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NS_E_WMPCORE_FAILED_TO_BUILD_PLAYLIST
Meaning at the producing boundary
Windows Media Player reports NS_E_WMPCORE_FAILED_TO_BUILD_PLAYLIST (0xC00D109E) when the core cannot turn the downloaded/loaded playlist representation into a usable Playlist object. The playback core failed to build playlist condition is owned by the layer that turns ASX/WAX/WVX/WMX or library playlists into Media objects, resolves REF and ENTRYREF URLs, expands nesting, handles EVENT and REPEAT blocks and advances to alternates.
An additional test is to record input format, parser result, item count and the first rejected construct; that evidence is more useful than reinstalling the Player or changing several unrelated settings at once.
Investigation order
- Find the first component that returned this result and label that event as the playback core failed to build playlist boundary.
- Freeze the input and object identity associated with the failing operation before WMP fallback or cleanup changes it.
- Reconstruct the immediately preceding successful state, then identify the call or event that crossed into failure.
- Perform the code-specific test: record input format, parser result, item count and the first rejected construct.
- Make the narrow correction—correct the first structural/semantic problem and rebuild from unchanged source bytes—and repeat the same producing operation.
The surrounding WMP state
Windows Media metafiles are XML documents, but a well-formed document can still violate required ASX element and attribute rules. A second relevant constraint is that relative references are resolved against the containing metafile URL, and nested playlists introduce a stack and a new base URL rather than a simple flat list.
Representative case: The XML parses, but required WMP playlist semantics are missing. The example isolates only the producing component.
Inputs that distinguish the causes
Preserve the first occurrence before retry or fallback changes the evidence. Capture one consistent object generation:
| Field | What to record |
|---|---|
| Decisive check | Record input format, parser result, item count and the first rejected construct |
| Artifact identity | Resolved base URL for REF or ENTRYREF targets for this reproduction |
| Runtime state | Current item index, alternate index and nested-playlist depth for this reproduction |
| Owning object | Repeat/event boundary and the media object expected at its start or end for this reproduction |
| Lower-level result | Playlist URL, format, response content type and exact downloaded bytes for this reproduction |
| Correlation | ASX version and element stack at the failure for this reproduction |
Log paths, hashes, IDs, offsets, and HRESULTs. Exclude secrets and unrelated content from logs.
Do not confuse it with nearby results
| Result | Different boundary |
|---|---|
NS_E_WMPCORE_ERROR_DOWNLOADING_PLAYLIST | The playlist resource could not be downloaded completely or with an acceptable response |
NS_E_WMPCORE_PLAYLIST_ITEM_ALTERNATE_NONE | The playlist item defines no alternate reference to use after its primary source fails |
NS_E_WMPCORE_PLAYLIST_ITEM_ALTERNATE_EXHAUSTED | All configured alternate references have already been attempted without success |
If this result is followed by a broader “cannot play,” “cannot load,” or “operation failed” result, preserve the earlier event. A later wrapper error may be secondary.
Verification after correction
Repeat the action that returned this result and verify that the same object crosses the former this checkpoint. Success means reaching the next expected load, parse, playlist, control or playback state—not merely suppressing a dialog.
What a real fix must change
Resolve this result where the relevant state is produced: correct the first structural/semantic problem and rebuild from unchanged source bytes. After correction, reload or recreate the owning object so cached failure state is not mistaken for a successful repair.
- Avoid flattening or rewriting a playlist before preserving the failing nesting and base-URL rules; it can destroy the artifact or state needed to explain it.
- Avoid assuming every unplayable item means the playlist parser itself failed; that can replace the original HRESULT with a secondary failure from another layer.
Code-specific operational note
Use it, 0xC00D109E and the symbolic phrase in traces. Correlate search keys with API and object.
Technical references
- Windows Media metafile reference — normative or platform material relevant to it.
- Metafile elements reference — API or format context for this HRESULT.
- ENTRYREF element — documentation used to identify the producing boundary of it.
- REPEAT element
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