In broadcast and cable television newscasts and other programs, there are often times when a program segment originates at a remote location and is communicated via satellite. As illustrated in FIGS. 1-3, satellite delays occur because communication signals 30 must go from the transmitting ground station 32 to the satellite 34 and then return to the receiving ground station 36. If the satellite 34 is in a synchronous orbit (22,236 miles above the Earth's surface), as shown in FIG. 1, the distance up and back is at least is 44,472 miles. The time for a transmitted signal 30 to reach a synchronous satellite 34 plus the time for the response to be received back on the ground is from 0.24 to 0.28 seconds, depending on the locations of the transmitter 32 and receiver 36. The propagation delay will be less for satellites 34 in low-Earth orbits, such as the Iridium constellation (485 miles above the surface). However, in many of these cases, as illustrated in FIGS. 2 and 3, it may require two or more satellite hops for the signal 30 to get from the remote location to the local studio.
Communication delays of the type described are most evident for satellite links, but terrestrial links can cause delays too. In addition to propagation delays purely due to distance, the communication signal likely undergoes one or more digital conversions, compressions/decompressions, encryptions/decryptions, and error corrections, all of which can introduce additional delays of 0.05 seconds or more per hop.
Although the travel times for signals to go in both directions between a local studio and a remote site might be the same, this is not necessarily the case, as the travel times depend on the communication circuits used for the two paths. An intercom function from the local studio to the remote site is often called an “IFB” (interrupted feedback). Typically, this intercom path is audio-only and relatively low quality because it is used only by a reporter at the remote site to hear the cues or questions spoken by the anchorperson at the local studio (it might even be a one-way circuit). In contrast, the signal from the remote site contains video and is usually carried by a high-quality circuit. For example, the intercom from the local studio might be carried over a terrestrial telephone circuit, while the remote program is sent via a satellite link. It is not uncommon, however, for the remote signal to be carried by satellite telephone, in which case the remote program audio and video quality is mediocre, but the single telephone circuit can perform both intercom and program duties.
Because of the distance the signal must travel from the remote location to the broadcasting studio (perhaps using multiple satellite hops) and because the signal likely undergoes digital processing en route, it could take nearly a second for remote program content to reach the local studio. Furthermore, if the reporter at the remote location is responding to a live cue from the local anchorperson, the perceived delay at the studio could be doubled since a full round trip is required. This total round-trip delay (RTD) is the delay perceived by a viewer, and is a combination of the time it takes for the anchorperson's cue to reach the remote location plus the time it takes for the reporter's response to reach the local studio. After the anchorperson introduces the remote reporter, there will be no apparent reply until the reporter hears his cue over the intercom, begins to speak, and his remote program is received back at the local studio. From the viewer's perspective, this delay manifests as an awkward (and often annoying) two- to three-second pause between the time the anchorperson finishes his introduction or question and when the remote reporter begins his response.
If a remote program segment can be recorded in advance of being put on the air, then the delays can be edited out of the recorded program. However, this technique is not always practical, especially for a program such as a newscast that needs to have a “live” quality.
What is desired, therefore, is a system and method for eliminating in real time the perceived delay between local and remote program elements of a live televised presentation.