Specula

The standard itself, running in this page.

Below is a working BS.1770-4 meter. The page synthesizes a 30-second program - verse, quiet passage, loud chorus, verse, fade - and meters it as it plays: K-weighted momentary and short-term, gated integrated loudness, true peak at 4× oversampling. Specula runs the same standard natively, on your files.

1.2 opens two doors: your own delivery spec as a first-class compliance target, and audio that arrives with no header at all.

Custom loudness targets put a house spec next to the platform presets. Give it a name, a mode, a measurement source (integrated, dialog-gated, or un-weighted RMS), a reference level, a tolerance band, and a true-peak ceiling. It then works everywhere a built-in target does: the verdict badge, the hover breakdown, Match, Normalize to target, and the report exports. Delivering at -18 LUFS ±1 under -1 dBTP stops being mental math against the nearest streaming preset. Loudness targets guide →

Raw PCM import opens headerless audio: a dump from a decoder under test, an I2S capture, a .bin of samples from a test harness. Declare the sample rate, channels, sample format, byte order, and layout, and the whole analysis stack applies. The sheet checks the file size divides into whole frames, ranks the byte formats that fit by decoding a few seconds of each, and previews the result with playback before you commit. It never guesses the sample rate, because nothing in a headerless file can reveal it and a wrong rate corrupts every number without an error. The same declaration works on the command line. Raw PCM guide →

1.2 also brings a readability pass: Text size scales the whole main window, the info panel honors the system Increase Contrast setting, and the live Momentary and Short-term readouts get a refresh-rate picker and a separate rolling-digits toggle. Plus zoom resets across the waveform, FFT, and Spectral canvas, and fixes to short-file spectrograms and high-zoom loudness curves. The release notes have the full list.

Specula shows what's in the file, in numbers and in pictures, before it ships.

Monitors won't flag what delivery QC will: integrated LUFS half a dB over Spotify's target, a dialog mix four LU under Netflix's speech-gated number, a polarity flip in one channel that nobody caught on headphones. Those numbers are already in the file. Specula reads them out.

Comparison has the same blind spot. Was rev 4 better than rev 3, or just half a dB louder? Specula loads up to six versions, normalises them by integrated LUFS, optionally inverts polarity, and computes a sample-accurate residual: everything that differs between two takes, audible on its own.

Before a file leaves the studio, one window confirms the loudness, the true-peak ceiling, the platform compliance, the phase, and the spectral content of the master you're actually sending.

Everything it measures

Every measurement, on every file you load. Live during playback, offline on any selection.

The same engine ships as a CLI. Five subcommands, analyze, compare, edit, generate, and report, return the numbers the app shows, as deterministic sorted-key JSON. Install it from Specula → Install Command-Line Tool…

$ specula analyze master.wav
$ specula compare revA.wav revB.wav --match-loudness --out-diff residual.wav
$ specula report mix.wav --mode music --format pdf --out report.pdf

Batch QC, CI hooks, and the eight App Intents are covered in the automation workflow; the full flag reference is in the user guide.

Four delivery modes, twenty-two platforms and standards. The gain each will apply to your master, or a hard pass/fail against the spec.

Music mode shows the streaming penalty rather than a verdict. A master at −10 LUFS reads "Spotify −4 dB"; that's the exact gain Spotify will apply at playback to hit its −14 LUFS reference. The dot is green within ±1.5 dB of zero, yellow within ±4 dB, orange beyond, and a separate triangle lights when the true peak breaches the platform's ceiling.

Quiet masters get the honest readout. Apple Music's Sound Check, YouTube, and Tidal are down-only: a −18 LUFS master plays at −18, and the panel reads "as-is" in green instead of promising a boost that won't come. Spotify, Amazon Music, Deezer, and SoundCloud do boost quiet tracks, and there the +X dB number is real.

VOD and Broadcast modes are hard pass/fail: a green dot means loudness sits inside the tolerance band and true peak is at or below the ceiling. FAIL L marks a loudness band miss, FAIL TP a true-peak overshoot, FAIL S↑ a max-short-term overshoot (EBU R128 S1's tighter short-form spec), FAIL NF an ACX noise-floor breach. When several gates fail at once, the loudness miss is the one named first.

Dialog-gated targets (Netflix, Prime Video, Apple TV+, Disney+, Max; Apple Podcasts, Spotify Podcasts; ATSC A/85) evaluate against the speech-gated path and lead with dialog · in the panel. A file with no detectable speech is labelled "no speech" rather than scored against a gate it can't meet. Pick up to four targets per mode in Settings → Targets.

Match to target is non-destructive audition: press a target row's toggle and playback shifts to that target's level with a true-peak limiter at the spec ceiling. Press it on Netflix and hear the file the way Netflix will play it; release, and unity gain returns. Normalize commits instead: one uniform gain to land the target, a two-pass limiter to hold the ceiling, saved as a new file. When only the true peak is over, one-click Limit TP caps the inter-sample peaks without touching loudness.

For audiobooks, the common ACX rejection is room tone above the −60 dB RMS ceiling. Specula shows a live Noise Floor readout over every non-speech sample, and the ACX preset scores it as part of the verdict: above −60 dB, the target lights FAIL NF. Chapter mode runs the full ACX set per chapter; the audiobook workflow has the details.

The panel tracks playback live. For a broadcast delivery you'll usually want the offline analysis (⌘Return) so the verdict covers the entire master, not a rolling estimate. Every target's reference, tolerance, and true-peak ceiling is listed in the user guide.

Standards

Specula implements the actual specifications, not approximations of them.

EBU R 128
loudness compliant

Specula doesn't replace your DAW, your mastering chain, or your ears. It catches what they miss: the hidden phase issue, the half-dB true-peak overshoot, the dialog mix three LU off Netflix's target. Load the file, read the numbers, then send it.

Take the long way through the user guide if you're new to loudness gating, or skim the keyboard reference if you just want to drive it.