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HDMI Specification Version 1.4 defines a set of link status monitor values, called LSM-Elements. These are found in the Physical Layer Packet (PLP) section of an HDMI frame and include information such as Cable Length, Bit Rate and Signal Quality. These parameters can be used by a Receiver Device to determine whether there is anything plugged into its connectors or not, and if there is, then what type it is (for example: gaming console vs. DVD player).
A large part of the HDMI specification is centered around the status of the link. This is called Link Status Monitoring. This section highlights some ways in which link status can determine how video is displayed to a user.
Link Status Monitoring is a large part of the HDMI specification, so it's important to understand how it works and what implications it has.
The most important use of Link Status Monitoring is to determine if a source is connected or not. For example, if you plug in an HDMI cable from your computer to your TV, then the link status will change from "inactive" to "connected". Once the link status changes from inactive to connected, then you will be able to view videos on your computer on your TV screen.
It should be noted that there are many other ways link status can be used; however these were covered briefly in other sections and this section focuses specifically on how links work together with video switching hardware
A Receiver Device has a set of physical input ports into which connectors for video sources can be plugged. If a source sends a signal to more than one input port, the Receiver Device can select which input port is used based upon Link Status Monitored information about the source connectors. For example, a TV with multiple HDMI inputs may have an Input 3 that is always selected when it detects a Wii gaming system connected to it, or use Input 2 whenever it detects a Blu-ray player connected to it.
An HDMI Cable must report its integrity and quality using its Link Status monitored information. If the detected parameters are within spec, then the cable will indicate that there is no problem and that no action needs to be taken; however, if any of the monitoring values are out of range or if any error conditions are present, then the receiver device can use this information to decide what action to take. Some possible actions include displaying an error message or powering down completely.
Link Status Monitoring is an essential part of the HDMI specification and provides the ability for an HDMI device to determine if an HDMI cable is operating properly or not.
An HDMI Cable must report its integrity and quality using its Link Status monitored information. If the detected parameters are within spec, then the cable will indicate that there is no problem and that no action needs to be taken; however, if any of the monitoring values are out of range or if any error conditions are present, then the receiver device can use this information to decide what action to take. Some possible actions include displaying an error message or powering down completely."
The Receiver Device can detect whether there are any display devices attached to it by observing link status monitored information from each of them. It can turn on and activate displays as appropriate, or power down and deactivate displays that aren't present.
To enable this feature:
Connect your HDMI-enabled receiver device (e.g., Roku, Chromecast, Apple TV) to one end of a cable that has an HDMI connector at its other end (known as a "cable TV" connection). Depending on where you're using it and what kind of monitor/TV you're using, also make sure that your receiver has video input ports for both audio and video; this depends on whether the monitor/TV supports analog signals (which most do not). For example: if you have an older TV without HDMI ports but only component inputs, you would need some sort of converter box or adapter between your cable TV connection and the component inputs on your TV set itself.
If necessary for troubleshooting purposes (for example if connecting with multiple devices), check which port is labeled "input" when looking at where it connects within the back panel of each device involved in linking together monitors/displays—you might want to label these clearly as needed so they don't get mixed up later!
If any of the monitoring values are out of range or if any error conditions are present, then the receiver device can use this information to decide what action to take. Some possible actions include displaying an error message or powering down completely.
