Mobile High-Definition Link

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MHL (Mobile High-Definition Link)
New MHL Logo.jpg
Type Digital audio/video/data connector
Designer
Designed June 2010
Hot pluggable Yes
External Yes
Pins MHL 1, 2, & 3 (5),[1]
superMHL (5–32)[2]

Mobile High-Definition Link (MHL) is an industry standard for a mobile audio/video interface that allows the connection of mobile phones, tablets, and other portable consumer electronics (CE) devices to high-definition televisions (HDTVs) and audio receivers. MHL-enabled products include adapters, automotive accessories, AV receivers, Blu-ray Disc players, cables, DTVs, media sticks, monitors, projectors, smartphones, tablets, TV accessories and more. MHL is a consortium made up of major companies in the mobile and CE industries, including Nokia, Samsung, Silicon Image, Sony and Toshiba.

History[edit]

Silicon Image, one of the founding companies of the HDMI standard, originally demonstrated a mobile interconnect at the January 2008 Consumer Electronics Show (CES), based on its transition-minimized differential signaling (TMDS) technology.[3] This interface was termed "Mobile High Definition Link" at the time of the demonstration, and is a direct precursor of the implementation announced by the MHL Consortium. The company is quoted as saying it did not ship that original technology in any volume, but used it as a way to get a working group started.[4]

The working group was announced in September 2009,[5] and the MHL Consortium founded in April 2010 by Nokia, Samsung, Silicon Image, Sony and Toshiba. The MHL specification version 1.0 was released in June 2010 and May 2011 marked the first retail availability of MHL-enabled products.

An abridged version of the specification was made available for download on April 14, 2010.[6] MHL specification version 1.0 was released in June 2010.[7] The Compliance Test Specification (CTS) was announced on December 21, 2010.[8]

MHL announced in 2014 that more than half a billion MHL-capable products had been shipped since the standard was created.[9]

Overview[edit]

MHL was originally intended for mobile devices such as smartphones and tablets.

To better accommodate the needs of mobile devices, MHL differs from HDMI as follows.

  • Five wires in place of HDMI's nineteen, namely ground, power, control, and a differential pair for data. This permits a much lighter cable and a much smaller connector on the mobile device.
  • Whereas HDMI uses the power line to provide 5 volts from the source at 50 mA (0.25 W) for the purpose of awakening a sleeping sink, MHL uses it to provide that voltage from the sink at 900 mA (4.5 W) to maintain the state of charge of the source. This allows a mobile device with only one port for both charging and MHL to operate indefinitely without exhausting the battery, provided 4.5 W is sufficient. Devices needing more power from the port used for MHL may not be suitable candidates for MHL 2.0; MHL 3.0 raises the power requirement to 2 A (10 W).
  • Although MHL ports can be dedicated to MHL alone, the standard is designed to permit port sharing with the most commonly used ports.
  • A typical MHL source will be shared with USB 2.0 on a standard 5-pin micro-usb receptacle, which switches from USB to MHL when it recognizes an MHL-qualified sink detected on the control wire.
  • A typical MHL sink will be shared with HDMI on a standard 19-pin HDMI receptacle. The standard uses the same pins for power (pin 18) and ground (pins 5, 11, and 17), HDMI's Hot Plug detect (pin 19) for MHL control, and HDMI's Data0 channel (pins 7 and 9) for MHL's data.
  • Whereas HDMI transmits the three bytes of a pixel in parallel over three physically separate differential pairs along with a fourth pair for a clock, with a separate ground for each pair (pins 1-12), MHL transmits them sequentially over one pair (7 and 9), with the clock added in as a common mode signal to the differential signal. The receiver then has both differential and common mode detection circuits.[10] In MHL 3 and superMHL the clock signal is instead carried separately on an extended CBUS, renamed the enhanced control bus (eCBUS).
  • Whereas HDMI uses three wires to cater for HDMI-CEC (13), and DDC (15 and 16), MHL controls these functions with a single wire (CBUS).
  • In normal mode MHL supplies the same 24 bit color signal as HDMI, at a pixel clock rate of up to 75 MHz for MHL 2.0, sufficient for 1080i and 720p. Each of the three bytes is in a 10-bit frame whence at 75 MHz the data channel operates at 2.25 Gbit/s.[11][12]
  • MHL 2.0 caters for 1080p with a PackedPixel mode utilizing only the first two of HDMI's three channels. This shrinks each pixel to 16 bits (using YCbCr 4:2:2 chroma subsampling) carried in two 10-bit frames. The pixel clock is doubled to 150 MHz and the data channel then operates at 3 Gbit/s.[11][12]
  • MHL's serial signaling makes it incompatible with the three-channel parallel signaling of HDMI and DVI. Hence both ends of an MHL channel must implement the standard in full. In particular an MHL source cannot drive an ordinary HDMI or DVI display, though this limitation is easily overcome with an MHL dongle converting MHL to HDMI. An MHL source must be realized in hardware as the typical 5-pin USB 2.0 port on mobile devices is much too slow at 480 Mbit/s for a software-only implementation.

