From TMDS to Thunderbolt and Everything in Between Digital Video Formats the Phrase “Digital Video” Is Ubiquitous, but Seldom Defined
Total Page：16
File Type：pdf, Size：1020Kb
From TMDS to Thunderbolt and Everything In Between Digital Video Formats The phrase “digital video” is ubiquitous, but seldom defined. What makes it digital? What are the rules for converting formats? Let’s find out… Joseph D. Cornwall, CTS-D PRODUCT LINE Welcome To Today’s Presentation: Understanding Digital Video Formats “AN EDUCATION ISN'T HOW MUCH YOU HAVE COMMITTED TO MEMORY, OR EVEN HOW MUCH YOU KNOW. IT'S BEING ABLE TO DIFFERENTIATE BETWEEN WHAT YOU DO KNOW AND WHAT YOU DON'T.” - JACQUES ANATOLE FRANCOIS THIBAULT PRODUCT LINE Our Agenda • Define digital ─ What are the elements of a digital signal? • Digital Rights Management • DisplayID ─ What is a DDC? Where’s the EDID? • TMDS explained • Digital Visual Interface DVI • High Definition Multimedia Interface HDMI • DisplayPort • Thunderbolt PRODUCT LINE Define “Digital” “Any sufficiently advanced technology is indistinguishable from magic.” ─ Arthur C. Clarke PRODUCT LINE The Elements of a Video Signal • RGB additive color model divides a video signal into 3 ”components” ─ RGB or YPbPr (YCbCr) • Bandwidth is directly proportional to visual detail ─ In analog systems, the ability to a pass higher frequencies equates to m the ability to display finer detail p l • Amplitude is directly i t proportional to color u d saturation e time PRODUCT LINE The Numbers Behind The Bits- Understanding Sampling .Analog signals are continuous in time ─ All waveforms consist of fundamental sine waves plus harmonics .Shannon-Nyquist says > 2 samples are necessary to recreate a waveform • Resolution is bound by sampling rate ─ Aliasing occurs when input frequency exceeds 2x sampling frequency PRODUCT LINE The Numbers Behind The Bits- Making Sense of Bit Depth • 3 bits = 2 x 2 x 2 = 8 total possible values, for example • Each bit represents a step in voltage • Values that fall between “steps” are lost information PRODUCT LINE Digital Rights Management “Obviously crime pays, or there'd be no crime.” ─ G. Gordon Liddy PRODUCT LINE HDCP • High Bandwidth Digital Content Protection ─ Because in the digital world there are no copies, only clones • Blom's Scheme is a symmetric threshold key exchange protocol used in cryptography ─ A trusted party gives each participant a secret key and a public identifier, which enables any two participants to independently create a shared key for communicating. ─ Keys updated after each encoded frame PRODUCT LINE Inside HDCP •HDCP makes use of a three-stage content protection process ─ Device authentication and key exchange ─ Encryption of content ─ Key-revocation procedures •Unique keys are assigned to each device ─ Consists of up to 40 different 'secret or private' keys, each 56 bits long, embedded in the device ─ For each set of keys, a special public key, called a “key selection vector”, is created ─ ‘Combining’ an embedded key with a public key creates a temporary session key, allowing for clear communication between the devices PRODUCT LINE Telling the Monitor What to Expect “If you're not scared or angry at the thought of a human brain being controlled remotely, then it could be this prototype of mine is finally starting to work.” - John Alejandro King PRODUCT LINE DDC, EDID and DisplayID • Display Data Channel • Extended Display Identification Data • DisplayID 1.3 (2013) is the most current iteration ─ Enables the display (sink) to communicate supported display modes to the source via a compact binary file format that describes the monitor's capabilities and supported graphics modes ─ Stored in a read-only memory chip programmed by the manufacturer of the monitor PRODUCT LINE PRODUCT LINE Making Signals Easier To Transport “All truths are easy to understand once they are discovered; the point is to discover them.” - Galileo Galilei PRODUCT LINE Transition Minimized Differential Signaling • TMDS is a two-stage process that converts a signal from parallel to serial and adds additional bits to balance DC • Makes signals smaller by converting them from 8 bit to 10 bit ─ 8b/10b line coding - 8-bit data plus 2 bits of control signals ─ 4 channels: red, green, blue, clock ─ Twisted pair for noise reduction ─ Current mode logic (CML), DC coupled and terminated to 3.3 volts PRODUCT LINE The TMDS Algorithm • TMDS adds a 9th bit to the digital