Summary of Filter Threading

[The feature associated with this page, DirectShow, is a legacy feature. It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation. Those features have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use MediaPlayer, IMFMediaEngine and Audio/Video Capture in Media Foundation instead of DirectShow, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

The following methods are called on the streaming thread:

• IMemInputPin::Receive
• IMemInputPin::ReceiveMultiple
• IPin::EndOfStream
• IPin::NewSegment
• IMemAllocator::GetBuffer

The following methods are called on the application thread:

• State changes: IBaseFilter::JoinFilterGraph, IMediaFilter::Pause, IMediaFilter::Run, IMediaFilter::Stop, IQualityControl::SetSink.
• Reference clock: IMediaFilter::GetSyncSource, IMediaFilter::SetSyncSource.
• Pin operations: IBaseFilter::FindPin, IPin::Connect, IPin::ConnectedTo, IPin::ConnectionMediaType, IPin::Disconnect, IPin::ReceiveConnection.
• Allocator functions: IMemInputPin::GetAllocator, IMemInputPin::NotifyAllocator.
• Flushing: IPin::BeginFlush, IPin::EndFlush.

This list is not exhaustive. When you implement a filter, you must consider which methods change the filter state, and which methods perform streaming operations.