The audio universe has a wide variety of audio file types that can be classified under three main groups: uncompressed audio formats, lossless audio formats, and lossy audio formats. There are essential differences between compressed and uncompressed audio file types. Also, it is important to understand that some compressed or lossy audio formats discard audio information in order to reduce the file size. It’s worth mentioning that when a file is compressed, it significantly decreases its size as it distributes its content more evenly. A common example of this is MP3s.
When the producer uses a lossy compressed audio source, such as MP3 or AAC, the effect might damage the file or make the processing useless. In order to prevent such effect from appearing, it is essential for the producer to try to maintain the compressed audio source intact from the very beginning. Nowadays, it is important to deliver the original audio file to mixing and mastering engineers in an uncompressed format.
It’s essential to know the basics of sample rate, bit rate, and bit depth when dealing with audio file formats. The sample rate is basically the number of times the audio is sampled per second. The sample rate is measured in Hertz (Hz), a unit of frequency that describes cycles per second. The quality of sample rates ranges from 8,000Hz to 192,000Hz. Extremely high sample rates are capable of delivering huge file that, most of the times, cannot be perceived as different by the human ear.
Both bit rate and bit depth are essential components of digitized sound. Bit depth is basically the number of bits of information contained in each sample; this number corresponds to the resolution of each sample. Bit rate is basically the number of bits within a unit of playback time to represent audio and describes the character of the sample.
When using lossy formats, sound engineers are able to customize the degree to which the MP3 will maintain or lose information during the encoding and compression process. This can be done by tweaking the bit settings. It’s worth mentioning that lower bitrate means the encoder will discard more audio data during the compression process, which will directly affect the audio quality on playback.