third_party/v4l2capture/v4l2capture.c

// python-v4l2capture
// Python extension to capture video with video4linux2
//
// 2009, 2010, 2011 Fredrik Portstrom
//
// I, the copyright holder of this file, hereby release it into the
// public domain. This applies worldwide. In case this is not legally
// possible: I grant anyone the right to use this work for any
// purpose, without any conditions, unless such conditions are
// required by law.

#include <Python.h>
#include <fcntl.h>
#include <linux/videodev2.h>
#include <sys/mman.h>

// LIBV4L is not needed for MJPEG capture.
#undef USE_LIBV4L

#ifdef USE_LIBV4L
#include <libv4l2.h>
#else
#include <sys/ioctl.h>
#define v4l2_close close
#define v4l2_ioctl ioctl
#define v4l2_mmap mmap
#define v4l2_munmap munmap
#define v4l2_open open
#endif

#define ASSERT_OPEN if(self->fd < 0)                                    \
    {                                                                   \
      PyErr_SetString(PyExc_ValueError,                                 \
          "I/O operation on closed file");                              \
      return NULL;                                                      \
    }

struct buffer {
  void *start;
  size_t length;
};

typedef struct {
  PyObject_HEAD
  int fd;
  struct buffer *buffers;
  int buffer_count;
} Video_device;

struct capability {
  int id;
  const char *name;
};

static struct capability capabilities[] = {
  { V4L2_CAP_ASYNCIO, "asyncio" },
  { V4L2_CAP_AUDIO, "audio" },
  { V4L2_CAP_HW_FREQ_SEEK, "hw_freq_seek" },
  { V4L2_CAP_RADIO, "radio" },
  { V4L2_CAP_RDS_CAPTURE, "rds_capture" },
  { V4L2_CAP_READWRITE, "readwrite" },
  { V4L2_CAP_SLICED_VBI_CAPTURE, "sliced_vbi_capture" },
  { V4L2_CAP_SLICED_VBI_OUTPUT, "sliced_vbi_output" },
  { V4L2_CAP_STREAMING, "streaming" },
  { V4L2_CAP_TUNER, "tuner" },
  { V4L2_CAP_VBI_CAPTURE, "vbi_capture" },
  { V4L2_CAP_VBI_OUTPUT, "vbi_output" },
  { V4L2_CAP_VIDEO_CAPTURE, "video_capture" },
  { V4L2_CAP_VIDEO_OUTPUT, "video_output" },
  { V4L2_CAP_VIDEO_OUTPUT_OVERLAY, "video_output_overlay" },
  { V4L2_CAP_VIDEO_OVERLAY, "video_overlay" }
};

static int my_ioctl(int fd, int request, void *arg)
{
  // Retry ioctl until it returns without being interrupted.

  for(;;)
    {
      int result = v4l2_ioctl(fd, request, arg);

      if(!result)
        {
          return 0;
        }

      if(errno != EINTR)
        {
          PyErr_SetFromErrno(PyExc_IOError);
          return 1;
        }
    }
}

static void Video_device_unmap(Video_device *self)
{
  int i;

  for(i = 0; i < self->buffer_count; i++)
    {
      v4l2_munmap(self->buffers[i].start, self->buffers[i].length);
    }
  free(self->buffers);
  self->buffers = NULL;
}

static void Video_device_dealloc(Video_device *self)
{
  if(self->fd >= 0)
    {
      if(self->buffers)
        {
          Video_device_unmap(self);
        }

      v4l2_close(self->fd);
    }

  self->ob_type->tp_free((PyObject *)self);
}

static int Video_device_init(Video_device *self, PyObject *args,
    PyObject *kwargs)
{
  const char *device_path;

  if(!PyArg_ParseTuple(args, "s", &device_path))
    {
      return -1;
    }

  int fd = v4l2_open(device_path, O_RDWR | O_NONBLOCK);

  if(fd < 0)
    {
      PyErr_SetFromErrnoWithFilename(PyExc_IOError, (char *)device_path);
      return -1;
    }

  self->fd = fd;
  self->buffers = NULL;
  self->buffer_count = 0;
  return 0;
}

static PyObject *Video_device_close(Video_device *self)
{
  if(self->fd >= 0)
    {
      if(self->buffers)
        {
          Video_device_unmap(self);
        }

      v4l2_close(self->fd);
      self->fd = -1;
    }

  Py_RETURN_NONE;
}

static PyObject *Video_device_fileno(Video_device *self)
{
  ASSERT_OPEN;
  return PyInt_FromLong(self->fd);
}

static PyObject *Video_device_get_info(Video_device *self)
{
  ASSERT_OPEN;
  struct v4l2_capability caps;

  if(my_ioctl(self->fd, VIDIOC_QUERYCAP, &caps))
    {
      return NULL;
    }

  PyObject *set = PySet_New(NULL);

  if(!set)
    {
      return NULL;
    }

  struct capability *capability = capabilities;

  while((void *)capability < (void *)capabilities + sizeof(capabilities))
    {
      if(caps.capabilities & capability->id)
        {
          PyObject *s = PyString_FromString(capability->name);

          if(!s)
            {
              Py_DECREF(set);
              return NULL;
            }

