Glossary

ndi-timecode

Per-frame timecode in ndi-time which is not used by the NDI® library but is passed through for applications to interpret/display as needed.

ndi-timestamp

Per-frame timestamp in ndi-time filled in by the NDI® library using a high-precision clock. This is used to ensure accuracy in stream synchronization across the network.

ndi-time

Time since the UNIX epoch in 100-nanosecond increments as a signed 64-bit integer. Conversion to seconds would be \(T_s = T_n*10^{-6}\) and conversion from seconds would be \(T_n = T_s*10^{6}\).

UNIX epoch

The point at which time starts: January 1, 1970 00:00:00 (UTC) on all platforms

uint8

Unsigned 8-bit integer

uint16

Unsigned 16-bit integer

line stride

The number of bytes needed for one horizontal line of a video frame

peak-to-peak

The difference between the maximum positive and maximum negative amplitudes of a waveform.

A waveform that ranges from -1.0 to +1.0 has a peak-to-peak value of 2.0.

normalized audio

Audio samples that are within the range of -1.0 to +1.0 (2.0 peak-to-peak).

dBFS

Decibels relative to full scale. 0 dBFS is the maximum possible digital level. All digital audio levels are negative numbers in dBFS.

The alignment levels for this scale are:

• SMPTE

  • \(-20\text{ dBFS} = 0\text{ dBVU} = +4\text{ dBu}\)

• EBU

  • \(-18\text{ dBFS} = -4\text{ dBVU} = 0\text{ dBu}\)

dBVU

Decibels relative to 1.0 volts RMS. Its amplitude is calculated as:

\[dBVU = 20 * log_{10}(V_{RMS})\]

where \(V_{RMS}\) is the RMS voltage of the signal.

This is also known as a Volume Unit (VU) and its alignment level is 0 dBVU.

dBu

Decibels relative to 0.775 volts RMS. Its amplitude is calculated as:

\[dBu = 20 * log_{10}(V_{RMS}/0.775)\]

where \(V_{RMS}\) is the RMS voltage of the signal.

The dBu alignment level is \(+4\text{ dBu} = 0\text{ dBVU}\).