Delivery Specifications and Technology Requirements
There are a number of different formats for audio to be stored digitally. These range in attributes such as size and quality, and knowing which specific file type or format is required for a submission or audio project can be important to ensure compatibility, consistency and quality.
Audio file storage is split into three main categories: lossy, lossless, uncompressed -
Lossy is a storage format which will degrade the quality of the audio over time by loosing information through either it’s duplication process, or by fragmentation. Examples of lossy storage formats include mp3 or AAC. These files can be beneficial for situations such as streaming where the file size is minimal and allows for higher transfer speed and, however due to the encoding they’re not suitable for a situation such as audio processing / mixing as they are of not of a high enough quality, with there resolution not comparing to the types of uncompressed audio files found typically in those working environments.
Uncompressed audio is the usual for audio recording and editing, these codecs are typically in the form of these filetypes - WAV, AIFF, or PCM - These files being uncompressed maintain their original sample-rate and bit-depth, as well as the digital representation of audio within which does not lose any amount of digital information when transferred or duplicated. Uncompressed files will however be very large in size due to their nature of not having any information adapted for compression as they are stored or transferred.
The final type, lossless filetypes such as FLAC, are a hybrid of compressed and uncompressed filetype. During its storage a lossless file type can be compressed to reduce storage space and transfer speed, however when it is opened for playback the audio uncompressed from the storage container file and the uncompressed audio is regained and played. This leads to an uncompressed file on playback and a compressed file in storage, bridging the gap between low storage size and high quality.
As well as file type, there is also another delivery specification which may be encountered with audio, Loudness. This measurement of an audio track gives an accurate representation of the volume of a track, and stands for loudness units in full scale. This measurement is specified at particular levels for different formats of audio application, such as radio, tv / film or for upload to streaming platforms. This LUFS measurement ensures that the perceived loudness of audio is consistent across different platforms and is a way for distributors to ensure consistency in volume for the quality of playback over the various audio mediums.
With our radio play edits we’re doing within this module, we have been instructed to provide the audio in an interleaved stereo format, at 48kHz sample rate and 24-bit depth, as well as with the project session in a DME format. This would be a typical format for an audio play for the radio, as the 48kHz is a high-quality which is typically used in streaming and broadcasting, over the 44.1kHz used mostly for CDs, as well as at a 24-bit depth to also provide a high quality, as the original audio assets were in the bit-depth and reduction to 16-bit would likely result in unwanted audible bit-crush distortion and the informations is crushed into the smaller resolution format.
