hyperion.ng/libsrc/grabber/v4l2/V4L2Grabber.cpp

#include <iostream>
#include <sstream>
#include <stdexcept>
#include <cstdio>
#include <cassert>
#include <cstdlib>
#include <cstring>
#include <sstream>

#include <fcntl.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <linux/videodev2.h>

#include <hyperion/Hyperion.h>
#include <hyperion/HyperionIManager.h>

#include <QDirIterator>
#include <QFileInfo>

#include "grabber/V4L2Grabber.h"

#define CLEAR(x) memset(&(x), 0, sizeof(x))

V4L2Grabber::V4L2Grabber(const QString & device
		, const unsigned width
		, const unsigned height
		, const unsigned fps
		, VideoStandard videoStandard
		, PixelFormat pixelFormat
		, int pixelDecimation
		)
	: Grabber("V4L2:"+device)
	, _deviceName()
	, _input(-1)
	, _videoStandard(videoStandard)
	, _ioMethod(IO_METHOD_MMAP)
	, _fileDescriptor(-1)
	, _buffers()
	, _pixelFormat(pixelFormat)
	, _pixelDecimation(-1)
	, _lineLength(-1)
	, _frameByteSize(-1)
	, _noSignalCounterThreshold(40)
	, _noSignalThresholdColor(ColorRgb{0,0,0})
	, _signalDetectionEnabled(true)
	, _noSignalDetected(false)
	, _noSignalCounter(0)
	, _x_frac_min(0.25)
	, _y_frac_min(0.25)
	, _x_frac_max(0.75)
	, _y_frac_max(0.75)
	, _streamNotifier(nullptr)
	, _initialized(false)
	, _deviceAutoDiscoverEnabled(false)
{
	setPixelDecimation(pixelDecimation);
	getV4Ldevices();

	// init
	setWidthHeight(width, height);
	setFramerate(fps);
	setDeviceVideoStandard(device, videoStandard);
}

V4L2Grabber::~V4L2Grabber()
{
	uninit();
}

void V4L2Grabber::uninit()
{
	// stop if the grabber was not stopped
	if (_initialized)
	{
		Debug(_log,"uninit grabber: %s", QSTRING_CSTR(_deviceName));
		stop();
	}
}

bool V4L2Grabber::init()
{
	if (! _initialized)
	{
		getV4Ldevices();
		QString v4lDevices_str;

		// show list only once
		if ( ! QString(QSTRING_CSTR(_deviceName)).startsWith("/dev/") )
		{
			for (auto& dev: _v4lDevices)
			{
				v4lDevices_str += "\t"+ dev.first + "\t" + dev.second + "\n";
			}
			if (!v4lDevices_str.isEmpty())
				Info(_log, "available V4L2 devices:\n%s", QSTRING_CSTR(v4lDevices_str));
		}

		if ( _deviceName == "auto" )
		{
			_deviceAutoDiscoverEnabled = true;
			_deviceName = "unknown";
			Info( _log, "search for usable video devices" );
			for (auto& dev: _v4lDevices)
			{
				_deviceName = dev.first;
				if ( init() )
				{
					Info(_log, "found usable v4l2 device: %s (%s)",QSTRING_CSTR(dev.first), QSTRING_CSTR(dev.second));
					_deviceAutoDiscoverEnabled = false;
					return _initialized;
				}
			}
			Info( _log, "no usable device found" );
		}
		else if ( ! _deviceName.startsWith("/dev/") )
		{
			for (auto& dev: _v4lDevices)
			{
				if ( _deviceName.toLower() == dev.second.toLower() )
				{
					_deviceName = dev.first;
					Info(_log, "found v4l2 device with configured name: %s (%s)", QSTRING_CSTR(dev.second), QSTRING_CSTR(dev.first) );
					break;
				}
			}
		}
		else
		{
			Info(_log, "%s v4l device: %s", (_deviceAutoDiscoverEnabled? "test" : "configured"), QSTRING_CSTR(_deviceName));
		}

