DisplayPort is a digital display interface standardized by the Video Electronics Standards Association( VESA) for connecting displays to personal computers and for external box-to-box communication. Box-to-box communication can be communication between a personal computer( PC) and a digital display or HDTV display, as well as internal PC board-to-board or chip-to-chip communication.
VESA publishes the specifications worked out by well-known companies as an industry standard. The communication concept of the DisplayPort is based on the transmission of data packets, just like Ethernet or PCI Express. There is one main link, the Main Link, which consists of four lanes and transmits the video and audio data unidirectionally from the data source to the data sink. In addition, there is a bidirectional auxiliary channel and a unidirectional return channel for Hot Plug Detect( HPD). There are also lines in the interface for the supply voltage. Optional features include audio transmission and High-Bandwidth Digital Content Protection( HDCP) copy protection.
The characteristics of the DisplayPort
DisplayPort characteristics include a 10.8 Gbit/s High Bit Rate( HBR) data rate in the main channel, which can be used to drive high- resolution monitors at 2,560 x 1,600 pixels or digital signage at 4K resolution.
The full data rate can be transmitted over a cable length of 3 m; for longer lengths of up to 15 m, the bandwidth is reduced to the values required for the transmission of high-definition television (HDTV) with progressive scan, namely 1,080p.
The DisplayPort 1.2 version supports displays in the 4K standard with an image resolution of 4,096 x 2,160 pixels. At a symbol rate of 540 MHz, the data transfer rateis 4.32 Gbit/s over one data channel and 17.28 Gbit/s over four channels. In theDisplayPort 1.3 version, the net data rate is 25.92 Gbit/s with four channels and a symbol rate of 810 MHz. This data rate supports high-resolution displays according to the 5K standard with a resolution of 5,120 x 2,880 pixels at 60 Hz and 8-bit color depth. The 8K standard is supported by the DisplayPort 1.4 version with a refresh rate of 60 Hz and a color subsampling of 4:2:2. The image resolution at 8K is 7,680 x 4,320 pixels.
As for audio transmission, all versions feature 1 to 8-channel audio transmission with a sampling rate of 32 kHz to 192 kHz.
The interface of the DisplayPort is comparable in its electrical characteristics to that of PCI-Express. It uses a small user-friendly connector and can work with cable lengths up to 15 meters. Four DisplayPort connectors can be accommodated on one PCI card. Since transmission via copper cables has reached its limits, fiber optic cables are available as an alternative. The LwL technology can transmit data rates of 21.6 GB/s over 100 m in DisplayPort 1.2. This corresponds to the 4K standard with 24-bit color depth and 60 Hz refresh rate.
The layer model of DisplayPort
DisplayPort has a layered architecture and can work with a wide variety of transmission media, without changing the link layer. The interface offers compatibility with High Definition Multimedia Interface( HDMI) and Digital Visual Interface( DVI), and is expected to replace them and Low Voltage Differential Signaling( LVDS) in the long term.
The DisplayPort connector is available in a reduced form as Mini DisplayPort for laptops and notebooks. Wireless DisplayPort( wDP) is a radio-based version, and Mobility DisplayPort( MyDP) is available for mobile devices. There is also the Internal DisplayPort( iDP) and as an embedded version the Embedded DisplayPort( eDP). The embedded version is used in laptops and tablets and replaces the Low Voltage Differential Signaling (LVDS) transmission method. In addition, the embedded DisplayPort compresses the data stream with Display Stream Compression( DSC).