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.