Skip to main content

How To Buy An Instant Replay System

Instant replay has become a fixture in many professional and collegiate sports. Whether it is being used by officials to double-check the outcome of a questionable call, or to entertain fans in the stands or those watching from home, instant replay has become a permanent part of today’s sports landscape.

Instant replay systems comprise two primary components. One is a device that records and plays back video clips. Early instant replay systems relied on tape decks for this purpose, but as digital technology has evolved, those decks have mostly been replaced by disk-based servers. The other component is a device that controls the server. Operators use controllers to create and organize highlight clips and play them at variable speeds, even in reverse.

Broadcasters looking to implement instant replay systems into their productions must first identify their overall expectations, their system requirements and—of course—their budget. Options range from basic systems with a single record and playback channel to highly sophisticated systems that support simultaneous record and playback with multiple channels and shared storage.

Instant replay systems are usually used in situations where failure is just not an option. Because unexpected problems can be crippling, purchasing a VDR built by a reputable manufacturer with proven reliability in the field is crucial.

When making your shopping list, make sure that first and foremost your VDR includes support for simultaneous record and playback—virtually essential for being able to provide instant replay during a game. Purchasing a VDR that can’t record and play back footage at the same time means that current action on the field will be missed and not recorded while your event is being replayed!

One of the most important considerations and one of the most complex aspects about choosing an instant replay system is the number of cameras that will be in action. Each camera generates a video stream, and the more video streams that can be recorded simultaneously, the greater the options for a broadcaster to choose from when preparing the instant replay. Relatively simple VDRs can record one channel at a time. If multiple cameras are in use, the broadcaster can switch between them via a video switcher, but ultimately will have to choose which video stream to record at any given time. More sophisticated VDRs can record two channels, and premium instant replay systems include a network of VDRs that can record all of the footage you’ll need for an all-star replay.

Video compression and storage are other important factors. Selecting a greater level of compression will hurt video quality, but enable more video to be stored in the same amount of space. Compression schemes for sports broadcasting generally range from 15 Mbps (a high level of compression) to 50 Mbps (a high level of quality). VDRs record material onto one or more hard drives, which in some quality systems can easily be interchanged. Some even support RAID5 storage, which provides redundancy and potentially unlimited amounts of storage. Some two-channel VDRs benefit from shared storage capabilities that enable both channels to be recorded onto a single storage device, which allows for slo-mo highlights from the two camera angles to be played out from the live play channel.

There are several other non-essential but beneficial features of VDRs, such as a full-featured front panel. Some of the better models include a VTR-like feel with knobs and buttons that help broadcast technicians who are familiar with tape-based devices to feel more comfortable with the disk-based version. An LCD screen on the front panel makes it easier to see exactly what is being recorded. Built-in fades, wipes and dissolves can make transitions between clips more seamless.

First and foremost, it doesn’t make sense to purchase a sports controller that doesn’t support the capabilities of the VDR it will be controlling. An important aspect to consider is how many record/playback channels the operator will be controlling. For fast moving games and events, it may be desirable to have one operator control only one or two record/playback channels. For slower moving games and events, it may be possible for the operator to effectively control more channels. Pick a controller that provides control over the minimum number of record/playback channels that the tape operator will be handling. It may be prudent to purchase a controller which supports more channels, for future operations that may call for it.

Operators control the speed of instant replay with either a T-bar, slider or with a tactile wheel or knob, depending in large part on personal preferences. Some operators feel that the T-bar provides more accurate slow motion speed control versus a wheel. Some controllers support forward and reverse playback with the T-bar or slider, while others require use of the wheel for reverse playback.

A primary function of an instant replay controller is to quickly access recorded highlights on the VDR for instant replay. The controller must provide a fast and easy way for the operator to select and save key highlights, then quickly recall them. Typically, controllers provide 100 or more cue points per channel, in which to save a start and end time for each video highlight. More basic systems save and recall “in” points—where the video highlight starts. More advanced systems save and recall both “in” and “out” points for each highlight, and top-of-the-line systems do both for multiple channels. That’s a helpful feature for playing back replays of the same action recorded on different cameras; it’s easy to play one after another to provide additional angles and points of view of a certain play. Top-of-the-line systems also provide the ability to create highlight lists from the saved cue points, to create a montage of game highlights.

Of course, as with VDRs, a controller’s reliability and ease of use is as important as any particular feature.

DNF Controls, an industry leader in the broadcast controller market, has recently partnered with Doremi Labs, a leading maker of video servers and disk recorders, to offer three complete instant replay solutions for simple, advanced, and high-end operations. While both companies’ products interface readily with devices from a wide range of manufacturers, these three solutions provide ready-made, turnkey instant replay systems.

For instant replay applications that require relatively basic control and a highly competitive price point, DNF paired its ST300 controller with a V1-MP2 VDR from Doremi. This combination provides up to four channels of video record and playback, similar to a video tape recorder. The ST300 controller can control up to four VDRs like the V1-MP2 individually or ganged, and store up to 100 clip “in” points per VDR. The V1-MP2 provides high-quality MPEG-2 compression in a standard box with a full-function front panel, two audio channels, and complete analog video inputs and outputs. Optional features include digital component video, embedded audio, up to eight channels of AES/EBU digital audio, and video transitions such as fade, wipe, and dissolve.

For advanced instant replay applications, DNF and Doremi have paired the V1-MP2 with the upgraded ST304-S/RP controller, which adds several more capabilities, such as simultaneous record and playback, the ability for users to save an “out” point as well as its “in” point. That helps users to create, save and recall video segments for later instant replay.

The most demanding instant replay applications call for top-of-the-line solutions from both companies. Their response was to pair Doremi’s MSC-2R2P multi-channel video server with DNF’s DMAT-O sports controller. Users can create cue points from two cameras providing different angles on the same event, and with a few keystrokes create a playlist of cue points, with playout of each cue point seamlessly following the other. The MSC-2R2P provides flexible storage options, with both internal storage that can handle 51 hours at 15 Mbps (or up to 50 Mbps for fewer hours) and an optional external RAID5 storage chassis with virtually unlimited storage potential. This high-end combination also enables the use of shared storage, in which incoming signals from both cameras are recorded onto, and played back from, the same storage medium. The MCS Server’s shared storage also allows for video clip highlights from both camera feeds to play back on any play channel.

Ramzi Shakra is Marketing Director of Doremi Labs ( and Dan Fogel is President of DNF Controls (