White Paper: Display Interfaces 101 – The past, present and future of display standards
Background In all things electronic, ongoing innovation delivers the welcome benefits of continual improvement. A somewhat less enjoyable corollary is the shifting landscape of speeds, feeds, specs and standards to which one must continually adjust. Display interfaces are no exception. Just over ten years ago the integration of audio and video, following on the heels of the transition from analog to digital, revolutionized the quality of video output. And along with the clarity of high definition and the ease of integrated audio came new interface standards and a host of new connectors, cables and adapters. Before this sea of change, life was simpler. VGA was the reigning standard in enterprise PCs. And while screens were smaller, CRT displays were bulky and the quality wasn't as good, the connectivity options were much more straightforward. Today, interface options include DVI, HDMI and DisplayPort, as well as the lingering availability of VGA to enable compatibility with older, legacy equipment. Below, an overview of today's display interface technologies and how they will likely impact the enterprise environment over the next few years. Technology overview: VGA Introduced in 1987, Video Graphics Array (VGA) was developed by IBM for inclusion with its original PC products. The legacy analog standard, VGA remains prevalent in emerging markets and continues to represent a sizable portion of the installed enterprise and consumer display base. [caption id=" align="alignleft" width="197"] 15-pin VGA connector[/caption] DVI Digital Visual Interface (DVI) was introduced in 1999 by the Digital Display Working Group (DDWG), which was organized by seven industry leaders including Intel, HP and IBM. Designed to create a standard for digital video content transfer, DVI remains the most common digital interface seen on PCs and LCD monitors today. DVI is the display interface most similar to VGA and supports analog as well as digital video, with configurations including DVI-A (analog only), DVI-D (digital only) and DVI-I (digital and analog). Like VGA, DVI is a video-only interface. DVI supports a maximum resolution of 1920x1200 HD video, and 2560x1600 with dual-link DVI connectors. DVI sources are compatible with VGA and HDMI devices via an adapter. HDMI Like DVI, High Definition Multimedia Interface (HDMI) is a high-bandwidth, unidirectional, uncompressed digital interface standard. Developed by a consortium of leading industry corporations and introduced in 2003, HDMI transfers video at the same quality levels as DVI (with resolutions up to 2560 x 1600), with the additional advantage of also carrying audio over a single cable. According to the hdmi.org learning center, HDMI is DVI with the addition of audio (up to 8-channels uncompressed) and a smaller connector Designed specifically to support consumer electronics (CE) applications, HDMI is currently the most popular digital connector for consumer devices including TVs, set-top boxes, Blu-ray players, A/V receivers, gaming consoles, camcorders, digital cameras and some smartphones, as well as most consumer PCs. HDMI connectors have 19 pins and come in three sizes: The most common, Type A (standard), plus Type C (mini), and Type D (micro). Type D connectors can be found on some smartphones and tablets. HDMI sources are compatible with DVI-D and DVI-I via an adapter [caption id=" align="alignleft" width="399"] From L to R: HDMI Standard, Mini, and Micro connectors.[/caption]
DisplayPortDesigned by VESA, an international non-profit organization that sets and supports industry-wide interface standards, DisplayPort was first introduced to the market in 2008. A fully digital, packet-based audio/video technology, DisplayPort is intended to be a direct replacement for VGA and DVI and features full backward compatibility with both, as well as with HDMI. Offering the ability to support up to four displays (at maximum resolution of 1920 x 1200 each), two displays (up to 2560 x 1600 each) or a single display at resolutions up to 3840 x 2160, DisplayPort has been specifically positioned to meet the needs of business and other high-end users. DisplayPort connectors have 20 pins and are available in standard DisplayPort and Mini DisplayPort sizes. Most full-size DisplayPort connectors have a locking mechanism that prevents them from being accidentally disconnected. [caption id=" align="alignleft" width="399"] DisplayPort Standard (L) and Mini (R)[/caption] **Some DVI cables or ports may include fewer pins if they are designed for lower resolution devices. If a port contains all the pins, it can