/// <summary>
/// Preload the buffers and prepare them for recording.
/// </summary>
/// <param name="curDevice">Device to use for recording</param>
/// <param name="hwnd">Handle to a message window that will receive
/// audio messages.</param>
/// <param name="maxRecordLength_ms">Maximum length of recording</param>
/// <param name="bufferSize">Size of buffers to use for recording. New
/// buffers are added when needed until the maximum length is reached
/// or the recording is stopped.</param>
/// <returns>MMSYSERR.NOERROR if successful</returns>
public Wave.MMSYSERR Preload(uint curDevice, IntPtr hwnd, int maxRecordLength_ms, int bufferSize)
{
// Do not allow recording to be interrupted
if (m_recording)
return Wave.MMSYSERR.ERROR;
// If this file is already initialized then start over
if (m_inited)
{
Stop();
FreeWaveBuffers();
}
// Create an instance of WAVEINCAPS to check if our desired
// format is supported
WAVEINCAPS caps = new WAVEINCAPS();
waveInGetDevCaps(0, caps, caps.Size);
if ((caps.dwFormats & Wave.WAVE_FORMAT_1S16) == 0)
return Wave.MMSYSERR.NOTSUPPORTED;
// Initialize a WAVEFORMATEX structure specifying the desired
// format
m_wfmt = new Wave.WAVEFORMATEX();
m_wfmt.wFormatTag = Wave.WAVEHDR.WAVE_FORMAT_PCM;
m_wfmt.wBitsPerSample = 16;
m_wfmt.nChannels = 2;
m_wfmt.nSamplesPerSec = 44110;//11025;
m_wfmt.nAvgBytesPerSec = (uint)(m_wfmt.nSamplesPerSec * m_wfmt.nChannels * (m_wfmt.wBitsPerSample / 8));
m_wfmt.nBlockAlign = (ushort)(m_wfmt.wBitsPerSample * m_wfmt.nChannels / 8);
// Attempt to open the specified device with the desired wave format
Wave.MMSYSERR result = waveInOpen(ref m_hwi, curDevice, m_wfmt, hwnd, 0, Wave.CALLBACK_WINDOW);
if (result != Wave.MMSYSERR.NOERROR)
return result;
if (bufferSize == 0)
return Wave.MMSYSERR.ERROR;
m_bufferSize = (uint)bufferSize;
// Force the buffers to align to nBlockAlign
if (m_bufferSize % m_wfmt.nBlockAlign != 0)
m_bufferSize += m_wfmt.nBlockAlign - (m_bufferSize % m_wfmt.nBlockAlign);
// Determine the number of buffers needed to record the maximum length
m_maxDataLength = (uint)(m_wfmt.nAvgBytesPerSec * maxRecordLength_ms / 1000);
m_numBlocks = (int)(m_maxDataLength / m_bufferSize);
if (m_numBlocks * m_bufferSize < m_maxDataLength)
m_numBlocks++;
// Allocate the list of buffers
m_whdr = new Wave.WAVEHDR[m_numBlocks + 1];
// Allocate and initialize two buffers to start with
m_whdr[0] = new Wave.WAVEHDR();
m_whdr[1] = new Wave.WAVEHDR();
result = InitBuffer(0);
if (result != Wave.MMSYSERR.NOERROR)
return result;
result = InitBuffer(1);
if (result != Wave.MMSYSERR.NOERROR)
return result;
m_curBlock = 0;
m_inited = true;
return Wave.MMSYSERR.NOERROR;
}
/// <summary>
/// Initialize a buffer for recording by allocating a data buffer,
/// preparing the header, and adding it to the read queue.
/// </summary>
/// <param name="bufIndex">Index of buffer to allocate</param>
/// <returns>MMSYSERR.NOERROR if successful</returns>
public Wave.MMSYSERR InitBuffer(int bufIndex)
{
// Determine the size of the buffer to create
uint writeLength = (uint)m_bufferSize;
if (bufIndex < m_numBlocks)
{
uint remainingDataLength = (uint)(m_maxDataLength - bufIndex * m_bufferSize);
if (m_bufferSize > remainingDataLength)
writeLength = remainingDataLength;
}
// If the header is not already instanced then instance it
if (m_whdr[bufIndex] == null)
m_whdr[bufIndex] = new Wave.WAVEHDR();
// Allocate memory if not already allocated
Wave.MMSYSERR result = m_whdr[bufIndex].Init(writeLength, false);
if (result != Wave.MMSYSERR.NOERROR)
return result;
// Prepare the header
result = waveInPrepareHeader(m_hwi, m_whdr[bufIndex], (uint)Marshal.SizeOf(m_whdr[bufIndex]));
if (result != Wave.MMSYSERR.NOERROR)
return result;
// Put the buffer in the queue
return waveInAddBuffer(m_hwi, m_whdr[bufIndex], (uint)Marshal.SizeOf(m_whdr[bufIndex]));
}