IAMBufferNegotiation Interface

Microsoft DirectShow 9.0

IAMBufferNegotiation Interface

The IAMBufferNegotiation interface requests the number of buffers for a filter to create and size of each buffer. This interface can be exposed by any pin that connects using the IMemInputPin pin interface, but is typically exposed on the output pins of capture filters.

When two pins connect through IMemInputPin, they agree on an allocator object that is responsible for creating buffers. Normally this process is transparent to the application, but in some situations the application needs more control. If a pin exposes IAMBufferNegotiation, the application can suggest how many buffers to create, the size of the buffers, and other properties. If your application performs preview of captured audio, you can specify a smaller buffer size to reduce latency. Teleconferencing applications should specify a minimal number of buffers.

To use this interface, call the SuggestAllocatorProperties method before the pins connect. After the pins connect, call the GetAllocatorProperties method to determine whether the pin honored the request.

Filter developers: Capture filters should always support this interface when possible.

In addition to the methods inherited from IUnknown, the IAMBufferNegotiation interface exposes the following methods.

Method	Description
GetAllocatorProperties	Retrieves the allocator properties that the pin is using.
SuggestAllocatorProperties	Informs the pin of the application's preferred allocator properties

Requirements

Header: Declared in Strmif.h; include Dshow.h.

Library: Use Strmiids.lib.