ebur128

Pure Go implementation of EBU R-128 / ITU-R BS.1770-4 loudness measurement.

Features

• Integrated loudness (LUFS) with absolute and relative gating
• True peak (dBTP) via 4x polyphase FIR oversampling
• Loudness range (LU) per EBU TECH 3342
• Stereo and 5.1 surround support

Input: interleaved []float64 or []float32 PCM at 48 kHz, stereo or 5.1.

Usage

meter, err := ebur128.New(ebur128.LayoutStereo, 48000)
if err != nil {
    log.Fatal(err)
}
meter.Write(buf) // []float64, interleaved L/R
res := meter.Loudness()
fmt.Printf("Integrated: %.1f LUFS\n", res.IntegratedLoudness)
fmt.Printf("True peak:  %.1f dBTP\n", res.TruePeak)
fmt.Printf("LRA:        %.1f LU\n", res.LoudnessRange)

See cmd/example for a complete CLI tool.

Also available: WriteFloat32, Reset, Finalize (zero-pads trailing partial sub-block), Reserve (pre-alloc for known duration).

Accuracy

Cross-validated with ffmpeg -af ebur128=peak=true on generated test signals (see testdata/generate.sh):

Metric	Tolerance
Integrated loudness	±0.2 LUFS
True peak	±0.5 dB
Loudness range	±1.0 LU

Example:

$ go run ./cmd/example testdata/sine_stereo_1k_loud.wav
Integrated loudness:  -20.0 LUFS
True peak:            -20.0 dBTP
Loudness range:         0.0 LU

$ ffmpeg -i testdata/sine_stereo_1k_loud.wav -af ebur128=peak=true -f null -
I: -20.0 LUFS
Peak: -20.0 dBFS
LRA: 0.0 LU

Testing

Integration tests require WAV files generated with ffmpeg:

bash testdata/generate.sh   # generates ~6 MB of test WAVs
go test -v -count=1

Tests skip automatically if the WAV files are missing.

Performance

Benchmarks (Apple M2 Max 16-core CPU):

Operation	Throughput	Allocations
Write (Stereo, float64)	~215 MB/s (>140x real-time)	0 allocs/op
WriteFloat32 (Stereo)	~115 MB/s (>75x real-time)	0 allocs/op
Loudness (60s analysis)	~20 µs	3 allocs/op

Write and WriteFloat32 are allocation-free in steady state.

References

• EBU R 128 / ITU-R BS.1770-4
• EBU TECH 3341 (loudness metering)
• EBU TECH 3342 (loudness range)