Computer Audio 101: File Formats

Lossy Compressed File Formats

Lossy compressed formats are used by streaming services like Pandora and Spotify and remain the download format of choice for sites like Amazon and the iTunes store. You can think of lossy compressed formats as the fast food of downloads and while they are suitable for streaming services due to their reduced file size, when paying for downloads we recommend sticking with lossless formats due to their superior sound quality.

AAC
Advanced Audio Coding (AAC also MPEG-4) is a lossy compressed file format designed to be the successor to and improvement over MP3. AAC is used by the iTunes Store for its music downloads and YouTube for its streaming audio.

MP3
The original and still most popular and widely supported lossy compressed file format which became an MPEG (Moving Picture Experts Group) standard in 1993. Amazon, among many others, uses MP3 as the delivery format for its music downloads.

OGG Vorbis
OGG Vorbis is an open source lossy compressed file format developed by the Xiph.Org Foundation. Among others, Spotify uses the Vorbis format for its streaming services.

WMA
Windows Media Audio (WMA) is Microsoft's proprietary codec and comes in a lossy compressed version as well as a lossless compressed version, WMA Lossless.

Lossless Compressed File Formats

Since lossless compression is just that, lossless, all of the original data remains in tact unlike lossy compression which discards musical data in order to achieve smaller file sizes. You can convert from one lossless format to another or to an uncompressed format with no loss of data.

ALAC
Apple Lossless Audio Codec (ALAC). ALAC is Apple's open source (since 2011) lossless compressed file format.

FLAC
Free Lossless Audio Codec (FLAC). The most common lossless compressed file format for music downloads. FLAC, which is open source, supports embedded metadata and typically reduces the original uncompressed file size by 50-60%. The only drawback for FLAC is Apple's iTunes does not support it.

Lossless Uncompressed File Formats

Uncompressed file formats are exact copies of the original data. As such they take up more space than compressed formats. Some suggest, and I'm one of them, that the cost of storage has reached a point where the extra storage requirements and associated cost for uncompressed formats is negligible.

AIFF
Audio Interchange File Format (AIFF). AIFF is Apple's proprietary uncompressed file format. iTunes users interested in an uncompressed file format with embedded metadata choose AIFF since iTunes does not support FLAC.

FLAC (uncompressed)
Free Lossless Audio Codec (FLAC). The application dbPoweramp offers an option to rip or convert your music data to uncompressed FLAC format (see review).

WAV
Waveform Audio File Format (WAVE or WAV) is another popular uncompressed format for music downloads developed by Microsoft and IBM. The one drawback for the WAV format is a lack of widespread support for its method of encoding metadata.

DSD File Formats

Direct Stream Digital (DSD) is also an uncompressed, lossless file format.

DFF
Digital Interchange File Format (DFF). A DSD format that does not support embedded metadata.

DSF
Direct Stream File (DSF). A DSD format that supports embedded metadata.

MQA

Master Quality Authenticated (MQA) is the newest format to hit the market. In essence, MQA was developed to do two things; reduce the file size of high-res music, and improve sound its quality. MQA encoded content is delivered in a FLAC container. When an MQA file is decoded by an MQA-enabled DAC, the DAC is presented with the original high-res content. When using a non-MQA-enabled DAC, the DAC is presented with essentially a CD-quality file (either 24/44.1 or 24/48 depending on the original resolution).


Further Reading

Resources: The Aging Anatomy of MP3 (why size matters)
Emil Torick On Why The MP3 Was Good Enough
MQA Reviewed

COMMENTS
monetschemist's picture

Michael, this is a useful overview. It might be useful to mention that MQA is a proprietary format that requires the DAC builder to license the IP from MQA.

For people like me who would never buy a proprietary format when an open one is available, this is good to know. For people who don't care, well... they don't care, but I don't see how it could hurt.

monetschemist's picture

Another way to describe the problem you ascribe to the FLAC format is to say something like "one of the many problems with iTunes is it does not support the FLAC format".

Just a thought :-)

mtymous1's picture

"one of the many problems with iTunes is it does not support the FLAC format".