		bool opened = false;
		try
		{
			// do not init with unknown device
			if(_deviceName != "unknown")
			{
				if (open_device())
				{
					opened = true;
					init_device(_videoStandard, _input);
					_initialized = true;
				}
			}
		}
		catch(std::exception& e)
		{
			if (opened)
			{
				uninit_device();
				close_device();
			}
			ErrorIf( !_deviceAutoDiscoverEnabled, _log, "V4l2 init failed (%s)", e.what());
		}
	}

	return _initialized;
}

void V4L2Grabber::getV4Ldevices()
{
	QDirIterator it("/sys/class/video4linux/", QDirIterator::NoIteratorFlags);
	while(it.hasNext())
	{
		//_v4lDevices
		QString dev = it.next();
		if (it.fileName().startsWith("video"))
		{
			QFile devNameFile(dev+"/name");
			QString devName;
			if ( devNameFile.exists())
			{
				devNameFile.open(QFile::ReadOnly);
				devName = devNameFile.readLine();
				devName = devName.trimmed();
				devNameFile.close();
			}
			_v4lDevices.emplace("/dev/"+it.fileName(), devName);
		}
    }
}

void V4L2Grabber::setSignalThreshold(double redSignalThreshold, double greenSignalThreshold, double blueSignalThreshold, int noSignalCounterThreshold)
{
	_noSignalThresholdColor.red   = uint8_t(255*redSignalThreshold);
	_noSignalThresholdColor.green = uint8_t(255*greenSignalThreshold);
	_noSignalThresholdColor.blue  = uint8_t(255*blueSignalThreshold);
	_noSignalCounterThreshold     = qMax(1, noSignalCounterThreshold);

	Info(_log, "Signal threshold set to: {%d, %d, %d}", _noSignalThresholdColor.red, _noSignalThresholdColor.green, _noSignalThresholdColor.blue );
}

void V4L2Grabber::setSignalDetectionOffset(double horizontalMin, double verticalMin, double horizontalMax, double verticalMax)
{
	// rainbow 16 stripes 0.47 0.2 0.49 0.8
	// unicolor: 0.25 0.25 0.75 0.75

	_x_frac_min = horizontalMin;
	_y_frac_min = verticalMin;
	_x_frac_max = horizontalMax;
	_y_frac_max = verticalMax;

	Info(_log, "Signal detection area set to: %f,%f x %f,%f", _x_frac_min, _y_frac_min, _x_frac_max, _y_frac_max );
}

bool V4L2Grabber::start()
{
	try
	{
		if (init() && _streamNotifier != nullptr && !_streamNotifier->isEnabled())
		{
			_streamNotifier->setEnabled(true);
			start_capturing();
			Info(_log, "Started");
			return true;
		}
	}
	catch(std::exception& e)
	{
		Error(_log, "start failed (%s)", e.what());
	}

	return false;
}

void V4L2Grabber::stop()
{
	if (_streamNotifier != nullptr && _streamNotifier->isEnabled())
	{
		stop_capturing();
		_streamNotifier->setEnabled(false);
		uninit_device();
		close_device();
		_initialized = false;
		Info(_log, "Stopped");
	}
}

bool V4L2Grabber::open_device()
{
	struct stat st;

	if (-1 == stat(QSTRING_CSTR(_deviceName), &st))
	{
		throw_errno_exception("Cannot identify '" + _deviceName + "'");
		return false;
	}

	if (!S_ISCHR(st.st_mode))
	{
		throw_exception("'" + _deviceName + "' is no device");
		return false;
	}

	_fileDescriptor = open(QSTRING_CSTR(_deviceName), O_RDWR | O_NONBLOCK, 0);

	if (-1 == _fileDescriptor)
	{
		throw_errno_exception("Cannot open '" + _deviceName + "'");
		return false;
	}

	// create the notifier for when a new frame is available
	_streamNotifier = new QSocketNotifier(_fileDescriptor, QSocketNotifier::Read);
	_streamNotifier->setEnabled(false);
	connect(_streamNotifier, SIGNAL(activated(int)), this, SLOT(read_frame()));
	return true;
}

void V4L2Grabber::close_device()
{
	if (-1 == close(_fileDescriptor))
	{
		throw_errno_exception("close");
		return;
	}

	_fileDescriptor = -1;

	if (_streamNotifier != nullptr)
	{
		delete _streamNotifier;
		_streamNotifier = nullptr;
	}
}

void V4L2Grabber::init_read(unsigned int buffer_size)
{
	_buffers.resize(1);

