DisplayPort (DP) is a digital display interface developed by a consortium of PC and chip manufacturers and standardized by the Video Electronics Standards Association (VESA). The interface is primarily used to connect a video source to a display device such as a computer monitor, and it can also carry audio, USB, and other forms of data.
DisplayPort was designed to replace VGA, DVI, and FPD-Link. The interface is backward compatible with other interfaces, such as HDMI and DVI, through the use of either active or passive adapters.
Video DisplayPort
Overview
DisplayPort is the first display interface to rely on packetized data transmission, a form of digital communication found in technologies such as Ethernet, USB, and PCI Express. It permits the use of internal and external display connections, and unlike legacy standards that transmit a clock signal with each output, the DisplayPort protocol is based on small data packets known as micro packets, which can embed the clock signal within the data stream. This allows for higher resolution using fewer pins. The use of data packets also makes DisplayPort extensible, meaning additional features can be added over time without significant changes to the physical interface.
DisplayPort can be used to transmit audio and video simultaneously, although each is optional and can be transmitted without the other. The video signal path can range from six to sixteen bits per color channel, and the audio path can have up to eight channels of 24-bit, 192 kHz PCM audio that is uncompressed. A bi-directional, half-duplex auxiliary channel carries device management and device control data for the Main Link, such as VESA EDID, MCCS, and DPMS standards. In addition, the interface is capable of carrying bi-directional USB signals.
The DisplayPort uses an LVDS signal protocol that is not compatible with DVI or HDMI. However, dual-mode DisplayPorts are designed to transmit a single-link DVI or HDMI protocol (TMDS) across the interface through the use of an external passive adapter. This adapter enables compatibility mode and converts the signal from 3.3 volts to 5 volts. For analog VGA/YPbPr and dual-link DVI, a powered active adapter is required for compatibility and does not rely on dual mode. Active VGA adapters are powered by the DisplayPort connector directly, while active dual-link DVI adapters typically rely on an external power source such as USB.
Maps DisplayPort
Versions
1.0 to 1.1
The first version, 1.0, was approved by VESA on 3 May 2006. Version 1.1 was ratified on 2 April 2007, and version 1.1a was ratified on 11 January 2008.
DisplayPort 1.0-1.1a allow a maximum bandwidth of 10.8 Gbit/s (8.64 Gbit/s data rate) over a standard 4-lane main link. DisplayPort cables up to 2 meters in length are required to support the full 10.8 Gbit/s bandwidth. DisplayPort 1.1 allows devices to implement alternative link layers such as fiber optic, allowing a much longer reach between source and display without signal degradation, although alternative implementations are not standardized. It also includes HDCP in addition to DisplayPort Content Protection (DPCP). The DisplayPort 1.1a standard can be downloaded for free from the VESA website.
1.2
DisplayPort version 1.2 was introduced on 7 January 2010. The most significant improvement of the new version is the doubling of the effective bandwidth to 17.28 Gbit/s in High Bit Rate 2 (HBR2) mode, which allows increased resolutions, higher refresh rates, and greater color depth. Other improvements include multiple independent video streams (daisy-chain connection with multiple monitors) called Multi-Stream Transport, facilities for stereoscopic 3D, increased AUX channel bandwidth (from 1 Mbit/s to 720 Mbit/s), more color spaces including xvYCC, scRGB and Adobe RGB 1998, and Global Time Code (GTC) for sub 1 µs audio/video synchronisation. Also Apple Inc.'s Mini DisplayPort connector, which is much smaller and designed for laptop computers and other small devices, is compatible with the new standard.
1.2a
DisplayPort version 1.2a was released in January 2013 and may optionally include VESA's Adaptive Sync. AMD's FreeSync uses the DisplayPort Adaptive-Sync feature for operation. FreeSync was first demonstrated at CES 2014 on a Toshiba Satellite laptop by making use of the Panel-Self-Refresh (PSR) feature from the Embedded DisplayPort standard, and after a proposal from AMD, VESA later adapted the Panel-Self-Refresh feature for use in standalone displays and added it as an optional feature of the main DisplayPort standard under the name "Adaptive-Sync" in version 1.2a. As it is an optional feature, support for Adaptive-Sync is not required for a display to be DisplayPort 1.2a-compliant.
1.3
DisplayPort version 1.3 was approved on 15 September 2014. This standard increases overall transmission bandwidth to 32.4 Gbit/s with the new HBR3 mode featuring 8.1 Gbit/s per lane (up from 5.4 Gbit/s with HBR2 in version 1.2), for a total data throughput of 25.92 Gbit/s after factoring in 8b/10b encoding overhead. This bandwidth is enough for a 4K UHD display (3840 × 2160) at 120 Hz with 24 bit/px RGB color, a 5K display (5120 × 2880) at 60 Hz with 30 bit/px RGB color, or an 8K UHD display (7680 × 4320) at 30 Hz with 24 bit/px RGB color. Using Multi-Stream Transport (MST), a DisplayPort port can drive two 4K UHD (3840 × 2160) displays at 60 Hz, or up to four WQXGA (2560 × 1600) displays at 60 Hz with 24 bit/px RGB color. The new standard includes mandatory Dual-mode for DVI and HDMI adapters, implementing the HDMI 2.0 standard and HDCP 2.2 content protection. The Thunderbolt 3 connection standard was originally to include DisplayPort 1.3 capability, but the final release ended up with only version 1.2. The VESA's Adaptive Sync feature in DisplayPort version 1.3 remains an optional part of the specification.
