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something can’t be done in real time, it’s out.” MAINTAINING LATENCY Away from the world of distribution, different fields clearly have varying expectations. Ciro Noronha is chief technical officer at Cobalt Digital, a company deeply embedded in the infrastructure on which broadcast production relies. The world of TV contribution is essentially the last bastion of entirely uncompressed video. “You have a continuum of solutions which start at high compression, middle compression and then uncompressed,” Noronha begins. “If you have plenty of bandwidth and also want the pure, perfect and pristine image, you pay for that with a very high bit rate. It’s 1.5Gbps HD – although you have almost no latency.” Latency is a key concern in live production, where the timing of cuts between shots relies on real-time decisions rather than a pre-edited timeline. Historically, codecs have used similarities between frames, implying they must have a delay of at least a few frames – making that sort of snappiness tricky. Recent developments, Noronha says, have found ways to both have your cake and eat it: “There’s mezzanine compression like JPEG XS, which offers almost the same latency as baseband uncompressed, but will compress it between a factor of four and ten. While there is a little degradation in quality, the latency remains outstanding.” This style of approach, Noronha estimates, is likely to become more common both in the high end of broadcast production and even

as overall progress in information technology makes uncompressed workflows easier to handle. “I have a gigabit at home, symmetrical, which was unthinkable a few years ago. However, I doubt everything is eventually going to be uncompressed SMPTE 2110.” A reason for this counterintuitive reality is that compression makes for some significant conveniences, as with remote production. That has sometimes meant replacing an expensive satellite link with the public internet, although it increasingly means moving the director, vision mixer and the rest of the gallery to a neighbouring time zone. Delay, again, is the bugbear, as Noronha happily acknowledges. “People have been avoiding codecs for remote production because of latency, but you can get the same class of latency with JPEG XS or HEVC, at a much lower bit rate. So, it became a viable solution.” Finding these solutions to latency requires painstaking engineering. Contrary to popular preconception, Noronha remarks: “You can get sub-frame latency, glass-to-glass in less than a frame. Cobalt has demonstrated the solution and will be shipping it in a few months, so it’s possible. You take a hit on bit rate; for an HD signal, you need around 30Mbps, but it’s not 1.5Gb or 600Mb, it’s 30.” Making that happen requires some under-the-hood knowledge of how codecs do their magic. Many use those similarities between nearby frames to improve performance. Bidirectional – or B-frames – can refer to frames from the past or the future, but that usually means

a return to that multi-frame delay. P-frames are predictive only. “For HEVC, you just don’t do B-frames,” Noronha explains. “You don’t look in the future; it’s perfectly fine to look in the past. There’s a technique for MPEG-2 called gradual decoder refresh. You can send [data] without waiting for the whole picture.” Despite all this cleverness – on top of the massive gains made since the nineties deployment of MPEG-2 – Noronha sees the writing on the wall for big gains in codec performance. “We are reaching a place of diminishing returns. The next-generation codecs really shine if the resolution is high. If you are using smaller resolutions, the gains are not that great, maybe 20-50% – the same quality at half the bit rate. The improvement from MPEG- 2 to H.264 to H.265 is not going to happen any more. There is a fundamental limit.” THINKING SMALL Either way, a codec might be designed for production work, distribution to consumers or all manner of things. One unusual approach is to implement image compression on a sensor itself. Jean-Baptiste Lorent is director of marketing and sales at Intopix, the company behind Tico, a product that’s quite literally named after the idea of being a tiny codec using minimal resources. “The company was created in 2006 as a spinoff from UCLouvain,” Lorent explains. “We came from the labs, which have strong expertise in image processing. We have 15 years of microelectronics optimisation for a field-programmable gate array, as


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