Meters

ADX enables the measurement of sound output through the following three types of meters.

Level Meter

The level meter enables you to acquire the RMS value, peak value, and peak hold value for each channel of sound output.

Attach the level meter with the criAtomMeter_AttachLevelMeter function.
Obtain the measurement results with the criAtomMeter_GetLevelInfo function.

Measurement result values are in dB (decibels).

• RMS Value
  The root-mean-square of all short-term samples. Also called the volume unit (VU).
  This value is close to the audible volume of the sound.
  
• Peak Value
  The maximum value of the amplitude at that instant. Primarily used to detect sound clipping.
  
• Peak Hold Value
  The value when the maximum peak value is temporarily held.
  Used to help prevent missing clipping that occurs at some instant.
  
  

Loudness Meter

Measures the loudness of the sound output and enables acquisition of the momentary, short-term, and integrated values.
Loudness is an indicator of how loud a sound is perceived by the listener and is considered more accurate than the RMS (VU).
This loudness meter is compliant with ITU-R BS.1770-3.

Attach the level meter with the criAtomMeter_AttachLoudnessMeter function.
Obtain the measurement results with the criAtomMeter_GetLoudnessInfo function.

The unit for the measurement result value is LKFS (Loudness K-weighting Full Scale).

• Momentary
  The ultra short-term (100 ms) loudness value. This value represents the loudness as it changes in real-time.
  
• Short-term
  The short-term (3 s) loudness value.
  
• Integrated
  The long-term loudness value. Used for measuring the loudness by scene.
  Use the criAtomMeter_ResetLoudnessMeter function to reset the loudness meter.
  

True Peak Meter

The true peak meter enables you to measure the true peak of the sound output and acquire the peak and peak hold values.

Attach the true peak meter with the criAtomMeter_AttachTruePeakMeter function.
Obtain the measurement results with the criAtomMeter_GetTruePeakInfo function.
Measurement result values are in dBTP (Decibel True Peak).

The true peak is also referred to as the inter-sample peak, and indicates the somewhat large amplitude peak that appears between samples when converting from a digital to analog signal.
When sound data is output such that the maximum amplitude is nearly reached (by a limiter or some other means), there may be clipping when converted to an analog signal, even if none is present in the digital signal.

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