1.4
DisplayPort version 1.4 was published 1 March 2016. No new transmission modes are defined, so HBR3 (32.4 Gbit/s) as introduced in version 1.3 still remains as the highest available mode. DisplayPort 1.4 adds support for Display Stream Compression 1.2 (DSC), Forward Error Correction, HDR10 metadata defined in CTA-861.3, including static and dynamic metadata and the Rec. 2020 color space, for HDMI interoperability, and extends the maximum number of inline audio channels to 32.
DSC is a "visually lossless" encoding technique with up to a 3:1 compression ratio. Using DSC with HBR3 transmission rates, DisplayPort 1.4 can support 8K UHD (7680 × 4320) at 60 Hz with 30 bit/px RGB color and HDR, or 4K UHD (3840 × 2160) at 120 Hz with 30 bit/px RGB color and HDR. 4K at 60 Hz with 30 bit/px RGB color and HDR can be achieved without the need for DSC. On displays which do not support DSC, the maximum limits are unchanged from DisplayPort 1.3 (4K 120 Hz, 5K 60 Hz, 8K 30 Hz).
Next version
According to a roadmap published by VESA in September 2016, a new version of DisplayPort was intended to be launched in "early 2017". It would have improved the link rate from 8.1 to 10.0 Gbit/s, a 24% increase. This would have increased the total bandwidth from 32.4 Gbit/s to 40.0 Gbit/s. It is unclear whether or not the new version would have continued using the 8b/10b scheme for transport encoding like previous versions, but if so, the maximum data rate for video would have been 32.0 Gbit/s.
However, no new version was released in 2017, likely delayed to make further improvements after the HDMI Forum announced in January 2017 that their next standard (HDMI 2.1) would offer up to 48 Gbit/s of bandwidth. According to a press release on 3 January 2018, "VESA is also currently engaged with its members in the development of the next DisplayPort standard generation, with plans to increase the data rate enabled by DisplayPort by two-fold and beyond. VESA plans to publish this update within the next 18 months." This implies a bandwidth of around 64.8 Gbit/s for the next version of DisplayPort. Assuming 8b/10b encoding, this would give a data rate of 51.84 Gbit/s.
This should allow for uncompressed RGB / YCBCR 4:4:4 video formats as high as:
- 8K (7680 × 4320) @ 60 Hz 8 bpc (24 bit/px) or 50 Hz 10 bpc (30 bit/px)
- 5K (5120 × 2880) @ 120 Hz 8 bpc or 100 Hz 10 bpc
- 4K (3840 × 2160) @ 200 Hz 8 bpc or 180 Hz 10 bpc
Higher resolutions/refresh rates should also be possible through the use of DSC (compression) or chroma subsampling (YCBCR 4:2:2 or 4:2:0). Higher uncompressed formats may also be possible if the new version replaces 8b/10b encoding with a more efficient encoding method.
Specifications
Main specifications
Main link
The DisplayPort main link is used for transmission of video and audio. The main link consists of a number of unidirectional serial data channels which operate concurrently, called lanes. A standard DisplayPort connection has 4 lanes, though some applications of DisplayPort implement more, such as the Thunderbolt 3 interface which implements up to 8 lanes of DisplayPort.
In a standard DisplayPort connection, each lane has a dedicated set of twisted-pair wires, and transmits data across it using differential signaling with ANSI 8b/10b encoding. This is a self-clocking system, so no dedicated clock signal channel is necessary. Unlike DVI and HDMI, which vary their transmission speed to the exact rate required for the specific video format, DisplayPort only operates at a few specific speeds; any excess bits in the transmission are filled with "stuffing symbols". DisplayPort's transmission modes are as follows:
- RBR (Reduced Bit Rate): 1.62 Gbit/s bandwidth per lane (162 MHz link symbol rate)
- HBR (High Bit Rate): 2.70 Gbit/s bandwidth per lane (270 MHz link symbol rate)
- HBR2 (High Bit Rate 2): 5.40 Gbit/s bandwidth per lane (540 MHz link symbol rate), introduced in DP 1.2
- HBR3 (High Bit Rate 3): 8.10 Gbit/s bandwidth per lane (810 MHz link symbol rate), introduced in DP 1.3
The bandwidth represents the rates at which signals representing 1s or 0s are physically transmitted across the interface on each lane. Since the DisplayPort main link uses 8b/10b encoding, only 8 out of every 10 transmitted bits represent data; the extra two bits are used for DC balancing (ensuring a roughly equal number of 1s and 0s). The transmission speeds are also sometimes expressed in terms of the "Link Symbol Rate", which is the rate at which these 8b/10b-encoded symbols are transmitted (i.e. the rate at which groups of 10 bits are transmitted, 8 of which represent data).
The total bandwidth of the main link in a standard 4-lane connection is the aggregate of all lanes:
- RBR: 04 × 1.62 Gbit/s = 06.48 Gbit/s bandwidth (data rate of 5.184 Gbit/s or 648 MB/s with 8b/10b encoding)
- HBR: 04 × 2.70 Gbit/s = 10.80 Gbit/s bandwidth (data rate of 8.64 Gbit/s or 1.08 GB/s)
- HBR2: 4 × 5.40 Gbit/s = 21.60 Gbit/s bandwidth (data rate of 17.28 Gbit/s or 2.16 GB/s)
- HBR3: 4 × 8.10 Gbit/s = 32.40 Gbit/s bandwidth (data rate of 25.92 Gbit/s or 3.24 GB/s)
The transmission mode used by the DisplayPort main link is negotiated by the source and sink device when a connection is made, through a process called Link Training. This process determines the maximum possible speed of the connection. If the quality of the DisplayPort cable is insufficient to reliably handle HBR2 speeds for example, the DisplayPort devices will detect this and switch down to a lower mode to maintain a stable connection. The link can be re-negotiated at any time if a loss of synchronization is detected.