	_buffers[0].length = buffer_size;
	_buffers[0].start = malloc(buffer_size);

	if (!_buffers[0].start)
	{
		throw_exception("Out of memory");
		return;
	}
}

void V4L2Grabber::init_mmap()
{
	struct v4l2_requestbuffers req;

	CLEAR(req);

	req.count = 4;
	req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
	req.memory = V4L2_MEMORY_MMAP;

	if (-1 == xioctl(VIDIOC_REQBUFS, &req))
	{
		if (EINVAL == errno)
		{
			throw_exception("'" + _deviceName + "' does not support memory mapping");
			return;
		}
		else
		{
			throw_errno_exception("VIDIOC_REQBUFS");
			return;
		}
	}

	if (req.count < 2)
	{
		throw_exception("Insufficient buffer memory on " + _deviceName);
		return;
	}

	_buffers.resize(req.count);

	for (size_t n_buffers = 0; n_buffers < req.count; ++n_buffers)
	{
		struct v4l2_buffer buf;

		CLEAR(buf);

		buf.type	= V4L2_BUF_TYPE_VIDEO_CAPTURE;
		buf.memory	= V4L2_MEMORY_MMAP;
		buf.index	= n_buffers;

		if (-1 == xioctl(VIDIOC_QUERYBUF, &buf))
		{
			throw_errno_exception("VIDIOC_QUERYBUF");
			return;
		}

		_buffers[n_buffers].length = buf.length;
		_buffers[n_buffers].start = mmap(NULL /* start anywhere */,
						buf.length,
						PROT_READ | PROT_WRITE /* required */,
						MAP_SHARED /* recommended */,
						_fileDescriptor, buf.m.offset
					);

		if (MAP_FAILED == _buffers[n_buffers].start)
		{
			throw_errno_exception("mmap");
			return;
		}
	}
}

void V4L2Grabber::init_userp(unsigned int buffer_size)
{
	struct v4l2_requestbuffers req;

	CLEAR(req);

	req.count  = 4;
	req.type   = V4L2_BUF_TYPE_VIDEO_CAPTURE;
	req.memory = V4L2_MEMORY_USERPTR;

	if (-1 == xioctl(VIDIOC_REQBUFS, &req))
	{
		if (EINVAL == errno)
		{
			throw_exception("'" + _deviceName + "' does not support user pointer");
			return;
		}
		else
		{
			throw_errno_exception("VIDIOC_REQBUFS");
			return;
		}
	}

	_buffers.resize(4);

	for (size_t n_buffers = 0; n_buffers < 4; ++n_buffers)
	{
		_buffers[n_buffers].length = buffer_size;
		_buffers[n_buffers].start = malloc(buffer_size);

		if (!_buffers[n_buffers].start)
		{
			throw_exception("Out of memory");
			return;
		}
	}
}

void V4L2Grabber::init_device(VideoStandard videoStandard, int input)
{
	struct v4l2_capability cap;
	if (-1 == xioctl(VIDIOC_QUERYCAP, &cap))
	{
		if (EINVAL == errno)
		{
			throw_exception("'" + _deviceName + "' is no V4L2 device");
			return;
		}
		else
		{
			throw_errno_exception("VIDIOC_QUERYCAP");
			return;
		}
	}

	if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE))
	{
		throw_exception("'" + _deviceName + "' is no video capture device");
		return;
	}

	switch (_ioMethod)
	{
		case IO_METHOD_READ:
		{
			if (!(cap.capabilities & V4L2_CAP_READWRITE))
			{
				throw_exception("'" + _deviceName + "' does not support read i/o");
				return;
			}
		}
		break;

		case IO_METHOD_MMAP:
		case IO_METHOD_USERPTR:
		{
			if (!(cap.capabilities & V4L2_CAP_STREAMING))
			{
				throw_exception("'" + _deviceName + "' does not support streaming i/o");
				return;
			}
		}
		break;
	}


