音效卡 PCM資料格式
阿新 • • 發佈：2019-02-09
ThewaveOutSetVolumefunction sets the volume level of the specified waveform-audio output device.
Volume-level values range from 0x0 (silence) to 0xFFFF (maximum volume) and are interpreted logarithmically.
dwVolume
New volume setting. The low-order word contains the left-channel volume setting, and the high-order word contains the right-channel setting. A value of 0xFFFF represents full volume, and a value of 0x0000 is silence.
If a device does not support both left and right volume control, the low-order word of dwVolume specifies the volume level, and the high-order word is ignored.
PCM Waveform-Audio Data Format
The lpData member of the WAVEHDR structure pointsetts to the waveform-audio data samples.
For 8-bit PCM data, each sample is represented by a single unsigned data byte. For 16-bit PCM data, each sample is represented by a 16-bit signed value. The following table summarizes the maximum, minimum, and midpoint values for PCM waveform-audio data.
| Data format | Maximum value | Minimum value | Midpoint value |
| 8-bit PCM | 255 (0xFF) | 0 | 128 (0x80) |
| 16-bit PCM | 32,767 (0x7FFF) | –32,768 (0x8000) | 0 |
PCM Data Packing
| PCM waveform-audio format | Description |
|---|---|
| 8-bit mono | Each sample is 1 byte that corresponds to a single audio channel. Sample 1 is followed by samples 2, 3, 4, and so on. |
| 8-bit stereo | Each sample is 2 bytes. Sample 1 is followed by samples 2, 3, 4, and so on. For each sample, the first byte is channel 0 (the left channel) and the second byte is channel 1 (the right channel). |
| 16-bit mono | Each sample is 2 bytes. Sample 1 is followed by samples 2, 3, 4, and so on. For each sample, the first byte is the low-order byte of channel 0 and the second byte is the high-order byte of channel 0. |
| 16-bit stereo | Each sample is 4 bytes. Sample 1 is followed by samples 2, 3, 4, and so on. For each sample, the first byte is the low-order byte of channel 0 (left channel); the second byte is the high-order byte of channel 0; the third byte is the low-order byte of channel 1 (right channel); and the fourth byte is the high-order byte of channel 1. |