Versions[edit]

All MHL specifications are backwards compatible to previous versions of the standard. MHL is connection agnostic (i.e., not tied to a specific type of hardware connector). The first implementations used the 5-pin MHL-USB connector described below, and all are supported over USB Type-C MHL Alternate Mode. Other proprietary and custom connections are also allowed.

MHL 1[edit]

Version 1.0 was introduced in June 2010, supporting uncompressed HD video up to 720p/1080i 60 Hz (with RGB and YCbCr 4:2:2/4:4:4 pixel encoding). Support for 1080p 60 Hz (YCbCr 4:2:2) was introduced in version 1.3.[1] The specification supports standard SD (Rec. 601) and HD (Rec. 709) color spaces, as well as those introduced in HDMI 1.3 and 1.4 (xvYCC, sYCC601, Adobe RGB, and AdobeYCC601).[13] Other features include 192 kHz 24-bit LPCM 8-channel surround sound audio, HDCP 1.4 content protection, and a minimum of 2.5 W (500 mA) power between sink (e.g., TV) and source (e.g., mobile phone) for charging. The MHL sideband channel (MSC) includes a built-in Remote Control Protocol (RCP) function allowing the remote control of the TV to operate the MHL mobile device through TV's Consumer Electronics Control (CEC) function, or allowing a mobile device to manage the playback of its content on the TV.[13]

MHL 2[edit]

Version 2.0 was introduced in April 2012, and raised the minimum charging supply to 4.5 W (900 mA), with an optional 7.5 W (1.5 A) maximum allowed. Support for 3D video was also introduced, permitting 720p/1080i 60 Hz, and 1080p 24 Hz 3D video modes. The specification also included additional MHL sideband channel (MSC) commands.[14]

MHL 3[edit]

Version 3.0 was introduced in August 2013, and added support for 4K Ultra HD (3840 × 2160) 30 Hz video, increasing the maximum bandwidth from 3 Gbit/s to 6 Gbit/s. An additional YCbCr 4:2:0 pixel encoding for 4K resolution was also introduced, while the maximum charging supply was increased to 10 W (2 A).[13] Support for compressed lossless audio formats were added with support for Dolby TrueHD and DTS-HD Master Audio.

The specification increased the speed of the bi-directional data channel from 1 Mbit/s to 75 Mbit/s to enable concurrent 4K video and human interface device (HID) support, such as mice, keyboards, touchscreens, and game controllers.[15] Other features include support for simultaneous multiple displays, improved Remote Control Protocol (RCP) with new commands, and HDCP 2.2 content protection.

superMHL[edit]

superMHL 1.0 was introduced in January 2015, supporting 8K Ultra HD (7680 × 4320) 120 Hz High Dynamic Range (HDR) video with wide color gamut (Rec. 2020) and 48-bit deep color.[2][16][17] Support for object-based audio formats were added, such as Dolby Atmos and DTS:X, with an audio-only mode also available. The Remote Control Protocol (RCP) was also extended to link multiple MHL devices together (e.g., TV, AVR, Blu-ray Disc player) and control them via one remote.

