[MLA] Loudness example with distortion on Sound Check

[Ian Shepherd]

Hi Kevin,

> Intersample clipping is rarely audible as clipping but it is distortion and it manifests differently in different playback systems. Are you basing your "intersample safe" claim on your ears or on a dBTP meter?

I’ve been mastering to -1 dBTP for years now, and telling my clients the results will be suitable for online delivery. When I read the Spotify recommendation of -2 dBTP for uploads (which they’ve now updated to -1 unless the loudness exceeds -14 LUFS) I pulled up a couple of recent albums I’ve worked on from Spotify to make sure I hadn’t missed something.

Post-decode (and without normalisation) the loudest albums still measure below 0 dBTP, which as I understand it means there will be no additional clipping distortion (or limiting) at the decoder. They certainly sound fine.

Of course this is all program-dependent, and especially depends on the codec data-rate, but just as I don’t master for earbuds, I’m not planning to compromise my work for super-low data rates, unless a client specifically asks me to.

My main concern was to make sure that the -1 dBTP max “rule of thumb” that I offer people was still reasonable advice (assuming sane LUFS levels) and this reassured me that it is. Since the loudest material on the albums was above -14 LUFS, I think it’s reasonable to say that in most cases, -14 LUFS material won’t introduce “problematic" ISPs.

Hope that makes sense,

Ian