IAMMultiMediaStream Interface

The IAMMultiMediaStream interface exposes Microsoft® DirectShow™ functionality to multimedia stream developers. You can use its methods to automatically generate filter graphs, open files or monikers for playback or capture of incoming data, and render a given filter graph.

When to Implement

Implement this interface when you want to provide multimedia stream-based support for DirectShow media types in your applications.

When to Use

Use this interface when you want to control DirectShow-supported media playback in your multimedia streaming applications.

Methods in Vtable Order

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

IAMMultiMediaStream methods	Description
Initialize	Sets the stream type. If the pFilterGraph parameter is non-NULL the filter graph passed in is used for the stream.
GetFilterGraph	Retrieves the associated filter graph's IGraphBuilder interface.
GetFilter	Retrieves the specified filter from the current filter graph.
AddMediaStream	Adds the specified media stream to the current filter graph.
OpenFile	Opens and automatically creates a filter graph for the specified media file. If DirectShow doesn't support the file format, this method does nothing.
OpenMoniker	Opens a file or device moniker; you can read media data from this moniker if DirectShow supports the media type.
Render	Renders the current filter graph.

---

IAMMultiMediaStream::AddMediaStream

IAMMultiMediaStream Interface

Adds the specified media stream to the current filter graph.

HRESULT AddMediaStream(
  IUnknown* pStreamObject,
  const MSPID *pPurposeID,
  DWORD dwFlags,
  IMediaStream** ppNewStream
  )

Parameters

pStreamObject

[in] Pointer to an IUnknown interface that points to either the media stream or underlying stream object you want to add to the current filter graph.

pPurposeID

[in] Pointer to the purpose ID for the newly added media stream.

dwFlags

[in] Value that modifies the media stream's behavior; it is a combination of one or more of the following values.

AMMSF_ADDDEFAULTRENDERER	Add a default renderer.
AMMSF_CREATEPEER	Create a peer stream based on the same object as a pStreamObject.

ppNewStream

[out] Address of a pointer to an IMediaStream interface that will point to the newly added media stream. This parameter is optional.

Return Values

Returns an HRESULT value, which can include the following values:

Value	Meaning
MS_E_PURPOSEID	Stream being added has a different purpose ID from the one specified or a stream with the specified purpose ID already exists.
E_POINTER	Null pointer argument.
S_OK	Success.

Remarks

If dwFlags specifies AMMSF_ADDDEFAULTRENDERER then the default renderer for the given purpose Id is created if possible. Currently the only default renderer supported is for audio using DirectSound. In this case the pStreamObject parameter must be NULL and any calls to the IMultiMediaStream::GetMediaStream or IMultiMediaStream::EnumMediaStreams methods will not recognize the stream.

If dwFlags specifies AMMSF_CREATEPEER then a Media Stream is created using pStreamObject and added to the current multimedia stream. pStreamObject varies depending on the stream type. In general pStreamObject can point to an IMediaStream object, in which case a stream with the sample purpose ID and format is created. For IDirectDraw streams it can also be a pointer to an IDirectDraw object.

If neither flag is set then pStreamObject can be one of the following:

An IAMMediaStream object	This stream is then added to the streams in the multimedia stream.
NULL	In this case a default IMediaStream object is added to the stream with a default underlying object if required.
A pointer to an underlying object	This is used to construct default streams. For video streams this can be an IDirectDraw pointer.

---

IAMMultiMediaStream::GetFilter

IAMMultiMediaStream Interface

Retrieves the specified filter from the current filter graph.

HRESULT GetFilter(
  IMediaStreamFilter** ppFilter
  )

Parameters

ppFilter

[out] Address of a pointer to an IMediaStreamFilter interface that will point to the current filter.

Return Values

Returns S_OK if successful or E_POINTER if one or more of the required parameters are NULL.

---

IAMMultiMediaStream::GetFilterGraph

IAMMultiMediaStream Interface

Retrieves the associated filter graph's IGraphBuilder interface.

HRESULT GetFilterGraph(
  IGraphBuilder **ppGraphBuilder
  );

Parameters

ppGraphBuilder

[out] Address of a pointer to an IGraphBuilder interface that will point to the current filter graph.

Return Values

Returns S_OK if successful or E_POINTER if one or more of the required parameters are NULL.

