TV networks and video distributors are required to handle video contribution so they can re-distribute it. The two categories of video are live and, of course, non-live video. Sports and news are prime examples of live video, where sitcoms and dramas are obviously non-live. The play-out distribution of these two types of video are fairly consistent, but the receiving aspects can be very different.
Non-live Video Contribution
Non-live video contribution has evolved from physically shipping tape reels to digital file transfers using multiple methods from proprietary satellite distribution networks to simple FTP transfers over the public Internet. Video contributed today does not have to be real-time, which means it may take 10 minutes to transfer a 2 hour program, or it may take an hour to transfer a 30 second spot if using left over bandwidth in an already paid-for data pipe. If something goes wrong with the original contribution feed, then do-overs are possible since there is ample time between the contribution and eventual distribution. Hand-off automation of non-live video contribution works well since any inadvertent misses can be corrected before a future “air” date.
Live Video Contribution
Live video contribution, on the other hand, is different in many ways and the tolerance for errors is extremely low. If the video of the Alabama surprise on-side kick during the College Football National Championship game gets interrupted, it’s impossible to recover and viewers miss the experience of that critical event. Likewise, dropping a few key words of a political candidate’s speech can alter voters’ opinions in ways that cannot be overcome. Historically the industry has chosen to use redundant contribution paths, which makes a lot of sense. Setting up each path can be time consuming, but there are ways, like using Crystal’s Discover and Smart Routing features, to make setup quicker and easier. The next challenge is switching from one contribution path to another – when should it be done, who makes that decision, how long does it take to execute the switch.
In a world of digital video, where discrete sequenced data packets are generated by video cameras and encoders, the concept of switching from one path to another starts to be obsolete. Establishing multiple contribution paths is still necessary and requires remote control capability to do so. But instead of deciding which path is “on-air”, the receiving (and decoding, if applicable) equipment should simply take the next sequenced data packet from any one of the available paths. Or the receiving equipment can compare the same data packet from each of the paths and use the one that seems to have fewer errors (if 2 of 3 are the same, then assume the third is bad.) All the contribution paths are considered “on-air”, but none are critical, so if there is a momentary or permanent interruption in one of the paths, the video content remains intact. For compressed video, it is completely possible to receive some video packets from one path, some audio packets from another, and some ancillary metadata from a third, then re-assemble them at the receiver based on sequencing and timing data.
When redundant video encoders are required are the video source, each encoder’s output data stream is split and flows through multiple contribution paths. The receivers must then be properly configured to receive the correct content flows from the right set of contribution paths. Even though this type of contribution configuration is a bit more complex than two single paths, it is much more resilient, and when using the public internet – less expensive.
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