7e4bc6d418
With GST_V4L2_USE_LIBV4L2=1, my laptop's touchpad shows up as a video
source device in gst-device-monitor, but attempting to stream from it
fails because the device doesn't actually support any video formats.
name : Synaptics RMI4 Touch Sensor
class : Video/Source
caps : video/x-raw, format=(string)I420, framerate=(fraction)[ 0/1, 2147483647/1 ], width=(int)0, height=(int)0, interlace-mode=(string)progressive, pixel-aspect-ratio=(fraction)1/1;
video/x-raw, format=(string)YV12, framerate=(fraction)[ 0/1, 2147483647/1 ], width=(int)0, height=(int)0, interlace-mode=(string)progressive, pixel-aspect-ratio=(fraction)1/1;
video/x-raw, format=(string)BGR, framerate=(fraction)[ 0/1, 2147483647/1 ], width=(int)0, height=(int)0, interlace-mode=(string)progressive, pixel-aspect-ratio=(fraction)1/1;
video/x-raw, format=(string)RGB, framerate=(fraction)[ 0/1, 2147483647/1 ], width=(int)0, height=(int)0, interlace-mode=(string)progressive, pixel-aspect-ratio=(fraction)1/1;
properties:
udev-probed = true
device.bus_path = /sys/devices/rmi4-00/rmi4-00.fn54/video4linux/v4l-touch0
sysfs.path = /sys/devices/rmi4-00/rmi4-00.fn54/video4linux/v4l-touch0
device.subsystem = video4linux
device.product.name = "Synaptics\ RMI4\ Touch\ Sensor"
device.capabilities = :capture:
device.api = v4l2
device.path = /dev/v4l-touch0
v4l2.device.driver = rmi4_f54
v4l2.device.card = "Synaptics\ RMI4\ Touch\ Sensor"
v4l2.device.bus_info = rmi4:rmi4-00.fn54
v4l2.device.version = 265480 (0x00040d08)
v4l2.device.capabilities = 2501902337 (0x95200001)
v4l2.device.device_caps = 354418689 (0x15200001)
gst-launch-1.0 v4l2src device=/dev/v4l-touch0 ! ...
v4l2-ctl -d /dev/v4l-touch0 --list-formats reports:
ioctl: VIDIOC_ENUM_FMT
Index : 0
Type : Video Capture
Pixel Format: 'TD16'
Name : 16-bit signed deltas
Index : 1
Type : Video Capture
Pixel Format: 'TD08'
Name : 8-bit signed deltas
Index : 2
Type : Video Capture
Pixel Format: 'TU16'
Name : 16-bit unsigned touch data
https://bugzilla.gnome.org/show_bug.cgi?id=789197
v4l2 plugins
============
The idea is a bit the same as the idea for the v4l1 plugins. We want
one generic v4l2element, and a few child objects (probably only two:
v4l2src and v4l2sink):
/-------- v4l2src
v4l2element ---=
\-------- v4l2sink
Both v4l2src and v4l2sink have a uncompressed and a compressed
recording-/playback-mode. Since this is all part of v4l2, the 'client'
of these elements, i.e. an application using v4l2src/v4l2sink, will
hardly notice this. All capsnego stuff is done inside, and the plugin
knows which formats are compressed and which are not.
Please note that the v4l1 and the v4l2 plugins are *not* compatible
concerning properties. Naming has been kept the same where possible,
but in some cases, properties had to be removed or added to make
full use of v4l2.
V4L2 API: http://linux.bytesex.org/v4l2/.
http://v4l2spec.bytesex.org/
/usr/include/linux/videodev2.h or
Kernel patches available from
http://dl.bytesex.org/patches/.
Articles:
http://lwn.net/Articles/203924/