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POC# DirectSound - Capture buffers not continuous
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copied!<p>I'm trying to capture raw data from my line-in using DirectSound.</p> <p>My problem is that, from a buffer to another the data are just inconsistent, if for example I capture a sine I see a jump from my last buffer and the new one. To detected this I use a graph widget to draw the first 500 elements of the last buffer and the 500 elements from the new one:</p> <p><img src="https://i.stack.imgur.com/LeOFn.jpg" alt="snapshot"> <a href="http://img199.imageshack.us/img199/206/demodsnap.jpg" rel="nofollow noreferrer">http://img199.imageshack.us/img199/206/demodsnap.jpg</a></p> <p>I initialized my buffer this way:</p> <pre><code> format = new WaveFormat { SamplesPerSecond = 44100, BitsPerSample = (short)bitpersample, Channels = (short)channels, FormatTag = WaveFormatTag.Pcm }; format.BlockAlign = (short)(format.Channels * (format.BitsPerSample / 8)); format.AverageBytesPerSecond = format.SamplesPerSecond * format.BlockAlign; _dwNotifySize = Math.Max(4096, format.AverageBytesPerSecond / 8); _dwNotifySize -= _dwNotifySize % format.BlockAlign; _dwCaptureBufferSize = NUM_BUFFERS * _dwNotifySize; // my capture buffer _dwOutputBufferSize = NUM_BUFFERS * _dwNotifySize / channels; // my output buffer </code></pre> <p>I set my notifications one at half the buffer and one at the end:</p> <pre><code> _resetEvent = new AutoResetEvent(false); _notify = new Notify(_dwCapBuffer); bpn1 = new BufferPositionNotify(); bpn1.Offset = ((_dwCapBuffer.Caps.BufferBytes) / 2) - 1; bpn1.EventNotifyHandle = _resetEvent.SafeWaitHandle.DangerousGetHandle(); bpn2 = new BufferPositionNotify(); bpn2.Offset = (_dwCapBuffer.Caps.BufferBytes) - 1; bpn2.EventNotifyHandle = _resetEvent.SafeWaitHandle.DangerousGetHandle(); _notify.SetNotificationPositions(new BufferPositionNotify[] { bpn1, bpn2 }); observer.updateSamplerStatus("Events listener initialization complete!\r\n"); </code></pre> <p>And here is how I process the events.</p> <pre><code>/* Process thread */ private void eventReceived() { int offset = 0; _dwCaptureThread = new Thread((ThreadStart)delegate { _dwCapBuffer.Start(true); while (isReady) { _resetEvent.WaitOne(); // Notification received /* Read the captured buffer */ Array read = _dwCapBuffer.Read(offset, typeof(short), LockFlag.None, _dwOutputBufferSize - 1); observer.updateTextPacket("Buffer: " + count.ToString() + " # " + read.GetValue(read.Length - 1).ToString() + " # " + read.GetValue(0).ToString() + "\r\n"); /* Print last/new part of the buffer to the debug graph */ short[] graphData = new short[1001]; Array.Copy(read, graphData, 1000); db.SetBufferDebug(graphData, 500); observer.updateGraph(db.getBufferDebug()); offset = (offset + _dwOutputBufferSize) % _dwCaptureBufferSize; /* Out buffer not used */ /*_dwDevBuffer.Write(0, read, LockFlag.EntireBuffer); _dwDevBuffer.SetCurrentPosition(0); _dwDevBuffer.Play(0, BufferPlayFlags.Default);*/ } _dwCapBuffer.Stop(); }); _dwCaptureThread.Start(); } </code></pre> <p>Any advise? I'm sure I'm failing somewhere in the event processing, but I cant find where.</p> <p>I had developed the same application using the WaveIn API and it worked well.</p> <p>Thanks a lot...</p>

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