	/* Select video input, video standard and tune here. */

	struct v4l2_cropcap cropcap;
	CLEAR(cropcap);

	cropcap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

	if (0 == xioctl(VIDIOC_CROPCAP, &cropcap))
	{
		struct v4l2_crop crop;
		crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
		crop.c = cropcap.defrect; /* reset to default */

		if (-1 == xioctl(VIDIOC_S_CROP, &crop))
		{
			switch (errno)
			{
				case EINVAL: /* Cropping not supported. */
				default: /* Errors ignored. */
					break;
			}
		}
	}
	else
	{
		/* Errors ignored. */
	}

	// set input if needed and supported
	struct v4l2_input v4l2Input;
	v4l2Input.index = input;

	if (input >= 0 && 0 == xioctl(VIDIOC_ENUMINPUT,&v4l2Input))
	{
		if (-1 == xioctl(VIDIOC_S_INPUT, &input))
		{
			throw_errno_exception("VIDIOC_S_INPUT");
			return;
		}
	}

	// set the video standard if needed and supported
	v4l2_std_id std_id;
	if (-1 != xioctl(VIDIOC_ENUMSTD, &std_id))
	{
		switch (videoStandard)
		{
			case VIDEOSTANDARD_PAL:
			{
				std_id = V4L2_STD_PAL;
				if (-1 == xioctl(VIDIOC_S_STD, &std_id))
				{
					throw_errno_exception("VIDIOC_S_STD");
					break;
				}
			}
			break;

			case VIDEOSTANDARD_NTSC:
			{
				std_id = V4L2_STD_NTSC;
				if (-1 == xioctl(VIDIOC_S_STD, &std_id))
				{
					throw_errno_exception("VIDIOC_S_STD");
					break;
				}
			}
			break;

			case VIDEOSTANDARD_SECAM:
			{
				std_id = V4L2_STD_SECAM;
				if (-1 == xioctl(VIDIOC_S_STD, &std_id))
				{
					throw_errno_exception("VIDIOC_S_STD");
					break;
				}
			}
			break;

			case VIDEOSTANDARD_NO_CHANGE:
			default:
				// No change to device settings
				break;
		}
	}

	// get the current settings
	struct v4l2_format fmt;
	CLEAR(fmt);
	fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
	if (-1 == xioctl(VIDIOC_G_FMT, &fmt))
	{
		throw_errno_exception("VIDIOC_G_FMT");
		return;
	}

	// set the requested pixel format
	switch (_pixelFormat)
	{
		case PIXELFORMAT_UYVY:
			fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_UYVY;
		break;

		case PIXELFORMAT_YUYV:
			fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV;
		break;

		case PIXELFORMAT_RGB32:
			fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_RGB32;
		break;

#ifdef HAVE_JPEG_DECODER
		case PIXELFORMAT_MJPEG:
		{
			fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_MJPEG;
			fmt.fmt.pix.field       = V4L2_FIELD_ANY;
		}
		break;
#endif

		case PIXELFORMAT_NO_CHANGE:
		default:
			// No change to device settings
			break;
	}

	// collect available device resolutions
	QString v4lDevice_res;
	v4l2_frmsizeenum frmsizeenum;
	CLEAR(frmsizeenum);
	frmsizeenum.index = 0;
	frmsizeenum.pixel_format = fmt.fmt.pix.pixelformat;
	while (xioctl(VIDIOC_ENUM_FRAMESIZES, &frmsizeenum) >= 0)
	{
		switch (frmsizeenum.type)
		{
			case V4L2_FRMSIZE_TYPE_DISCRETE:
				v4lDevice_res += "\t"+ QString::number(frmsizeenum.discrete.width) + "x" + QString::number(frmsizeenum.discrete.height) + "\n";
			break;
			case V4L2_FRMSIZE_TYPE_CONTINUOUS:
			case V4L2_FRMSIZE_TYPE_STEPWISE:
			{
				for(unsigned int y = frmsizeenum.stepwise.min_height; y <= frmsizeenum.stepwise.max_height; y += frmsizeenum.stepwise.step_height)
				{
					for(unsigned int x = frmsizeenum.stepwise.min_width; x <= frmsizeenum.stepwise.max_width; x += frmsizeenum.stepwise.step_width)
					{
						v4lDevice_res += "\t"+ QString::number(x) + "x" + QString::number(y) + "\n";
					}
				}
			}
		}
		frmsizeenum.index++;
	}