The specification introduces a reversible 32-pin superMHL connector, which (along with USB Type-C) supports a higher charging power of up to 40 W (20 V / 2 A), and is designed for future bandwidth expansion. The increase in bandwidth over previous MHL versions is achieved by using multiple A/V lanes, each operating at 6 Gbit/s, with a maximum of six A/V lanes supported depending on device and connector type.[2] For example, Micro-USB and HDMI Type-A support one A/V lane, USB Type-C supports up to four A/V lanes, and the superMHL connector supports up to six A/V lanes (36 Gbit/s).

In addition to supporting a variable number of lanes, the specification supports VESA Display Stream Compression (DSC) 1.1, a "visually lossless" (but mathematically lossy) video compression standard. In cases when the bandwidth of the available lane(s) is unable to meet the rate of the uncompressed video stream, bandwidth savings of up to 3:1 can be achieved with a DSC compression rate of 3.0×.[2] For example, 4K 60 Hz is possible using a single lane (e.g., Micro-USB / HDMI Type-A) with a DSC rate of 3.0×.[2]

superMHL can use a variety of source and sink connectors with certain limitations: micro-USB or proprietary connectors can be used for the source only, HDMI Type-A for the sink only, while the USB Type-C[18] and the superMHL connectors can be for used for the source or sink.[2]

Connectors[edit]

Not all micro USB 2.0 ports are identical. Compare connectors for original Galaxy Note with the Note II.

Micro-USB-to-HDMI (five-pin)[edit]

The first implementations use the most common mobile connection (Micro-USB) and the most common TV connection (HDMI). There are two types of connection, depending whether the display device directly supports MHL.

Passive cable[edit]

Passive cables allow MHL devices to connect directly to MHL-enabled TVs (i.e., display devices or AV receivers with an MHL-enabled HDMI port) while providing charging power upstream to the mobile device. Other than the physical connectors, no USB or HDMI technology is being used. Exclusively MHL signaling is used through the connectors and over the cable.

Active adapter[edit]

With an active adapter, MHL devices are able to connect to HDMI display devices that do not have MHL capability by actively converting the signal to HDMI. These adapters often feature an additional Micro-USB port on them to provide charging power to the mobile device because standard HDMI ports do not supply sufficient current.

Samsung Micro-USB-to-HDMI adapter and tip (eleven-pin)[edit]

The Samsung Galaxy S III, and later Galaxy Note II and Galaxy S4, use an 11-pin connector and the six additional connector pins in order to achieve functional improvements over the 5-pin design (like simultaneous USB-OTG use[19]). However, if consumers have a standard MHL-to-HDMI adapter all they need to purchase is a tip. With the launch of the Samsung Galaxy S4, Samsung also released a Samsung 2.0 smart adapter with a built-in 11-pin connector. The first generation Samsung MHL 2.0 smart adapter released with the Galaxy S III requires external power and is able to work with HDMI TVs at 1080p at 24 Hz.[20] The second generation adapter released with the Galaxy S4 can output 1080p at 60 Hz and does not need external power.

USB Type-C (MHL Alternate Mode)[edit]

Main article: USB Type-C

The MHL Alternate Mode for USB Type-C specification allows MHL enabled source and display devices to be connected through the USB Type-C port. The standard was released on November 17, 2014, and is backward compatible with existing MHL specifications: supporting MHL 1, 2, 3 and superMHL.[21] The standard supports the simultaneous transfer of data (at least USB 2.0, and depending on video resolution: USB 3.1 Gen 1 or 2) and power charging (up to 40W via USB Power Delivery), in addition to MHL audio/video.[2] This allows the connection to be used with mobile/laptop docks, allowing devices to connect to other peripherals while charging. The use of passive cables is possible when both devices support the standard, i.e., when connecting to superMHL, USB Type-C, and MHL-enabled HDMI, otherwise, an active cable adapter/dongle is necessary to connect to standard HDMI devices.[18]

Depending on the bandwidth requirement, the standard makes use of a variable number of USB Type-C's four SuperSpeed differential pairs to carry each TMDS lane: a single lane is required for resolutions up to 4K/60 Hz, two lanes for 4K/120 Hz, and all four lanes for 8K/60 Hz.[18] The MHL eCBUS signal is sent over a side-band (SBU) pin on the USB Type-C connector. When one or two lanes are used, USB 3.1 data transfer is supported.

