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VFW_E_STATE_CHANGED
Meaning
Windows documents VFW_E_STATE_CHANGED as “The state changed while waiting to process the sample”. In practical terms, it is returned when a DirectShow filter changes state while another operation is waiting to process a sample, invalidating the wait result.
Evidence to collect
- Capture 1: state before and after the wait, including transition timestamps.
- Capture 2: streaming thread, control thread and flush events.
- Capture 3: sample identity, timestamp and graph generation.
Where the failure belongs
This result belongs to DirectShow filter-graph processing. The relevant condition is that a DirectShow filter changes state while another operation is waiting to process a sample, invalidating the wait result.
Likely causes
- Possible cause 1: the graph is stopped or paused from another thread.
- Possible cause 2: flush or reconnection occurs during sample processing.
- Possible cause 3: application control and streaming callbacks race on filter state.
Diagnostic sequence
- Confirm that the observed path matches this condition: a DirectShow filter changes state while another operation is waiting to process a sample, invalidating the wait result.
Correct handling and retry
- Corrective action 1: serialize graph-control operations with component expectations.
- Corrective action 2: treat state change as cancellation rather than sample corruption.
- Corrective action 3: discard or requeue work according to the new state.
Retry guidance. Retry only after obtaining the new stable graph state and deciding whether the sample still belongs to that generation.
Difference from nearby HRESULTs
VFW_E_WRONG_STATE means an operation begins in an unsuitable state; it means the state changed while work was already waiting.
Practical scenario
A stop command arrives while a renderer waits for a sample deadline; recognizing the stop generation prevents misreporting it as a media error.
Official Microsoft references
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