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waveOutGetPlaybackRate

  • Статья

The waveOutGetPlaybackRate function retrieves the current playback rate for the specified waveform-audio output device.

MMRESULT waveOutGetPlaybackRate(
  HWAVEOUT hwo,    
  LPDWORD pdwRate  
);

Parameters

hwo

Handle to the waveform-audio output device.

pdwRate

Pointer to a variable to be filled with the current playback rate. The playback rate setting is a multiplier indicating the current change in playback rate from the original authored setting. The playback rate multiplier must be a positive value.

The rate is specified as a fixed-point value. The high-order word of the variable contains the signed integer part of the number, and the low-order word contains the fractional part. A value of 0x8000 in the low-order word represents one-half, and 0x4000 represents one-quarter. For example, the value 0x00010000 specifies a multiplier of 1.0 (no playback rate change), and a value of 0x000F8000 specifies a multiplier of 15.5.

Return Values

Returns MMSYSERR_NOERROR if successful or an error otherwise. Possible error values include the following.

Value Description
MMSYSERR_INVALHANDLE Specified device handle is invalid.
MMSYSERR_NODRIVER No device driver is present.
MMSYSERR_NOMEM Unable to allocate or lock memory.
MMSYSERR_NOTSUPPORTED Function isn't supported.

Remarks

Changing the playback rate does not change the sample rate but does change the playback time. Not all devices support playback rate changes. To determine whether a device supports playback rate changes, use the WAVECAPS_PLAYBACKRATE flag to test the dwSupport member of the WAVEOUTCAPS structure (filled by the waveOutGetDevCaps function).

Requirements

**  Windows NT/2000/XP:** Included in Windows NT 3.1 and later.
**  Windows 95/98/Me:** Included in Windows 95 and later.
**  Header:** Declared in Mmsystem.h; include Windows.h.
**  Library:** Use Winmm.lib.

See Also

Waveform Audio, Waveform Functions, WAVEOUTCAPS, waveOutGetDevCaps