and DVD Black Levels Part 2
(continued from DV and DVD Black Level Part 1)
Note: If you need more info on the basics of DVD burning, take a look at our DVD burning instructional video.
Digital video to analog
The problem for DV users in North America is that DV 25 video equipment (named for the 25 megabit per second data rate of this popular video format), whether it is PAL or NTSC has an analog output of 0 IRE. In other words, your DV equipment uses the Japan NTSC standard and if you plug your DV gear into a video monitor or TV designed and calibrated for the North America NTSC system, the black level or levels you see will be wrong.
Your DV camcorder is wrong
So if they're wrong, we need to change the black level, right? Nope, what you need to change is the way you view the video. You do need to change the black level if you dub your DV tape to VHS and other NTSC analog formats, but you never want to change the DV tape black level during capture to a digital editing system (i.e. your computer). Likewise you never change the black level to 7.5 IRE while working with the video in your editing software.
How does this tie in with that DVD black level that looks different than the DV source tape's black level? Well, while much of the DV 25 equipment sold in North America outputs 0 IRE analog, the DVD players sold in North America "add setup," meaning they do output the legal 7.5 IRE black levels (some players do have an option to output 0 IRE 0 - they often call it something like "enhanced black").
Assuming your MPEG2 encoder does not alter the black level (and we'll get to that), if you watch - on the same TV/monitor - your DV tape and the DVD you made from it, they will look different just because the DV analog output is 0 IRE and the DVD player is 7.5 IRE. The picture you see from the DV tape looks darker than it really is, and the DVD will look lighter than the tape. The DVD player is most likely showing you the correct black levels and for many DV users, the first time they ever see their video with correct levels is when they encode it to MPEG2, burn it to DVD and play it on a standalone player plugged into an NTSC TV or monitor.
In the example above, there is a pretty clear difference between the water when the analog output of the DV tape is changed from 0 IRE to 7.5 IRE and between the 0 IRE tape output and the DVD player output. However, with some scenes, depending upon the lighting and contgent, there may be almost no noticeable difference. In other instances, the DVD may show color in areas that appeared as dark shadows when watching the "uncorrected" DV tape output. In the image below, the uncorrected DV tape output shows the lawn as black, while the DVD output and the corrected DV output show a touch of green in the grass.
NOTE: The DV output is from a Canon GL-1 with the 7.5 IRE setup added by a Sign Video proc amp. The proc amp includes a calibrated meter for setting the black and white levels, and has a function which allows split screen viewing as in the one image of the ship on the water. The DVD was encoded with one of the most widely used MPEG2 encoders. The screenshots were taken from an NTSC video monitor with a Sony digital still camera.
So how do you solve this discrepancy between what you see and what you get? Well, as we said, there are some DVCAM units that can be set to output 7.5 IRE through their analog outputs, such as the JVC BR-DV3000U VTR, but a more affordable option is to simply use a "proc amp" in line between your DV camcorder's analog outputs and your monitor's analog inputs. You then adjust the the proc amp so your black level is 7.5 IRE. This will not affect the levels on the camcorder's Firewire connection to your editing system, but simply adjust the viewing levels to make them match the North American NTSC standard. By the way, if you make VHS copies from your DV tapes, you should also put the proc amp between your DV source and VHS VCR so that the VCR is fed the correct 7.5 IRE black level.
Read more of this article in DV and DVD Black Level Part 3
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