MHL Alternate Mode USB Type-C pin mapping[18]

In common MHL Alt Mode implementations on mobile/tablet/laptops, the video from the GPU will be converted to MHL signal by using a MHL transmitter chip. The transmitter chips often accept video in MIPI (DSI/DPI) or HDMI format and covert it to MHL format. The USB Type-C port controller functions as a switch/mux, passing through the MHL signal to the external devices. The dock/display devices may use an MHL bridge chip to covert the MHL signal to HDMI signal format.

superMHL (32-pin)[edit]

On January 6, 2015, MHL introduced the new reversible superMHL connector. This 32 pin connector can carry concurrent video, data and power charging all in a slim, consumer-friendly form factor. A reversible design means that consumers don't have to worry about the plug's orientation or the cable's direction.

Comparison with SlimPort / Mobility DisplayPort (MyDP)[edit]

SlimPort is a proprietary alternative to MHL, based on the DisplayPort standard integrated into common microUSB ports and supports up to 1080p60 or 1080p30 with 3D content over HDMI 1.4 (up to 5.4 Gbit/s of bandwidth), in addition to support for DVI, VGA (up to 1920 x 1080 at 60 Hz), and DisplayPort.[22] Implementers of SlimPort may be subject to the MPEG-LA patent pool license for DisplayPort. On March 5, 2015, the MPEG LA announced their DisplayPort license, which is US$0.20 per DisplayPort product.

Announcements and products[edit]

  • MHL announced on January 6, 2015 the superMHL, the first audio/video specification with support up to 8K and a new consumer-friendly, reversible superMHL connector for CE devices
  • MHL announced on November 17, 2014 MHL Alternate Mode ("Alt Mode") for the USB Type-C specification
  • MHL announced on August 20, 2013 the MHL 3.0 specification with major advancements for mobile and CE connectivity
  • MHL announced on August 26, 2013 its MHL Experience Program with SEGA, PowerA, Nyko, MobiSystems, Green Throttle and FilmOn.TV
  • MHL announced on May 28, 2013 that it had reached 200 adopter milestone
  • Samsung March 14, 2013, Samsung release Galaxy S4 with MHL 2.0
  • HTC February 19, 2013, HTC release the New HTC One with MHL
  • MHL announced on January 7, 2013 that there was an installed base of more than 220 million products and greater than 200 products in the marketplace.
  • Hyundai announced on January 4, 2013 that it would be showing working versions of future vehicle infotainment systems, including MHL technology.
  • Silicon Image expanded its MHL product line with four new products that included the latest MHL 2.0 features on September 25, 2012.[23]
  • LG Electronics available on December 4, 2011 AT&T Wireless and LG Electronics Nitro HD (AT&T) / Optimus LTE (LTE carriers), a True HD AH-IPS panel display on the device with MHL output abilities for any TV equipped with HDMI input.[24][25][26]
  • HTC announced at the 2011 CTIA that their "EVO 3D" mobile device supports MHL output and in addition that the HTC "Sensation" will also have this capability, as well as its successor, the "Sensation XE". The HTC Rezound, which is a sister device to the Sensation XE also has the MHL port.
  • Samsung announced at the 2011 Mobile World Congress that their Galaxy S II mobile devices feature MHL connections.[27][28][29]
  • Onkyo and Silicon Image announced on December 21, 2011 the world's first A/V receivers featuring InstaPrevue and MHL technologies.[30]

See also[edit]

References[edit]

