/// <summary>
/// Creates a buffer to be used with Video4Linux streaming I/O.
/// </summary>
/// <param name="adapter">The parental Video4Linux device.</param>
/// <param name="buffer">The struct holding the buffer information.</param>
internal Buffer(Analog.Adapter adapter, v4l2_buffer buffer)
{
this.adapter = adapter;
this.buffer = buffer;
mapMemory();
}
/// HACK: we should read until we reached count
/// HACK: offset is ignored
private int readMM(byte[] buffer, int offset, int count)
{
if (!adapter.Capabilities.Contains(AdapterCapability.Streaming))
throw new Exception("Device does not support streaming.");
v4l2_buffer buf = new v4l2_buffer();
buf.type = adapter.Buffers[0].Type;
buf.memory = adapter.Buffers[0].Memory;
// read one image
if (adapter.IoControl.DequeueBuffer(ref buf) == 0)
{
Analog.Buffer dbuf = adapter.Buffers[(int)buf.index];
// max length = buffer length
if ((int)dbuf.Length < count)
count = (int)dbuf.Length;
// copy all the data from the buffer
Marshal.Copy(dbuf.Start, buffer, 0, count);
// re-enqueue the buffer
dbuf.Enqueue();
return count;
}
return 0;
}
/// <summary>
/// Queries the device for information about each requested buffer.
/// </summary>
/// <param name="req">Struct with information about the request buffers.</param>
private void fetchBuffers(v4l2_requestbuffers req) {
for(uint i=0; i < req.count; i++) {
v4l2_buffer buffer = new v4l2_buffer();
buffer.index = i;
buffer.type = req.type;
buffer.memory = req.memory;
if(ioControl.QueryBuffer(ref buffer) < 0)
throw new Exception("VIDIOC_QUERYBUF");
buffers.Add(new Analog.Buffer(this, buffer));
}
}
/// <summary>
/// Calls VIDIOC_QBUF.
/// </summary>
public int EnqueueBuffer(ref v4l2_buffer buffer)
{
return ioctl(deviceHandle, v4l2_operation.EnqueueBuffer, ref buffer);
}
/// <summary>
/// Calls VIDIOC_QUERYBUF.
/// </summary>
public int QueryBuffer(ref v4l2_buffer buffer)
{
return ioctl(deviceHandle, v4l2_operation.QueryBuffer, ref buffer);
}
ioctl(int device, v4l2_operation request, ref v4l2_buffer argp);
/// <summary>
/// Tries to dequeue a buffer and fires the 'BufferFilled' event if the buffer was filled by the driver.
/// </summary>
private void captureFromBuffers()
{
v4l2_buffer buf = new v4l2_buffer();
buf.type = Buffers[0].Type;
buf.memory = Buffers[0].Memory;
while (ioControl.DequeueBuffer(ref buf) == 0)
{
Analog.Buffer dbuf = Buffers[(int)buf.index];
// invoke the event
if (BufferFilled != null)
BufferFilled(this, dbuf);
// re-enqueue the buffer
dbuf.Enqueue();
}
}
private static extern int ioctl(int device, v4l2_operation request, ref v4l2_buffer argp);
