New Video Format could be in trouble without the compression technology it needs
4K has four times the pixels of today’s 1080p HD. The information for all those pixels can eat a lot of bandwidth. Yet the delivery infrastructure for video — satellite links, over-the-air and cable channels and Blu-ray discs — isn’t getting more bandwidth any time soon, and most consumer Internet connections can barely handle simple HD streaming.
So dreams of next-generation broadcasting and consumer electronics firms’ hopes for billions of dollars in new TV sales rest upon an arcane combination of high tech and black art: video compression.
In a nutshell, compression turns the beautiful but huge digital images coming out of video cameras into smaller, but hopefully still beautiful, digital files. Or, more precisely, it reduces the bitrate of the video stream to something the TV and Internet infrastructure can handle.
When video engineers worry over whether 4K will ever live up to its promise, it’s the bitrate they’re concerned about. The pixels will be there, but will there be enough data to make them worthwhile?
The bitrate for video can be squeezed in many ways. Color can be sampled less frequently than the rest of the picture. Pixels that don’t change, or barely change, from one frame to the next can be transmitted less frequently. Subtle information that average viewers probably won’t be able to see in a frame can be trimmed away. Or some resolution can simply be tossed out.
Peter Putnam, president of Roam Consulting and an expert on video compression, explains that the signal coming out of an HD camera has a bitrate of 1.5 gigabits per second. But the broadcast TV channels they feed are limited by law to just 19 megabits per second. Neverthess, he adds, “You’ve watched CBS, NBC, PBS high definition, and it looks pretty good.”
Peter Symes, director of standards and engineering for the Society of Motion Picture and Television Engineers says CBS pushes hard for its affiliates to use their full 19Mbps to deliver the best HD picture their bandwidth will allow. “Most broadcasters don’t do that,” he says. “They allow maybe 12 megabits for HD, and the quality is less. Maybe it’s got a resolution corresponding to about 1200 pixels instead of 1920 or whatever, but it certainly isn’t the full 1920 x 1080.”
So even today, the HD picture on some channels isn’t delivering the full potential of the format. Squeezing 4K into the same infrastructure is likely exacerbate that problem.
Today’s TVs and other devices have decompression software on a chip inside the device. But chips with 4K decompression haven’t hit the market, so the 4K TVs arriving in the marketplace are improvising their decompression solutions. Sony’s new 4K TVs and accompanying 4K media player use compression from tech company eyeIO, but the media player sidesteps the problem by downloading content instead of streaming it.
Eventually, the software and hardware for encoding and decoding commercial 4K will make it to market. The new High Efficiency Video Codec is up for official approval, and should squeeze 4K video down enough to fit into today’s infrastructure. The encoders and decoders will also improve, so 4K broadcasting and streaming should improve over time, as HD has.