// ksmedia.h

typedef struct {
  UINT64 u64PositionInBlocks;
  UINT64 u64QPCPosition;
} KSAUDIO_PRESENTATION_POSITION, *PKSAUDIO_PRESENTATION_POSITION;
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Windows Driver Kit DDI reference (ns-ksmedia-ksaudio_presentation_position)

KSAUDIO_PRESENTATION_POSITION structure

Description

The KSAUDIO_PRESENTATION_POSITION structure specifies the current cursor position in audio data stream that is being rendered to the endpoint.

Members

`u64PositionInBlocks`

Specifies the block offset from the start of the stream to the current post-decoded, uncompressed position in the stream. A "block" refers to the group of channels in the same sample. So, for example, in a PCM stream a block is the same as a frame. However, for compressed formats a block is a single sample within a frame. This means that for a typical MP3 stream that has 1152 samples in a frame, there are 1152 blocks.

`u64QPCPosition`

Specifies the value of the performance counter at the time that the audio driver reads the presentation position in response to the KSAUDIO_PRESENTATION_POSITION call. A driver writes to this field with the value read from calling KeQueryPerformanceCounter when a snapshot is taken of the presentation position.

KSAUDIO_PRESENTATION_POSITION - NtDoc