APU Software

Audio Processing Units

APU Software, LLC is a small company creating innovative audio tools.

Adaptive loudness windows

January 23, 2024

Adaptive loudness windows

Although the relatively long window durations of LUFS and RMS are useful for capturing the audio's dynamics accurately, the relatively slow response times can lead to artifacts in certain scenarios. For example, when the audio is first played, the initial loudness measurements will be very low. This is because the window is initially filled with silence, weighing the measurements down. This ultimately leads to a delay in the measurement response, which ultimately can prevent the initial transient from being compressed at all.

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Optimizing LUFS

October 12, 2023

Optimizing LUFS

In my previous blog post about LUFS, we delved into some details of the LUFS algorithm. One of the key elements of the algorithm is the calculation of the sum of all amplitudes within the audio waveform. For the purpose of this discussion, we'll refer to this sum as the energy of the waveform.

When measuring LUFS, we typically focus on a continuous stream of measurements. This approach allows us to observe the loudness fluctuations over time, providing insights into the audio's dynamic range.

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Loudness Units, Full-Scale (LUFS)

October 06, 2023

Loudness Units, Full-Scale (LUFS)

When working with audio, there often arises a fundamental need for an objective way to measure loudness. Historically, RMS (Root Mean Square) has served this role, providing a good first-order approximation. This style of measurement quickly became ubiquitous across audio tools of all sorts. Even though it has limitations, which we'll get into, it is a whole lot better than nothing.

Technology has advanced over time and more accurate forms of measurement have become feasible. One of the leading algorithms for this purpose today is LUFS. Its use is becoming increasingly common, especially given its adoption by many popular streaming platforms.

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