Outputting Accurate Analog Black Levels Using DV FireWire
Outputting analog video from Final Cut Pro requires a video interface with a
digital-to-analog converter. Many third-party interfaces include analog outputs.
Alternatively, you can use a DV deck or camcorder to convert a digital signal via FireWire
to an analog signal for recording to tape. This is the same configuration you would use to
monitor DV FireWire output from Final Cut Pro on a standard video monitor.
Analog or digital VTR
Color Correction and Video Quality Control
If you output to analog tape using the built-in FireWire interface of your computer with
a consumer DV device, keep in mind that not all DV devices use the same analog black
level. Digital video always has a digital black value of 0 percent, but some DV devices
convert this value to 0 IRE and others convert this value to 7.5 IRE.
Professional video facilities are fairly stringent about keeping black setup levels at
precisely 0 IRE for PAL and for NTSC in Japan, and at 7.5 IRE for NTSC in North America.
If your DV device outputs at the wrong analog black level, you may need to use a
hardware proc amp to adjust your analog video signal accordingly.
If you are outputting back to analog tape using a third-party analog video interface,
you should check the documentation that came with the video interface to determine
how to configure the video interface for the North American standard for setup (7.5 IRE)
or the Japanese standard (0 IRE). Most vendors of analog video interfaces include a
software control panel that allows you to select which black level to use. Most vendors
label this as “7.5 Setup” versus “0 Setup,” or in some cases “NTSC” versus “NTSC-J.” For
more information, see “
How Analog Video Signals Are Measured
” on page 534.
The following is a typical configuration for calibrating the analog black levels coming
from your digital-to-analog converter (in a DV deck or digital-to-analog converter).
Â Using FireWire, Final Cut Pro outputs video with black at the industry-standard digital
value of 16 (as specified by the ITU-R BT.601-4 engineering specification for video).
This is the correct level for black for digital video.
Â The analog outputs of your VTR are connected to a proc amp that you can use to
adjust the analog black level, or setup.
Â The signal from the proc amp is connected to a video monitor and then to a
waveform monitor, where you can measure to make sure the proc amp is adjusted
for proper black levels. For NTSC signals in North America, you should adjust the proc
amp so that the waveform monitor shows a black level of 7.5 IRE. For PAL and NTSC
in Japan, the output signal should be 0 IRE.
Analog video out
to recording deck
Measuring and Setting Video Levels