To obtain the best results, master and distribute your music into the necessary, dedicated formats; each online music service has a different target loudness level!
iTunes uploads require uncompressed, 24 bit (or more) .WAV or .AIFF (PCM) files which are transcoded to 256 kbps .AAC further down the line. And a maximum of –16 LUFS of psycho-acoustic perceived loudness (because of the ‘Sound Check’ option in the player).
The "Mastered for iTunes" initiative is both a technical improvement and a change in practice for mixing and mastering engineers, because it is helping to usher the industry away from super-loud mixes and masters, process called the Loudness War. Anyone listening on a high-quality playback system, in an environment that allows them to hear all of the details of the music, will be potentially rewarded with a wider dynamic range (a.k.a. the difference between the very loudest and the very quietest parts of the music), a slightly lower noise floor, and less distortion (which translates into more sonic detail in the music).
SoundCloud transcodes uploaded audio to 128 kbps .MP3, requiring ideally 24 bits .WAV files and a margin between –0.3 and –1.5 dBFS to prepare the audio to stream from the site. If an audio file on SoundCloud is made available for download, the downloaded version will be in the original format.
SoundCloud does not have a feature like Apple’s SoundCheck, so an audio master destined for SoundCloud has more freedom to raise the overall RMS level for competitive loudness.
YouTube can only down-convert video, so it’s best to upload the highest quality level you can within the H.264 codec. Why not upload a .MOV with uncompressed audio? For best results, YouTube actually recommends uploading media that is already encoded, rather than uploading a .MOV that contains a full quality .WAV file.
CD Audio (Compact Disc Digital Audio, CDDA or CD-DA) is the standard format for audio compact discs. The standard is defined in the Red Book, one of a series of "Rainbow Books" (named for their binding colors) that contain the technical specifications for all CD formats.
The Red Book CD Audio protocol determines the format to 16 bits of dynamic range and 44.1 kHz sampling frequency, requiring .WAV or .AIF (Apple) files to compile; –16 to –11 LUFS typical.
Thanks to Mr. Rob Stewart & iZotope
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