Playout & Transmission Global Viewpoint – September 2021

Media Is Special

In this world of IP, COTS servers and SDN, it’s worth just taking a step back and reminding ourselves that video and audio is not just data, it has some rather special properties that make it unique.

Video is an illusion, there are no moving pictures, just a succession of rapidly changing frames that give the illusion of motion. In essence, cameras take an infinitely varying light scene and sample it at the frame rate of our choice, we then further sample the frame to provide lines, luminance and chrominance data. We throw most of the data away from the original scene and just keep enough to convince the human visual system that moving images exist in front of us.

We take a similar illusory approach to audio. Most of the audio data available to us is dispensed with during the sampling, recording and playback processes. Anybody who has read John Watkinson’s recent series on microphones will fully appreciate that all is not as it seems with sound recording and reproduction.

The point is, television or media, depending on what we’re calling our industry this week, delivers just a hint of the available data to convince our combined human visual and audio systems that moving pictures and sound exists. Our brains literally fill in the gaps. Engineers over the past hundred years have been working in harmony with the intricacies of the brain, eyes and ears, to enhance this illusion. Its intrinsically connected to the quality and value of the viewing and listening experience.

When video and audio was being developed for television, in parallel, our engineering predecessors and innovators considered and designed the transport stream. That is, the distribution mechanism and video and audio essence were one and the same, hence the reason we have PAL, NTSC, SECAM, SDI, AES etc.

IP was developed for a very different landscape than we now find ourselves in. Back in the 1970s and 80s, video and audio streaming didn’t exist, and IP networks were still being developed. Ethernet was one of a host of different transport streams being experimented with. Fast forward forty or fifty years and we now find ourselves distributing moving pictures and sound over packet switched, asynchronous networks.

Clearly this can be achieved as we are streaming and distributing video and audio over all kinds of networks, from private LANs to internet WANs and even WiFi. However, these networks were primarily developed for the exchange of transactional asynchronous data.

I’m a great supporter of IP, especially the adoption of ST2110 where, for the first time in the history of television, the video and audio essence has been abstracted away from the underlying transport stream. However, we should also remember that video and audio have inherent cyclical properties that make television possible.

I believe we must constantly hold onto this knowledge, that is, television is special because of the relationship between the essence data and the human visual and auditory system, they simply cannot be separated. We should remember this when working in the IP world as media is not just any kind of data!

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