enhancement video coding (LCEVC), which is designed to work as a layer on top of conventional codecs such as H.264 or H.265. It seems likely that early deployments will be in television broadcasting. It’s a field which likes to create the option for more capable receivers to decode improved pictures, but in a broader sense, LCEVC is talismanic of a world that perpetually wants to fit bigger pictures down smaller pipes. Perhaps most importantly, it wants to do that without exhausting either the computational or battery resources of anyone’s cellphone, so V-Nova’s engineers took care to build their enhancement layer around modern, multi-core computer hardware. “Legacy compression had this idea of dividing the image into blocks,” Meardi notes. “If you zigzag across an image from top left to bottom right, you’re forcing sequential operations into the process.” LCEVC, however, is built to do several things at once. “I have something lean, mean and very efficient at compressing dots and lines because that’s what it is.” Viewed alone, the dots and lines of the LCEVC enhancement layer resemble an edge-detection filter. Traditional techniques – which work on image blocks around eight pixels square and often larger – don’t compress that type of data well. Meardi emphasises the importance of understanding the nature of the data. “Once you understand what you are compressing, it’s easy to compress with very small transforms. We used some sophisticated neural networks to understand the limits, discovering you can indeed be 10% more efficient than LCEVC. But at
that point, do you care if it costs you five times the processing power?” That question seems to be the core concern of codec engineers – and in some ways, always has been. Concern over computing power has provoked the adoption and retirement of whole techniques – for example, the vector compression used in designs like Cinepak in the early nineties. Despite the light weight of the codec’s mathematics (and the power of modern hardware), rolling out LCEVC as a format for broadcasting to consumers meant carefully analysing what hardware the average set-top box has to offer. Meardi describes most of them as ‘designed to do H.264, H.265, VVC, but it’s possible to leverage hardware blocks of very low-power systems- on-a-chip (SoC) which haven’t yet implemented LCEVC in silicon.’ “All video SoCs come with scalers, overlay hardware and hardware blocks which can be repurposed to implement LCEVC,” he continues. “We always start from mapping every hardware block they have, including the ones they forgot about. Then, we worked with Nvidia and presented a showcase together.” Attention to that level of detail, Meardi concludes, is sometimes new to people doing advanced theoretical work on video compression. “Many people, including companies such as Huawei and others, agree. Several scientists working on codecs weren’t considering that compression needs to happen in real time. You can design something which reaches the Shannon optimum [a mathematical performance limit], but it doesn’t matter. The principle we had from the very beginning in our company is if
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