          PySet_Add(set, s);
        }

      capability++;
    }

  return Py_BuildValue("sssO", caps.driver, caps.card, caps.bus_info, set);
}

static PyObject *Video_device_set_format(Video_device *self, PyObject *args)
{
  int size_x;
  int size_y;
  if(!PyArg_ParseTuple(args, "ii", &size_x, &size_y))
    {
      return NULL;
    }

  struct v4l2_format format;
  format.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  format.fmt.pix.width = size_x;
  format.fmt.pix.height = size_y;
  format.fmt.pix.pixelformat = V4L2_PIX_FMT_MJPEG;
  format.fmt.pix.field = V4L2_FIELD_NONE;
  format.fmt.pix.bytesperline = 0;

  if(my_ioctl(self->fd, VIDIOC_S_FMT, &format))
    {
      return NULL;
    }

  return Py_BuildValue("ii", format.fmt.pix.width, format.fmt.pix.height);
}

static PyObject *Video_device_set_fps(Video_device *self, PyObject *args)
{
  int fps;
  if(!PyArg_ParseTuple(args, "i", &fps))
    {
      return NULL;
    }
  struct v4l2_streamparm setfps;
  memset(&setfps, 0, sizeof(struct v4l2_streamparm));
  setfps.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  setfps.parm.capture.timeperframe.numerator = 1;
  setfps.parm.capture.timeperframe.denominator = fps;
  if(my_ioctl(self->fd, VIDIOC_S_PARM, &setfps)){
        return NULL;
  }
  return Py_BuildValue("i",setfps.parm.capture.timeperframe.denominator);
}

static PyObject *Video_device_start(Video_device *self)
{
  ASSERT_OPEN;
  enum v4l2_buf_type type;
  type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

  if(my_ioctl(self->fd, VIDIOC_STREAMON, &type))
    {
      return NULL;
    }

  Py_RETURN_NONE;
}

static PyObject *Video_device_stop(Video_device *self)
{
  ASSERT_OPEN;
  enum v4l2_buf_type type;
  type = V4L2_BUF_TYPE_VIDEO_CAPTURE;

  if(my_ioctl(self->fd, VIDIOC_STREAMOFF, &type))
    {
      return NULL;
    }

  Py_RETURN_NONE;
}

static PyObject *Video_device_create_buffers(Video_device *self, PyObject *args)
{
  int buffer_count;

  if(!PyArg_ParseTuple(args, "I", &buffer_count))
    {
      return NULL;
    }

  ASSERT_OPEN;

  if(self->buffers)
    {
      PyErr_SetString(PyExc_ValueError, "Buffers are already created");
      return NULL;
    }

  struct v4l2_requestbuffers reqbuf;
  reqbuf.count = buffer_count;
  reqbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  reqbuf.memory = V4L2_MEMORY_MMAP;

  if(my_ioctl(self->fd, VIDIOC_REQBUFS, &reqbuf))
    {
      return NULL;
    }

  if(!reqbuf.count)
    {
      PyErr_SetString(PyExc_IOError, "Not enough buffer memory");
      return NULL;
    }

  self->buffers = malloc(reqbuf.count * sizeof(struct buffer));

  if(!self->buffers)
    {
      PyErr_NoMemory();
      return NULL;
    }

  int i;

  for(i = 0; i < reqbuf.count; i++)
    {
      struct v4l2_buffer buffer;
      buffer.index = i;
      buffer.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
      buffer.memory = V4L2_MEMORY_MMAP;

      if(my_ioctl(self->fd, VIDIOC_QUERYBUF, &buffer))
        {
          return NULL;
        }

      self->buffers[i].length = buffer.length;
      self->buffers[i].start = v4l2_mmap(NULL, buffer.length,
          PROT_READ | PROT_WRITE, MAP_SHARED, self->fd, buffer.m.offset);

      if(self->buffers[i].start == MAP_FAILED)
        {
          PyErr_SetFromErrno(PyExc_IOError);
          Video_device_unmap(self);
          return NULL;
        }
      ++self->buffer_count;
    }

  Py_RETURN_NONE;
}

static PyObject *Video_device_queue_all_buffers(Video_device *self)
{
  if(!self->buffers)
    {
      ASSERT_OPEN;
      PyErr_SetString(PyExc_ValueError, "Buffers have not been created");
      return NULL;
    }

  int i;
  int buffer_count = self->buffer_count;

  for(i = 0; i < buffer_count; i++)
    {
      struct v4l2_buffer buffer;
      buffer.index = i;
      buffer.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
      buffer.memory = V4L2_MEMORY_MMAP;

      if(my_ioctl(self->fd, VIDIOC_QBUF, &buffer))
        {
          return NULL;
        }
    }

