By Ashley Dove, general manager at Vislink
Technology trends over the last year have travelled in the direction of bigger, better, faster and higher quality. We saw it with the growth of HD, and we are now seeing the same trend with 4K Ultra HD technology. There is no question that the future of TV viewing is 4K Ultra HD – consumers will continue to demand better picture quality and TV manufacturers will respond. 4K is the natural progression of technology advancement in relation to viewing monitor resolution. With four times the number of pixels per inch as 1080p60, images are clearer, more detailed, and of better clarity, and 4K televisions are slowly making their way onto the market.
Consumers are also demanding greater flexibility to when and how they watch television. Internet streaming of IP encapsulated video to televisions and peripheral devices has become a mainstream method of video consumption.
HD signals (1920 x 1080) are composed of 2 million pixels, while a 4K signal (3840 x 2160) is comprised of 8 million pixels. As a result, an important issue quickly becomes apparent: 4K has four times the resolution, and subsequently requires four times the amount of data to move video across the network, which quadruples the amount of bandwidth required to transmit when compared with HD.
The increased bandwidth required to transmit video at 4K translates to higher costs for cable and internet companies. At present, streaming HD content is already taxing network video traffic. As more and more videos are provided to viewers at 4K, the bandwidth required to stream the video will increase demand on cable providers, who may begin imposing bandwidth limits on consumers. This will dramatically increase buffering times for online 4K content viewing.
To counter this effect, engineers have been hard at work on better compression techniques that will reduce the bandwidth required to transmit data. Much like 4K is to next generation video, H.265 (also known as HEVC) is the next generation of video compression.
By employing advanced encoding techniques, and combining them with sophisticated modulation schemes, H.265 requires less bandwidth for transmission. H.265 is expected to deliver the same, or even superior, picture quality for both HD/SD and 4K resolutions, at up to a 50 per cent reduction in bitrate versus its predecessors, MPEG-4/H.264. There are a number of microwave transmission technologies that can be used to compensate for the remaining 25 per cent of additional bandwidth.
For example, in point-to-point microwave or satcom applications, DVB-S2X (DVB-S2 with extensions) enables steeper roll-offs in the modulation scheme enabling more carriers to be squeezed into the available bandwidth.
Also, for non line-of-sight MIMO (multi-input multi-output) OFDM transmission techniques can be used to increase throughput by utilising multiple antenna techniques with antenna de-correlation to create two independent video streams.
Other improvements can be achieved using LDPC (low density parity check codes) FEC techniques can alternatively be used to help offset the additional 4K bandwidth. LMS-T modulation techniques with LDPC codes increases data throughput for a comparative signal to noise ratio.
Additionally, LTE technology, as used in 4G cellular transmissions, can be utilised in private frequency bands for local networks
To make way for broadcasting 4K efficiently and cost effectively, encoders and decoders will need to incorporate H.265 compression schemes. There is some debate over the timeline of implementation and adoption, but some equipment manufacturers are already developing encoders with H.265 compression capabilities.
Much of the focus has been on last mile delivery of video (ie, to playout devices via IP or cable). However, H.265 will also play an important role in the collection of video from the field, as better compression and modulation schemes will result in lower bandwidth requirements for broadcasters. For example, the impact on cellular newsgathering would be beneficial. Right now, cellular transmitters can stream in HD, but with H.265, they would be able to deliver the same quality video at half the bandwidth, lowering the cost and improving the quality of transmission.
