Clipping in een digitaal systeem

[dekkersj]

...

[Guest Kraus vonBentinck]

ik heb er de ballen verstand van maar misschien heb je hier iets aan?

 

Level Meters - From Peak to K-system

 

When working with digital audio equipment, precise level metering is indispensible. If signals surpass the highest digital level available, clipping occurs. The signal is hard-limited, or 'shaved off' at this level, since no higher level can be represented. All information beyond this level is lost, and unlike overdriven tube amps, the distortion sounds rather awful.

 

Peak

When digital audio recording became popular, the Peak Level Meter quickly became a new standard. As opposed to previous metering methods used for tape machines (Quasi Peak, Peak Program), which had a certain useful delay (attack time) before reacting, not a single sample should go off unnoticed. On the other hand, the recording had to have a certain signal level, since early AD-converters had a relatively high noisefloor and distortion. As a result, recordings soon were only measured with Peak Level Meters, and the level was set as close to 0dBFS as possible. Everything else didn't matter anymore.

 

However, level meters can do far more than displaying peak levels and indicating overloads. As an example, analyzing loudness and dynamics is not only useful and important to experienced mastering specialists, but also in the recording studio, and can be beneficial for a production all the way to the final mixdown.

 

RMS

One of the most frequently overlooked features of DIGICheck, a simple loudness analysis, is found in the outer RMS meters in the Stereo & Phase Level Meter (since version 1.0!). RMS (Root Mean Square) does not analyze the maximum level of a signal, but its energy content. And this changes a lot. Look at any production (be it your own or others) with said level meter. RMS will be about 15 dB less than the peak levels, which - surprise, surprise - will reach 0dBFS.

 

This is most obvious with individual instruments. A percussion instrument will show high peak values, but low RMS values, whereas a synthesizer or bass will show almost the same values for both. Signal processing with compressors not only changes the perceived loudness, but also the readings in the RMS level meter significantly.

 

In Mastering, the difference between peak and RMS, which is also called crest factor, indicates the amount of compression and the remaining dynamic range of a production. Due to the constant race for the loudest CD, the crest factor has decreased constantly during the last years. And as commonly agreed, the constant increase of RMS did not help to improve the sound quality.

Slow

Compared to peak metering, RMS allows for a relatively good detection of 'loudness'. And many sound engineers are accustomed to the way RMS meters display levels for many years. More precise loudness measurements would require very complex methods (Zwicker, Sone). In DIGICheck, this would not only use CPU resources and in some cases even cause a delayed reading, it would also require the user to re-learn the way he reads meters completely.

 

Therefore we have tried to further improve the RMS meter, and we've come across a simple method to do so. Calculating the energy level becomes increasingly precise with a slower RMS measurement. You can test this for yourself: With a release time of 100dB/s, RMS behaves almost like a Peak Meter, while at 10dB/s, inaudible peak levels are nearly completely ignored. Of course this works even better at 2dB/s, but reading the RMS meters would not be any fun anymore (see 'used to RMS' above).

 

That's why DIGICheck 4.1 has two RMS meters: the normal bar graph, which is set to 20dB/sec by default, and a Slow marker, which usually moves around the top end of the bar graph, representing an extremely slow RMS meter. Its current value is optionally shown in numbers on top of the display. Voil

[Guest Kraus vonBentinck]

Het K-system blijkt de volgende 3 headroom classificaties te hebben:

K-12

K-14

K-20

 

Bij deze mijn excuses voor mijn slecht geheugen.

 

Groet,

Jacco

dit klopt, zo staat het op mijn metertje en dit is wat er bedoeld wordt met "strijd om de luidste cd"

 

 

voor het overige moet ik het antwoord schuldig blijven en zal me er verder niet mee bemoeien