Audio data is transmitted across the main link during the video blanking intervals (short pauses between each line and frame of video data).
Auxiliary channel
The DisplayPort AUX channel is a half-duplex bidirectional data channel used for miscellaneous additional data beyond video and audio (such as I2C or CEC commands) at the device manufacturer's discretion. AUX signals are transmitted across a dedicated set of twisted-pair wires. DisplayPort 1.0 specified Manchester encoding with a 2 Mbaud signal rate (1 Mbit/s data rate). DisplayPort 1.2 introduced a second transmission mode called FAUX (Fast AUX), which operates at 720 Mbaud with 8b/10b encoding (576 Mbit/s data rate). This can used to implement additional transport protocols such as USB 2.0 (480 Mbit/s) without the need for an additional cable, but has seen little practical use as of 2018.
Cables and connectors
Cables
Compatibility and feature support
All DisplayPort cables are compatible with all DisplayPort devices, regardless of the version of each device or the cable certification level.
All features of DisplayPort will function across any DisplayPort cable. DisplayPort does not have multiple cable designs; all DP cables have the same basic layout and wiring, and will support any feature including audio, daisy-chaining, G-Sync/FreeSync, HDR, and DSC.
DisplayPort cables differ in their transmission speed support. DisplayPort specifies four different transmission modes (RBR, HBR, HBR2, and HBR3) which support progressively higher bandwidths. Not all DisplayPort cables are capable of all four transmission modes. VESA offers certifications for each level of bandwidth. These certifications are optional, and not all DisplayPort cables are certified by VESA.
Cables with limited transmission speed are still compatible with all DisplayPort devices, but may place limits on the maximum resolution or refresh rate available.
DisplayPort cables are not classified by "version". Although cables are commonly labeled with version numbers, with HBR2 cables advertised as "DisplayPort 1.2 cables" for example, this notation is not permitted by VESA. The use of version numbers with cables can seem to imply that a DisplayPort 1.4 display requires a "DisplayPort 1.4 cable", or that features introduced in DP 1.4 such as HDR or DSC will not function with older "DP 1.2 cables", when in reality neither of these are true. DisplayPort cables are classified only by their bandwidth certification level (RBR, HBR, HBR2, HBR3), if they have been certified at all.
Cable bandwidth and certifications
Not all DisplayPort cables are capable of functioning at the highest levels of bandwidth. Cables may be submitted to VESA for an optional certification at various bandwidth levels. VESA offers the following certifications:
In April 2013, VESA published an article stating that the DisplayPort cable certification did not have distinct tiers for HBR and HBR2 bandwidth, and that any certified standard DisplayPort cable--including those certified under DisplayPort 1.1--would be able to handle the 21.6 Gbit/s bandwidth of HBR2 that was introduced with the DisplayPort 1.2 standard. The DisplayPort 1.2 standard defines only a single specification for High Bit Rate cable assemblies, which is used for both HBR and HBR2 speeds, although the DP cable certification process is governed by the DisplayPort PHY Compliance Test Standard (CTS) and not the DisplayPort standard itself.
The DP8K certification was announced by VESA in January 2018, and certifies cables for proper operation at HBR3 speeds (8.1 Gbit/s per lane, 32.4 Gbit/s total).
It should also be noted that the use of Display Stream Compression (DSC), introduced in DisplayPort 1.4, greatly reduces the bandwidth requirements for the cable. Formats which would normally be beyond the limits of DisplayPort 1.4, such as 4K (3840 × 2160) at 144 Hz 8 bpc RGB/4:4:4 (31.4 Gbit/s data rate when uncompressed), can only be implemented by using DSC. This would reduce the physical bandwidth requirements by 2-3x, placing it well within the capabilities of an HBR2-rated cable.
This exemplifies why DisplayPort cables are not classified by "version"; although DSC was introduced in version 1.4, this does not mean it needs a so-called "DP 1.4 cable" (an HBR3-rated cable) to function. HBR3 cables are only required for applications which exceed HBR2-level bandwidth, not simply any application involving DisplayPort 1.4. If DSC is used to reduce the bandwidth requirements to HBR2 levels, then an HBR2-rated cable will be sufficient.
Cable length
The DisplayPort standard does not specify any maximum length for cables, though the DisplayPort 1.2 standard does set a minimum requirement that all cables up to 2 meters in length must support HBR2 speeds (21.6 Gbit/s), and all cables of any length must support RBR speeds (6.48 Gbit/s). Cables greater than 2 meters may or may not support HBR/HBR2 speeds, and cables of any length may or may not support HBR3 speeds.
Connectors and pin configuration
DisplayPort cables and ports may have either a "full-size" connector or a "mini" connector. These connectors differ only in physical shape--the capabilites of DisplayPort are the same regardless of which connector is used. Using a Mini DisplayPort connector does not affect performance or feature support of the connection.