---

IAMMultiMediaStream::Initialize

IAMMultiMediaStream Interface

Sets the stream type. If the pFilterGraph parameter is non-NULL the filter graph passed in is used for the stream.

HRESULT Initialize(
  STREAM_TYPE StreamType,
  DWORD dwFlags,
  IGraphBuilder * pFilterGraph
  )

Parameters

StreamType

[in] STREAM_TYPE enumeration value that specifies the new filter graph's stream type.

dwFlags

[in] Either contains the AMMSF_NOGRAPHTHREAD flag, which creates a filter graph object on the current thread, or zero.

pFilterGraph

[in] [optional] Address of an IGraphBuilder interface that will point to the new filter graph. This parameter is optional; only pass in a valid pointer if you must access the filter graph at a later time.

Return Values

Returns S_OK if successful or E_POINTER if one or more of the required parameters are NULL.

Remarks

Using the AMMSF_NOGRAPHTHREAD flag is safe provided the current thread does not exit before the stream object is released by the application and the current thread processes window messages.

---

IAMMultiMediaStream::OpenFile

IAMMultiMediaStream Interface

Opens and automatically creates a filter graph for the specified media file. If DirectShow doesn't support the file format, this method does nothing.

HRESULT OpenFile(
  LPCWSTR pszFileName,
  DWORD dwFlags
  )

Parameters

pszFileName

[in] Name of the file you want to open.

dwFlags

[in] Value that modifies how the filter graph will render the specified file. This value is a combination of one or more of the following flags:

Value	Meaning
AMMSF_RENDERTOEXISTING	Only render to existing streams
AMMSF_RENDERALLSTREAMS	Render all streams, including those that do not have an existing media stream.
AMMSF_NORENDER	Open the file, but do not render any streams. This flag should always be accompanied with the AMMSF_RUN flag.
AMMSF_NOCLOCK	Run the stream with no clock.
AMMSF_RUN	Set the stream into the run state.

Return Values

Returns one of the following values.

Value	Meaning
E_INVALIDARG	The dwFlags parameter is invalid.
E_POINTER	This method tried to access an invalid pointer.
S_OK	Success.

Remarks

The AMMSF_RENDERALLSTREAMS flag will create default rendering filters for video and audio if they do not exist. However, these default filters cannot be accessed by the IStreamSample::GetMediaStream method.

---

IAMMultiMediaStream::OpenMoniker

IAMMultiMediaStream Interface

Opens a file or device moniker; you can read media data from this moniker if DirectShow supports the moniker.

HRESULT OpenMoniker(
  IBindCtx *pCtx,
  IMoniker* pMoniker,
  DWORD dwFlags
  )

Parameters

pCtx

[in] Pointer to the bind context associated with the moniker.

pMoniker

[in] Pointer to an IMoniker interface that specifies the moniker you want to open.

dwFlags

[in] Value that modifies how the filter graph will render the specified file. This value is a combination of one or more of the following flags:

Value	Meaning
AMMSF_RENDERTOEXISTING	Only render to existing streams
AMMSF_RENDERALLSTREAMS	Render all streams, including those that do not have an existing media stream.
AMMSF_NORENDER	Open the file, but do not render any streams. This flag should always be accompanied with the AMMSF_RUN flag.
AMMSF_NOCLOCK	Run the stream with no clock.
AMMSF_RUN	Set the stream into the run state.

Return Values

Returns S_OK if successful or E_INVALIDARG if the dwFlags parameter is invalid.

---

IAMMultiMediaStream::Render

IAMMultiMediaStream Interface

Renders the current filter graph.

HRESULT Render(
  DWORD dwFlags
  )

Parameters

dwFlags

[in] Value that specifies how the filter graph renders the current multimedia stream. This value currently must be AMMSF_NOCLOCK.

Return Values

Returns S_OK if successful or E_INVALIDARG if the dwFlags parameter is invalid.

Remarks

This method renders each of the source streams for a stream of type STREAMTYPE_WRITE. This can be called several times, for instance, each time a source stream is added, the stream is not set into running mode. Use the IMultiMediaStream::SetState method to set the stream into running mode after calling this method.

The AMMSF_RENDERALLSTREAMS flag will create default rendering streams for video and audio if they do not exist.

© 1998 Microsoft Corporation. All rights reserved. Terms of Use.

Top of Page