Audio Format

Audio files come in three flavors.

• uncompressed
• lossless compression
• lossy compression

Uncompromising Uncompressed

Well-known examples are  WAV (Waveform audio format, developed by Microsoft and IBM) and AIFF (Audio Interchange File Format, a format was co-developed by Apple Computer in 1988).
They contain uncompressed audio in the pulse-code modulation (PCM) format. PCM audio is the standard audio format for CD's.

There is no loss of quality using any of these formats as lossless=lossless.

The only difference is the sequence of the bits, WAV is in little-endian, AIFF in big-endian (most-significant byte first) and this corresponds with the processor architecture used by Windows (Intel X86=little-endian) and Apple (Power PC=big-endian).

Apple has created a new version of AIFF in little endian. This is the format used on Intel based Mac’s.
http://en.wikipedia.org/wiki/Audio_Interchange_File_Format

 

Pro:

• no loss of quality. If you rip a CD straight to WAV, you rip 16 bit/44.1 kHz PCM Red book audio format to 16 bit/44.1 kHz PCM in WAV format, this is as close as you can get to the original source.

Cons:

• Uses a lot of disk space.
  In case of Redbook audio:
  bits * sample rate * channels = 16 * 41000 * 2=1411200 Bits/sec ≈ 172 Kb per second.
  

  Today a 1 Tb HD sells at € 100,-
  You can store approximately 1600 CD’s on it.

• Tagging WAV is a problem.

  Due to a lack of standardization portability of the tags is poor.
  Best practice is probably to act as if tags in WAV are not supported at all.

Uncompromising compressed

The data is compressed without any loss of information. This is similar to how WinZip works, except you will get a better compression because the software  is designed specifically for audio. Examples are: FLAC  (Free lossless Audio Codec), Monkey's Audio (APE), WavPack (WV), Tom's lossless Audio Kompressor (TAK), Apple Lossless (ALAC) and Windows Media Audio Lossless (WMAL).

 

Pro:

• No loss of quality.
• Reduces file size 40 to 60% depending on the kind of music.

Cons:

• Limited support. Apple and Microsoft support their own proprietary lossless formats only.
• Not as frugal on disk space as MP3.

WAV versus FLAC

One of the many endless  debates is WAV versus FLAC.
There are claims that WAV sounds better.
Of course there are also claims that there is no audible difference at all.

In general the differences are explained as that the decompression of FLAC requires more CPU power and this will affect sound quality negative.
Effectively this means that the system has a sound card whose quality fluctuates with system load. Reason why some conclude that this is not a matter of a difference between WAV and FLAC but a badly designed system.

 

An argument in favor of  WAV is the cost of storage. Why bother, why running even an hypothetical risk as storage is very cheap today?

The advantage of FLAC is its support of tagging. As mentioned above, tagging WAV is a problem.

One things is obvious, if you rip to FLAC, you have a collection in a lossless format and each file is self documenting (the tags).
You will appreciate this the moment you use another player.
Another advantage is that FLAC has a checksum which will detect data corruption.

 

My advise is an obvious one:
Rip a couple of tracks to WAV and to FLAC
Do a listening test
Best practice is of course to do so unsighted.
Don't let your expectation bias fooling you.

Compromising compression

MPEG-1 Audio Layer 3, more commonly referred to as MP3, is a popular digital audio encoding, lossy compression format, an algorithm designed to greatly reduce the amount of data required to represent audio, yet still sound like a faithful reproduction of the original uncompressed audio to most listeners. It was invented by a team of European engineers of Philips, CCETT (Centre commun d'études de télévision et télécommunications), IRT and Fraunhofer Society, who worked in the framework of the EUREKA 147 DAB digital radio research program, and it became an ISO/IEC standard in 1991.

 

Pro:

• high compression so frugal on disk space.
• can be used on any MP3 player.

Cons:

• the stronger the compression the higher the loss of quality.
• you can't convert back to a lossless format (it is technically possible, but what is lost in converting to MP3, is lost forever).

Several bit rates are specified in the MPEG-1 Layer 3 standard: 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 192, 224, 256 and 320 Kbit/s, and the available sampling frequencies are 32, 44.1 and 48 kHz.

Higher rates then 320 don't make sense, the file size will equal those of lossless compression.

What to choose?

Increased bandwidth and decreasing prices of hard disk lowers the need for a compact format. Why temper with sound quality if  € 100,- buys you a 1 Tb hard disk.
Maybe today you don't hear the difference between a high bit rate MP3 and a lossless format.
Maybe tomorrow you buy that revealing piece of high end equipment.

Lossless

To have a collection in a lossless format is a good strategy.
Often people worry if this format is future proof.
Don't worry, there are many programs allowing you to convert from one format to another.
That’s one of the advantages of lossless formats, you can convert to another lossless format without sacrificing sound quality.

Lossless allows you to convert your music to any format you need without suffering generation loss.

Transcoding

You choose a lossless format but your MP3 player accepts MP3 files only.

To maintain two libraries, one in FLAC and an identical one in MP3 is a horrible job.

The answer is transcoding. A lot of players support conversion to another format on the fly.

How low can you go

If you have the same audiophile neurosis as I have, the idea only that there is some information removed (that’s what MP3 does in a very clever way) spoils your listening pleasure.
All of a sudden you see on Amazon the track you wanted to have for years.

Wow! Eureka!

Oh no, it is only available in MP3. Shit!!!!

 

Amazon MP3s are made with LAME at 256 kbps.
Lots of people can't hear the difference between the original CD and a 192 kbps MP3.
So don't worry, get it and enjoy. MP3 is not that bad.

Higher and highest

Lot’s of people don't hear the difference between high bit rate MP3 and CD quality. Makes you wonder if CD is simply too good.

But like everything in audio, there are opposite views.
CD audio (16 bit/44.1 kHz) is blown away by 24 bits/96 kHz or 192 kHz recordings.

CD is simply not good enough.
A couple of online stores offer high resolution recordings.

 

How to test

If you want to hear the differences between file formats and especially between lossless and lossy you must use music putting the compression to test.

Small settings are recommended, there ain't much to mask in it. (No, a recording of John Cage's 2"33 is not a good example).

Harpsichord is often mentioned, its generates a lot of high pitch harmonics.

Likewise cymbals.

Iinstruments requiring high rise times (percussion).

SQAM=Sound Quality Assessment Material

The EBU (European Broadcasting Union) SQAM can be found here.

How to set up the listening conditions can be found here.

Some 'killer' samples can be found here.

References

J. D. Johnston. Perceptual Coding