DisplayPort

Displayport is standardized by VESA, universal and royalty-free connectivity standard for the transmission of video and audio signals. Applications are mainly for monitors and televisions to computers, DVD players and similar devices.

History

The first DisplayPort specification was published on 1 May 2006.

In April 2007, the VESA adopted the version 1.1, which includes among others the support of encryption with HDCP 1.3. This copy protection (DRM ) is already used in DVI and HDMI. In addition to HDCP also DPCP ( DisplayPort Content Protection) is supported.

On 11 January 2008, the revision was published 1.1a, which initially contained mainly corrections.

Version 1.2 was released on 22 December 2010, new features include support for multi-stream transport ( MST), stereoscopic ("3D " ), the color spaces xvYCC, scRGB and Adobe RGB 1998. Besides, the data rate of the AUX channels was increased from 1 Mbit / s to 720 Mbit / s, which allows applications with higher bandwidth. In addition, the DisplayPort specification since version 1.2 no longer freely available, but only against payment or ( also paid ) membership in the VESA Group of cost.

Mini DisplayPort

In October 2008, Apple introduced a smaller, proprietary version, the Mini DisplayPort, published the specifications of the manufacturer in November 2008 under a free license, to encourage its spread. This Mini DisplayPort has been adopted in the VESA specification 1.1a in November 2009. In February 2011, Intel and Apple introduced an extension to the mini display port called Thunderbolt. Thus, this is not a pure display interface more, but a universal data interface, and in addition is in competition with USB 3.0.

Characteristics of the display ports

The DisplayPort was originally designed to accelerate the transition to digital interfaces, which are a prerequisite for a higher quality screen. In addition to the port require less space and is therefore better suited for portable display devices, such as notebooks.

Technically, the display port on a main connection (English Main Link ) with high bandwidth and low latency, which allows data to flow in only one direction. Version 1.0 should support a video stream including audio, DisplayPort standard but will be easily extensible to multiple video streams.

DisplayPort 1.0 will also support an auxiliary channel, which allows a bidirectional connection with low latency and constant bandwidth to allow, among others, a device controller according VESA-standard E-DDC, E- EDID, DDC / CI and MCCS. This true plug and play is possible. This channel is called AUX Channel (English auxiliary, in this context, with auxiliary channel translatable ).

The AUX channel can be used for various purposes, including but not limited Consumer Electronics Control or USB.

The DisplayPort is designed to replace the commonly used in notebooks for the internal connection of the screen LVDS interface.

Reminiscent of USB plug connector is much smaller than D -Sub and DVI connectors, and therefore allows the easy integration of more than two connection ports on the slot bracket of graphics cards. Moreover, in contrast to competing HDMI connector, an optional locking device is provided.

DisplayPort 1.1 enables compatibility with DVI and HDMI, so that a connection via inexpensive adapter is possible, the need to make only one adjustment of electrical signaling level of TMDS to LVDS. This reach the graphics chip manufacturer Intel, AMD and Nvidia with a trick that already attaches to the video card and not only behind the actual output: detects the graphics card that it is with the connected device is a model with DisplayPort, the signals in this format output. Contrast, for example, an adapter to HDMI is used, signals the card, switch internally to the HDMI protocol. The adaptation of the different signal levels and impedances of the signaling method (LVDS DisplayPort) and TMDS (DVI / HDMI) on electrical level is then in the downstream impedance converter / level shifter, which is passed through the signal edges unchanged, but signal level and impedance adapts to the target interface. However, this support is optional, so that the support of each port by the manufacturer depends. Also, dual-link DVI and analog VGA you can connect, needed in these cases, but active adapter, which is opposite to the imaging device as a signal sink (monitor) and output compared to the image-receiving device as the source.

DisplayPort 1.3 will have in the 8k resolution compatibility with Ultra -HD. Both the 8k resolutions of 7680 × 4320 pixels and 8192 × 4320 pixels are supported. For this extremely high volume of data to increase the bit rate to 8.1 Gbps per channel will occur. Compared to DisplayPort 1.2, the bit rate, increasing by 2.7 Gbps.

Advantages over DVI

  • Allows a simple extension of the standard
  • Can directly drive a display panel. This eliminates scaling and control circuits, cheaper and thinner screens are possible. Latencies are reduced.
  • Replace internal LVDS links to notebook panels by a general standardized interface
  • Compatible with low voltage signal environment, which finds application in 45 -nanometer CMOS fabrication

Disadvantages

Data transfer rates

  • 3 lines / DVI -D: 495 MByte / s (3.96 Gb / s ): sufficient for 1920 × 1200
  • 6 lines / DVI -D: 990 MByte / s (7.92 Gb / s ): sufficient for 2560 × 1600
  • 3 lines / HDMI 1.0-1.2: 495 MByte / s (3.96 Gb / s ): sufficient for 1920 × 1200
  • 3 lines / HDMI 1.3 1020 MB / s ( 8.16 Gb / s ): sufficient for 2560 × 1600
  • All resolution data refer to 60 Hz frame rate and 3 × 8 bit color depth ( without sub-sampling ).
  • In the literature, symbol rates are specified as bit rates. However, one can only transmit 8 bits ( ANSI 8B10B modulation ) with 10 symbols, insofar as such information is false. The same problem can be found but also in other interfaces such as Serial ATA (1.5 / 3 Gbit / s) and HDMI (4.95 / 10.2 Gbit / s ) even at the classical RS- 232 interface ( 300 bit / s to 115,200 bit / s).

Alternative multimedia interfaces

  • SDI (Serial Digital Interface) - Video image transmission including audio studios
  • HDSDI (High Definition Serial Digital Interface) - Video image transmission including audio studios
  • DVI ( Digital Visual Interface) - first successful digital interface for computer monitors without audio (encryption optional), in variant DVI -A and DVI-I suitable for analog monitor connection (downward- compatible with VGA )
  • HDMI (High Definition Multimedia Interface) - extended video (next image and audio data as well as encryption and alternative video modes ), pure digital, including DVI compatibility mode
  • Should replace a failed digital video standard of Samsung, Intel and Apple, VGA - UDI (Unified Display Interface )
  • MHL ( Mobile High - Definition Link ) - HD video and audio interface optimized for connecting mobile phones and portable devices to HDTVs
Electronic visual display MacBook Transmission delay Bidirectional (disambiguation) Low Voltage Differential Signaling YCbCr SMPTE 292M Mobile High-Definition Link
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