	// print available device resolutions in debug mode
	if (!v4lDevice_res.isEmpty())
		Debug(_log, "available V4L2 resolutions:\n%s", QSTRING_CSTR(v4lDevice_res));

	// set the settings
	fmt.fmt.pix.width = _width;
	fmt.fmt.pix.height = _height;

	if (-1 == xioctl(VIDIOC_S_FMT, &fmt))
	{
		throw_errno_exception("VIDIOC_S_FMT");
		return;
	}

	// initialize current width and height
	_width = fmt.fmt.pix.width;
	_height = fmt.fmt.pix.height;

	// display the used width and height
	Debug(_log, "Set resolution to width=%d height=%d", _width, _height );

	// Trying to set frame rate
	struct v4l2_streamparm streamparms;
	CLEAR(streamparms);
	streamparms.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
	if (-1 == xioctl(VIDIOC_G_PARM, &streamparms))
	{
		Debug(_log, "Frame rate settings not supported");
		// continue
	}
	else
	{
		// Check the capability flag is set to V4L2_CAP_TIMEPERFRAME
		if (streamparms.parm.capture.capability == V4L2_CAP_TIMEPERFRAME)
		{
			// Driver supports the feature. Set required framerate
			CLEAR(streamparms);
			streamparms.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
			streamparms.parm.capture.timeperframe.numerator = 1;
			streamparms.parm.capture.timeperframe.denominator = _fps;
			if(-1 == xioctl(VIDIOC_S_PARM, &streamparms))
			{
				throw_errno_exception("VIDIOC_S_PARM");
				// continue
			}
			else
				// display the used framerate
				Debug(_log, "Set framerate to %d fps", _fps);
		}
	}

	// set the line length
	_lineLength = fmt.fmt.pix.bytesperline;

	// check pixel format and frame size
	switch (fmt.fmt.pix.pixelformat)
	{
		case V4L2_PIX_FMT_UYVY:
		{
			_pixelFormat = PIXELFORMAT_UYVY;
			_frameByteSize = _width * _height * 2;
			Debug(_log, "Pixel format=UYVY");
		}
		break;

		case V4L2_PIX_FMT_YUYV:
		{
			_pixelFormat = PIXELFORMAT_YUYV;
			_frameByteSize = _width * _height * 2;
			Debug(_log, "Pixel format=YUYV");
		}
		break;

		case V4L2_PIX_FMT_RGB32:
		{
			_pixelFormat = PIXELFORMAT_RGB32;
			_frameByteSize = _width * _height * 4;
			Debug(_log, "Pixel format=RGB32");
		}
		break;

#ifdef HAVE_JPEG_DECODER
		case V4L2_PIX_FMT_MJPEG:
		{
			_pixelFormat = PIXELFORMAT_MJPEG;
			Debug(_log, "Pixel format=MJPEG");
		}
		break;
#endif

		default:
#ifdef HAVE_JPEG_DECODER
			throw_exception("Only pixel formats UYVY, YUYV, RGB32 and MJPEG are supported");
#else
			throw_exception("Only pixel formats UYVY, YUYV, and RGB32 are supported");
#endif
		return;
	}

	switch (_ioMethod)
	{
		case IO_METHOD_READ:
			init_read(fmt.fmt.pix.sizeimage);
		break;

		case IO_METHOD_MMAP:
			init_mmap();
		break;

		case IO_METHOD_USERPTR:
			init_userp(fmt.fmt.pix.sizeimage);
		break;
	}
}

void V4L2Grabber::uninit_device()
{
	switch (_ioMethod)
	{
		case IO_METHOD_READ:
			free(_buffers[0].start);
		break;

		case IO_METHOD_MMAP:
		{
			for (size_t i = 0; i < _buffers.size(); ++i)
				if (-1 == munmap(_buffers[i].start, _buffers[i].length))
				{
					throw_errno_exception("munmap");
					return;
				}
		}
		break;

		case IO_METHOD_USERPTR:
		{
			for (size_t i = 0; i < _buffers.size(); ++i)
				free(_buffers[i].start);
		}
		break;
	}

