진정한 피크 제한: 디지털 오디오의 정확도 및 영향

### 진정한 피크 리미팅: 디지털 오디오에서 정확한 신호 측정을 위한 핵심 요소
* 🔊 트루 피크 리미터는 PCM 인코딩된 샘플 피크의 신호 레벨을 측정하여 신호를 해석하지만, 기존 샘플링 속도에서는 **개별 PCM 샘플 값과 결과 파형 간에 최대 3데시벨의 차이**가 발생할 수 있어 판독값이 부족할 수 있습니다.
* 📏 이 문제를 해결하기 위해 **트루 피크 리미터는 아날로그 트루 피크 리미터와 동일한 물리적 동작**을 달성하기 위해 D to A 변환기를 에뮬레이션하고 현재 샘플 값 사이에 새로운 샘플 값을 보간하여 디지털 방식으로 출력을 측정합니다.
* 🎯 ITU-R BS.1770.4 표준은 언더리드를 **0.668데시벨까지 최소화하기 위해 4배 오버샘플링**을 권장하는 반면, **FabFilter Pro-L 2의 진정한 피크 리미터는 8배 오버샘플링**을 사용하여 **0.169데시벨의 언더리드를 달성**합니다.
* 오버샘플링 없이 FabFilter Pro-L 2의 트루 피크 리미터와 Pro-L 2를 사용하여 실시한 널 테스트에서 **트루 피크 리미터는 샘플 포인트를 정확하게 인식**한 반면 **일반 리미터는 오버샘플링을 켜기 전까지는 인식하지 못하는 것**으로 나타났습니다.
* 🎚 실제로 진정한 피크 리미팅은 소리가 나지 않지만 신호 측정의 정확도가 높기 때문에 **네이티브 PCM 인코더 리미팅에 비해 상당한 양의 게인 감소**를 가져올 수 있습니다.
* 🔮 진정한 피크 리미팅을 사용하지만 기본 리미팅과 동일한 수준의 게인 감소를 목표로 하는 경우 **리미터의 게인 또는 임계값을 2~2.5 데시벨 정도 낮추는 것**이 좋습니다.
* 🔄 리미터를 **4배 또는 8배로 오버샘플링**하는 것이 가장 좋은 방법인데, 언더읽기와 오버슈트를 최소화할 뿐만 아니라 리미터의 정확도를 높이고 에일리어싱 왜곡을 줄일 수 있기 때문입니다.

트루 피크 리미터는 3~0.668데시벨의 언더독을 최소화하고 게인 감소를 개선하며 에일리어싱 왜곡을 줄여 정확도를 높입니다.

I have to admit, I've been wrong about something. Many believe that true peak limiting sounds worse. The matter of the fact is we've been using it wrong. And on my last video, I had multiple people ask if I could debunk or look into true peak limiters. I had a theory that I'd present to mastering engineers. I knew a bunch of blind A/B tests. I'd plot the results and then I'd call it a day. But that didn't happen because I reached out to Fabian from TDR Labs. And he's an incredible developer and has a great knowledge of DSP. He explained to me everything he knew about true peak limiting. And that put me down a rabbit hole. A rabbit hole of research, learning sync wave functions, Whitaker Shannon interpolation formula, having a friend compile some code for some tests I needed to do, get a confirmation from iZotope's engineering team on their true peak limiter, and putting this video together. So stick with me. This is a meaty video filled with my research, interpretation, tests, and recommendations.

I invite anyone that has information on the topic to share so in the comments. Challenge my ideas, and we can learn and be better Engineers together. These are videos which I get excited to make, and if you get excited to watch them, don't forget to smash the like button and subscribe for more. So all limiters measure their Max Peak and reduce gain relative to it. The difference is in how various limiters interpret that signal. Interpreting the signal now, this is what differentiates one limiter from the next. An analog limiter measures the level of a signal, which is a continuous waveform, so it's always got a true reading on it, whereas digital limiters measure the level of a signal from the PCM encoded data. Pulse code modulation is the method used to digitally represent sampled analog signals. Now you might be familiar with looking something like this. However, each of these samples don't represent an instant moment in time. In fact, each of these samples are a scaled sync wave which extends in theory infinitely wide both past and present. The resulting waveform we see in our Daw.