support the max resolution. Future focus At midway through 2013, DVI remains the most prevalent digital/analog standard in enterprises, both among installed systems and those currently shipping. However, DVI has been slowly losing share to HDMI and DisplayPort. A 2012 NPD In-Stat report predicted that legacy VGA and DVI display ports will no longer be used in PCs by 2017, with Intel and Advanced Micro Devices (AMD) planning to phase out support for VGA by 2015, and AMD planning to do the same for DVI by 2015. Fueling this transition is the stagnation in DVI development. Having remained essentially unchanged since its introduction in 1999, there are no further plans to update the DVI spec and its development group, the DDWG, has been inactive since the last (and very minor) update made in 2001. By contrast, HDMI and DisplayPort have continually updated their respective specs. HDMI recently released its 5th update, 1.4a, which added support for new 3Dvideo formats. DisplayPort version 1.2 was approved in December 2009, doubling the effective bandwidth to 17.28 Gbit/s, for increased resolution support, higher refresh rates, and greater color depth. And despite its many years of popularity, DVI connectors now seem bulky and cumbersome compared to the slimmer designs offered by HDMI and DisplayPort, which are ideally suited to supporting emerging thin and light laptops, and Windows 8 Pro tablets. The question of supremacy between HDMI and DisplayPort has been a hot topic of discussion for several years. The dust has begun to settle and the consensus seems to be that they will complement one another, rather than compete, at least for the foreseeable future. According to Brian O'Rourke, research director at NPD In-Stat, referring to the 2012 report, "Though DisplayPort and HDMI are different in nature and compete at a certain level, both can coexist and make significant strides in different market segments. DisplayPort is a digital, packet-based technology, making it a fit for PCs. HDMI is a mixed-signal, streaming technology, making it less optimal for PCs and more for consumer electronics." And as stated by the DisplayPort developers in the displayport.com FAQs: "DisplayPort and HDMI are very different technically, and each has a different product focus. HDMI is the de-facto connection in the home theatre and is used widely on HDTVs as an A/V interface.... DisplayPort is focused on PC, monitor, and projector usages as a replacement for DVI and VGA where high performance and backwards and forwards compatibility over standard cables are valued." HDMI has been tremendously successful and has a huge installed base in the CE market; it's clearly not going anywhere anytime soon. DisplayPort on the other hand is distinctly positioned to meet the needs of the enterprise and high-end users. Chief among the benefits for these users is DisplayPort's support for up to four monitors and the ability to connect via an inexpensive adapter to nearly any other type of display, as well as its thin, more-manageable cables and uniquely secure locking mechanism. Additionally, manufacturers will likely favor the royalty-free DisplayPort over HDMI, which demands an annual fee plus a per-unit royalty. A review of products shipping today shows these predictions coming to pass. DisplayPort is frequently seen integrated along with HDMI in the latest add-in video cards, as well as in laptops marketed to business users. New higher-end desktop displays, desktop PC and all-in-one PCs tend to support DisplayPort in addition to HDMI and DVI. Laptops and Windows 8 Pro tablets, with less available space for connectors, often offer one or the other, with consumer displays generally featuring HDMI and enterprise models supporting DisplayPort. Summary The old-faithful VGA is on its last legs, though we'll continue to see lingering support for legacy equipment for a few more years. DVI will continue to gradually lose share to DisplayPort in the enterprise and HDMI in the consumer market. DisplayPort offers several useful advantages for the enterprise, including multi-monitor support, backward compatibility, secure connections and thinner, more-manageable cables, along with the capability to support resolutions up to 4k x 2k with better color depth, higher refresh and data transfer rates along with HD audio formats. At present and in the near-term, however, implementation of DisplayPort is expected to slowly accelerate as corporations invest in larger displays and multi-display arrays. During the transition, DisplayPort's backward compatibility with its three major predecessors will be a distinct advantage to enterprises that wish to leverage existing equipment.