Full-size DisplayPort connector
The standard DisplayPort connector (now generally called "full-size" to distinguish it from the mini connector) was the sole connector type introduced in DisplayPort 1.0. It is a 20-pin single-orientation connector with a friction lock and an optional mechanical latch. The standard DisplayPort receptacle has dimensions of 16.10 mm (width) × 4.76 mm (height) × 8.88 mm (depth).
The standard DisplayPort connector pin allocation is as follows:
- 12 pins for the main link -- the main link consists of four shielded twisted pairs. Each pair requires 3 pins; one for each of the two wires, and a third for the shield. (pins 1-12)
- 3 pins for the auxiliary channel -- the auxiliary channel uses another 3-pin shielded twisted pair (pins 15-17)
- 1 pin for HPD -- hot-plug detection pin (pin 18)
- 2 pins for power -- 3.3 V power and return line (pins 19 and 20)
- 2 additional ground pins -- (pins 13 and 14)
Mini DisplayPort connector
The Mini DisplayPort connector was developed by Apple for use in their computer products. It was first announced in October 2008 for use in the new MacBook Pro, MacBook Air, and Cinema Display. In 2009, VESA adopted it as an official standard, and in 2010 the specification was merged into the main DisplayPort standard with the release of DisplayPort 1.2. Apple freely licenses the specification to VESA.
The Mini DisplayPort (mDP) connector is a 20-pin single-orientation connector with a friction lock. Unlike the full-size connector, it does not have an option for a mechanical latch. The mDP receptacle has dimensions of 7.50 mm (width) × 4.60 mm (height) × 4.99 mm (depth). The mDP pin assignments are the same as the full-size DisplayPort connector.
DP_PWR Pin
Pin 20 on the DisplayPort connector, called DP_PWR, provides 3.3 V (±10%) DC power at up to 500 mA (minimum power delivery of 1.5 W). This power is available from all DisplayPort receptacles, on both source and display devices. DP_PWR is intended to provide power for adapters, amplified cables, and similar devices, so that a separate power cable is not necessary.
Standard DisplayPort cable connections do not use the DP_PWR pin. Connecting the DP_PWR pins of two devices directly together through a cable can create a short circuit which can potentially damage devices, since the DP_PWR pins on two devices are unlikely to have exactly the same voltage (especially with a ±10% tolerance). For this reason, the DisplayPort 1.1 and later standards specify that passive DisplayPort-to-DisplayPort cables must leave pin 20 unconnected.
However, in 2013 VESA announced that after investigating reports of malfunctioning DisplayPort devices, it had discovered that a large number of non-certified vendors were manufacturing their DisplayPort cables with the DP_PWR pin connected:
Recently VESA has experienced quite a few complaints regarding troublesome DisplayPort operation that ended up being caused by improperly made DisplayPort cables. These "bad" DisplayPort cables are generally limited to non-DisplayPort certified cables, or off-brand cables. To further investigate this trend in the DisplayPort cable market, VESA purchased a number of non-certified, off-brand cables and found that an alarmingly high number of these were configured improperly and would likely not support all system configurations. None of these cables would have passed the DisplayPort certification test, moreover some of these cables could potentially damage a PC, laptop, or monitor.
The stipulation that the DP_PWR wire be omitted from standard DisplayPort cables was not present in the DisplayPort 1.0 standard. However, DisplayPort products (and cables) did not begin to appear on the market until 2008, long after version 1.0 had been replaced by version 1.1. The DisplayPort 1.0 standard was never implemented in commercial products.
Resolution and refresh frequency limits
To support a particular format, the source and display devices must both support the required DisplayPort version or higher. Note that the "version" of a connection depends on the versions of the DisplayPort ports on the source and sink devices, not on the DisplayPort cable itself.
8 bpc color depth (24 bit/px or 16.7 million colors) is assumed for all formats in this table. This is the standard color depth used on most computer displays. Please note that some operating systems refer to this as "32-bit" color depth--this is the same as 24-bit color depth. The 8 extra bits are for alpha channel information, which is only present in software. At the transmission stage, this information has already been incorporated into the primary color channels, so the actual video data transmitted across the cable only contains 24 bits per pixel.
Features
DisplayPort Dual-Mode (DP++)
DisplayPort Dual-Mode (DP++), also called Dual-Mode DisplayPort, is a standard which allows DisplayPort sources to use simple passive adapters to connect to HDMI or DVI displays. Dual-mode is an optional feature, so not all DisplayPort sources necessarily support DVI/HDMI passive adapters, though in practice nearly all devices do. Officially, the "DP++" logo should be used to indicate a DP port that supports dual-mode, but most modern devices do not use the logo.
Devices which implement dual-mode will detect that a DVI or HDMI adapter is attached, and send DVI/HDMI TMDS signals instead of DisplayPort signals. The original DisplayPort Dual-Mode standard (version 1.0), used in DisplayPort 1.1 devices, only supported TMDS clock speeds of up to 165 MHz (4.95 Gbit/s bandwidth). This is equivalent to HDMI 1.2, and is sufficient for up to 1920 × 1080 or 1920 × 1200 at 60 Hz.