	_buffers.resize(0);
}

void V4L2Grabber::start_capturing()
{
	switch (_ioMethod)
	{
		case IO_METHOD_READ:
			/* Nothing to do. */
			break;

		case IO_METHOD_MMAP:
		{
			for (size_t i = 0; i < _buffers.size(); ++i)
			{
				struct v4l2_buffer buf;

				CLEAR(buf);
				buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
				buf.memory = V4L2_MEMORY_MMAP;
				buf.index = i;

				if (-1 == xioctl(VIDIOC_QBUF, &buf))
				{
					throw_errno_exception("VIDIOC_QBUF");
					return;
				}
			}
			v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
			if (-1 == xioctl(VIDIOC_STREAMON, &type))
			{
				throw_errno_exception("VIDIOC_STREAMON");
				return;
			}
			break;
		}
		case IO_METHOD_USERPTR:
		{
			for (size_t i = 0; i < _buffers.size(); ++i)
			{
				struct v4l2_buffer buf;

				CLEAR(buf);
				buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
				buf.memory = V4L2_MEMORY_USERPTR;
				buf.index = i;
				buf.m.userptr = (unsigned long)_buffers[i].start;
				buf.length = _buffers[i].length;

				if (-1 == xioctl(VIDIOC_QBUF, &buf))
				{
					throw_errno_exception("VIDIOC_QBUF");
					return;
				}
			}
			v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
			if (-1 == xioctl(VIDIOC_STREAMON, &type))
			{
				throw_errno_exception("VIDIOC_STREAMON");
				return;
			}
			break;
		}
	}
}

void V4L2Grabber::stop_capturing()
{
	enum v4l2_buf_type type;

	switch (_ioMethod)
	{
		case IO_METHOD_READ:
			break; /* Nothing to do. */

		case IO_METHOD_MMAP:
		case IO_METHOD_USERPTR:
		{
			type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
			ErrorIf((xioctl(VIDIOC_STREAMOFF, &type) == -1), _log, "VIDIOC_STREAMOFF  error code  %d, %s", errno, strerror(errno));
		}
		break;
	}
}

int V4L2Grabber::read_frame()
{
	bool rc = false;

	try
	{
		struct v4l2_buffer buf;

		switch (_ioMethod)
		{
			case IO_METHOD_READ:
			{
				int size;
				if ((size = read(_fileDescriptor, _buffers[0].start, _buffers[0].length)) == -1)
				{
					switch (errno)
					{
						case EAGAIN:
							return 0;

						case EIO: /* Could ignore EIO, see spec. */
						default:
							throw_errno_exception("read");
						return 0;
					}
				}

				rc = process_image(_buffers[0].start, size);
			}
			break;

			case IO_METHOD_MMAP:
			{
				CLEAR(buf);

				buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
				buf.memory = V4L2_MEMORY_MMAP;

				if (-1 == xioctl(VIDIOC_DQBUF, &buf))
				{
					switch (errno)
					{
						case EAGAIN:
							return 0;

						case EIO: /* Could ignore EIO, see spec. */
						default:
							throw_errno_exception("VIDIOC_DQBUF");
						return 0;
					}
				}

				assert(buf.index < _buffers.size());

				rc = process_image(_buffers[buf.index].start, buf.bytesused);

				if (-1 == xioctl(VIDIOC_QBUF, &buf))
				{
					throw_errno_exception("VIDIOC_QBUF");
					return 0;
				}
			}
			break;

			case IO_METHOD_USERPTR:
			{
				CLEAR(buf);

				buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
				buf.memory = V4L2_MEMORY_USERPTR;

				if (-1 == xioctl(VIDIOC_DQBUF, &buf))
				{
					switch (errno)
					{
						case EAGAIN:
							return 0;

						case EIO: /* Could ignore EIO, see spec. */
						default:
							throw_errno_exception("VIDIOC_DQBUF");
						return 0;
					}
				}

				for (size_t i = 0; i < _buffers.size(); ++i)
				{
					if (buf.m.userptr == (unsigned long)_buffers[i].start && buf.length == _buffers[i].length)
					{
						break;
					}
				}

				rc = process_image((void *)buf.m.userptr, buf.bytesused);

