IAsyncReader Interface

The IAsyncReader 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 an Apple® QuickTime® parser filter, can use this interface to read from a filter that reads from a file, the network, or memory.

Methods in Vtable Order

IUnknown methods Description
QueryInterface Retrieves pointers to supported interfaces.
AddRef Increments the reference count.
Release Decrements the reference count.
IAsyncReader methods 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.

 Last updated on Tuesday, July 13, 2004

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