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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