Transcript
Product: General Application Note Abstract: HDMI Over UTP Applications Document: AN-11-004 Version: 1.0 (3/10/2011)
HDMI video transmission and distribution over UTP: Some Application Advice Overview: When an HDMI source such as a Blu-ray (BD) player, PC, or set top box needs to be extended or distributed, special precautions should be taken to ensure that the video fidelity is preserved. With HDMI extension UTP products, there are several factors that play a vital role in the ability to achieve acceptable performance at longer distances, including:
Extension-cable type (UTP or CATx cables) Interconnect cable type (HDMI cables) EMI/RFI/ESD interference sources HDCP issues Video formats Grounding issues
Also, the signal-quality tolerance of the receiving device (for example, an HDMI display) can be a significant factor. Extension cable type (CATx): HDMI signal integrity and performance will be increased by using high-speed CAT6 cable constructed with 23AWG wires, and containing bonded pairs and a pair separator. If the environment is prone to EMI/RFI interference, a shielded CAT6 version with appropriate shielded-RJ45 connectors is highly recommended. HDMI interconnect cable quality: The quality of the HDMI interconnect cables being used is also important. A cable constructed with larger wire-gauge conductors and 100% shield coverage is highly recommended. Thicker conductors help preserve signal integrity, while shielding helps to minimize the effects of nearby EMI/RFI sources. EMI/RFI/ESD interference: In addition to the types of cables in use throughout, EMI/RFI/ESD interference is a factor that can cause serious problems. EMI (Electromagnetic Interference), RFI (Radio Frequency Interference), and ESD (Electro Static Discharge), are disturbances that affects HDMI transmission due to either electromagnetic induction, electromagnetic radiation, or high-voltage discharges, which exist in the vicinity of HDMI equipment or cabling. This interference can interrupt, degrade or limit the performance of the equipment. In some cases, ESD can permanently damage sensitive electronics. In order to prevent EMI/RFI/ESD interference, the environment must be specially designed or equipped. This includes a facility that is climate controlled, has minimal carpeting, properly grounded equipment, and in extreme cases, anti-static treatment of entire rooms where equipment is housed.
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HDCP issues: HDCP, or High-bandwidth Digital Content Protection, is an encryption technology meant to protect copyrighted digital video content from piracy and other illegal uses. It is also meant to stop HDCP-encrypted content from being played on devices that do not support HDCP. The authentication process involves the source sending a query to each receiving device to ensure that it is compliant before allowing video output. If any device inserted into the HDMI signal path does not support HDCP, or has difficulty in responding to the HDCP authentication process, or is simply not HDCP compliant, then the source device (BD player) will not allow video output. The fix: Ensure that all connected devices and cables are HDCP compliant. Video formats: The choice of video resolution, refreshrate and color-depth, has an effect on the maximum required data-rate sent over the UTP cable. In some cases, a lower setting (example: 720p/24Hz/24-bit color) may work compared to a much higher setting (1080p/60Hz/48bit color) which may not work at all. Signal degradation, and sensitivity to signal distortion, increases with maximum data rate. Possible fixes: Lower the resolution, disable deep color, or reduce the refresh-rate. If the source device allows it, try to select the “reduced blanking interval” timing option. This will also help reduce the data-rate over the UTP cable. Grounding issues: If the building does not have a properly bonded grounding system, then lightning and other electrical disturbances (EMI/RFI/ESD) could lead to limited video quality or even damage to equipment. The easiest way to avoid problems related to ground disturbances is to ensure ALL equipment is connected to a proper electrical service ground that is bonded to the building’s steel structure. The ground path between the source side and destination side must be continuous and connected to the same electrical service ground reference. If a building has more than one electrical service entrance the grounds must be connected together. A problem with building grounds can result in equipment damage or even personal injury. Before attempting to correct any perceived grounding issues yourself, it is highly recommended that a qualified electrician be consulted. Receiving device “quality”: Finally, some issues encountered with HDMI transmission are related to the different electronics and hardware implementations within the receiving device (displays, switchers, etc.). A device’s ability to re-clock and re-equalize the incoming HDMI signal may cause video loss if it is not highly tolerant of signal integrity problems. In short, some displays just work better than others, some extenders work better than others and some switchers work better than others.
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