HDMI and DRM

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HDMI and DRM: a reader asks…

I have a home theater system with components plugged into the HDMI ports in my AV receiver, and HDMI connected to my flat-screen TV. Every once in a while, instead of seeing the video from a component, I get a blue or blank screen. The only way to fix it is to turn everything off and then back on again. Is my equipment malfunctioning?

Most likely, nothing is malfunctioning from a hardware perspective. What you’re running into is problems with Digital Rights Management (DRM). DRM is intended to make sure that consumers are paying for the digital content they consume, so the artists and others involved in producing and distributing that digital content get paid. As a result of DRM legislation, manufacturers have come up with various ways of ensuring that pirated content is blocked. Since you’re dealing with multiple manufacturers, there may be slight variances in how each component in your home theater system verifies that the content is legal.

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Simplified, this verification process consists of information exchange between components, called ‘handshaking’ and is usually done when the components are first powered on. That’s why you can solve the problem by shutting everything down and turning it back on. What happens sometimes is that component A is powered on before component B is awake, and since component B doesn’t respond to the handshaking protocol, component A doesn’t know that component B is verified to receive the DRM content. That makes component A refuse to send the DRM content.
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It’s a real mess sometimes, particularly when you mix old and new components together in a home theater system. That mess is by design, and your solution (powering off and on) is the only realistic answer.

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