In 2013, VESA released the Dual-Mode 1.1 standard, which added support for up to a 300 MHz TMDS clock (9.00 Gbit/s bandwidth), and is used in newer DisplayPort 1.2 devices. This is slightly less than the 340 MHz maximum of HDMI 1.4, and is sufficient for up to 1920 × 1080 at 120 Hz, 2560 × 1440 at 60 Hz, or 3840 × 2160 at 30 Hz. Older adapters, which were only capable of the 165 MHz speed, were retroactively termed "Type 1" adapters, with the new 300 MHz adapters being called "Type 2".
With the release of the DisplayPort 1.3 standard, VESA added dual-mode support for up to a 600 MHz TMDS clock (18.00 Gbit/s bandwidth), the full bandwidth of HDMI 2.0. This is sufficient for 1920 × 1080 at 240 Hz, 2560 × 1440 at 144 Hz, or 3840 × 2160 at 60 Hz. However, no passive adapters capable of the 600 MHz dual-mode speed have been produced as of 2018.
Dual-Mode limitations
- Limited adapter speed - Although the pinout and digital signal values transmitted by the DP port are identical to a native DVI/HDMI source, the signals are transmitted at DisplayPort's native voltage (3.3 V) instead of the 5 V used by DVI and HDMI. As a result, dual-mode adapters must contain a level-shifter circuit which changes the voltage. The presence of this circuit places a limit on how quickly the adapter can operate, and therefore newer adapters are required for each higher speed added to the standard.
- Unidirectional - Although the dual-mode standard specifies a method for DisplayPort sources to output DVI/HDMI signals using simple passive adapters, there is no counterpart standard to give DisplayPort displays the ability to receive DVI/HDMI input signals through passive adapters. As a result, DisplayPort displays can only receive native DisplayPort signals; any DVI or HDMI input signals must be converted to the DisplayPort format with an active conversion device. DVI and HDMI sources cannot be connected to DisplayPort displays using passive adapters.
- Single-link DVI only - Since DisplayPort dual-mode operates by using the pins of the DisplayPort connector to send DVI/HDMI signals, the 20-pin DisplayPort connector can only produce a single-link DVI signal (which uses 19 pins). A dual-link DVI signal uses 25 pins, and is therefore impossible to transmit natively from a DisplayPort connector through a passive adapter. Dual-link DVI signals can only be produced by converting from native DisplayPort output signals with an active conversion device.
- Unavailable on USB-C - The DisplayPort Alternate Mode specification for sending DisplayPort signals over a USB-C cable does not include support for the dual-mode protocol. As a result, DP-to-DVI and DP-to-HDMI passive adapters do not function when chained from a USB-C to DP adapter.
Multi-Stream Transport (MST)
Multi-Stream Transport is a feature first introduced in the DisplayPort 1.2 standard which allows multiple independent displays to be driven from a single DP port on the source device. The displays can be connected using a hub, or by daisy-chaining, or any combination of the two. There's no technical difference between daisy-chaining and a hub, from a topology perspective they're both a branch device. In less technical terms, a monitor capable of daisy-chaining is simply embedding a hub. Theoretically, up to 63 displays can be supported, but the combined data rate requirements of all the displays cannot exceed the limits of a single DP port (17.28 Gbit/s for a DP 1.2 port, or 25.92 Gbit/s for a DP 1.3/1.4 port). With the release of MST, standard single-display operation has been retroactively named "SST" mode (Single-Stream Transport).
Daisy-chaining is a feature that must be specifically supported by each intermediary display; not all DisplayPort 1.2 devices support it. Daisy-chaining requires a dedicated DisplayPort output port on the display. Standard DisplayPort input ports found on most displays cannot be used as a daisy-chain output. Only the last display in the daisy-chain does not need to support the feature specifically or have a DP output port. DisplayPort 1.1 displays can also be connected to MST hubs, and can be part of a DisplayPort daisy-chain if it is the last display in the chain.
The host system's software also needs to support MST for hubs and daisy-chains to work. While Microsoft Windows environments have full support for it, Apple operating systems currently do not support MST hubs or DisplayPort daisy-chaining as of macOS 10.13 ("High Sierra").
DisplayPort-to-DVI and DisplayPort-to-HDMI adapters/cables will not function from a daisy-chain output port. They can, however, be used with DisplayPort MST hubs.
MST is supported by USB Type-C DisplayPort Alternate Mode, so standard DisplayPort daisy-chains and MST hubs do function from Type-C sources with a Type-C to DisplayPort adapter without any conversion.
High Dynamic Range (HDR)
Support for HDR video was introduced in DisplayPort 1.4. It implements the CTA 861.3 standard for transport of static HDR metadata in EDID.
Content protection
DisplayPort 1.0 includes optional DPCP (DisplayPort Content Protection) from Philips, which uses 128-bit AES encryption. It also features full authentication and session key establishment. Each encryption session is independent, and it has an independent revocation system. This portion of the standard is licensed separately. It also adds the ability to verify the proximity of the receiver and transmitter, a technique intended to ensure users are not bypassing the content protection system to send data out to distant, unauthorized users.
DisplayPort 1.1 added optional implementation of industry-standard 56-bit HDCP (High-bandwidth Digital Content Protection) revision 1.3, which requires separate licensing from the Digital Content Protection LLC.
DisplayPort 1.3 added support for HDCP 2.2, which is also used by HDMI 2.0.
