When cutting a movie or television show editors use computer programs such as Final Cut Pro, Adobe Premiere, or Avid. These programs offer a set of video scopes, specifically waveform monitors and vector scopes, which editors can use to measure the luminance and chroma levels of the work they are doing. This can become problematic in that these scopes are not the most accurate and often don’t show the true peaks which leads to shows and movies being sent out with Illegal video levels.
These software based scopes are very rudimentary and are only to be used as a rough guide while editing. They do not show the luminance signal in millivolts but in percent, so that 100 percent is supposed to be as high as your luminance level can go. Such measurements are not the correct way to verify the signal level.
Broadcast specs call for Luminance levels that go no higher than 700 mV (or millivolts) or below 0 mV; many editors are not aware of this, which can lead to problems.
Software waveform monitors also don’t have the capacity to measure Horizontal or Vertical Blanking. (aka line count) which is an important specification that must be correct. Similarly, I have seen times when chroma over saturation appears in a program that was not caught by the editor using inferior software based vector scopes. Computer editing programs also offer “Broadcast Safe” options that don’t always seem to do the job properly.
The best way to ensure that your levels are correct and to avoid having clients send back work to be redone is to have a Video/Audio Quality Control Check done on the work. A QC facility will use only the best high quality professional waveform monitors and vector scopes, such as the Leader LV series which is designed for today’s Hi-Def programming. Often a Quality Control Operator will find that the broadcast safe tool on the editing program did not do the job correctly. If the QC was done before the show was put to tape the problems can be fixed (if necessary) using a piece of hardware called a broadcast legalizer. If, however, the edited program was laid off to tape first and the levels are not correct, the program will have to be re-laid using the legalizer resulting in double the cost to the client. If other clones or dubs were made from the master they will have to be redone as well.
The best way to ensure that your final edited project is correct, and to save time and money, is to have a quality control check done on the file, ideally a self-contained quicktime file, before the show is laid off to tape. You will receive a report that tells you what problems you have and what needs to be fixed before you start the costly video post layoffs and dubs. Fixing these problems first will result in time and money saving for you and your clients.
