IMemoryData Interface

The IMemoryData interface contains methods that set and retrieve memory data on audio data objects. Audio data objects provide the underlying data which stream samples access. This interface provides a way to initialize memory buffers and to set actual amounts of audio data in the objects. Additionally, the GetInfo method can be used to retrieve audio memory data.

Implement this interface on underlying audio data objects that audio stream sample objects will access.

Typically these methods are called by the IAudioMediaStream or IAudioStreamSample object, rather than by the application.

Methods in Vtable Order

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

IMemoryData methods Description

SetBuffer Initializes a memory buffer with a pointer to memory and length.
GetInfo Retrieves information describing an audio data object.
SetActual Sets the amount of audio data currently in the object, in bytes.

IUnknown methods	Description
QueryInterface	Retrieves pointers to supported interfaces.
AddRef	Increments the reference count.
Release	Decrements the reference count.
IMemoryData methods	Description
SetBuffer	Initializes a memory buffer with a pointer to memory and length.
GetInfo	Retrieves information describing an audio data object.
SetActual	Sets the amount of audio data currently in the object, in bytes.

IMemoryData::GetInfo

IMemoryData Interface

Retrieves information describing an audio data object.

Syntax

HRESULT GetInfo(
  DWORD *pdwLength,
  BYTE **ppbData,
  DWORD *pcbActualData );

Parameters

pdwLength
[out] Length of memory in bytes, if non-NULL.
ppbData
[out] Pointer to the memory, if non-NULL.
pcbActualData
[out] Length of data in bytes, if non-NULL.

Return Value

Returns an HRESULT value.

Remarks

This method determines how much data the object currently contains as last set by SetActual.

IMemoryData::SetActual

IMemoryData Interface

Sets the amount of audio data currently in the object.

Syntax

HRESULT SetActual(
  DWORD cbDataValid
  );

Parameters

cbDataValid
[in] Amount of data, in bytes.

Return Value

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

Remarks

This method is usually called by the IAudioMediaStream or IAudioStreamSample object, rather than by the application.

IMemoryData::SetBuffer

IMemoryData Interface

Initializes a memory buffer with a pointer to memory and length.

Syntax

HRESULT SetBuffer(
  DWORD cbSize,
  BYTE *pbData,
  DWORD dwFlags );

Parameters

cbSize
[in] Size of memory pointed to by pbData, in bytes.
pbData
[in] Pointer to memory that this object will use.
dwFlags
[in] Reserved for flag data. Must be zero.

Return Value

Returns S_OK if successful or E_INVALIDARG if cbSize is zero or pbData is NULL.

Remarks

This method can be called as often as needed. When using IStreamSample::Update to update samples asynchronously, make sure that SetBuffer is never called before an update is completed.