Audio File Formats
As an audio engineer you will come across a lot of different audio file formats. You are probably really familiar with mp3 or .wav; but what about OGG, FLAC or Mp2? Today’s blog is all about the different formats & the differences between them, so that as a mastering engineer you are familiar with these files and can deliver in whichever file format is best suited for the client and project.
A technical word you need to know:
Codec: encode/decode reduces the file size by encoding the data more efficiently & decoding it for playback .
Compressed, Lossless & Lossy
All audio files can be grouped into 3 different categories.
1. Uncompressed (wav, AIFF & FLAC) An uncompressed track is a reproduction of the original audio file, where no compression algorithm (codec) has been used to compress the audio within the file, resulting in no loss in sound quality.
2. Lossless (ALAC, FLAC & WMA) Lossless file : a compressed file that can be reduced to almost half the file size of an uncompressed audio file with no ‘loss’ in terms of sound quality
3. Lossy (aac & MP3) Lossy: a compressed file that has to discard some of the original data in order to compress the fie into a smaller size, resulting in audio quality loss.
Let's explore this a little more.
WAV vs AIFF vs FLAC: uncompressed file formats
WAV and AIFF are two popular uncompressed audio file formats based on Pulse Code Modulation (PCM). PCM is recognised as a really straightforward audio storage mechanism in the digital domain. Both WAV and AIFF files use similar technology, Their difference is in that they store data in different ways.
Developed by Microsoft & IBM , the Wav uncompressed audio file format is typically used in a windows-based system, and is the standard format that all audio CDs are encoded in. In fact, the universally acceptable Redbook CD audio standard is 44.1Khz, 16bit, .wav files. No CD manufacturer can press/stamp audio CDs unless it is delivered in the Redbook standard.
Apple (mac based system) developed AIFF as an alternative to WAV. One of the features of the AIFF format is that they offer good metadata support, so you can include album artwork, and other relevant text and info in the file.
Both Wav And AIFF file formats store CD-quality (44.1 Khz, 16 bit) which we call high-resolution audio files. They also store higher resolution such as 48, 88.2,96, 192Khz and 24, 32 and 64 bit information.
The file sizes for uncompressed file formats is typically very large.
ALAC vs FLAC vs WMA Lossless: lossless audio formats
FLAC (Free Lossless Audio Codec) is a lossless audio file format that can compress an original uncompressed file to almost half the size of uncompressed WAV or AIFF of equivalent sample rate., without audio quality ‘loss’ . Another major advantage of FLAC format is that it offers up to 32 bit, 96Khz resolution (bit and sample rates). Well above the standard CD quality of 44.1Khz and 16 bit.
There are other lossless audio file formats include WMA Lossless (Windows Media Audio) & ALAC (Apple Lossless). ALAC is an alternative to FLAC for IOS and iTunes; although the file sizes are larger than their FLAC equivalent. You would also need to just check for tablet and smartphone compatibility for ALAC files.
AAC vs MP3: lossy audio formats
Probably the most common audio file format is mp3. It can really reduce (compress) an audio file to a fraction of its size which is really useful for storage purposes. However, it is a lossy compression format; and in order to achieve small file sizes, some of the original data has to be discarded, and as a result you have audio quality loss. This is noticed especially in the high and low frequency bands. And really low bit formats (128kbps and lower) can result in that ‘phasey sound quality’. Although, the mp3 is pretty much a standard on most download stores; and most commercial radio stations prefer radio adverts delivered in mp3 format.
There are different bit rates at which you can encode an mp3. These bit rates are kilobits per second and labelled as kbps. Literally each bit is a piece of the track. The bit-rate at which an MP3 is encoded really affects the sound quality. As mentioned previously, MP3s encoded at 128kbps will definitely have more noticeable sound loss than those encoded at 320kbps
AAC (Advanced Audio Coding) is also a lossy compression audio file format; but sounds ‘better’ than an Mp3. The AAC file format is used for iTunes downloads, Apple Music streaming (at 256kbps) and YouTube streaming.
The Vorbis format (Ogg Vorbis) or simply known as Ogg also a lossy compression format, and an alternative to MP3 and AAC. Spotify Streaming uses the Ogg Vorbis file format used (at 320kbps).
Finally:
ALL original masters should be in the uncompressed PCM format. Ideally .wav files. These full quality master files should be used for professional applications. Mp3, mp4 and aac files should not be used as references for your mastering. Only PCM files can provide a suitable full quality reference.
Learn the differences in the various audio file formats, and use the information to make the right choices for your work!