  Py_RETURN_NONE;
}

static PyObject *Video_device_read_internal(Video_device *self, int queue)
{
  if(!self->buffers)
    {
      ASSERT_OPEN;
      PyErr_SetString(PyExc_ValueError, "Buffers have not been created");
      return NULL;
    }

  struct v4l2_buffer buffer;
  buffer.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  buffer.memory = V4L2_MEMORY_MMAP;

  if(my_ioctl(self->fd, VIDIOC_DQBUF, &buffer))
    {
      return NULL;
    }

  PyObject *result = PyString_FromStringAndSize(
      self->buffers[buffer.index].start, buffer.bytesused);

  if(!result)
    {
      return NULL;
    }

  if(queue && my_ioctl(self->fd, VIDIOC_QBUF, &buffer))
    {
      return NULL;
    }

  return result;
}

static PyObject *Video_device_read(Video_device *self)
{
  return Video_device_read_internal(self, 0);
}

static PyObject *Video_device_read_and_queue(Video_device *self)
{
  return Video_device_read_internal(self, 1);
}

static PyMethodDef Video_device_methods[] = {
  {"close", (PyCFunction)Video_device_close, METH_NOARGS,
       "close()\n\n"
       "Close video device. Subsequent calls to other methods will fail."},
  {"fileno", (PyCFunction)Video_device_fileno, METH_NOARGS,
       "fileno() -> integer \"file descriptor\".\n\n"
       "This enables video devices to be passed select.select for waiting "
       "until a frame is available for reading."},
  {"get_info", (PyCFunction)Video_device_get_info, METH_NOARGS,
       "get_info() -> driver, card, bus_info, capabilities\n\n"
       "Returns three strings with information about the video device, and one "
       "set containing strings identifying the capabilities of the video "
       "device."},
  {"set_format", (PyCFunction)Video_device_set_format, METH_VARARGS,
       "set_format(size_x, size_y) -> size_x, size_y\n\n"
       "Request the video device to set image size and format. The device may "
       "choose another size than requested and will return its choice. The "
       "image format will be MJPEG."},
  {"set_fps", (PyCFunction)Video_device_set_fps, METH_VARARGS,
       "set_fps(fps) -> fps \n\n"
       "Request the video device to set frame per seconds.The device may "
       "choose another frame rate than requested and will return its choice. " },
  {"start", (PyCFunction)Video_device_start, METH_NOARGS,
       "start()\n\n"
       "Start video capture."},
  {"stop", (PyCFunction)Video_device_stop, METH_NOARGS,
       "stop()\n\n"
       "Stop video capture."},
  {"create_buffers", (PyCFunction)Video_device_create_buffers, METH_VARARGS,
       "create_buffers(count)\n\n"
       "Create buffers used for capturing image data. Can only be called once "
       "for each video device object."},
  {"queue_all_buffers", (PyCFunction)Video_device_queue_all_buffers,
       METH_NOARGS,
       "queue_all_buffers()\n\n"
       "Let the video device fill all buffers created."},
  {"read", (PyCFunction)Video_device_read, METH_NOARGS,
       "read() -> string\n\n"
       "Reads image data from a buffer that has been filled by the video "
       "device. The image data is in MJPEG format. "
       "The buffer is removed from the queue. Fails if no buffer "
       "is filled. Use select.select to check for filled buffers."},
  {"read_and_queue", (PyCFunction)Video_device_read_and_queue, METH_NOARGS,
       "read_and_queue()\n\n"
       "Same as 'read', but adds the buffer back to the queue so the video "
       "device can fill it again."},
  {NULL}
};

static PyTypeObject Video_device_type = {
  PyObject_HEAD_INIT(NULL)
      0, "v4l2capture.Video_device", sizeof(Video_device), 0,
      (destructor)Video_device_dealloc, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, Py_TPFLAGS_DEFAULT, "Video_device(path)\n\nOpens the video device at "
      "the given path and returns an object that can capture images. The "
      "constructor and all methods except close may raise IOError.", 0, 0, 0,
      0, 0, 0, Video_device_methods, 0, 0, 0, 0, 0, 0, 0,
      (initproc)Video_device_init
};

static PyMethodDef module_methods[] = {
  {NULL}
};

PyMODINIT_FUNC initv4l2capture(void)
{
  Video_device_type.tp_new = PyType_GenericNew;

  if(PyType_Ready(&Video_device_type) < 0)
    {
      return;
    }

  PyObject *module = Py_InitModule3("v4l2capture", module_methods,
      "Capture video with video4linux2.");

  if(!module)
    {
      return;
    }

  Py_INCREF(&Video_device_type);
  PyModule_AddObject(module, "Video_device", (PyObject *)&Video_device_type);
}