from a stream of PCM samples is a sum of these scaled sink waves, and the sum of the sync wave values represented as a waveform. Which we digitally see in our Daw can produce over and undershoot below and above the given peak of the given sample value. Now this presents a significant issue with the accuracy of digital limiters. At most conventional sampling rates 44.1 or 48k, there can be up to three decibels of difference between the discrete PCM sample values and the resulting waveform. Which means there's often audio passing through the threshold of a digital limiter without a corresponding PCM sample point for it to react to. Now this is an issue, and in fact a major flaw in the function of normal digital limiters. So how does a true Peak limiter seek to solve this? To achieve the same physical Behavior as analog true Peak digital limiters, emulate the D to a converter and measure its output digitally. Speaking one way to emulate the d2a conversion process is to interpolate more discrete values in between the

present ones so the limiter can measure the level of a signal from a more accurate sample. Point itu rbs1770.4 lays out a consideration for accurate Peak metering of digital signals. Now, with the standard of four times oversampling, this minimizes a sample piece underread from three decibels down to 0.668 decibels. And at eight times oversampling, this minimizes a sample peak's underread down to 0.169, which is the same standard used for fabfilter pro l2's true Peak limiter. I found this article published in 2015 by Isotope's principal software engineer, where he lays out some code in Python to compile this sync wave offset a fraction of a sample. The sample Point has been offset by 3 3 8 of a sample or 0.375. Now, I actually failed to compile this code, so I reached out to a few friends within the programming space, and one of them was able to compile the code and produce me with the necessary PCM encoded sync.

wave for my tests which is this one here. So a big shout out to Kevin, thanks for that. The test is simple. Given that we've now established that limitus function by how they interpret the signal, a digital limiter interprets that signal by the PCM encoded sample Peaks. PCM encoded data can under read up to three decibels at 48 kilohertz. By interpolating new sample values, we minimize this under read within 0.668 decibels and 0.169 decibels using four and eight times oversampling respectively, as calculated and presented in the itu r documentation. So can I get fabfilter Pro L2 true peak limiter to null with fabfilter Pro 2 using eight times oversampling when setting the threshold to the PCM encoded sample peak and in a second test matching the threshold to the reconstructed or interpolated true peak. Now with this shifted sync wave, we have a sample point at negative 8.13. So here I have a true peak limiter set to 8.13 and here I have

a normal limiter set to 8.13 fan filter Pro 2. Interpolates the data at eight times oversampling. This one does not. So what we're going to do is we're going to play this back in a loop. And then what I'm going to do is in the middle of that Loop, I'm going to switch eight times oversampling on here and null it. And you'll see that it almost nulls absolutely perfectly well below the noise floor. So let's do that now. Okay, so one thing we notice is the true peak limiter is definitely doing some limiting. The normal one isn't recognizing that sample point. But what happens when we turn oversampling on? Ah, we've reconstructed sample points or interpolated sample points in between the existing ones. And it's now recognizing that it has to be limiting. It's actually missing that information. So take a look at this null test. When I, so it's about negative 140 decibels is the difference indistinguishable to the naked ear if I turn this off.

look how much higher it is up eight negative 80 negative 75. It's absolutely doing it's actually doing nothing there so again. I'll put the oversampling on completely nulls. So that's me doing a test there between the over sampling here and eight times. I mean the true Peak limiting here and over sampling here. So what happens if we set this to 6.37. Okay and then we're going to interpolate this data by up sampling it because what's actually going to happen is the other limiter won't pick up anything at all. So if we resample this we're going to have new data points up here and one of those data points just happens to be at 6.1 which is perfect because it's just right over that little threshold here. The way it's interpolated that now look at this so this one here is set to 8.1 8.6.37 sorry set to 6.37 a true Peak there and this one here we'll bypass that we'll turn the

oversampling off, so we can hear what a normal one and a true peak one is doing. Not here, but analyze what it's doing, and then we can put the oversampling on, and we'll get a new data point to work from. So here again, because there's much less gain reduction, they almost null anyway, but the whole idea of this test and exercise is to show that the oversampling then allows this limiter to start working and recognizing those sample points above it. The null becomes much more like it's almost nothing there. So yeah, so what does this mean in practice? Well, true peak limiting doesn't have a sound. The gain reduction algorithms look ahead, attack, release, and ceiling all theoretically should function in the same manner. Simply put, it measures a signal with greater accuracy, and when that accuracy reduces underreads from three decibels to 0.668 decibels at four times oversampling, that can create a considerable amount more of gain reduction that wasn't present in the signal before. Now, if you choose to turn true peak limiting on, but

