Copyright © 2026 Lewis James Seals Jr. All rights reserved. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.# Little sQrt v2.0.1

Production-oriented Python loudness measurement, normalization, and true-peak verification utility.

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What it does

• BS.1770-4 K-weighting: Precise filter stages adhering to ITU-R BS.1770 specifications.
• Loudness Gating: Energy-domain absolute ($-70\text{ LUFS}$) and relative ($-10\text{ LU}$) gating.
• Integrated LUFS: Accurate broadcast-grade integrated loudness calculation.
• Momentary & Short-Term: $400\text{ ms}$ momentary and $3\text{ s}$ short-term loudness measurement.
• EBU LRA: EBU Tech 3342 loudness range distribution measurement.
• True-Peak Detection: $4\times$ interpolated true-peak measurement.
• Multichannel Support: Explicit channel-weight support for up to 8 channels.
• Normalization & Limiting: Loudness normalization to target LUFS with configurable true-peak ceiling.
• High-Rate PCM: Optional $8\times$ high-rate PCM output rendering.
• Post-Render Verification: Automated forensic verification report.
• Batch Processing: Multi-process batch execution with per-job error isolation.
• Deterministic JSON Reports: Detailed forensic reporting separating measurement, render actions, and verification.
• Numba Acceleration: Optional high-performance JIT execution.

The regression tests in tests/ assert the BS.1770‑4 Table 1 coefficients at 48 kHz and an end‑to‑end −20 LUFS reference; these run on every pytest invocation.

BONUS BOOK

Installation

Clone the repository and install the required dependencies:

git clone [https://github.com/ljrseals-dev/Little-sQrt.git](https://github.com/ljrseals-dev/Little-sQrt.git)
cd Little-sQrt
python -m pip install -r requirements.txt

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Important terminology

--no-8x disables the output sample-rate conversion.

Without it, a 48 kHz source becomes 384 kHz and a 44.1 kHz source becomes 352.8 kHz. The project therefore calls this 8x high-rate PCM output rather than claiming that every source/output is technically DXD.

The true-peak detector is separate from the 8x output SRC.

Install

python -m pip install -r requirements.txt

Numba is optional:

python -m pip uninstall numba

The program falls back to NumPy/SciPy when Numba is unavailable.

Examples

python littlesqrt.py in.wav out.wav --target -23 --bits 24

Podcast-style target:

python littlesqrt.py in.wav out.wav --target -16 --no-8x

No input high-pass:

python littlesqrt.py in.wav out.wav --hp 0 --target -23

Batch:

python littlesqrt.py --batch list.txt --target -23 --workers 8 --report report.json

list.txt:

in/a.wav out/a.wav
in/b.wav out/b.wav

Report semantics

The JSON report deliberately separates:

1. measurement — properties of the input after the optional high-pass, before normalization;
2. render — requested gain and true-peak ceiling actions;
3. verification — properties actually measured on the final rendered file.

If the requested loudness gain would violate the true-peak ceiling, the processor applies a final gain trim. The resulting loudness_error_lu therefore reports the actual deviation from target rather than hiding it.

Validation status

This release is a production-oriented implementation, not a claim of independent standards certification.

Before broadcast certification, validate against the organization's reference BS.1770/EBU test vectors and the exact delivery-channel layout. In particular, verify:

• K-weighting reference vectors
• gated integrated loudness reference files
• LRA reference files
• true-peak intersample test signals
• mono, stereo and delivery-specific multichannel layouts
• 44.1/48/88.2/96/192 kHz
• PCM16/PCM24/float32 output
• long-form and short-form material

Design rule

Measurement and rendering are separate concepts. The utility never uses an arbitrary pre-gain merely to make the meter look convenient.

The Python and Web implementations were cross-checked against a −20 dBFS 997 Hz stereo reference after v2.0.1 and agree within 0.05 LU.