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NS_E_SOURCE_CANNOT_LOOP
The failing boundary in the Encoder object model
The useful reading of NS_E_SOURCE_CANNOT_LOOP (0xC00D1BD3) is not merely the standard message shown above. It locates Repeat is enabled for a source type that cannot be replayed inside source timeline and clipping.
Windows Media Encoder builds a timeline for every selected source before samples enter the codec in a session that returns this result. Mark-in, mark-out, repeat and time-compression settings are therefore validated against the source duration and against each other before encoding begins.
Evidence that separates this code from a wrapper error
A file that opens and reports a duration can still fail here because timeline validation happens after source discovery but before the first encoded sample in a session that returns this result. For example, a live capture device is configured to loop like a file. Preserve the result distinction before a UI layer converts the result into a broad start, capture or profile failure.
| Field | What to preserve |
|---|---|
| Decisive values | source scheme/type, Repeat flag and whether the input is seekable and finite |
| Producing object | source-group name, source URL or device moniker, MarkIn and MarkOut in milliseconds, detected duration, Repeat flag, preprocessing mode and encoder state |
| Session correlation | the same source-group generation, audience index, object identity and callback sequence that produced this result |
| Lower-level evidence | the first COM, driver, file-system or codec HRESULT observed before the Encoder mapped the condition to this result |
| Controlled comparison | a known-good session that changes only the setting named in the source cannot loop boundary |
Interpret the next measurement
| Observation | How to interpret it |
|---|---|
| Observation that supports it | The decisive evidence is source scheme/type, Repeat flag and whether the input is seekable and finite. It confirms Repeat is enabled for a source type that cannot be replayed in the same object generation. |
| Observation that points to an earlier failure | The recorded values satisfy the source cannot loop rule, but a source, driver, COM activation or file operation returns a different HRESULT first. |
| Observation that points to a later failure | The Encoder passes this boundary (Repeat is enabled for a source type that cannot be replayed), but a codec, archive or broadcast sink then fails in a subsequent stage. |
| Verification after correction | Apply this isolated change: disable Repeat or use a seekable file source. The original source cannot loop call should then advance past the same checkpoint. |
The operational impact of it is limited to the source timeline and clipping transition that owns Repeat is enabled for a source type that cannot be replayed. In the representative case where a live capture device is configured to loop like a file, keep the first failing call and its object identity so a later wrapper cannot replace the source cannot loop evidence.
Test the condition without rewriting the session
- Record
0xC00D1BD3, it, the Encoder version and the exact API call or property access that returned it. - Export the current
.wmeor.prxconfiguration, then capture source scheme/type, Repeat flag and whether the input is seekable and finite. - verify the source timeline and clipping precondition without changing the source, profile and output sink at the same time.
- Run one controlled comparison in which only this condition changes: disable Repeat or use a seekable file source.
- After the change, recreate the affected Encoder object rather than assuming the existing graph discarded its earlier source cannot loop state.
Interpret neighboring results carefully
| Result | Why it is a different boundary |
|---|---|
NS_E_BAD_MARKOUT | validation of IWMEncSource.MarkOut against MarkIn and the end of the source |
NS_E_MARKIN_UNSUPPORTED | MarkIn or MarkOut clipping is requested for a source type that does not support seeking to marks |
NS_E_BAD_MARKIN | validation of IWMEncSource.MarkIn before the source timeline is committed |
Resolution and verification
The direct repair for this occurrence is to disable Repeat or use a seekable file source. Recreate the affected source group, profile or output object, repeat the same operation, and confirm that the first failing HRESULT no longer comes from the source cannot loop checkpoint.
Do not re-encode or trim the only copy of the input while diagnosing the timeline; preserve the original duration and timestamps so the invalid interval can be reproduced in a session that returns it.
References for the boundary
- IWMEncSource.MarkOut.
- IWMEncSource.Repeat.
- Preparing a source group for encoding.
- Two-pass encoding.
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