OR NOT TO WAVEFORM
This topic raises its head a couple of times a year. I imagine a user is upgrading a system and his/her VAR recommends an external scope and the customer balks and says “Hey, there’s already a built-in scope, why should I pay for another scope?”
My position, and most of the system designers I know, is that a software plug-in scope is better than nothing. However, an editor’s product is the output of the system. A software scope measures the video stream somewhere within the application. In some cases, it is measuring in another color space and calculating what the output levels will equal.
The software algorisms are quite sophisticated and will generally give a reasonably accurate evaluation, within certain limitations. The problem is that any change in the video after the measurement will not be measured.
The product (video) is always manipulated in the latter portion of the application. This could include downstream hardware conversion to SDI (SMPTE 259), HD-SDI (SMPTE 292), to a compression algorithm for DVD production or file transfer. The internal scope cannot access these formats for evaluation. If delivery is via tape to a network, measuring what the tape deck records is vitally important.
Most networks, and cable channels such as Discovery, History, National Geographic and even the Comedy Channel have tightened the delivery requirements for outside sources. Some of these networks require all programs be delivered in some flavor of high definition. In addition to simply conforming to SMPTE standards, additional requirements are added.
A growing delivery specification is to prohibit text in certain areas of the screen. Most channels have some sort of channel ID onscreen at almost all times. In addition program promos can appear at almost any time or place on screen. Therefore, exact verification of line placement in the final output is now a necessity.
When a program is refused, without an external scope, an editor hasn't a leg to stand on. I have known programs to be rejected because of mistakes made by the receiving QC technicians (everyone’s human). Having a scope available, and the knowledge to use it, can help in resolving the issue.
Virtually all editing applications now perform color correction. Anyone using this feature without an external scope is looking for trouble. High-level colorists use multiple external scopes, grade 'A' monitors and specially designed suites. Editors who are 'just making a CC tweak' can move a video signal out of its proper color space. This will push the conversion hardware past its design limits for proper color placement.
In the final analysis, nothing beats an external scope. The cost will be higher than a software scope but being able to verify your product for your client …..PRICELESS
Jim Alfonse, owner of Tri-Sys Designs, is a Systems Integrator with twenty-five years experience in the Broadcast Industry. He's designed, built and commissioned installations from Satellite News Vehicles to Production Suites to OB vans. Jim has been involved with several equipment manufacturers performing video standards compliance and signal integrity testing.
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