				if (-1 == xioctl(VIDIOC_QBUF, &buf))
				{
					throw_errno_exception("VIDIOC_QBUF");
					return 0;
				}
			}
			break;
		}
	}
	catch (std::exception& e)
	{
		emit readError(e.what());
		rc = false;
	}

	return rc ? 1 : 0;
}

bool V4L2Grabber::process_image(const void *p, int size)
{
	// We do want a new frame...
#ifdef HAVE_JPEG_DECODER
	if (size != _frameByteSize && _pixelFormat != PIXELFORMAT_MJPEG)
#else
	if (size != _frameByteSize)
#endif
	{
		Error(_log, "Frame too small: %d != %d", size, _frameByteSize);
	}
	else
	{
		process_image(reinterpret_cast<const uint8_t *>(p), size);
		return true;
	}

	return false;
}

void V4L2Grabber::process_image(const uint8_t * data, int size)
{
	Image<ColorRgb> image(_width, _height);

/* ----------------------------------------------------------
 * ----------- BEGIN of JPEG decoder related code -----------
 * --------------------------------------------------------*/

#ifdef HAVE_JPEG_DECODER
	if (_pixelFormat == PIXELFORMAT_MJPEG)
	{
#endif
#ifdef HAVE_JPEG
		_decompress = new jpeg_decompress_struct;
		_error = new errorManager;

		_decompress->err = jpeg_std_error(&_error->pub);
		_error->pub.error_exit = &errorHandler;
		_error->pub.output_message = &outputHandler;

		jpeg_create_decompress(_decompress);

		if (setjmp(_error->setjmp_buffer))
		{
			jpeg_abort_decompress(_decompress);
			jpeg_destroy_decompress(_decompress);
			delete _decompress;
			delete _error;
			return;
		}

		jpeg_mem_src(_decompress, const_cast<uint8_t*>(data), size);

		if (jpeg_read_header(_decompress, (bool) TRUE) != JPEG_HEADER_OK)
		{
			jpeg_abort_decompress(_decompress);
			jpeg_destroy_decompress(_decompress);
			delete _decompress;
			delete _error;
			return;
		}

		_decompress->scale_num = 1;
		_decompress->scale_denom = 1;
		_decompress->out_color_space = JCS_RGB;
		_decompress->dct_method = JDCT_IFAST;

		if (!jpeg_start_decompress(_decompress))
		{
			jpeg_abort_decompress(_decompress);
			jpeg_destroy_decompress(_decompress);
			delete _decompress;
			delete _error;
			return;
		}

		if (_decompress->out_color_components != 3)
		{
			jpeg_abort_decompress(_decompress);
			jpeg_destroy_decompress(_decompress);
			delete _decompress;
			delete _error;
			return;
		}

		QImage imageFrame = QImage(_decompress->output_width, _decompress->output_height, QImage::Format_RGB888);

		int y = 0;
		while (_decompress->output_scanline < _decompress->output_height)
		{
			uchar *row = imageFrame.scanLine(_decompress->output_scanline);
			jpeg_read_scanlines(_decompress, &row, 1);
			y++;
		}

		jpeg_finish_decompress(_decompress);
		jpeg_destroy_decompress(_decompress);
		delete _decompress;
		delete _error;

		if (imageFrame.isNull() || _error->pub.num_warnings > 0)
			return;
#endif
#ifdef HAVE_TURBO_JPEG
		_decompress = tjInitDecompress();
		if (_decompress == nullptr)
			return;

		if (tjDecompressHeader2(_decompress, const_cast<uint8_t*>(data), size, &_width, &_height, &_subsamp) != 0)
		{
			tjDestroy(_decompress);
			return;
		}

