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| NS_E_WMPCORE_CODEC_NOT_TRUSTED | NS_E_WMPCORE_CODEC_DOWNLOAD_NOT_ALLOWED |
NS_E_WMPCORE_CODEC_NOT_FOUND
The exact condition behind the dialog
The symbolic result NS_E_WMPCORE_CODEC_NOT_FOUND narrows 0xC00D109B to the playback core codec not found condition: the graph cannot find the specific codec required for a media stream. Keep the playback core codec not found boundary visible when a later dialog reduces it to a general media error.
An additional test is to record the failing stream subtype or FourCC and the exact component lookup result; that evidence is more useful than reinstalling the Player or changing several unrelated settings at once.
What succeeds before this failure
Representative case: The container is parsed, but its video subtype has no registered decoder.
State worth preserving
Capture state before Player cleanup:
- What to verify: record the failing stream subtype or FourCC and the exact component lookup result.
- Artifact: ordered ErrorItem queue with errorCode, errorContext and media object.
- State: Player.URL, current media sourceURL and resolved final URL.
- Object identity: play state and transition immediately before failure.
- Underlying evidence: selected graph/source/filter or codec identity and version.
- Correlation: audio/video device identity and driver generation.
Reproduce without destroying evidence
- Preserve
0xC00D109B, the ErrorItem context and the object instance involved in the failing operation. - Confirm the failure directly: record the failing stream subtype or FourCC and the exact component lookup result.
- After you install a trusted compatible decoder for that subtype or transcode the stream, recreate the owning WMP object and verify that the corrected generation completes.
Related HRESULTs with different meanings
| Result | Different condition |
|---|---|
NS_E_WMPCORE_CODEC_DOWNLOAD_NOT_ALLOWED | The required codec is absent and Player policy/settings prohibit automatic acquisition |
NS_E_WMPCORE_CODEC_NOT_TRUSTED | The candidate codec fails the trust/signature policy required for installation/use |
NS_E_WMPCORE_MISNAMED_FILE | The file extension/name disagrees with the content or supported media interpretation |
Recovery at the right layer
Change the responsible precondition rather than masking the symptom: install a trusted compatible decoder for that subtype or transcode the stream.
How to know the repair is real
Keep one fixture that reproduces 0xC00D109B and one corrected fixture that changes only the identified precondition.
Technical references
- Windows Media Player SDK — API or format context.
- Player MediaError event — documentation for this result.
- ErrorItem object — normative or platform material relevant to this result.
- Supported protocols and file types
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