Issue link: https://www.e-digitaleditions.com/i/1156106
8 I ICT TODAY FIGURE 1: Digital video resolutions and how they have increased over time. Cinema 4K 4096x2160 4K/UHD 3840x2160 2K 2048x1080 Full HD 1920x1080 HD 12080x720 SD 720x480 and control data in one cable. It is arguably the most popular AV interface right now. With abilities to carry 8K video, multichannel audio, and control data, Display- Port aspires to compete with HDMI. However, it remains mostly a computer display interface, which is its original application. USB-C is gaining acceptance as a pro AV interface. It has a reversible double-sided connector, supports up to 8K video, multichannel audio,"superspeed" data, and up to 100 watts of power delivery. USB-C's Alternate Mode enables connection via adapters to HDMI, DisplayPort, Thunderbolt, and other video connectors. Video Resolution Resolution is the number of distinct pixels in each dimension (width x height) that can be displayed. Pixels are the smallest component of a screen image, composed of red, green and blue primary colors. The higher the resolution, the sharper and more detailed the image. Viewers demand the highest resolution to obtain the most life-like experience possible, and the makers of video cameras and video displays continue to deliver. 4K/ultra high definition (UHD) is rapidly eclipsing full HD for market dominance as prices fall. On the horizon is 8K, aiming to hit the limit of human visual acuity. Figure 1 shows the evolution of video resolution. Cinema 2K and 4K are targeted toward professional digital cinema. Unlike consumer video, where resolution is stated as number of vertical lines (480p, 720p, 1080p), cinema resolutions are stated as width. This is because film has many different aspect ratios, making width the only constant value. 4K/UHD, which is 3840 x 2160 and can be considered 2160p, is the consumer equivalent of Cinema 4K. Cinema 4K is 6% wider than 4K/UHD. Extended Display Identification Data (EDID) EDID is a standardized data format that contains video display parameter information. Its purpose is to allow video displays to communicate their identity and capa- bilities to video source devices so that the source can deliver content in the formats compatible with the dis- play. This provides plug-and-play compatibility between devices. EDID data is transmitted over the display data channel (DDC). DDC is the communications protocol and the physical link for EDID transmission. The DDC link is a bidirectional serial data line, a clock line, and a +5 volt line. The data and clock lines support EDID data transmission. The +5 volt line powers the EDID circuitry in the display, allowing the source to read the EDID data even if the display is powered off. All mainstream AV interfaces, including HDMI, DVI, video graphics array (VGA) and DisplayPort, support EDID and DDC. EDID message mishandling by devices along the signal path can create EDID issues resulting in incor- rect display resolutions. These issues can be mitigated by EDID management devices that can supply the sources with a resolution selected by the user or the native resolution captured from the display. EDID management de- vices also improve reliability by keeping the EDID handshake closer to the sources, reducing attenuation or interference pos- sible with long cable runs. The original DDC protocol defined 128 bytes of EDID data. As display capabilities increased, 128 bytes were not enough. The latest specification is called E-EDID/E-DDC. It retains the first 128 bytes as a mandatory base EDID to which up to 255 extension blocks can be appended.