True peak measures the reconstructed waveform between samples; capping at -1 dBTP leaves headroom for inter-sample peaks and lossy encoding

True Peak Level measures the maximum of the audio waveform in the continuous time domain, not just at sample points. Between digital samples the reconstructed analog signal (after DAC conversion or after MP3/AAC codec encoding) can rise above the numerical peak stored in the file — an inter-sample peak, or ‘over.’ A meter reading only sample values can therefore show 0.0 dBFS yet still clip after encoding or playback. To protect against this distortion, engineers set the limiter ceiling to -1 dBTP rather than 0 dBFS. This matches the EBU R128 recommendation that the Maximum True Peak Level not exceed -1 dBTP during production (linear audio), measured with a meter compliant with ITU-R BS.1770 and EBU Tech 3341 (tolerance ±0.3 dB up to 20 kHz); Spotify similarly advises below -1 dBTP (or -2 dBTP for files louder than -14 LUFS). Because lossy encoding can push a -1 dBTP file above 0 dBFS, re-check true peaks after encoding; the margin costs little perceived loudness.

Examples

Set a limiter ceiling to -1.0 dBTP (not 0 dBFS); after rendering, verify with a true-peak meter. A master at -1.2 dBTP is compliant; one at -0.5 dBTP is not. For Spotify, aim below -1 dBTP and re-measure after MP3/AAC encoding.

Assessment

What is the difference between a sample peak and a true peak, and why does a file showing 0.0 dBFS on a standard meter sometimes clip after MP3 encoding? At what dBTP value does EBU R128 draw the production limit, and what measurement standard does it require?