word to “minimize” the transitions from digital ones to digital zeros ─ This decreases high frequency content making the signal more robust and easier to transport • The algorithm then adds a 10th bit to provide for DC balancing ─ DC balancing inverts the digital word so the signal has an equal number of zeros and ones ─ Provides a stable, predictable signal to the differential amplifiers PRODUCT LINE Typical Signal Flow “I HAVE YET TO SEE ANY PROBLEM, HOWEVER COMPLICATED, WHICH, WHEN YOU LOOKED AT IT IN THE RIGHT WAY, DID NOT BECOME STILL MORE COMPLICATED.” ̶ POUL ANDERSON PRODUCT LINE PRODUCT LINE Putting It All Together “To manage a system effectively, you might focus on the interactions of the parts rather than their behavior taken separately.” ─ Russell l. Ackoff PRODUCT LINE Digital Visual Interface - DVI R R G G B B S S PRODUCT LINE Are DVI Connections Obsolete? In December 2010, Intel, AMD, and several computer and display manufacturers announced they would stop supporting DVI-I, VGA and LVDS-technologies by 2015. These will be replaced by DisplayPort and HDMI. "Legacy interfaces such as VGA, DVI and LVDS have not kept pace, and newer standards such as DisplayPort and HDMI clearly provide the best connectivity options moving forward. In our opinion, DisplayPort 1.2 is the future interface for PC monitors, along with HDMI 1.4a for TV connectivity". PRODUCT LINE High Definition Multimedia Interface HP DDC DDC CEC B B R R V S S G G 5 + DDC HEAC PRODUCT LINE HDMI(e) HEAC HEAC is the HDMI Ethernet and Audio-return Channel and supports up to 100Mbits data transfer. Signal selection is excusive. PRODUCT LINE HDMI 2.0 Features and Upgrades Noise Reduction UltraHD and 4K Video Increase bandwidth System For TMDS Support from 10.2 to 18 Gbps Lanes Support for additional Up To 21:9 Aspect Ratio Multi-stream Video color space formats Support Capable (MST) including 4:2:0 Improved audio ability CEC 2.0 Error correction with support to 32 channels PRODUCT LINE SDI - Serial Digital Interface • SDI (1989) • HD SDI (1998) • 3G SDI (2006) • 3 Gbit/s and 1080p • 16 Channels of embedded audio • 6G SDI • 6 Gbit/s and 4Kp30 • 12G SDI • 12 Gbit/s and 4Kp60 • 24G SDI • 24Gbit/s and 8Kp60 PRODUCT LINE DisplayPort Power HP Ret Hot Plug Aux Config Lane 3 Lane 2 Lane 1 Lane 0 PRODUCT LINE DisplayPort Tech Specs • Native MST for extended DisplayPort Dual Mode supports desktop and multi-display passive conversion to HDMI or DVI installations CH 0 Sync • Up to 8.1 Gbit/s per lane CH 2 Blue ─ Dual lane allocation supports DP++ HDMI UltraHD resolutions CH 1 Green • Supports RGB And CH 0 Red YPrPb Color Spaces ─ Up to 16 bit color • Up to 8-channels audio • DP++ Embedded in new USB Type C Standard ─ SlimPort provides mobile device support PRODUCT LINE Thunderbolt & Mini-DP • Thunderbolt is built on the Mini DisplayPort connector and can “shift” from TB to Mini-DP to HDMI based on configuration commands • Thunderbolt uses data lanes for PCIe content and other “tunneling” data transport techniques PRODUCT LINE Thunderbolt & Mini-DP •Thunderbolt controllers on the host and peripherals multiplex the PCIe and DisplayPort data into packets and de-multiplex them at the destination ─ When connected to a DP++ compatible device, the Thunderbolt port can provide a native DisplayPort signal with 4 lanes of output data at up to 5.4 Gbit/S per lane ─ When connected to a Thunderbolt device the per-lane data rate may be as high as 10 Gbit/s and the 4 lanes are configured as 2 channels with each bidirectional 10 Gbit/s channel comprising one lane of input and one lane of output PRODUCT LINE In Conclusion… “Knowledge is a process of piling up facts; wisdom lies in their simplification.” − Martin H. Fischer PRODUCT LINE What We’ve Learned… • In the digital video domain, sampling rate bounds resolution and bit depth (word length) bounds saturation (intensity) • High-bandwidth Digital Copyright Protection is an important element of digital video • TMDS is Transition Minimized Differential Signaling and is the basis for DVI and HDMI technology • DVI is inside of HDMI; the two formats are fundamentally identical in the video domain • DisplayPort leverages four data lanes, which it can reassign as RGBs TMDS connections making DP++ compatible with HDMI topology • Thunderbolt is built on DisplayPort technology, but uses “tunneling” to include PCIe data into the communication lanes PRODUCT LINE Questions? PRODUCT LINE.