Link Electronics HDC-925 Converter

Following the trend of modern television technology, the world of video processors has evolved right at the cutting edge.

With the explosion of new digital television technologies just a few years ago, some of the first advances in processors were (in this reviewer's opinion)greatly enhanced feature sets.

As technologies matured, both product reliability and picture quality increased also. With many products today having Web-based control, it seems that we have also gained heretofore unparalleled feature accessibility and an ease of operation that operators couldn't have even dreamed of back in the analog TV era.

The Link Electronics HDC-925 up/down/cross converter
A shining example of some of that technology is the Link Electronics HDC-925 up/down/cross converter. It is equipped for both front panel and IP control for manipulating high quality video.


The HDC-925 chassis occupies 1RU and is 11-inches deep. The unit's front panel is populated by a lighted power switch, several operating controls and several status-reporting LEDs, including DC Power, Fault Status, Reference, Audio Status, and System Status. Immediate action controls include: In Select (which steps through the various input format choices—480, 576, 720/59, 1080/59, 1080/50 and 1080/23, with the user's selection indicated by an LED). Other immediate action buttons include: Noise Reduction, System Function, Output Select (which allows stepping through the same format choices as were provided on the input side of things). There's also a "Left/Right/Up/Down, Menu, Enter" button cluster for on-screen display functionality.

The rear of the unit contains the DVI-I output connector, along with HD/SD-SDI in/out BNC's, HD/SD-SDI output BNC's for output A and B, Ref in Loop BNC's, an RJ-45 Ethernet connector, a DB-9 connector for GPI, a DB-9 connector for RS-232, a fuse, and a power cord jack.

The unit employs PixelMotion de-interlacing and multi-directional diagonal filter (MDDF) algorithms, to provide reduction of "jaggies" on diagonal lines, and per-pixel temporal recursive noise reduction that results in cleaner output video. For anamorphic conversion, the HDC-925 uses Flexview technology, and the format converter is based on Teranex's award winning HQV technology. AFD can be read and inserted for down-converting or passed-through for cross-converting. The unit supports full both 608 and 708 closed captioning. A genlock input can be either in the form of black burst, or tri-level sync. Other features include frame synching, audio error checking, audio delay, HD captioning line selection, and ATC (ancillary time code) support.

With its 3:2 film pulldown detection capabilities, the HDC-925 is able to recognize redundant fields inserted during the conversion of film to video and filters out the resulting frame rate conversion artifacts, thus making vertical resolution as high as possible. Supported standards are SMPTE-259-C, SMPTE 292-1997, SMPTE 272M, and SMPTE-299. The unit can operate with manual input format selection or in an automatic selection mode, and there is a loop output for both signal and reference.


After unpacking the HDC-925, I cabled it up for testing. I connected a feed from my station's Concerto SD/HD main plant router to serve as an input, fed the converter a color black signal for reference purposes, and finally connected the HDC-925's "A" output to an Evertz 2430DAC-HD converter in order to provide a video display on the Optiquest monitor that I had.

Hookup of the unit proved to be quick and easy. When I applied power to the HDC-925, I was rewarded with a mixture of green and red LED's on the front panel. And after a few flashes, the unit auto-detected the applied video signal and I could see the input video (which was a studio camera that I'd selected) on the monitor. At this time, I was feeding standard-definition video through the router, and the picture looked as good coming out of the HDC-925 as it did going in. I then put it through its paces by selecting different formats from the front panel, and as I scrolled through these, the LED responded with a yellow tint when the format was incorrect. (In the HDC-925's manual mode of operation, after scrolling the LED to the desired format, you have to depress the "enter" button on the front panel.

I decided to play with the unit's aspect ratio conversion (ARC) function next. I changed the aspect ratio of the camera video from 4:3 to 16:9. Understandably, this resulted in a "scrunched" picture on my display screen. By using the front panel OSD "Menu" button, I was able to see a presentation of the system menu overlaid on the output video, and by using the "Common Top and Bottom" selection, I was able to center cut my picture so that the geometry once again was sensible.

I really liked the aspect ratio conversion terminology used on the Link unit—"Common Top and Bottom" and "Common Sides." This was my first exposure to those terms as they apply to aspect ratio conversion and after I wrapped my head around this nomenclature for just a bit, it actually made sense.

The HDC-925's other aspect ratio options include anamorphic, FlexView, and 14:9. While I was bouncing around through the menus, I discovered the selection of test pattern choices, and in addition to the normal ones that you might expect, Link has also included a "Circle" and "Grid." This is really great in ensuring that aspect ratios are correct. (It really works a lot better than trying to decide if the people being viewed are really tall and skinny, or naturally short and stocky.)

As easy as the OSD (on screen display) menu is to operate, I decided that it was time to try out the unit's Web interface.

After connecting an Ethernet cable between my laptop computer and the HDC-92 converter—and using Mozilla Firefox—I was able to type the proper IP address into the browser and gain immediate access.

The unit's Web control window is both basic and easy to understand and use—and best of all—you can make changes without having to use the OSD.

There are seven tabs on the GUI I/O settings for format selection and ARC controls. The video settings access auto detection functionality, full proc amp features and test pattern selection. The audio settings provide access to group assignment, delay management, and audio error checking on/off. There are advanced settings for control of noise reduction management, source selection and more. The setup tab gives you access to reference, closed captioning and timecode management windows, while "preset" lives up to its name by providing management of preset parameters. "Info" reveals IP information, along with software/firmware versions and serial numbers.

I moved through these tabs, and tested most all of the features. In the proc amp section it was easy to change any of the levels, as you can either type in a plus or minus value or use slow/fast arrows and see immediate results in the picture. If you get a bit carried away and lose your way, there's a default button for most items and groups.


Near the end of my testing, I tried the HDC-925's standard-definition up-conversion, cross-conversion, and high-definiton down-conversion functions, as well as turning its noise reduction function off and on—basically every combination that I could come dream up.

The bottom line was that the output video quality was excellent at each and every turn. However, it should be noted that I was using only high quality video for an input. (In our age of digital TV, it's getting harder and harder to find really bad video.)

While I might like to see such features as redundant power supplies, a signal bypass at power-off, and an LCD status screen, as it is, the HDC-925 is really packed with features and is constructed in the solid "Link" fashion. It would be a welcome addition to any TV station or video production facility.

Joey Gill is chief engineer at WPSD-TV in Paducah, Ky. He has been with the station for 25 years and been in broadcasting since 1977. He may be contacted