MFFOLDDOWN_MATRIX structure (mfapi.h)

Contains coefficients used to transform multichannel audio into a smaller number of audio channels. This process is called fold-down.

Syntax

typedef struct _MFFOLDDOWN_MATRIX {
  UINT32 cbSize;
  UINT32 cSrcChannels;
  UINT32 cDstChannels;
  UINT32 dwChannelMask;
  LONG   Coeff[64];
} MFFOLDDOWN_MATRIX;

Members

cbSize

Size of the structure, in bytes.

cSrcChannels

Number of source channels.

cDstChannels

Number of destination channels.

dwChannelMask

Specifies the assignment of audio channels to speaker positions in the transformed audio. This member is a bitwise OR of flags that define the speaker positions. For a list of valid flags, see MF_MT_AUDIO_CHANNEL_MASK attribute.

Coeff[64]

Array that contains the fold-down coefficients. The number of coefficients is cSrcChannels×cDstChannels. If the number of coefficients is less than the size of the array, the remaining elements in the array are ignored. For more information about how the coefficients are applied, see Windows Media Audio Professional Codec Features.

Remarks

To specify this information in the media type, set the MF_MT_AUDIO_FOLDDOWN_MATRIX attribute.

The ASF media source supports fold-down from six channels (5.1 audio) to two channels (stereo). It gets the information from the g_wszFold6To2Channels3 attribute in the ASF header. This attribute is documented in the Windows Media Format SDK documentation.

Requirements

See also

Media Foundation Structures