What Is True Peak and Why Is It Set to -1 dBTP?

True peak is the actual maximum level a piece of audio reaches once it is turned back into a continuous waveform, as happens in a digital-to-analogue converter or a lossy encoder. It can be higher than the highest sample value because the real waveform passes between samples. A ceiling of -1 dBTP, one decibel below full scale measured as true peak, leaves enough headroom that MP3, AAC and streaming playback do not clip.

Sample peak versus true peak

Digital audio is a series of samples. The sample peak is the largest sample value. But the waveform the listener hears is reconstructed between those samples, and the curve can overshoot: two adjacent samples just under full scale can describe a peak above full scale between them. These are inter-sample peaks. True-peak meters estimate them by oversampling the signal, typically four times, and reading the result.

A file whose sample peak is exactly 0 dBFS can have a true peak of +0.5 dBTP or more. On a converter or after lossy encoding, that overshoot becomes clipping.

Why -1 dBTP

The broadcast standards that defined loudness measurement, EBU R128 and ITU BS.1770, specify a maximum true peak of -1 dBTP for programme audio. Streaming services adopted the same figure in their guidance, and Spotify recommends -2 dBTP for masters louder than -14 LUFS because its encoder has less headroom on dense material. Mastering engineers use -1 dBTP as a safe default: inaudible as a loss of loudness, and enough to absorb encoder overshoot.

True peak and loudness together

Loudness normalisation sets the average level, measured in LUFS. True peak is the ceiling. A master is described by both: -8 LUFS integrated with -1 dBTP peaks is a club master; -14 LUFS with -1 dBTP is a streaming master. The limiter in the mastering chain holds the peaks under the ceiling while the gain stage brings the average to the target.

Pushing the average up against a fixed ceiling means more limiting. That is why a -6 LUFS master sounds denser and less dynamic than a -10 LUFS master at the same -1 dBTP ceiling.

True peak in Club Ready Music

Every file Club Ready Music produces goes through a loudness stage with a true-peak ceiling of -1 dBTP:

• Generated tracks and DJ edits use a two-pass loudness normalisation: the first pass measures integrated loudness, loudness range and true peak after the pre-filters, and the second pass applies the exact correction to hit the target (default -8 LUFS) with peaks held at -1 dBTP.
• Drops, jingles and spots are short, where a single-pass normaliser undershoots, so Club Ready Music measures, applies gain with a brickwall limiter at the ceiling, then re-measures once and tops up what the limiter took away, within a cap.

The ceiling does not change when you move the loudness target. Choosing Streaming -14 or Club max -6 moves the average; the peaks stay at -1 dBTP.

Checking true peak

Most DAWs and metering plugins show true peak alongside sample peak. If a meter only shows sample peak, assume lossy encoding adds up to about one decibel of overshoot on loud material and leave room for it.