The DisplayPort™ Interface – What is DisplayPort™?  

The DisplayPort™ Interface – What is DisplayPort™?

DisplayPort™ is a universal connection standard standardized by the VESA (Video Electronics Standards Association). It is a digital interface for the transmission of video and audio signals. In contrast to HDMI, which is mainly used for TV and multimedia devices such as beamers, game consoles and DVD players, DisplayPort™ is primarily used in information technology, i.e. PCs, notebooks, tablets and monitors in general.

 

One Displayport™ 1.2 Splug on one Delock adapter

 

DisplayPort™ should have more high performance features than any other digital interface. The technology was developed to replace older standards such as DVI and VGA. DisplayPort™ is intended to open up new possibilities in the areas of PC technology, digital displays and consumer electronics. It is called the standard of the future and is already available today.

DisplayPort™ Version History

Version 1.0

In May 2006 the specification of the standard is published for the first time by VESA.

Version 1.1

The first final version is defined in April 2007. DP 1.1 allows data transmission in two different data rates (HBR and RBR: High Bit Rate and Reduced Bit Rate). The maximum transmission rate using all lanes with a cable up to two meters long is 8.64 Gb/s, which is sufficient for HDTV and larger monitors.

Copy protection is provided by encryption with HDCP 1.3 (High-bandwidth Digital Content Protection) and DPCP (DisplayPort™ Content Protection). In this version also the dual-mode DisplayPort™ (short: DP++) is introduced, more about this below at The feature DP++. The first devices with DisplayPort™ will be launched at the beginning of 2008.

Version 1.2

DP 1.2 will be released in December 2009. A significant change is the increase in the data transfer rate to a maximum of 17.28 Gb/s using the four lanes. For the first time the resolution UHD-1 (4 K Ultra HD) and MST (Multi stream transport) is supported. Now several independent video streams can be transmitted and several monitors can be connected according to the daisy chain principle – via a single DisplayPort™ connection.

Version 1.3

In the version confirmed in September 2014, the data rate per lane has been increased again, now a total of up to 25.92 Gb/s can be transmitted. Via MST it is now also possible to control several UHD-1 (4K Ultra HD with 3840 × 2160 pixels) or WQXGA displays.

For the support of upcoming UHD-2 monitors (8K with 7680 x 4320 pixels) the 4:2:0 color scanning is integrated. The dual-mode (DP++), introduced for the first time in 2007, is modified so that it is suitable for HDMI and DVI adapters with 4K Ultra HD resolution (HDMI™ 2.0) and copy protection according to HDCP 2.2.

Version 1.4

In March 2016, a version will be released that does not show a further increase in the data transfer rate, but the further development of some features. The Display Stream Compression 1.2 (DSC) offers up to three times the compression rate of the stream, with no visual loss: this means that an average viewer under typical conditions should not be able to distinguish between compressed and uncompressed image or video.

DSC allows playback of UHD-2 (8K with 7680 x 4320 pixels) and HDR as well as UHD-1 (4K with 3840 x 2160 pixels) and HDR. Of course, monitors that do not support DSC can only display the corresponding resolutions. Two other improvements in DP 1.4 are the forward error correction, which reduces transmission errors, and the extension of audio channels to 32.

Which version supports which resolution?

DP Version Maximum resolution
DisplayPort™ 1.13840 x 2160 @ 30 Hz and 2560 x 1600 @ 60 Hz
DisplayPort™ 1.23840 x 2160 @ 60 Hz
DisplayPort™ 1.35120 x 2880 @ 60 Hz and 7680 x 4320 @ 30 Hz
DisplayPort™ 1.4 4320 @ 60 Hz / 10 Bit Chroma / HDR and
3840 x 2160 @ 120 Hz / 10 Bit Chroma / HDR

Data transmission system at DisplayPort™

Technically, DisplayPort™ has a main connection, the Main Link, which consists of four lanes. The data transfer goes in one direction and takes place in packets, making DisplayPort™ the first video interface with this principle.
In comparison to DVI or HDMI, where continuous data transfer takes place, DisplayPort™ uses data packets with fixed rates – comparable to the transfer principle with Ethernet, PCI Express or USB.
The transmission paths of a DisplayPort™ connection

The specification Mini DisplayPort™

Mini DisplayPort™ is a smaller version of the DisplayPort™ connector and electrically compatible to this. Apple had introduced MiniDP in October 2008 as a proprietary technology. In November 2009, VESA included the Mini DisplayPort™ in the DisplayPort™ specification.

A DisplayPort™ plug compared to the Mini DisplayPort™ plug

DisplayPort™ and USB Type-C™

Mobile devices like Smartphones, Notebooks or Tablets are more and more equipped with the USB Type-C™ connection. Now DisplayPort™ is a non-USB protocol; the DisplayPort™ and USB Type-C™ technologies are each designed for completely different purposes. However, during the development of the USB Type-C™ interface, emphasis was placed on the intelligent feature of also being able to transmit DisplayPort™ signals. So an alternative mode was integrated.

