareware arrangements and author's contact details is here: sonarc.txt .
 
 

LTAC and LPAC

Tilman Liebchen has a program specifically for lossless compression of audio: LTAC.        http://www-ft.ee.tu-berlin.de/~liebchen/ltac.html It is available for Windows, MS-DOS and Solaris.  As of 4 December 1998, he is now working on a replacement: LPAC which is at the beta stage for Windows: http://www-ft.ee.tu-berlin.de/~liebchen/lpac.html

There is an excellent looking paper (a Gzipped PostScript file) : "Lossless Transform Coding of Audio Signals" by Tilman Liebchen, Marcus Purat and Peter Noll.

On 4 December 1998, Tilman wrote to me about LPAC:

Soon there will also be an LPAC archiver for the UNIX world.  LPAC's file format is designed to be compatible (i.e. really  lossless) across different platforms and processors, because  the decoder only has to perform integer operations.
Apparently reliance on floating point can lead to slightly different results depending on the CPU, and those results could lead to differing rounding to integers - and so to different decoding of a file depending on the CPU.
 

Mat Hans' thesis

Mat Hans  http://users.ece.gatech.edu/~hans/ has written a magnificent PhD thesis on lossless audio compression.  It is in PDF format and is available zipped from his web site. (Actually, PDF is highly compressed - its generally better not to compress them with another algorithm.)  The thesis looks at both lossy and lossless algorithms.  In the lossless area, Hans tests and explores the inner workings of all but one of of the algorithms I have tested.
 
 

Smacker

A program and software development kit for games, called "Smacker" http://www.smacker.com/smkmain.htm does lossless audio compression.  A demo program is available for Windows.  I was told about this after I did these tests - perhaps I will test it in the future.
 
 

DAKX

(Added 6 June 1999.  Thanks to Alexandre Enkerli <aenkerli@indiana.edu> for alerting me to this.)  A new algorithm suitable for lossless or lossy compression of audio and other similar signals has been developed by DAKX in North Carolina: http://www.dakx.com The algorithm is patented in the US: http://www.patents.ibm.com/details?patent_number=5825830 . My impression is that it focuses on the most efficient way of storing the differences between one sample and another.  This largely concerns setting a bit-length to hold each diff value in the output stream, with snappy ways of increasing or decreasing that bit-length.  There is a Macintosh executable for audio files.  I don't have a Mac, so I won't be testing it.

At present, my enthusiasm for improving lossless compression algorithms is low.  No-doubt improvements can be made, but they are likely to be no more than 10 to 20% at most reduction in file size.  With bandwidth and storage cost-effectiveness perhaps doubling each year, such progress would bring the future of lossless electronic music delivery forward by only a few months.
 

DVD-AUDIO and Meridian Lossless Packing (MLP)

(Added 9 June 1999.)  I have not been following this at all, due to shortage of time, my belief that there's nothing wrong with 44.1 kHz 16 bit digital audio when it is properly done, and my interest in binaural sound, rather than multi-channel surround sound.

Click here to search Alta Vista Advanced text mode ( http://www.altavista.com/cgi-bin/query?pg=aq&what=web&text=yes ) for material on "meridian lossless packing".
 

• Meridian's site: http://www.meridian.co.uk/m_news.htm .
• Some news about DVD-Audio from Eliott James:  http://eliottjames.com/dvd_audio_news.htm .
• Frequently Asked Questions about Surround Sound: http://www.surroundassociates.com/fqmain.html . More than 12 hours of 44.1 kHz 16 bit stereo with MLP will apparently be possible with DVD-A.  It is extraordinary that there are still plans to add watermarking noise to material released on this potentially impeccable format!
• Dolby's Frequently Asked Questions about Dolby Digital is one of the files available at: http://www.dolby.com/tech/ .

 

 
 
 

 

Note! This is an archival page from 1998, with a few updates. For the current version of this page, click here: index.html


 
 

David Bryant's WavPack 3.0

David Bryant <david@bryant.org> has released version 3.0 of this MSDOS program.  WavPack is freely available, without source code but with a good explanation of the compression algorithm.  It is intended as a fast compressor with good compression ratios for .wav files.  Compression and decompression rates of 8 times faster than audio are achieved on a Pentium 300 MHz machine. The algorithm makes use of the typical correlation which exists between left and right channels in a stereo file.  Two additional features are lossless compression of any file, with high compression for those containing audio (such as CD-R image files) and selectably lossy compression.

