IAudioMediaStream Interface

The IAudioMediaStream interface controls audio media streams by providing methods that set and get the stream's format. This interface inherits from the IMediaStream interface and is used to create one or more IAudioStreamSample objects. You can also use it to set and retrieve the stream data's current format.

This interface is currently defined only for PCM format audio data.

For sample code that implements the audio streaming interfaces, see Multimedia Streaming Sample Code.

When to Implement

Like video, audio is contained in a self-describing container object. Implement this interface when an object needs to control streaming audio.

When to Use

Use this interface when you want to generate audio in your application.

Methods in Vtable Order

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

IAudioMediaStream methods	Description
GetFormat	Retrieves the stream data's current format.
SetFormat	Sets the format for the stream.
CreateSample	Creates an audio stream sample for use with this stream.

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IAudioMediaStream::CreateSample

IAudioMediaStream Interface

Creates an audio stream sample for use with the specified stream.

HRESULT CreateSample(
  IAudioData *pAudioData,
  DWORD dwFlags,
  IAudioStreamSample **ppSample
  );

Parameters

pAudioData

[in] Pointer to an IAudioData container. IAudioData objects can be referenced by samples in more than one stream.

dwFlags

[in] Reserved for flag data. Must be zero.

ppSample

[out] Address of a pointer to the new IAudioStreamSample interface.

Return Values

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

Remarks

The pAudioData object defines the data's format.

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IAudioMediaStream::GetFormat

IAudioMediaStream Interface

Retrieves the stream data's current format.

HRESULT GetFormat(
  WAVEFORMATEX *pWaveFormatCurrent );

Parameters

pWaveFormatCurrent

[out] Pointer to a WAVEFORMATEX structure that contains the stream data's current format.

Return Values

Returns S_OK if successful or E_POINTER if the required parameter is NULL.

Remarks

Currently, DirectShow only supports PCM wave data.

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IAudioMediaStream::SetFormat

IAudioMediaStream Interface

Sets the format for the stream.

HRESULT SetFormat(
  const WAVEFORMATEX *lpWaveFormat
  );

Parameters

lpWaveFormat

[in] Pointer to a WAVEFORMATEX structure that contains stream format information.

Return Values

Returns an HRESULT value, which can include the following values or others not listed.

Value	Meaning
MS_E_INCOMPATIBLE	Format of the IAudioData object is not compatible with stream.
E_POINTER	Null pointer argument.
E_INVALIDARG	Invalid argument.
S_OK	Success.

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