		QImage imageFrame = QImage(_width, _height, QImage::Format_RGB888);
		if (tjDecompress2(_decompress, const_cast<uint8_t*>(data), size, imageFrame.bits(), _width, 0, _height, TJPF_RGB, TJFLAG_FASTDCT | TJFLAG_FASTUPSAMPLE) != 0)
		{
			tjDestroy(_decompress);
			return;
		}

		tjDestroy(_decompress);

		if (imageFrame.isNull())
			return;
#endif
#ifdef HAVE_JPEG_DECODER
		QRect rect(_cropLeft, _cropTop, imageFrame.width() - _cropLeft - _cropRight, imageFrame.height() - _cropTop - _cropBottom);
		imageFrame = imageFrame.copy(rect);
		imageFrame = imageFrame.scaled(imageFrame.width() / _pixelDecimation, imageFrame.height() / _pixelDecimation,Qt::KeepAspectRatio);

		if ((image.width() != unsigned(imageFrame.width())) || (image.height() != unsigned(imageFrame.height())))
			image.resize(imageFrame.width(), imageFrame.height());

		for (int y=0; y<imageFrame.height(); ++y)
			for (int x=0; x<imageFrame.width(); ++x)
			{
				QColor inPixel(imageFrame.pixel(x,y));
				ColorRgb & outPixel = image(x,y);
				outPixel.red   = inPixel.red();
				outPixel.green = inPixel.green();
				outPixel.blue  = inPixel.blue();
			}
	}
	else
#endif

/* ----------------------------------------------------------
 * ------------ END of JPEG decoder related code ------------
 * --------------------------------------------------------*/

		_imageResampler.processImage(data, _width, _height, _lineLength, _pixelFormat, image);

	if (_signalDetectionEnabled)
	{
		// check signal (only in center of the resulting image, because some grabbers have noise values along the borders)
		bool noSignal = true;

		// top left
		unsigned xOffset  = image.width()  * _x_frac_min;
		unsigned yOffset  = image.height() * _y_frac_min;

		// bottom right
		unsigned xMax     = image.width()  * _x_frac_max;
		unsigned yMax     = image.height() * _y_frac_max;


		for (unsigned x = xOffset; noSignal && x < xMax; ++x)
		{
			for (unsigned y = yOffset; noSignal && y < yMax; ++y)
			{
				noSignal &= (ColorRgb&)image(x, y) <= _noSignalThresholdColor;
			}
		}

		if (noSignal)
		{
			++_noSignalCounter;
		}
		else
		{
			if (_noSignalCounter >= _noSignalCounterThreshold)
			{
				_noSignalDetected = true;
				Info(_log, "Signal detected");
			}

			_noSignalCounter = 0;
		}

		if ( _noSignalCounter < _noSignalCounterThreshold)
		{
			emit newFrame(image);
		}
		else if (_noSignalCounter == _noSignalCounterThreshold)
		{
			_noSignalDetected = false;
			Info(_log, "Signal lost");
		}
	}
	else
	{
		emit newFrame(image);
	}
}

int V4L2Grabber::xioctl(int request, void *arg)
{
	int r;

	do
	{
		r = ioctl(_fileDescriptor, request, arg);
	}
	while (-1 == r && EINTR == errno);

	return r;
}

void V4L2Grabber::setSignalDetectionEnable(bool enable)
{
	if (_signalDetectionEnabled != enable)
	{
		_signalDetectionEnabled = enable;
		Info(_log, "Signal detection is now %s", enable ? "enabled" : "disabled");
	}
}

void V4L2Grabber::setPixelDecimation(int pixelDecimation)
{
	if (_pixelDecimation != pixelDecimation)
	{
		_pixelDecimation = pixelDecimation;
		_imageResampler.setHorizontalPixelDecimation(pixelDecimation);
		_imageResampler.setVerticalPixelDecimation(pixelDecimation);
	}
}

void V4L2Grabber::setDeviceVideoStandard(QString device, VideoStandard videoStandard)
{
	if (_deviceName != device || _videoStandard != videoStandard)
	{
		// extract input of device
		QChar input = device.at(device.size() - 1);
		_input = input.isNumber() ? input.digitValue() : -1;

		bool started = _initialized;
		uninit();
		_deviceName = device;
		_videoStandard = videoStandard;

		if(started) start();
	}
}

bool V4L2Grabber::setFramerate(int fps)
{
	if(Grabber::setFramerate(fps))
	{
		bool started = _initialized;
		uninit();
		if(started) start();
		return true;
	}
	return false;
}

bool V4L2Grabber::setWidthHeight(int width, int height)
{
	if(Grabber::setWidthHeight(width,height))
	{
		bool started = _initialized;
		uninit();
		if(started) start();
		return true;
	}
	return false;
}