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VFW_S_DUPLICATE_NAME
DirectShow filter added with an adjusted duplicate name
VFW_S_DUPLICATE_NAME is HRESULT 262701 (0x0004022D) from Video for Windows. AllStat describes this result as “An attempt to add a filter with a duplicate name succeeded with a modified name.” The high-order severity bit is clear, so this is a success result, but it carries more information than plain S_OK.
The filter was added successfully, but the graph changed its display name because the requested name duplicated an existing filter name.
Where the result is encountered
- This result can appear in IFilterGraph::AddFilter; record the producing interface and method rather than inferring behavior from the symbolic name alone.
- This result can appear in graph-building tools that address filters by friendly name; record the producing interface and method rather than inferring behavior from the symbolic name alone.
- It can appear in applications loading multiple instances of the same filter; record the producing interface and method rather than inferring behavior from the symbolic name alone.
The same numeric success value can be mishandled when a wrapper exposes only a Boolean. Keep the original HRESULT until the code-specific outputs and state transition have been evaluated.
State boundary that must be proved
The central question for it is whether the filter identity is tracked by its interface pointer or graph membership rather than by the originally requested name alone. The HRESULT alone confirms neither unrelated work nor the quality of optional outputs.
A reliable interpretation of it names the exact method contract, the object generation, and the outputs that remain valid. This prevents a success-with-information result from being promoted to full success or demoted to a generic error.
Evidence and telemetry to preserve
- preserve requested and actual filter names.
- preserve filter CLSID and interface pointer.
- preserve graph filter list before and after addition.
- preserve application lookup strategy.
- preserve saved graph representation if persisted.
Also record vfw_s_duplicate_name_operation, vfw_s_duplicate_name_object, vfw_s_duplicate_name_state_before, vfw_s_duplicate_name_state_after, UTC time, process and thread identifiers, and a correlation ID. Keep secrets out of logs while retaining GUIDs, CLSIDs, media subtypes, property IDs, row identities, and hashes needed to distinguish objects.
Correct handling, retry, and recovery
Use the actual assigned name or, preferably, retain the filter interface directly. Avoid assuming that a friendly name is globally unique inside a graph.
Retry it only when the recorded state can change the documented outcome. Repeating the same call is inappropriate for a stable end marker, cancellation, unsupported format, adjusted property, or partial result whose completed side effects have not been reconciled.
Diagnostic sequence
- capture the raw HRESULT
0x0004022Dimmediately after the returning method and record whether the caller usedSUCCEEDED,FAILED, equality testing, or exception translation. - Identify the exact owner of it: interface, method, object instance, provider or filter version, thread or apartment, and operation phase.
- Validate the decisive contract boundary for it: the filter identity is tracked by its interface pointer or graph membership rather than by the originally requested name alone.
- inspect every output parameter, count, status array, returned interface, or side effect that the method documentation associates with this success-with-information result.
- Compare the observed state before and after it; do not assume that a success severity bit means every optional sub-operation completed.
- reproduce the smallest request with the same object state and then change only the condition identified by the evidence before repeating the operation.
Practical validation scenario
An application adds two decoder instances both named Decoder. The second call returns it and assigns a modified name; the application stores each IBaseFilter pointer and displays the actual graph names.
The negative test should preserve the condition that produces it; the recovery test should alter only that condition and verify the final state as well as the HRESULT.
Difference from nearby HRESULT values
S_OK means the requested name was accepted without this adjustment; VFW_E_DUPLICATE_NAME-style failures would not add the filter.
This distinction determines whether the caller should consume partial outputs, stop iteration, wait, reconfigure, notify the user, or perform no error recovery at all.
Developer and administrator guidance
Tests for it should verify both the encoded condition and the resulting outputs. A test for it that checks only SUCCEEDED cannot detect stale counts, partial streams, adjusted properties, missing callbacks, or other code-specific effects.
A support report for it should include decimal 262701, hexadecimal 0x0004022D, the AllStat meaning, the owning API, and the first detailed status or output that explains why the method did not return ordinary S_OK.
References
- Microsoft: DirectShow error and success codes
- Microsoft: DirectShow overview
- Microsoft: IFilterGraph::AddFilter
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