Gefen HDMI to HD-SDI scaler – Prosumer VP in a HDMI to HD-SDI adapter


Nov 26, 2009

The introduction of high performance video processing chips that feature per-pixel motion adaptive de-interlacing, high quality scaling and a host of other features has transformed the high-end consumer video experience.  The performance of HQV, VXP and ABT video processing chips has become well known and the use of these chips has gone from the realm of dedicated $2000 set top boxes to being used in high volume displays, receivers and players.  The use of these powerful chips, while no longer a novelty, has been restricted to mostly the  consumer market.  With the release of a couple of products by Gefen that are geared towards post production and the professional broadcast industry, this is about to change.  Gefen has introduced two new products that include the use of the Sigma Designs (formerly Gennum) VXP chips.  Both of these products are designed to facilitate HDMI to HD-SDI connectivity,  while also providing quality scaling, de-interlacing, denoise and detail enhance filters.  This article focuses on the HDMI to HD-SDI product called the, “EXT-HDMI-2-HDSDIS”, which lists for $1499.  Another similar product called the “EXT-HDSDI-2-HDMIS” is also available which converts HD-SDI to HDMI and also includes VXP processing.  This unit is available for $1299 but was not covered in this article.

For this article, we took a close look at the Gefen and the first thing that is apparent is that it’s meant for serious broadcast quality usage.  It’s a rugged unit that comes with the hardware needed for rack mounting and there is a lot of attention to detail to ensure that it works reliably in this environment.  As an example, the unit is shipped with both a DC power cord and a HDMI cable and both have integrated fasteners designed to keep the cables from being easily disconnected.  As a nice touch, both are blue and match the color scheme of the enclosure.


The unit also comes bundled with an easy to use remote control (shown at the left) along with two batteries (one for a replacement backup).   The remote is essential as there are no front panel switches or displays and all settings are accessed through the remote.

In providing conversion between HDMI and HD-SDI, Gefen has targeted a relatively small, niche market where there is a need but few products to satisfy this need.  Other less expensive HDMI/HD-SDI converters exist (most notably the HI5 and HA5 adapters by AJA), but these support only a few video formats and are missing key formats like 480p and 1080p60.  By contrast, the Gefen supports these and a host of other formats via pass through mode and will also up and downscale to other formats and resolutions.  Frame rate control is also performed and the unit can do reverse 2-3 pull-down in order to generate native 24hz frame rates from 60hz telecined content.   Also included are picture adjustments for denoise, detail enhance, color and gamma adjustments.

Feature Set

In addition to basic HDMI to HD-SDI conversion, the Gefen adapter contains a host of features, including:

  • 10-bit resolution for greater precision and dynamic range
  • Proprietary 10-bit motion adaptive video de-interlacing with edge interpolation for HD/SD formats
  • Support for all HDMI 1.2 audio formats
  • Advanced noise reduction and enhancement.
  • Max. active image size of 2048 samples x 2048 lines PBP processing for various combinations of video and graphics with alpha blending.
  • Fully integrated sprite based multi-plane OSD controller.
  • Frame rate conversion to/from any refresh rate.
  • Pattern mode w/ color bars & coarse hatch patterns.
  • Color correction.
  • Noise Reduction.
  • Detail Enhancement.
  • Brightness Adjustment.
  • Gamma Selection.
  • Aspect Ratio Select.
  • Custom Timing output mode.
  • French/English Menu set.
  • RS-232 upgreadeable firmware.

A Closer look

Let’s take the Gefen for a spin and look at some of the OSD menus and examine some of the features in detail.


Main OSD Menu (click to enlarge)

The menu above is the main menu that comes up when the menu button on the remote is pressed.  As mentioned there are no front panel indications and all interactions are handled via menu overlays that are inserted into the video stream.  So a person needs an HD-SDI monitor or similar equipment in order to navigate through the menus.

At the bottom of the main menu, one can see both the input and output video formats  (1080p24 in this case).


Output Format Menu (click to enlarge)

The menu above shows the available output video format options. As can be seen the choices are extensive and include most if not all of the video formats that one would want.


Link Options (click to enlarge)

The link configuration menu to the left allows the user to select between RGB and YCbCr (4:4:4 or 4:2:2) colorspace options.

Not shown is the Genlock Reference menu which allows the user to lock the output timing based on the input signal or based on an external clock provided at the rear of the unit.

Next let’s take a look at the available input formats from the menu below.  The unit can auto detect the timing being used or it can be forced to lock onto the various video and computer formats shown on the two screens below.


Input Video Formats (click to enlarge)


Input Computer Formats (click to enlarge)

Next let’s take a look at the menus used to control the various picture settings


Color Controls (click to enlarge)

Here we see the basic brightness and contrast settings.  Independent adjustments for R,G or B are a nice touch.


Gamma adjustments (Click to enlarge)

Here we see provisions for basic gamma adjustments.


Detail Enhance Controls

Here are the detail enhance settings (more on that later).


Noise Reduction Menu (click to enlarge)


Overall, the Gefen works very well in performing HDMI to HD-SDI conversion.   Scaling between various input and output video formats worked fine and without a hitch.  There was an initial concern that it might be difficult to sync the device properly since there is no built-in display, but Gefen thought about this and provided a video output format toggle on the remote so that the user can get it out of whatever mode it may be in and force it to use one of the common video formats (480i, 576i, 720p and 1080i).  In this way the user can quickly get the unit sync’ed up to a display and back into the OSD menu.  The unit also allows the user to specify a power on video format so that no user intervention is required on powerup even with rare video formats.

The only issues encountered were with features that are probably low on the priority list for a product such as this.  The filter settings for detail enhance did not seem to work as well as other VXP implementations that we’ve tried.  Similarly, 24p reverse 2-3 pulldown seemed to suffer from occasional motion studders.

Overall, the unit worked very well and if one wants HDMI to HD-SDI conversion across many different video formats or support for uncommon video formats such as 2Kp24, the Gefen is the only game in town.

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