The following V4L2 API elements are currently experimental and may change in the future.
Video Output Overlay (OSD) Interface, Section 4.4.
V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY,
enum v4l2_buf_type, Table 3-2.
V4L2_CAP_VIDEO_OUTPUT_OVERLAY,
VIDIOC_QUERYCAP ioctl, Table 2.
VIDIOC_ENUM_FRAMESIZES and
VIDIOC_ENUM_FRAMEINTERVALS ioctls.
VIDIOC_G_ENC_INDEX ioctl.
VIDIOC_ENCODER_CMD and VIDIOC_TRY_ENCODER_CMD
ioctls.
VIDIOC_DBG_G_REGISTER and VIDIOC_DBG_S_REGISTER
ioctls.
VIDIOC_G_CHIP_IDENT ioctl.