The video revolution
It is placing increased requirements on local, metropolitan and wide area networks for bandwidth, reliability and quality of service.
July 1, 2010
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A recent forecast by Cisco Systems Inc. indicates that Internet video alone will account for 57% of all consumer Internet traffic in 2014.
Another impressive statistic is that global IP traffic will grow from 15 exabytes per month in 2009 to 64 exabytes per month in 2014, for a compound annual growth rate (CAGR) of 34%. How much is one exabyte of information? 1 exabyte (EB) = 1 billion gigabytes of information.
At a transmission rate of 10 Gigabits/second it would take 800 million seconds or 25 years to transmit 1 EB of information. So the amount of information flowing over the Internet is truly staggering.
One technological change fueling demand for more bandwidth is the transition to High Definition and 3D video from the traditional Standard Definition video format.
By 2014, the same Cisco forecast estimates that 3D and HD Internet video will comprise 46% of consumer Internet video traffic.
The forecast also shows that video communications (video conferencing) traffic growth is accelerating. Although it is still a small fraction of total Internet traffic, video communications is expected to increase sevenfold from 2009 to 2014.
First, let’s look at the standards that apply to high definition (HD) video, commonly known as 1080p, 1080i or 720p as well as enhanced definition (ED) and standard definition (SD) video.
The family of Serial Digital Interface (SDI) standards published by the Society of Motion Picture and Television Engineers (SMPTE) is shown in Table 1 below.
The high definition video format 1080p or 1080i represents 1,080 lines of vertical resolution while the letter “p” stands for progressive scan and the letter “i” stands for interlaced scan.
The term 1080p or 1080i usually applies for a widescreen aspect ratio of 16:9. This creates a frame resolution of 1920×1080 pixels. The frame rate is usually specified after the letter p (or i), such as 1080p30, meaning 30 progressive frames per second, or 1080i60, meaning 60 interlaced fields per second.
1080p24 has become an established production standard for digital cinematography and is the format generally used for Blu-ray Disc/HD DVD Movies.
The SMPTE 424M standard, as shown in Table 1, allows for bit-rates of 2.970 Gb/s, which are sufficient for 1080p video at 50 or 60 frames per second in uncompressed format.
Another related digital interface is the HDMI Standard for widescreen liquid crystal displays (LCDs) and computer monitors.
The latest version 1.4a of HDMI standard was published in March 2010 and provides additional formats for supporting 3D displays, a resolution up to 4096×2160p at 24Hz and a Transition Minimized Differential Signaling (TMDS) throughput for video, audio, and auxiliary data of 10.2 Gb/s.
When high definition digital video and audio content is transmitted over the air, over cable, over satellite networks or over the Internet, it is first reduced to a coded bit stream using one of three compression algorithm: MPEG-2 Part 2, H.264/MPEG-4 AVC, or SMPTE VC-1.
MPEG-2 is the codec used on regular DVDs, which allows backwards compatibility. The compression algorithms are quite efficient. For example, Blue Ray Disk Video movies have a maximum data transfer rate of 54 Mb/s and a maximum bit rate of 48 Mb/s for both audio and video data.
For video over IP systems, the coded bit stream is encapsulated in IP packets. Video over IP systems have special challenges compared to most non-time-critical IP traffic.
Video over IP systems will only work if the network is capable of carrying the content with negligible packet loss and minimal network delay variation.
Resending packets is not an option because of the sequential nature of the underlying video signal. Video over IP does not work very well on overloaded networks.
One approach to this is the “quantity of service” approach which simply allocates sufficient bandwidth to video-carrying traffic so that it will not congest under any possible load pattern.
Other approaches include dynamic reduction in frame rate or resolution, network admission control, bandwidth reservation, and traffic prioritization techniques.
As you can see the growing demand for high definition video content as well video conferencing places increased requirements on local, metropolitan and wide area networks for bandwidth, reliability and quality of service.
Meeting these demands requires networks that can segment and prioritize video carrying traffic and that have sufficient capacity to meet the demand without congestion. CNS
Footnote: The TIA-1152 standard also includes a section on alien crosstalk measurement requirements and procedures for Category 6A cabling.
Paul Kish is Director, Systems and Standards at Belden. The information presented is the author’s view and is not official TIA correspondence.