What does Windows error code 15201 (ERROR_MCA_INVALID_VCP_VERSION) mean?

 
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ERROR_MCA_INVALID_CAPABILITIES_STRING ERROR_MCA_MONITOR_VIOLATES_MCCS_SPECIFICATION

ERROR_MCA_INVALID_VCP_VERSION

The special role of VCP feature 0xDF

ERROR_MCA_INVALID_VCP_VERSION is about one defined Virtual Control Panel feature: 0xDF, VCP Version. It is not a report that an arbitrary brightness, contrast, or input-source VCP code was unsupported. Monitor-control software uses this response as a runtime statement of the MCCS version implemented by the display, so an invalid value prevents a trustworthy interpretation of version-dependent feature semantics.

Keep the two version sources separate

A monitor can expose a version in the text capability string through mccs_ver(...) and can separately answer a VCP Feature Request for 0xDF. This code means the latter answer is not a valid version value. It differs from ERROR_MCA_MCCS_VERSION_MISMATCH, where both sources are usable but disagree, and from ERROR_MCA_UNSUPPORTED_MCCS_VERSION, where the version is recognized but outside the Windows API support range.

Useful diagnostic sequence

  1. Identify the physical monitor handle used for the request and keep it open for the whole diagnostic sequence.
  2. Retrieve and preserve the raw capabilities string, including mccs_ver, without treating it as authoritative.
  3. Read VCP feature 0xDF through the low-level API and record both the returned code type and value.
  4. Probe only the feature operations the application truly needs. Continuous VCP codes require a current and maximum value; non-continuous codes require a supported-value list.

Do not substitute a guessed MCCS version merely to make subsequent commands run. The value changes how VCP feature values are interpreted, so a forced assumption can turn a diagnosis problem into an unintended monitor configuration change.

References

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