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VFW_E_MPEG_NOT_CONSTRAINED
Meaning
Windows documents VFW_E_MPEG_NOT_CONSTRAINED as “ActiveMovie cannot play this video stream because it falls outside the constrained standard”. Here, an ActiveMovie playback path rejects an MPEG stream because its parameters fall outside the constrained standard supported by that implementation.
Relevant contract
This result describes a capability or format boundary in a component graph. Container recognition, elementary-stream parsing, decoder selection, property metadata and renderer acceptance are different stages and need separate evidence.
Start with the source filter, decoder or codec property provider and downstream connection.
Conditions that can produce it
- Cause 1: resolution or bitrate exceeds the constrained profile.
- Cause 2: sequence headers advertise unsupported MPEG parameters.
- Cause 3: the file was encoded for a broader MPEG profile than the legacy decoder accepts.
Evidence worth preserving
- Evidence 1: MPEG sequence header values.
- Evidence 2: bitrate, dimensions and frame-rate codes.
- Evidence 3: decoder module and documented profile limits.
Correction strategy
- Action 1: re-encode the stream within the supported profile.
- Action 2: use a modern decoder with broader MPEG support.
- Action 3: report the exact out-of-range parameter instead of a generic codec message.
Retry and recovery
Retry rule: Retry after the stream or decoder capability changes; modifying graph order cannot make an out-of-profile bitstream conform.
How it differs from nearby results
VFW_E_UNSUPPORTED_VIDEO is general video incompatibility, while it identifies a specific constrained-MPEG profile violation.
Example incident
A legacy training player accepts low-resolution MPEG files but rejects a high-bitrate encode; inspecting the sequence header explains it.
Official Microsoft references
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