This article was originally published at www.display-central.com
Harmonic was showing a 120 Hz frame rate demo of 4K UHD content at NAB 2014. The display screen was split, with 30 frames on one side and 120 on the other (see video below). The content started as 4K/30-frame, and a processor built by Sigma Designs handled the frame rate quadrupling, as well as motion interpolation, so it had capabilities to do scaling within those frames to produce the 120-Hz content. The content was very slow and not the best kind that could have been chosen for the demo. So, there was not a lot of motion to illustrate the benefits of the higher frame rate.
There was one piece where we could see a snake going diagonally across the middle of the split-screen, and on the 120 fps side, the scales on the snake’s back were clear and crisp, but were a little blurred out on the 30 frame content side.
So, the debate about delivering more pixels and higher frame rates continues. You could argue that one way to do it is to capture in 4K/120, and deliver that through the infrastructure via compression methods and into the home. Or, you could argue that you capture 4K/120 and down res and/or down frame rate to deliver it as a more standard traditional signal with some metadata. You would then re-inflate to the 4K/120 signal at the home. The latter would be more bandwidth-efficient, but the question is will the image quality be good enough, which is an open debate at this point.
Harmonic’s Ian Trow wondered the same thing about the delivery of native 4K content to the home. Might it be better to encode 1080p content using AVC/H.264 and deliver it at 5Mbp over legacy system and let the TV scale it to 4K compared to 4K native content encoded with HEVC at 15Mbps?
Harmonic also showed live 4K/60 encoding at 20 megabits, with some content at 15. Its goal was to prove that live 4K encoding is now feasible. The content was decoded on the prototype set top box supplied by ViXS and looked acceptable. One point that Trow also made was that the encoding biot depth is independt of the bit depth of the content. They used the Main 10 HEVC profile which encodes at 10 bits, but the original content was only 8-bits in depth. –Chris Chinnock