Cost
VESA, the creators of the DisplayPort standard, state that the standard is royalty-free to implement. However, in March 2015, MPEG LA issued a press release stating that a royalty rate of $0.20 per unit applies to DisplayPort products manufactured or sold in countries that are covered by one or more of the patents in the MPEG LA license pool, which includes patents from Hitachi Maxell, Philips, Lattice Semiconductor, Rambus, and Sony. In response, VESA updated their DisplayPort FAQ page with the following statement:
MPEG LA is making claims that DisplayPort implementation requires a license and a royalty payment. It is important to note that these are only CLAIMS. Whether these CLAIMS are relevant will likely be decided in a US court.
As of October 2017 there still seems to be no royalty, according to the VESA's official FAQ.
While the standard may not require any per-device royalty fees, VESA requires membership for access to said standards. The minimum cost is presently $5,000.
Advantages over DVI, VGA and FPD-Link
In December 2010, several computer vendors and display makers including Intel, AMD, Dell, Lenovo, Samsung and LG announced they would begin phasing out FPD-Link, VGA, and DVI-I over the next few years, replacing them with DisplayPort and HDMI. One notable exception to the list of manufacturers is Nvidia, who has yet to announce any plans regarding future implementation of legacy interfaces.
DisplayPort has several advantages over VGA, DVI, and FPD-Link.
- Open standard available to all VESA members with an extensible standard to help broad adoption
- Fewer lanes with embedded self-clock, reduced EMI with data scrambling and spread spectrum mode
- Based on a micro-packet protocol
- Allows easy expansion of the standard with multiple data types
- Flexible allocation of available bandwidth between audio and video
- Multiple video streams over single physical connection (version 1.2)
- Long-distance transmission over alternative physical media such as optical fiber (version 1.1a)
- High-resolution displays and multiple displays with a single connection, via a hub or daisy-chaining
- HBR2 mode with 17.28 Gbit/s of effective video bandwidth allows four simultaneous 1080p60 displays (CEA-861 timings), two 2560 × 1600 × 30 bit @ 120 Hz (CVT-R timings), or 4K UHD @ 60 Hz
- HBR3 mode with 25.92 Gbit/s of effective video bandwidth, using CVT-R2 timings, allows eight simultaneous 1080p displays (1920 × 1080) @ 60 Hz, stereoscopic 4K UHD (3840 × 2160) @ 120 Hz, or 5120 × 2880 @ 60 Hz each using 24 bit RGB, and up to 8K UHD (7680 × 4320) @ 60 Hz using 4:2:0 subsampling
- Designed to work for internal chip-to-chip communication
- Aimed at replacing internal FPD-Link links to display panels with a unified link interface
- Compatible with low-voltage signaling used with sub-micron CMOS fabrication
- Can drive display panels directly, eliminating scaling and control circuits and allowing for cheaper and slimmer displays
- Link training with adjustable amplitude and preemphasis adapts to differing cable lengths and signal quality
- Reduced bandwidth transmission for 15-metre (49 ft) cable, at least 1920 × 1080p @ 60 Hz at 24 bits per pixel
- Full bandwidth transmission for 3 metres (9.8 ft)
- High-speed auxiliary channel for DDC, EDID, MCCS, DPMS, HDCP, adapter identification etc. traffic
- Can be used for transmitting bi-directional USB, touch-panel data, CEC, etc.
- Self-latching connector
Comparison with HDMI
Although DisplayPort has much of the same functionality as HDMI, it is a complementary connection used in different scenarios. A dual-mode DisplayPort port can emit an HDMI signal via a passive adapter.
HDMI charges an annual fee of US$10,000 to each high-volume manufacturer and a per-unit royalty rate of US$0.04 to US$0.15. HDMI Licensing countered the "royalty-free" claim by pointing out that the DisplayPort specification states that companies can charge a royalty rate for DisplayPort implementation. DisplayPort 1.2 has more bandwidth at 21.6 Gbit/s (17.28 Gbit/s with overhead removed) as opposed to HDMI 2.0's 18 Gbit/s (14.4 Gbit/s with overhead removed). DisplayPort 1.3 raises that to 32.4 Gbit/s (25.92 Gbit/s with overhead removed), and HDMI 2.1 raises that up to 48 Gbit/s (42.67 Gbit/s with overhead removed), adding an additional TMDS link in place of clock lane. DisplayPort also has the ability to share this bandwidth with multiple streams of audio and video to separate devices.
DisplayPort in native mode lacks some HDMI features such as Consumer Electronics Control (CEC) commands. The CEC bus allows linking multiple sources with a single display and controlling any of these devices from any remote. DisplayPort 1.3 added the possibility of transmitting CEC commands over the AUX channel
From its very first version HDMI features CEC to support connecting multiple sources to a single display as is typical for a TV screen. The other way round, Multi-Stream Transport allows connecting multiple displays to a single computer source. This reflects the facts that HDMI originated from consumer electronics companies whereas DisplayPort is owned by VESA which started as an organization for computer standards.
HDMI uses unique Vendor-Specific Block structure, which allows for features such as additional color spaces. However, these features can be defined by CEA EDID extensions.
Figures from IDC show that 5.1% of commercial desktops and 2.1% of commercial notebooks released in 2009 featured DisplayPort. The main factor behind this is the phase-out of VGA, and that both Intel and AMD will also stop building products with FPD-Link by 2013. Nearly 70% of LCD monitors sold in August 2014 in the US, UK, Germany, Japan, and China were equipped with HDMI/DisplayPort technology, up 7.5% on the year, according to Digitimes Research. DisplayPort is expected to surpass HDMI in 2019.