want the same amount of game reduction dial back the gain or threshold of your limit up around two to two and a half decibels. Then you'll have a similar ballpark amount of game reduction as the native PCM encoder limiting. But the best bet is to throw the voodoo of true Peak limiting out the window and just start by oversampling your limiter at four or eight times. Not only because it minimizes underreads and overshoots, but it helps the limiter function with greater accuracy and reduced aliasing distortion. Consider especially the aliasing distortion. Now everything I've spoken about is pretty fresh information to me, and I'm going to do my best to answer all the comments as best as I can in the comment section below. So please feel free to share with me your experiences with true Peak limiters and any knowledge you have on the technology below.

Is True Peak Limiting a Lie? What You Need to Know!

Hello. I'm Nicholas Di Lorenzo. I'm a mixing and mastering engineer and owner of Panorama Mastering Studio in Melbourne, Australia. I’m an Italian-Australian. born and raised in Melbourne.

This channel is for anyone involved in the music making process, artists, engineers, producers or musicians.

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Panorama Mixing & Mastering

진정한 피크 제한 논쟁: 발견의 여정

많은 사람들이 트루 피크 리미터에 대해 오해하고 있지만, 한 개발자의 설명에 따라 심층적인 연구와 테스트가 진행되었습니다.

진정한 피크 리미터는 아날로그 리미터는 연속 파형의 레벨을 측정하고 디지털 리미터는 PCM 인코딩 데이터에서 레벨을 측정하는 등 신호를 다르게 해석합니다.

이 동영상은 이 주제에 대한 포괄적인 탐색을 통해 엔지니어링 관행을 개선하기 위한 토론과 도전적인 아이디어를 유도합니다.

PCM 샘플 파형에서 디지털 리미터의 과제

PCM 샘플 값은 파형의 오버슈트 및 언더슈트로 이어져 디지털 리미터의 정확도 문제를 일으킬 수 있습니다.

트루 피크 리미터는 D에서 A로의 변환 프로세스를 에뮬레이션하고 오버샘플링을 사용하여 샘플 피크의 언더리딩을 최소화함으로써 이 문제를 해결하고자 합니다.

668데시벨로 언더리딩을 줄일 수 있고, 8배 오버샘플링은 0.

169데시벨로 최소화할 수 있습니다(팹필터 프로 L2 리미터에서 볼 수 있듯이).

Isotope의 수석 소프트웨어 엔지니어는 2015년에 샘플 포인트를 오프셋하고 동기화 웨이브를 컴파일하여 궁극적으로 디지털 리미터 기능의 문제를 해결하는 Python 코드를 제공하는 기사를 발표했습니다.

오버샘플링이 실제 피크 제한에 미치는 영향

오버샘플링은 PCM 인코딩 데이터의 언더 리딩을 최소화하여 0.

일반 리미터는 샘플 포인트를 인식하고 제한하는 데 어려움을 겪는 반면, 8배 오버샘플링이 적용된 Fabfilter Pro L2 트루 피크 리미터는 신호를 효과적으로 무효화하여 오버샘플링이 트루 피크 리미터에 미치는 상당한 영향을 보여줍니다.

오버샘플링은 실제 피크 리미팅에 상당한 영향을 미쳐 리미터가 그 이상의 샘플 지점을 더 정확하게 인식할 수 있게 해줍니다.

트루 피크 리미팅이 반드시 사운드에 영향을 주는 것은 아니지만, 신호 측정의 정확도를 높여 게인 감소를 증가시킵니다.

오버샘플링을 사용하면 신호에서 상당한 양의 게인 감소가 발생할 수 있습니다.

더 나은 리미팅을 위한 게임 감소 및 오버샘플링 조정

5데시벨까지 높여 기본 PCM 인코더와 유사하게 게임을 줄입니다.

리미터를 4배 또는 8배로 오버샘플링하여 언더읽기, 오버슈트, 에일리어싱 왜곡을 최소화하여 정확도를 개선합니다.

아래 댓글에 실제 피크 리미터에 대한 경험과 지식을 공유해 주세요.