The program is available from    ftp://syv.com/david/wavpack.zip  .

David writes: "WAVPACK is the fastest lossless audio compressor I have tested, and this newest version achieves significantly improved compression without any reduction is speed.  However, I have added a "fast" mode for those cases where speed is paramount.  The cost is a couple percent less compression in the lossless mode and a couple decibels more noise in the lossy mode."
 
 

AudioZip from Centre for Signal Processing, Nanyang Technological University, Singapore

(Added 22 March 2000)  http://www.csp.ntu.edu.sg:8000/MMS/MMCProjects.htm .   Lin Xiao (Dr) <EXLIN@ntu.edu.sg> contacted me about their AudioZip program.  This is a Windows executable (no source) lossless compression program which apparently compares favourably with Shorten, WA, LPAC, LTAC.  He wrote, in part:
 
We haven't done the optimization on the speed, but put more
focus on the compress ratio.  If we are among the best in the
world(compress ratio), we will do the programming nicely and
make it much faster.  Inside this package, we just encode the
stereo signal separately that leaves much room for further
improvement on stereo signal.  I actually have done some
comparison with WA, LPAC, LTAC and find that we are the same
good, if not better.

. . .

Our algorithm is LPC based with Rice code.
 
 
 

Lin Xiao pointed out an error in my table of results: the compression ratio for WaveArc level 4 should have been 1.854 instead of 1.845.  Thanks!
 
 

Monkey - from Matthew T. Ashland

(Added 24 April 2000) A new lossless compressor for Windows is designed to play back using the ubiquitous WinAmp program, which normally plays MP3 files.  http://www.monkeysaudio.com/ . It is optimised for low CPU load when compressing and playing back and also supports "tagging", which I understand is the embedding of text and other information into the compressed file.  This is not an open-source program, but the author is tempted . . .  There is also a discussion forum on Monkey (AKA MAC) and lossless audio compression.

Sites of general interest regarding audio compression

• The FAQ for Usenet newsgroup comp.compression is at: http://www.cis.ohio-state.edu/hypertext/faq/usenet/compression-faq/top.html
• A formidable list of MS-DOS / Windows archiving programs, including some real antiques, is maintained by Jeff Gilchrist at his ACT Archive Compression Test site: http://web.act.by.net/~act/act-indx.html . There is a test there on lossless compression of 8 bit audio files, but I am really only interested in 16 bit stereo files, which are a very different thing.
• Index to Multimedia Information Sources http://viswiz.gmd.de/MultimediaInfo/ by Simon Gibbs and Gabor  Szentivanyi has links to many resources regarding compression and multimedia file formats.
• Compression Pointers from Stuart Inglis:  http://www.internz.com/compression-pointers.html .
• A paper called "Coding High Quality Digital Audio" available in PDF format from http://www.meridian.co.uk/ara/jas98.htm has some interesting arguments about why 16 bit 44.1 kHz audio is supposedly not good enough, and mentions lossless compression for 96 kHz 24 bit digital audio for DVD discs.  This is part of the ARA Acoustic Renaissance for Audio project.
• Seneschal  http://seneschal.net/infoannex.htm?external has an excellent set of links and papers regarding high sample-rate and bit resolution audio, including with new DVD audio formats.  One article there by Seneshal's Oliver Masciarotte from the July 1998 Mix magazine, discussing various audio formats for DVD (DVD-Audio - which was then being finalised) and potentially lossless compression based the ARA proposal.  In June 99 there is an article interviewing a Dolby engineer about Meridian Lossless Packing as used in DVD-Audio.
• Not a lossless algorithm, but a relatively low loss system used for broadcasting is Audio Processing Technology's 4:1 fixed rate apt-X system. http://www.aptx.com This is a real-time, high quality, low delay system (2.76ms for encode and decode combined) - which does not rely on psycho-acoustic models etc.  The FAQ describes it:
 

ADPCM as used by APT for its apt-X 4:1 compression algorithm
takes the digital signal and breaks it into four frequency sub bands
by means of a QMF digital filter. Each of these sub bands is
subsequently coded by means of predictive analysis; the coder predicts
what the next digital sample in the audio signal will be and subtracts this
prediction from the actual sample. The resulting, small error signal is
transmitted to the decoder which then adds back in the prediction from
identical tables stored in the decoder. NO psycho-acoustic auditory
mask is used to throw away any of the original audio signal resulting in
a near lossless compression system.
 