Companion standards
Mini DisplayPort
Mini DisplayPort (mDP) is a standard announced by Apple in the fourth quarter of 2008. Shortly after announcing Mini DisplayPort, Apple announced that it would license the connector technology with no fee. The following year, in early 2009, VESA announced that Mini DisplayPort would be included in the upcoming DisplayPort 1.2 specification. On 24 February 2011, Apple and Intel announced Thunderbolt, a successor to Mini DisplayPort which adds support for PCI Express data connections while maintaining backwards compatibility with Mini DisplayPort based peripherals.
Micro DisplayPort
Micro DisplayPort will target systems that need ultra-compact connectors, such as phones, tablets and ultra-portable notebook computers. This new standard will be physically smaller than the currently available Mini DisplayPort connectors. The standard was expected to be released by Q2 2014. This project seems aborted to be replaced by DisplayPort Alt Mode for USB Type-C Standard.
DDM
Direct Drive Monitor (DDM) 1.0 standard was approved in December 2008. It allows for controller-less monitors where the display panel is directly driven by the DisplayPort signal, although the available resolutions and color depth are limited to two-lane operation.
Display Stream Compression
Display Stream Compression (DSC) is a VESA-developed low-latency compression algorithm to overcome the limitations posed by sending high-resolution video over physical media of limited bandwidth. It is a visually lossless low-latency algorithm based on delta PCM coding and YCoCg-R color space; it allows increased resolutions and color depths and reduced power consumption.
DSC has been tested to meet the requirements of ISO/IEC 29170-2 Evaluation procedure for nearly lossless coding using various test patterns, noise, subpixel-rendered text (ClearType), UI captures, and photo and video images.
DSC version 1.0 was released on 10 March 2014, but was soon deprecated by DSC version 1.1 released on 1 August 2014. The DSC standard supports up to 3:1 compression ratio with constant or variable bit rate, 4:4:4 chroma subsampling, optional 4:2:2 conversion and 6/8/10/12 bits per color component.
DSC version 1.2 was released on 27 January 2016 and is included with DisplayPort 1.4; version 1.2a was released on 18 January 2017. The update includes native encoding of 4:2:2 and 4:2:0 formats in pixel containers, 14/16 bits per color, and minor modifications to the encoding algorithm.
DSC compression works on a horizontal line of pixels encoded using groups of three consecutive pixels for native 4:4:4 and simple 4:2:2 formats, or six pixels (three compressed containers) for native 4:2:2 and 4:2:0 formats. If RGB encoding is used, it is first converted to reversible YCgCo. Simple conversion from 4:2:2 to 4:4:4 can add missing chroma samples by interpolating neighboring pixels. Each luma component is coded separately using three independent substreams (four substreams in native 4:2:2 mode). Prediction step is performed using one of the three modes: modified median adaptive coding (MMAP) algorithm similar to the one used by JPEG-LS, block prediction (optional for decoders due to high computational complexity, negotiated at DSC handshake), and midpoint prediction. Bit rate control algorithm tracks color flatness and buffer fullness to adjust the quantization bit depth for a pixel group in a way that minimizes compression artifacts while staying within the bitrate limits. Repeating recent pixels can be stored in 32-entry Indexed Color History (ICH) buffer, which can be referenced directly by each group in a slice; this improves compression quality of computer-generated images. Alternatively, prediction residuals are computed and encoded with entropy coding algorithm based on delta size unit-variable length coding (DSU-VLC). Encoded pixel groups are then combined into slices of various height and width; common combinations include 100% or 25% picture width, and 8-, 32-, or 108-line height.
On 4 January 2017, HDMI 2.1 was announced which supports up to 10K resolution and uses DSC 1.2 for video that is higher than 8K resolution with 4:2:0 chroma subsampling.
eDP
Embedded DisplayPort (eDP) 1.0 standard was adopted in December 2008. It aims to define a standardized display panel interface for internal connections; e.g., graphics cards to notebook display panels. It has advanced power-saving features including seamless refresh rate switching. Version 1.1 was approved in October 2009 followed by version 1.1a in November 2009. Version 1.2 was approved in May 2010 and includes DisplayPort 1.2 data rates, 120 Hz sequential color monitors, and a new display panel control protocol that works through the AUX channel. Version 1.3 was published in February 2011; it includes a new Panel Self-Refresh (PSR) feature developed to save system power and further extend battery life in portable PC systems. PSR mode allows GPU to enter power saving state in between frame updates by including framebuffer memory in the display panel controller. Version 1.4 was released in February 2013; it reduces power consumption with partial-frame updates in PSR mode, regional backlight control, lower interface voltage, and additional link rates; the auxiliary channel supports multi-touch panel data to accommodate different form factors. Version 1.4a was published in February 2015; it is based on DisplayPort 1.3 and supports HBR3 data rate, Display Stream Compression 1.1, Segmented Panel Displays, and partial updates for Panel Self-Refresh. Version 1.4b was published in October 2015; its protocol refinements and clarifications are intended to enable adoption of eDP 1.4 in production by mid-2016.
iDP
Internal DisplayPort (iDP) 1.0 was approved in April 2010. The iDP standard defines an internal link between a digital TV system on a chip controller and the display panel's timing controller. It aims to replace currently used internal FPD-Link lanes with DisplayPort connection. iDP features unique physical interface and protocols, which are not directly compatible with DisplayPort and are not applicable to external connection, however they enable very high resolution and refresh rates while providing simplicity and extensibility. iDP features non-variable 2.7 GHz clock and is nominally rated at 3.24 Gbit/s data rate per lane, with up to sixteen lanes in a bank, resulting in six-fold decrease in wiring requirements over FPD-Link for a 1080p24 signal; other data rates are also possible. iDP was built with simplicity in mind and it doesn't have AUX channel, content protection, or multiple streams; however it does have frame sequential and line interleaved stereo 3D.
