Digital splicing
May 1, 2007 12:00 PM, BY PETER CHAVE
DPI platforms create ad insertion growth and revenue for broadcasters.
In any difficult transition, the elements that contribute revenue generally top the list of priorities. This is true for TV advertising as it moves along the inevitable digital transition path. Specifically, the cue tones, contact closures and video switchers long known as the means to airing a local advertisement are now well on their way toward digital splicing.
Figure 1. In this splicing event diagram, the ad within the insertion channel is spliced into the primary channel at the indicated in-splice point. The outgoing channel illustrates the primary channel with the alternate ad.
The reason for the transition is clear. Local cable TV advertising revenues topped $4.68 billion in 2006. Broadcasters collect a fee each time they issue a cue that allows a local ad to override a national ad. Meanwhile, as more cable and broadcast networks are digitally simulcast, and as consumers purchase more digital and HD displays, it is critical that advertisements reach all intended audiences.
This article describes the steps involved in digital program insertion (DPI), or the splicing and delivery of MPEG-compressed video streams. I'll briefly review the existing world of advertising cues and the new, spliced world, focusing specifically on how a digital splicer knows what to do in the few seconds preceding and following a local ad avail.
A brief history of ad insertion
Since the beginning of local advertising insertion, broadcasters indicated that an advertising avail was coming by broadcasting a series of in-band dual-tone multifrequency (DTMF) subcarrier audio cue tones. The tones triggered the cutover sequence from a nationally shown ad to a pod of local ads.
DPI is the digital counterpart for analog insertion and cue tones. As a technology suite, it automatically and cleanly places digitized, compressed ads into an MPEG-compressed transport stream.
Inserting digital ads into digital programs requires two core technologies: cueing and insertion. Cueing defines a digital cue delivery in-band with the video and audio programming. Insertion consists of two parts: the technology to splice compressed video together and the interface standard between splicers and video asset servers.
The ANSI/SCTE 35 standard defines how local avails are signaled to video splicers, while ANSI/SCTE 30 defines the interface characteristics between video ad servers and splicing gear. An example of this is shown in Figure 1 on page 46. The advertisement within the insertion channel, shown on the top reel, is spliced into the primary channel in the middle reel at the indicated in-splice point. The outgoing channel (shown in the bottom reel) illustrates the primary channel with the alternate advertisement.
Splicing basics and signal flow
In a network playout environment enabled for DPI splicing, several steps occur. Digitized, uncompressed audio and video streams enter a video encoder, either from studio feeds or video storage servers. The encoder receives cue triggers from an automation system driven by the associated ad avail schedule. When a cue trigger is imminent, the encoder injects an ANSI/SCTE 35-based cue message into the outgoing, compressed video stream.
At the local cable headend, the integrated receiver and decoder (IRD) moves the cue message to the splicer to initiate the sequence of events that will result in a local ad insertion. When the cue message triggering a local avail transits through the IRD to the splicer, it responds by informing the ad server to retrieve the ad spots scheduled for that particular time. Then the ad server initiates the splice. The outgoing video streams the replaced (local) ad into the cable operator's distribution network.
In homes, the impact of DPI happens behind the scenes. For example, instead of seeing a nationally broadcast Ford F-150 ad, home viewers see an ad by the local Ford dealer.
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