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IAsyncReader Interface

This interface allows multiple overlapped reads from different positions in the media stream. This interface is supported by source filters.

Note that during connection an output pin supporting the IAsyncReader should check whether its QueryInterface method is called asking for the IAsyncReader interface. If it is not, then the output pin should fail the connect unless it establishes some other transport to use during the connection.

When to Implement

Implement this interface on a pin if your filter reads data of media type MEDIATYPE_Stream from some source.

When to Use

A parser, such as a WAVE parser filter, can use this interface to read from a filter that reads from a file, the network, or memory.

Methods in Vtable Order

The following table shows the methods that appear in the Vtable beneath the standard COM methods inherited from IUnknown.

Method Description
RequestAllocator Retrieves the actual allocator to be used.
Request Queues a request for data.
WaitForNext Blocks until the next sample is completed or the time-out occurs.
SyncReadAligned Performs an aligned synchronized read.
SyncRead Performs a synchronized read.
Length Retrieves the total length of the stream, and the currently available length.
BeginFlush Causes all outstanding reads to return.
EndFlush Ends the flushing operation.

Requirements

DirectShow applications and DirectShow filters have different include file and link library requirements. See Setting Up the Build Environment for more information.

OS Versions: Windows CE 2.12 and later. Version 2.12 requires DXPAK 1.0 or later.
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Last updated on Wednesday, April 13, 2005

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