Audio formats

Almost all audio files contain both audio and tags.
Tags are small pieces of information like album title, track number, track title, artist, cover art, etc.
Tags makes the file self-documenting.
If you move an audio file to e.g. a portable, the media player on the portable reads the tags and displays them in the interface.

More about tagging.

Types

Audio files come in three flavors.

• lossless uncompressed
• lossless compression
• lossy compression

Lossless and uncompressed

Well-known examples are WAV (Waveform audio format, developed by Microsoft and IBM) and AIFF (Audio Interchange File Format, a format developed by Apple Computer in 1988).
Most of the time they contain audio in uncompressed PCM (Pulse Code Modulation) format.
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.

 

Pro:

• No loss of quality.
• If you have your audio in a lossless format, you can convert to any other lossless format without generation loss.

Cons:

• Uses a lot of disk space.
  In case of Redbook (CD) audio: 2 x 16 x 44100= 1411 kb/s (kilobits per second). An hour of music requires approximately 600 MB of storage.
  A calculator can be found here.

Today a 1 TB HD sells at € 50,-

You can store approximately 1600 CD’s on it.

Makes you wonder if size (or better cost) is still an issue today.

Tagging WAV is a problem.

The standard supports many tags but only a few are of relevance for the user.
Many media players don’t support reading/writing tags in WAV.
Best practice is probably to act as if tags in WAV are not supported at all.

Lossless compression

The data is compressed without any loss of information. This is similar to how WinZip works, except you 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).

Over the years FLAC has gained momentum.
It is probably the most popular non-proprietary format in this category.

 

Pro:

• No loss of quality.
• Reduces file size 40 to 60% depending on the complexity of the signal.
• Excellent Tagging support.

Cons:

• No support by Apple (iTunes). Microsoft added native FLAC support to Windows 10.

Lossy compression

MPEG-1 Audio Layer 3, more commonly referred to as MP3, is a very popular lossy compression format
It greatly reduces the amount of data required to represent audio.

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.

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 much sense; the file size will approach the size of a lossless compression.

 

Pro:

• High compression so frugal on disk space.
• Strong support, few players have the nerve not to support this format.
• Tagging standard (ID3)

Cons:

• The stronger the compression the higher the loss of quality.
• You can't convert back to a lossless format (Technically you can but what is lost in the compression will be lost forever).
• Generation loss. If you convert to another lossy format you accumulate the artifacts of MP3 plus the artifacts of the other lossy format.

A good read: What Data Compression Does To Your Music

If you can choose between AAC and MP3, AAC is your best bet.

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.

More...

 

An argument in favor of  WAV is the cost of storage. Why bother, why running even a 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 thing 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 advice 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 cognitions fooling you.

Lossless vs. lossy

On audio forums with a very skeptical attitude they will tell you that nobody is able to hear the difference between the original CD quality and a MP3 in an unsighted listening test.
On typical audiophile forums they will tell you that there is a profound difference and of course, MP3 is a disgrace. It really sounds horrible.
Now audiophiles and debunkers have one thing in common, they do detest nuance.

 

Rip a CD to a lossless format and convert it to e.g. 64, 128, 256 and 320 Kbit/s MP3.

Do an unsighted test!

If you don’t hear a difference between CD quality and 64, see a doctor
If you don’t hear a difference with 128, get better gear
If you don’t hear a difference at 192, you are not alone
At 256 you will probably struggle and at 320 even more.

Still at 320 you can hear differences. This is called the killer samples.
Often this is music made with electronics like Kraftwerk and you can hear artifacts like pre-echoes even at 320.

Obvious the higher the bit rate the more transparent lossy codecs like MP3 becomes but they will never obtain 100% transparency.

 

Ripping

When you rip your CDs, you have to choose a file format.
The decreasing price of a hard disk lowers the need for a compact format.
Why temper with sound quality if € 50,- 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.
Rip to a lossless format.

Best is choosing a lossless format with good support of tagging.

The format itself is not really crucial.
There are plenty of good converters like dBpoweramp enabling you to convert to any other format if needed.
Observe, lossless=lossless, sound quality won’t degrade when converting to another lossless format. It remains the same bits stored in a different format.

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.

High resolution

Recordings are often made with a greater bit depth (24) and a higher sample rate.

One of the benefits of computer based audio is that you are not in need of recordings down sampled to CD format.
You can play the original recording at its original bit depth and sample rate (if your sound card allows for it).

Audio with a bit depth of 24 and a sampling rate > 44.1 kHz is called high resolution audio.

 

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 isn't much to mask in it. (No, a recording of John Cage's 4"33 is not a good example).

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

Likewise cymbals.

Instruments requiring high rise times (percussion).

SQAM=Sound Quality Assessment Material

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

 

1. Perceptual Coding - J. D. Johnston.
2. Psychoacoustic Models for Perceptual Audio Coding - Jürgen Herre, Sascha Dick 2019
3. The Pre-echo Machine, ABXing Kraftwerk's The Man Machine at 320kbps CBR Mp3 - Hydrogenaudio
4. I found a really bad killer sample. Very easy to ABX with any mp3 encoder at 320 kbps. - Hydrogenaudio
5. MP3 320 kbs vs Redbook ripped to WAV, Positive ABX test result with foobar on classical material (Ravel) - Hydrogenaudio
6. MP3 and other HiRes formats - Jörn Druhmann
7. TIDAL is NOT Worth it! Listening Test - Audio Science Review
8. What Data Compression Does To Your Music - Ian Corbett