  1. ^ a b "Mobile High-Definition Link (MHL) - Technology White Paper" (PDF). MHL. October 2013. Retrieved 7 February 2017. 
  2. ^ a b c d e f g "superMHL Specification - White Paper" (PDF). MHL. September 2015. Retrieved 7 February 2017. 
  3. ^ "HDMI plugs into cameras, cellphones". EETimes.com. January 8, 2008. Retrieved 2010-04-14. 
  4. ^ "Consortium backs mobile interface for high def video". EETimes.com. EE Times. April 14, 2010. Retrieved 2010-04-14. 
  5. ^ "Leading Companies Form Mobile High-Definition Interface Working Group to Drive Industry Standard for Mobile Wired Connectivity" (Press release). Silicon Image. September 28, 2009. Archived from the original on 2011-07-16. Retrieved 2009-09-30. 
  6. ^ "Adopter Information". MHL, LLC. June 30, 2010. Retrieved 2010-06-30. 
  7. ^ "MHL 1.0 Specification and Adopter Agreement Now Available". MHL, LLC. June 30, 2010. Retrieved 2010-06-30. 
  8. ^ "MHL CONSORTIUM RELEASES COMPLIANCE TEST SPECIFICATION TO GROWING ADOPTER BASE". MHL, LLC. December 21, 2010. Retrieved 2010-12-22. 
  9. ^ "MHL Consortium Announces More Than Half A Billion MHL Products Have Shipped Worldwide" (Press release). MHL Consortium. 24 February 2014. Retrieved 9 January 2016. 
  10. ^ "Enable New Generation of Display Interface: Introducing MHL 3.2" (PDF). Keysight Technologies. pp. 21–33. Retrieved 15 February 2017. 
  11. ^ a b Manmeet Walia. "MHL: The New Mobile-to-TV Protocol". Synopsys.com. Retrieved 15 February 2017. 
  12. ^ a b "MHL (Mobile High-Definition Link) Technical overview" (PDF). Rohde & Schwarz. Retrieved 15 February 2017. 
  13. ^ a b c Masud Syed (17 November 2014). "MHL: A multimedia connectivity standard". Electronic Products. Retrieved 17 March 2017. 
  14. ^ "MHL 2.0 Compliance Testing" (PDF). Rohde & Schwarz. 
  15. ^ "MHL Consortium Announces New Specification with Major Advancements for Mobile and Consumer Electronics Connectivity" (Press release). MHL, LLC. 20 August 2013. Retrieved 21 March 2017. 
  16. ^ "MHL Consortium Announces SuperMHL – The First Audio/Video Specification With Support Up To 8k". mhltech.org. MHL, LLC. 6 January 2016. 
  17. ^ "MHL at CES 2016". slideshare.net. MHL Consortium. 6 January 2016. 
  18. ^ a b c d "MHL Alt Mode: Optimizing Consumer Video Transmission" (PDF). usb.org. MHL, LLC. 18 November 2015. 
  19. ^ "Galaxy S3 MHL explanation". 
  20. ^ "MHL 2.0 HDTV Smart Adapter". 
  21. ^ "MHL Releases Alternate Mode for New USB Type-C Connector". mhltech.org (Press release). November 17, 2014. Retrieved 2014-11-20. 
  22. ^ http://www.slimportconnect.com/support/
  23. ^ "Silicon Image Unveils First MHL Products". Silicon Image. October 4, 2010. Retrieved 2011-02-15. 
  24. ^ "LG Nitro HD Delivers First True High-Definition Experience for AT&T Customers" (Press release). AT&T Wireless. November 28, 2011. Retrieved 2011-11-28. 
  25. ^ "WORLD'S FIRST HD LTE SMARTPHONE ANNOUNCED IN CANADA" (Press release). LG Electronics. November 8, 2011. Retrieved 2011-11-08. 
  26. ^ "LG LAUNCHES OPTIMUS LTE, FIRST 4G HD SMARTPHONE IN KOREAN MARKET" (Press release). LG Electronics. October 4, 2011. Retrieved 2011-10-04. 
  27. ^ "MHL High-definition Link". YouTube. February 15, 2011. Retrieved 2011-02-15. 
  28. ^ "The Samsung Galaxy S2 is Announced". MobileReview. February 15, 2011. Retrieved 2011-02-15. 
  29. ^ "HDMI 2.1".  Wednesday, 1 February 2017
  30. ^ "Onkyo and Silicon Image Announce the World's First A/V Receivers Featuring InstaPrevue and MHL Technologies." (Press release). Onkyo US. December 21, 2011. Retrieved 2012-06-06. 

External links[edit]