 

• OggSquish http://world.std.com/~xiph/OggSquish/  is an ambitious software project on which (as at 2 December 1998) nothing seems to have happened since April 1997.  It promises lossless compression - but I have not researched it further.
• RAR is a shareware archive program by Eugene Roshal: http://www.geocities.com/SiliconValley/Lakes/2797/ which provides a "multimedia" option when compressing files.  I tried it out with a couple of my test files, but the results were not as good as the worst results of the programs already tested.  The Kylie Minogue track was compressed to 79.6% of its normal size, and the Hildergard von Bingen choral track was compressed to 50.5%.
• (Update 8 Jan 1999.)  Leonardo Maffi has some detailed material, mainly in Italian, testing the performance of lossy audio and other compression algorithms:  http://computer.digiland.it/1609/ .
• (Update 13 September 1999) Malcolm Taylor has a lossless .wav file compressor at: http://members.tripod.com/~malcolmt/ .  It is a Windows executable – no source or principles of operation.  I have not tested it.

My work

In November 1997 I spent some time pursuing an old interest - lossless compression of audio signals.  As far as I could tell, my approach had not been used.  It seemed simple and obvious to me - so maybe it was genuinely inspired, or maybe it was not in use because its performance was too low.

My interest is in lossless compression of music for electronic delivery by the Internet - now and in the future when more people at home have broadband ( > 2 Megabit/sec ) links.

I wrote some C code and ran part of the algorithm on some samples from CDs.  While I never did the final data-packing part of it, my system did not appear to be dramatically more efficient at reducing the data than existing systems. It did promise:

• Easy implementation with 32 bit integer mathematics.
• Adaptable to lower data rates in which only very low level detail was lost in passages of great complexity.
• No filtering in either the encoder or decoder.

Assuming that my algorithm could have improved on the state-of-the-art by 10% - which I doubt and which would have been a major achievement - then all it would do is some combination of:

• Reduce bandwidth and therefore costs for Internet delivery of perfect quality music.
• Increase the uptake of electronic delivery of perfect quality music - compared to the use of lossy algorithms such as MP3 and AAC.

However, assuming that bandwidth is doubling each year - for instance considering that the uptake of HFC cable modems and ADSL (see here for more info) is growing rapidly and these are 30 to 150 times faster than a telephone modem - then all this fab new algorithm would do is bring progress forward by a month or two.  On the other hand, saving 10% of storage requirements forever more in the music field would be well worth doing!

While I still think my approach to packing the variable length binary numbers (which are used in all these lossless algorithms to encode the difference between the predicted and the actual waveform) could be superior to the Huffman or Rice approaches generally used, I decided to pursue other things.  That approach is not easily explained, without a few pieces of paper, a pen or pencil a cup of tea and some good chocolate biscuits!
 

Updates in reverse order:

2000 July 15: Updated link to Monkey.2000 April 24: Added link to Monkey.2000 March 22: Added mention of AudioZip and fixed a crook compression ratio figure for WavArc level 4.1999 September 13:  Added link to Malcolm Taylor's site.1999 June 9: Updated URL for Seneschal and added material about MLP - Meridian Lossless Packing for DVD-A.1999 June 6:  Added link to DAKX.1999 January 9: Added link to Leonardo Maffi's site.1998 December 8: Added link to "Smacker".1998 December 3 - 6:  Added Sonarc, LTAC / LPAC and Archive Compressor - and a link to Mat Hans' thesis.1998 December 3:  Added link to RAR.1998 December 2:  Updated with material relating to Waveform Archiver and Pegasus SPS.1998 December 2:  Page established - testing Shorten and WaveZIP - and just as I finished, I found Waveform Archiver and later Pegasus SPS..

Robin Whittle  rw@firstpr.com.au
Return to the main page of the First Principles web site.
 
 

Note! This is an archival page from 1998, with a few updates. For the current version of this page, click here: index.html