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VFW_E_DUPLICATE_NAME
Meaning
Windows documents VFW_E_DUPLICATE_NAME as “An attempt to add a filter with a duplicate name failed”. In practical terms, it is returned when a DirectShow graph cannot add a filter under a name already used by another filter when the operation requires an exact unique name.
Evidence to collect
- Capture 1: requested name and existing filter CLSID using it.
- Capture 2: graph contents before AddFilter.
- Capture 3: topology generation and modification thread.
Where the failure belongs
This result belongs to DirectShow filter-graph processing. The relevant condition is that a DirectShow graph cannot add a filter under a name already used by another filter when the operation requires an exact unique name.
Likely causes
- Possible cause 1: application code reuses a fixed name for multiple filters.
- Possible cause 2: a prior failed rebuild left the old filter in the graph.
- Possible cause 3: concurrent graph modification adds the same logical component twice.
Diagnostic sequence
- Confirm that the observed path matches this condition: a DirectShow graph cannot add a filter under a name already used by another filter when the operation requires an exact unique name.
Correct handling and retry
- Corrective action 1: generate or choose unique graph names.
- Corrective action 2: remove old filters before rebuilding a branch.
- Corrective action 3: serialize graph modifications.
Retry guidance. Retry with a unique name or after removing the previous filter; unchanged retry repeats the collision.
Difference from nearby HRESULTs
VFW_S_DUPLICATE_NAME is successful addition under a modified name, while it indicates the requested add operation failed.
Practical scenario
A preview graph rebuild adds a second renderer named Video Renderer without removing the first; generation-based names prevent it.
Official Microsoft references
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