The so-called DisplayPort™ Alt Mode for USB Type-C™ is also standardized by VESA. Devices that support the DisplayPort™ Alt Mode can also transfer signals via the USB Type-C™ port. For example, a notebook with DisplayPort™ Alt Mode support can be connected to a DisplayPort™ monitor. The means of choice in this case would be an adapter with USB Type-C™ plug to DisplayPort™ socket.

 

More flexibility with the USB Type-C™ interface thanks to DisplayPort™ Alt Mode

Please note that not all devices that support the DisplayPort™ Alt Mode are marked accordingly. According to the DisplayPort™ Organization, by 2016, most video devices on the market with a USB Type-C™ connection will also support the DisplayPort™ Alt Mode. Typically, this can be found on all products marked with video via USB Type-C™.

The MST Feature

What is MST?

As of DisplayPort™ Version 1.2 (December 2009), a second transmission mode, the Multi Stream Transport Mode (MST), will be introduced in addition to the Single Stream Transport Mode (SST). Now multiple monitors can be used via a single DisplayPort™ connection. One possibility is that the monitors support daisy-chaining*. Alternatively, a DisplayPort™ MST hub can be used, where the number of connected monitors is limited by the data transfer rate of the DP interface.
*Daisy-chaining (= “daisy connection”): Several peripheral devices (e.g. monitors) are connected in series on a data line in the form of a chain. The output of one device is connected to the input of the next device.

The matter of bandwidth

Of course, the bandwidth of a single DisplayPort™ 1.2 connection is also limited. This limits the number of screens and supported resolutions that can be connected and used via an MST hub. Here again it depends on the respective monitor resolution, the timing and the refresh rate.
Which resolution needs which bandwidth?

Resolution Bandwidth – usage

1920 x 1080 @ 60 Hz – 22 %
1920 x 1200 @ 60 Hz – 30 %
2560 x 1440 @ 60 Hz – 35 %
2560 x 1600 @ 60 Hz – 38 %
3840 x 2160 @ 30 Hz – 43 %
3840 x 2160 @ 60 Hz – 95 %

Bandwidth & Monitor Configuration – Example 1

Three monitors with 2560 x 1440 @ 60 Hz each are connected to the graphics card via an MST splitter. Each monitor consumes 35% of the bandwidth. In total they need 105 %, which means that one of the monitors is deactivated.
35% + 35% + 35% = 105%

Bandwidth & Monitor Configuration – Example 2

Two MST splitters are connected to the graphics card. Three monitors of 1920 x 1080 @ 60 Hz each are connected to splitter 1. Each monitor requires 22% bandwidth, a total of 66% of Splitter 1’s bandwidth. Three monitors with different resolutions are also connected to Splitter 2, using 79% of the Splitter 2 bandwidth. In this example, the connection of six monitors to a graphics card with two outputs and the sufficient supply of the monitors with bandwidth is guaranteed.

Via Splitter 1: 22% + 22% + 22% = 66% – Via Splitter 2: 35% + 22% + 22% = 79%

Up to two MST splitters can be used on one graphics card if it has two outputs. It then depends on the number of display lines on the card how many monitors are supported. If the number of available display lines is unclear, the manufacturer of the graphics card should be contacted. DisplayPort™ Splitters with MST also allow all connected monitors to operate independently as an extended desktop.

The feature DP++

Compatibility via passive adapters

The dual mode DisplayPort™ or DisplayPort++™, short DP++, offers compatibility to DVI and HDMI. The connection is made possible by comparatively inexpensive adapters that only have to adapt the electrical signaling level: from LVDS at DisplayPort™ to TMDS at HDMI / DVI. The graphics card of the PC is involved here, because as soon as it recognizes that the connected device is one with DisplayPort™ interface, the signals are also output in this format.

However, if, for example, an adapter to HDMI is connected, the graphics card is signaled to use the HDMI protocol. In the downstream passive adapter (so-called impedance converter / level shifter / level converter), the different signal levels and impedances of the signaling levels LVDS and TMDS are then adjusted; in each case corresponding to the target interface. The support of DP++ and a corresponding marking on the devices is optional and depends on the manufacturers.

 


1 Transfer natively from PC to DP monitor 2 Passive adapter fits signal to 3 Active adapter converts signal

When is an active adapter necessary?

One limitation of DP++ is that it can only transfer single-link DVI (and HDMI) because the number of pins in the DisplayPort™ connector is too small for dual-link connections. Dual-Link DVI and analog VGA can be connected, but an active adapter is required. Active adapters act as a signal sink (monitor) to the imaging device and as a signal source to the image receiving device.

