CDynamicOutputPin.ChangeMediaType method

Article
07/27/2023

[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 It has been superseded by MediaPlayer, IMFMediaEngine, and Audio/Video Capture in Media Foundation.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 ChangeMediaType method dynamically changes the media type for the connection. The change can occur while the filter graph is running. Once this method is called, samples with the old media type cannot be delivered. The caller must ensure that no old samples are pending.

Syntax

HRESULT ChangeMediaType(
   const CMediaType *pmt
);

Parameters

pmt: Pointer to an AM_MEDIA_TYPE structure that specifies the media type.

Return value

Returns an HRESULT value. Possible values include those shown in the following table.

Return code	Description
S_OK	Success.
E_FAIL	Failure. Possibly the owning filter did not call CDynamicOutputPin::SetConfigInfo.
VFW_E_NOT_CONNECTED	The pin is not connected.

Remarks

Call the CDynamicOutputPin::StartUsingOutputPin method before calling this method.

This method first checks whether the downstream input pin can accept the new format without reconnecting. It queries the input pin for the IPinConnection interface. If the input pin supports IPinConnection, the method calls the IPinConnection::DynamicQueryAccept method with the proposed media type. If the input pin accepts the new media type, the method calls the IPin::ReceiveConnection method and renegotiates the allocator requirements.

On the other hand, if the downstream pin does not support IPinConnection, or if it rejects the new media type, the method calls the CDynamicOutputPin::DynamicReconnect method to perform a dynamic reconnection.

Requirements

Requirement	Value
Header	Amfilter.h (include Streams.h)
Library	Strmbase.lib (retail builds); Strmbasd.lib (debug builds)