DBFS

of a digital waveform. The red lines indicate full scale, and the waveform is shown before and after hard clipping (grey and black outlines respectively). dBFS or dB FS (decibels relative to full scale) is a unit of measurement for amplitude levels in digital systems, such as pulse-code modulation (PCM), which have a defined maximum peak level. The unit is similar to the units dBov and decibels relative to overload (dBO). The level of 0 dBFS is assigned to the maximum possible digital level. For example, a signal that reaches 50% of the maximum level has a level of −6 dBFS, which is 6 dB below full scale. Conventions differ for root mean square (RMS) measurements, but all peak measurements smaller than the maximum are negative levels. A digital signal that does not contain any samples at 0 dBFS can still clip when converted to analog form due to the signal reconstruction process interpolating between samples. This can be prevented by careful digital-to-analog converter circuit design. Measurements of the true inter-sample peak levels are notated as dBTP or dB TP (decibels true peak).

of a digital waveform. The red lines indicate full scale, and the waveform is shown before and after hard clipping (grey and black outlines respectively). dBFS or dB FS (decibels relative to full scale) is a unit of measurement for amplitude levels in digital systems, such as pulse-code modulation (PCM), which have a defined maximum peak level. The unit is similar to the units dBov and decibels relative to overload (dBO). The level of 0 dBFS is assigned to the maximum possible digital level. For example, a signal that reaches 50% of the maximum level has a level of −6 dBFS, which is 6 dB below full scale. Conventions differ for root mean square (RMS) measurements, but all peak measurements smaller than the maximum are negative levels. A digital signal that does not contain any samples at 0 dBFS can still clip when converted to analog form due to the signal reconstruction process interpolating between samples. This can be prevented by careful digital-to-analog converter circuit design. Measurements of the true inter-sample peak levels are notated as dBTP or dB TP (decibels true peak). \mathrm{DR} = \mathrm{SNR} = 20\log_{10}{\left(2^n \sqrt{\tfrac{3}{2}}\right)} \approx 6.0206 n + 1.761 The value of n equals the resolution of the system in bits or the resolution of the system minus 1 bit (the measure error). For example, a 16-bit system has a theoretical minimum noise floor of −98.09 dBFS relative to a full-scale sine wave: \mathrm{DR} = \mathrm{SNR} = 20\log_{10}{\left(2^{16} \sqrt{\tfrac{3}{2}}\right)} \approx 6.0206 \cdot 16 + 1.761 \approx 98.09\, In any real converter, dither is added to the signal before sampling. This removes the effects of non-uniform quantization error, but increases the minimum noise floor. European and UK calibration for is −18 dBFS = 0 VU. US installations use +24 dBu for 0 dBFS. American and Australian Post: −20 dBFS = 0 VU = +4 dBu. In Japan, France, and some other countries, converters may be calibrated for +22 dBu at 0 dBFS. BBC specification: −18 dBFS = PPM "4" = 0 dBu German ARD and studio, PPM +6 dBu = −10 (−9) dBFS. +16 (+15) dBu = 0 dBFS. No VU. Belgium VRT: 0 dB (VRT ref.) = +6 dBu; −9 dBFS = 0 dB (VRT ref.); 0 dBFS = +15 dBu.

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