Product examples DisplayPort™ from Delock

Delock Adapter mini DisplayPort 1.2 Plug > DVI socket 4K

Connections:

  • mini DisplayPort™ 20 Pin male > DVI 24+5 female with nuts
  • DVI-D (Single Link), VGA not wired
  • Resolution up to 3840 x 2160 @ 30 Hz (depending on monitor / system)
  • Contacts with gold plating
  • 1 x ferrite core
  •  Cable length: approx. 20 cm (without connections)

Cable DisplayPort™ > DisplayPort™ 8K

Connections:

  • DisplayPort™ 20 Pin Connector > DisplayPort™ 20 Pin Connector
  • DisplayPort™ 1.4 Specification
  •  DisplayPort® DP 8K certified
  • Resolution up to 8K Ultra HD (depending on monitor / system)
  • Data transfer rate up to 32.4 Gbps
  • contacts gold-plated
  • Triple shielded cable
  • copper line
  • Cable Ø approx. 4.5 mm / Wire cross section: 34 AWG
  • Length: 1 m (incl. connections)

Cable Mini DisplayPort™ > DisplayPort™ 8K

Connections:

  • Mini DisplayPort™ 20 Pin Connector > DisplayPort™ 20 Pin Connector
  • DisplayPort™ 1.4 Specification
  • DisplayPort® DP 8K certified
  • Resolution up to 8K Ultra HD (depending on monitor / system)
  • Data transfer rate up to 32.4 Gbps
  • contacts gold-plated
  • Triple shielded cable
  • copper line
  • Cable Ø approx. 4.5 mm / Wire cross section: 34 AWG

 

Cable Mini DisplayPort™ Plug > Mini DisplayPort™ Plug 4K

Connections:

  • mini DisplayPort™ 20 Pin Connector > mini DisplayPort™ 20 Pin Connector
  • DisplayPort™ 1.2 Specification
  • Resolution up to 3840 x 2160 @ 30 Hz (depending on monitor / system)
  • Data transfer rate up to 21.6 Gb/s
  • Contacts with gold plating
  • braided shielding
  • Cable Ø approx. 5.5 mm / Wire cross section: 32 AWG
  • copper line

 

Splitter 1 x DisplayPort™ 1.2 in > 4 x DisplayPort™ out 4K

Connections:

  • Input >
    1 x DisplayPort™ 20 Pin Connector
    1 x 5 V DC current socket
  • Output > 4 x DisplayPort™ 20 Pin Socket
  • DisplayPort™ 1.2a Specification
  • Active converter, Single / Multi Stream Transport Hub (SST / MST)
  • Resolutions (depending on monitor / system)
  • DisplayPort™ 1.1 or 1.2 Single Stream Transport (SST) > up to 1920 x 1080 @ 60 Hz (Mirrored)
  • DisplayPort™ 1.2 Multi Stream Transport (MST) > up to 2560 x 1440 @ 60 Hz or 3840 x 2160 @ 30 Hz (mirrored / extended) max. 4 x 1920 x 1080 @ 60 Hz
  • Supports HDCP 1.3
  • Supports Eyefinity / Single Large Surface (SLS)
  • Audio input formats: 7.1 channel with a sampling rate up to 192 kHz
  • Cable length: approx. 30 cm (without connections)
  • Dimensions (LxWxHx): approx. 143 x 67 x 23 mm

 

Splitter 1 x DisplayPort™ 1.2 in > 2 x HDMI out 4K

Connections:

  • Input > 1 x Displayport 20 Pin Connector
  • Output > 2 x HDMI-A 19 Pin Socket
  • DisplayPort™ 1.2a and High Speed HDMI Specification
  • Active converter, Single / Multi Stream Transport Hub (SST / MST)
  • Resolutions (depending on monitor / system)
  • DisplayPort™ 1.1 or 1.2 Single Stream Transport (SST) > up to 1920 x 1080 @ 60 Hz (Mirrored)
  • DisplayPort™ 1.2 Multi Stream Transport (MST) > up to 3840 x 2160 @ 30 Hz (mirrored / extended)
  • Supports 3D displays
  • Supports HDCP 1.3
  • Supports Eyefinity / Single Large Surface (SLS)
  • Audio input formats: 7.1 channel with up to 192 kHz sampling rate
  • Cable length: approx. 30 cm (without connections)
  • Dimensions (LxWxHx): approx. 100 x 67 x 23 mm

DisplayPort™ KVM Switch 2 > 1 USB and Audio

Connections:

  • Input >
    2 x DisplayPort™ socket (connection for PC1 and PC2)
    2 x USB 2.0 type B sockets (connection for PC1 and PC2)
    1 x Sub-D 9 pin socket RS232 (for control)
    1 x DC power connection
    1 x 3.5 mm jack socket for additional IR receiver (optional)
  • Output >
    1 x DisplayPort™ socket (monitor or TV)
    1 x HDMI-A socket (monitor or TV)
    3 x USB 2.0 Type A socket (keyboard, mouse, hard disk, USB stick etc.)
    2 x 3.5 mm jack socket (1 x loudspeaker, 1 x microphone)
  • DisplayPort™ 1.1a Specification
  • Resolutions (depending on monitor / system)
    DisplayPort™ Output > up to 2560 x 1440 @ 60 Hz / 3840 x 2160 @ 30 Hz
    HDMI output > up to 1920 x 1080 @ 60 Hz
    DisplayPort™ Output DP++ capable > up to 1920 x 1080 @ 60 Hz
  • 2 switch buttons with LED indicators for source and destination
  • Dimensions (LxWxHx): approx. 257 x 112 x 33 mm
 

What do you think about this topic? Leave a reply:

Your email address will not be published. Required fields are marked *