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Solving HDMI Compliance and Interoperability Issues During Product Development


The HDMI standard has been tremendously successful. In 5 years HDMI has become the worldwide/global standard for digital connectivity in the home theatre. By 2010 there will be an estimated 1 billion HDMI-enabled consumer electronics and PC products deployed in the market (Source:12/2008, In-Stat). As one of the leading test equipment vendors, Quantum Data has been asked to provide test solutions for HDMI compliance and interoperability problems encountered during product development in R&D labs.

HDMI Port Usage

Despite the clear benefits of HDMI connectivity and its impressive penetration into both consumer electronics and PC market segments, many HDMI ports remain unconnected. Multiple Service Operators (MSOs) do not routinely connect their digital set-top boxes using the HDMI port during installation. And home theatre installers may use the analog component connection where comparable video resolutions are available. Why? Primarily because there is a perception that connecting the HDMI ports may be prone to interoperability problems.

HDCP Interoperability

Many potential interoperability issues are related to content protection. The HDMI Standard, like many digital interface standards, has a companion high-definition content protection system. HDMI uses the HDCP specification licensed by Digital Content Protection, LLC. There are many details about HDCP authentication, hot plug and EDID that developers have to get right to ensure interoperability, especially when repeater devices are involved. When authentication fails, consumers may be left in mute, watching a blank screen, blinking video, or snow. Historically, most HDCP handshake problems can be traced back to missing infrastructure. Test equipment and certification procedures are critical to any new technology.

A New Ecosystem Based on HDMI Connectivity

The advent of a new A/V interface standard such as the HDMI Standard has been likened to an ecosystem. All the various inter-related pieces—interface specifications, compliance test specification, authorized testing facilities, test equipment—for all functions—have to come together to achieve interoperability. For product development and interoperability testing, a variety of test equipment is needed. For the most part these test instruments exist for the HDMI technology; but not all. There have been no commercially available test instruments—until now—that provide complete visibility into, and analysis of, the encrypted HDMI protocol transactions including all infoframes, audio packet headers, etc. Without visibility into the HDMI protocol, developers are blind to the root cause of interoperability problems and as a result have a more difficult time resolving them during product development.

An HDMI "Protocol Scope"

The ideal solution to eliminate most if not all potential HDMI interoperability issues is an HDMI "protocol scope" that would enable developers in R&D to see all the transactions across the DDC and all data within the encrypted TMDS stream, as well as the timing relationship between DDC transactions, data island packets, video data, and mode changes.

One of the challenges in creating a test instrument such as an HDMI protocol scope is ensuring that a user can capture the particular frames of data within which a specific event occurs. Pre-capture filtering along with user defined triggering on multiple values and changes in value(s) of any HDMI metadata, is critically important to ensure that the required data is captured.

Once the capture and trigger criteria are met, the instrument should log and display all data types including DDC transactions and video and audio metadata. Search and navigation mechanisms to locate specific events, in the vast collection of captured HDMI frames, are necessary to facilitate rapid location of data inconsistencies.

A protocol scope should depict the relative positioning of the video, audio and control data through an intuitive time-based interface. For example, showing encryption controls in relation to the HDCP transactions, data islands and sync controls is very useful for solving certain potential HDMI interoperability issues.

In addition to providing basic visibility and techniques for examining the data, an HDMI protocol scope should provide a set of useful analysis tools that address common problem types. Analysis tools that provide basic timing information and detect timing instabilities are essential. But much more is required. For example, analyzing audio data and comparing the sampling rate derived from multiple sources, is important to ensure consistency in the data.

An HDMI protocol scope test instrument is a key element of the HDMI ecosystem. By providing visibility into the HDMI data this type of instrument can greatly reduce potential interoperability problems and thereby ensure that HDMI interfaces are fully utilized in both Consumer Electronics equipment and PC applications.