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NS_E_INVALIDCALL_WHILE_ENCODER_RUNNING
Diagnostic meaning beyond the standard text
For NS_E_INVALIDCALL_WHILE_ENCODER_RUNNING (0xC00D1B66), the actionable event is attempt to change a topology-affecting property after WMEncoder.Start. Keep the result producing boundary attached to the original Encoder callback or COM call.
Why the session can reach this point
WMEncoder exposes configuration, preparation, running, paused, stopped and archival states in a session that returns this result. Properties that alter graph topology are normally set before Start, while statistics and some control operations are meaningful only after a session reaches the matching state.
The same method can be valid in one encoder state and rejected in another without any file, codec or network defect in a session that returns this result. One concrete way to reach the condition is that automation changes the profile while samples are already flowing. The result test should therefore preserve the object generation and numeric settings, not just a screenshot of the final dialog.
Trace fields with diagnostic value
| Field | What to preserve |
|---|---|
| Decisive values | RunState, method/property name, calling thread and preceding Start or state callback |
| Producing object | current encoder RunState, active source group, PrepareToEncode calls, Start/Pause/Stop order, archive state, thread and callback that issued the operation, and the first state-transition HRESULT |
| 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 invalidcall while encoder running boundary |
Decision matrix
| Observation | How to interpret it |
|---|---|
| Observation that supports it | The decisive evidence is RunState, method/property name, calling thread and preceding Start or state callback. It confirms attempt to change a topology-affecting property after WMEncoder.Start in the same object generation. |
| Observation that points to an earlier failure | The recorded values satisfy the invalidcall while encoder running 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 (attempt to change a topology-affecting property after WMEncoder.Start), but a codec, archive or broadcast sink then fails in a subsequent stage. |
| Verification after correction | Apply this isolated change: move the configuration change before Start or stop and rebuild the session deliberately. The original invalidcall while encoder running call should then advance past the same checkpoint. |
The operational impact of it is limited to the encoder state-machine sequencing transition that owns attempt to change a topology-affecting property after WMEncoder.Start. In the representative case where automation changes the profile while samples are already flowing, keep the first failing call and its object identity so a later wrapper cannot replace the invalidcall while encoder running evidence.
Decision path
- Record
0xC00D1B66, it, the Encoder version and the exact API call or property access that returned it. - Export the current
.wmeor.prxconfiguration, then capture RunState, method/property name, calling thread and preceding Start or state callback. - verify the encoder state-machine sequencing precondition without changing the source, profile and output sink at the same time.
- Run one controlled comparison in which only this condition changes: move the configuration change before Start or stop and rebuild the session deliberately.
- After the change, recreate the affected Encoder object rather than assuming the existing graph discarded its earlier invalidcall while encoder running state.
Codes with similar symptoms but different owners
| Result | Why it is a different boundary |
|---|---|
NS_E_CANNOT_DELETE_ACTIVE_SOURCEGROUP | removal of the source group currently active in the running encoder graph |
NS_E_NO_ACTIVE_SOURCEGROUP | an operation that requires SourceGroupCollection.Active when no group is selected |
NS_E_INVALIDCALL_WHILE_ARCHIVAL_RUNNING | attempt to alter archive configuration while the archive sink is active |
Safe recovery
Resolve the producing condition by ensuring that you move the configuration change before Start or stop and rebuild the session deliberately. Then rebuild only the portion of the Encoder graph affected by it and verify the original call.
Do not hide the ordering problem behind unconditional retries; log the transition sequence and make the operation occur at the documented lifecycle point in a session that returns it.
Source material
- WMEncoder.Start.
- Preparing a source group for encoding.
- WMEncoder.Flush.
- Saving a Windows Media Encoder configuration.
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