What does Windows error code 15200 (ERROR_MCA_INVALID_CAPABILITIES_STRING) mean?

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: A monitor returned a malformed DDC/CI capability string.

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ERROR_PRI_MERGE_INVALID_FILE_NAME	ERROR_MCA_INVALID_VCP_VERSION

ERROR_MCA_INVALID_CAPABILITIES_STRING

Where the string is used

This error belongs to the physical-monitor control path in Dxva2.dll, not to normal graphics-mode enumeration. Windows first maps an HMONITOR to one or more physical monitor handles, asks for the size of the DDC/CI capabilities string, retrieves that ASCII string, and then parses it to learn which VCP features and discrete values the display advertises. A failure here means the application cannot safely treat the advertised feature list as a reliable contract.

What to capture before changing anything

Record the exact physical monitor, cable path, dock or adapter, graphics driver version, and the API call that failed. An HMONITOR can represent more than one physical display.
Save the raw capability string together with its reported length. The vcp(...) and mccs_ver(...) sections are especially important because they affect later VCP probing.
Compare the string against the expected parenthesized structure. Microsoft documents historical parser restrictions, including enclosing the whole string in parentheses and avoiding a space between adjacent sections.
Test only the specific VCP features required by the application after discovery. A claimed feature list is not proof that every feature request will work on the actual monitor.

What this error does not establish

It does not by itself prove a bad cable, a corrupted DDC/CI transaction, or a defective GPU driver. It identifies a capabilities-string compliance problem. A separate DDC/CI transport error, checksum error, or unsupported VCP response needs its own evidence. Likewise, editing a monitor INF capability override is an administrative deployment decision, not a routine end-user fix; Microsoft explicitly warns that it requires knowledge of the INF layout and DDC/CI.

References

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