PDMI
Portable Digital Media Interface (PDMI) is an interconnection between docking stations/display devices and portable media players, which includes 2-lane DisplayPort v1.1a connection. It has been ratified in February 2010 as ANSI/CEA-2017-A.
wDP
Wireless DisplayPort (wDP) enables DisplayPort 1.2 bandwidth and feature set for cable-free applications operating in 60 GHz radio band; it was announced on November 2010 by WiGig Alliance and VESA as a cooperative effort.
SlimPort
SlimPort, a brand of Analogix products, complies with Mobility DisplayPort, also known as MyDP, which is an industry standard for a mobile audio/video Interface, providing connectivity from mobile devices to external displays and HDTVs. SlimPort implements the transmission of video up to 4K-UltraHD and up to eight channels of audio over the micro-USB connector to an external converter accessory or display device. SlimPort products support seamless connectivity to DisplayPort, HDMI and VGA displays. The MyDP standard was released in June 2012, and the first product to use SlimPort was Google's Nexus 4 smartphone.
SlimPort is an alternative to Mobile High-Definition Link (MHL).
DisplayID
DisplayID is designed to replace the E-EDID standard. DisplayID features variable-length structures which encompass all existing EDID extensions as well as new extensions for 3D displays and embedded displays.
The latest version 1.3 (announced on 23 September 2013) adds enhanced support for tiled display topologies; it allows better identification of multiple video streams, and reports bezel size and locations. As of December 2013, many current 4K displays use a tiled topology, but lack a standard way to report to the video source which tile is left and which is right. These early 4K displays, for manufacturing reasons, typically use two 1920×2160 panels laminated together and are currently generally treated as multiple-monitor setups. DisplayID 1.3 also allows 8K display discovery, and has applications in stereo 3D, where multiple video streams are used.
DockPort
DockPort, formerly known as Lightning Bolt, is an extension to DisplayPort to include USB 3.0 data as well as power for charging portable devices from attached external displays. Originally developed by AMD and Texas Instruments, it has been announced as a VESA specification in 2014.
USB-C
On 22 September 2014, VESA published the DisplayPort Alternate Mode on USB Type-C Connector Standard, a specification on how to send DisplayPort signals over the newly released USB-C connector. One, two or all four of the differential pairs that USB uses for the SuperSpeed bus can be configured dynamically to be used for DisplayPort lanes. In the first two cases, the connector still can carry a full SuperSpeed signal; in the latter case, at least a non-SuperSpeed signal is available. The DisplayPort AUX channel is also supported over the two sideband signals over the same connection; furthermore, USB Power Delivery according to the newly expanded USB-PD 2.0 specification is possible at the same time. This makes the Type-C connector a strict superset of the use-cases envisioned for DockPort, SlimPort, Mini and Micro DisplayPort.
Products
Since its introduction in 2006, DisplayPort has gained popularity within the computer industry and is featured on many graphic cards, displays, and notebook computers. Dell was the first company to introduce a consumer product with a DisplayPort connector, the Dell UltraSharp 3008WFP, which was released in January 2008. Soon after, AMD and Nvidia released products to support the technology. AMD included support in the Radeon HD 3000 series of graphics cards, while Nvidia first introduced support in the GeForce 9 series starting with the GeForce 9600 GT.
Later the same year, Apple introduced several products featuring a Mini DisplayPort. The new connector - proprietary at the time - eventually became part of the DisplayPort standard, however Apple reserves the right to void the license should the licensee "commence an action for patent infringement against Apple". In 2009, AMD followed suit with their Radeon HD 5000 Series of graphics cards, which featured the Mini DisplayPort on the Eyefinity versions in the series.
Nvidia launched NVS 810 with 8 Mini DisplayPort outputs on a single card on 4 November 2015.
Nvidia revealed the GeForce GTX 1080, the world's first graphics card with DisplayPort 1.4 support on 6 May 2016. AMD followed with the Radeon RX 480 to support Displayport 1.3/1.4 on 29 June 2016. The Radeon RX 400 Series will support DisplayPort 1.3 HBR and HDR10, dropping the DVI connector(s) in the reference board design.
In February 2017, VESA and Qualcomm announced that DisplayPort Alt Mode video transport will be integrated into the Snapdragon 835 mobile chipset, which powers smartphones, VR/AR head-mounted displays, IP cameras, tablets and mobile PCs.
Support for DisplayPort Alternate Mode over USB-C
Participating companies
The following companies have participated in preparing the drafts of DisplayPort, eDP, iDP, DDM or DSC standards:
The following companies have additionally announced their intention to implement DisplayPort, eDP or iDP:
See also
- HDBaseT
- HDMI
- List of video connectors
- Thunderbolt (interface)
Notes
References
External links
- Crowdsourced comparison table EN-FR video connectors
- DisplayPort - the official site operated by VESA
- Bridging the new DisplayPort standard
- Introducing the Panel Self Refresh Technology
- SlimPort Consumer website
- SlimPort Enabled Devices
Source of the article : Wikipedia
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