mirror of https://github.com/Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
159 lines
6.8 KiB
159 lines
6.8 KiB
.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later |
|
|
|
.. _dv-controls: |
|
|
|
******************************* |
|
Digital Video Control Reference |
|
******************************* |
|
|
|
The Digital Video control class is intended to control receivers and |
|
transmitters for `VGA <http://en.wikipedia.org/wiki/Vga>`__, |
|
`DVI <http://en.wikipedia.org/wiki/Digital_Visual_Interface>`__ |
|
(Digital Visual Interface), HDMI (:ref:`hdmi`) and DisplayPort |
|
(:ref:`dp`). These controls are generally expected to be private to |
|
the receiver or transmitter subdevice that implements them, so they are |
|
only exposed on the ``/dev/v4l-subdev*`` device node. |
|
|
|
.. note:: |
|
|
|
Note that these devices can have multiple input or output pads which are |
|
hooked up to e.g. HDMI connectors. Even though the subdevice will |
|
receive or transmit video from/to only one of those pads, the other pads |
|
can still be active when it comes to EDID (Extended Display |
|
Identification Data, :ref:`vesaedid`) and HDCP (High-bandwidth Digital |
|
Content Protection System, :ref:`hdcp`) processing, allowing the |
|
device to do the fairly slow EDID/HDCP handling in advance. This allows |
|
for quick switching between connectors. |
|
|
|
These pads appear in several of the controls in this section as |
|
bitmasks, one bit for each pad. Bit 0 corresponds to pad 0, bit 1 to pad |
|
1, etc. The maximum value of the control is the set of valid pads. |
|
|
|
|
|
.. _dv-control-id: |
|
|
|
Digital Video Control IDs |
|
========================= |
|
|
|
``V4L2_CID_DV_CLASS (class)`` |
|
The Digital Video class descriptor. |
|
|
|
``V4L2_CID_DV_TX_HOTPLUG (bitmask)`` |
|
Many connectors have a hotplug pin which is high if EDID information |
|
is available from the source. This control shows the state of the |
|
hotplug pin as seen by the transmitter. Each bit corresponds to an |
|
output pad on the transmitter. If an output pad does not have an |
|
associated hotplug pin, then the bit for that pad will be 0. This |
|
read-only control is applicable to DVI-D, HDMI and DisplayPort |
|
connectors. |
|
|
|
``V4L2_CID_DV_TX_RXSENSE (bitmask)`` |
|
Rx Sense is the detection of pull-ups on the TMDS clock lines. This |
|
normally means that the sink has left/entered standby (i.e. the |
|
transmitter can sense that the receiver is ready to receive video). |
|
Each bit corresponds to an output pad on the transmitter. If an |
|
output pad does not have an associated Rx Sense, then the bit for |
|
that pad will be 0. This read-only control is applicable to DVI-D |
|
and HDMI devices. |
|
|
|
``V4L2_CID_DV_TX_EDID_PRESENT (bitmask)`` |
|
When the transmitter sees the hotplug signal from the receiver it |
|
will attempt to read the EDID. If set, then the transmitter has read |
|
at least the first block (= 128 bytes). Each bit corresponds to an |
|
output pad on the transmitter. If an output pad does not support |
|
EDIDs, then the bit for that pad will be 0. This read-only control |
|
is applicable to VGA, DVI-A/D, HDMI and DisplayPort connectors. |
|
|
|
``V4L2_CID_DV_TX_MODE`` |
|
(enum) |
|
|
|
enum v4l2_dv_tx_mode - |
|
HDMI transmitters can transmit in DVI-D mode (just video) or in HDMI |
|
mode (video + audio + auxiliary data). This control selects which |
|
mode to use: V4L2_DV_TX_MODE_DVI_D or V4L2_DV_TX_MODE_HDMI. |
|
This control is applicable to HDMI connectors. |
|
|
|
``V4L2_CID_DV_TX_RGB_RANGE`` |
|
(enum) |
|
|
|
enum v4l2_dv_rgb_range - |
|
Select the quantization range for RGB output. V4L2_DV_RANGE_AUTO |
|
follows the RGB quantization range specified in the standard for the |
|
video interface (ie. :ref:`cea861` for HDMI). |
|
V4L2_DV_RANGE_LIMITED and V4L2_DV_RANGE_FULL override the |
|
standard to be compatible with sinks that have not implemented the |
|
standard correctly (unfortunately quite common for HDMI and DVI-D). |
|
Full range allows all possible values to be used whereas limited |
|
range sets the range to (16 << (N-8)) - (235 << (N-8)) where N is |
|
the number of bits per component. This control is applicable to VGA, |
|
DVI-A/D, HDMI and DisplayPort connectors. |
|
|
|
``V4L2_CID_DV_TX_IT_CONTENT_TYPE`` |
|
(enum) |
|
|
|
enum v4l2_dv_it_content_type - |
|
Configures the IT Content Type of the transmitted video. This |
|
information is sent over HDMI and DisplayPort connectors as part of |
|
the AVI InfoFrame. The term 'IT Content' is used for content that |
|
originates from a computer as opposed to content from a TV broadcast |
|
or an analog source. The enum v4l2_dv_it_content_type defines |
|
the possible content types: |
|
|
|
.. tabularcolumns:: |p{7.3cm}|p{10.2cm}| |
|
|
|
.. flat-table:: |
|
:header-rows: 0 |
|
:stub-columns: 0 |
|
|
|
* - ``V4L2_DV_IT_CONTENT_TYPE_GRAPHICS`` |
|
- Graphics content. Pixel data should be passed unfiltered and |
|
without analog reconstruction. |
|
* - ``V4L2_DV_IT_CONTENT_TYPE_PHOTO`` |
|
- Photo content. The content is derived from digital still pictures. |
|
The content should be passed through with minimal scaling and |
|
picture enhancements. |
|
* - ``V4L2_DV_IT_CONTENT_TYPE_CINEMA`` |
|
- Cinema content. |
|
* - ``V4L2_DV_IT_CONTENT_TYPE_GAME`` |
|
- Game content. Audio and video latency should be minimized. |
|
* - ``V4L2_DV_IT_CONTENT_TYPE_NO_ITC`` |
|
- No IT Content information is available and the ITC bit in the AVI |
|
InfoFrame is set to 0. |
|
|
|
|
|
|
|
``V4L2_CID_DV_RX_POWER_PRESENT (bitmask)`` |
|
Detects whether the receiver receives power from the source (e.g. |
|
HDMI carries 5V on one of the pins). This is often used to power an |
|
eeprom which contains EDID information, such that the source can |
|
read the EDID even if the sink is in standby/power off. Each bit |
|
corresponds to an input pad on the receiver. If an input pad |
|
cannot detect whether power is present, then the bit for that pad |
|
will be 0. This read-only control is applicable to DVI-D, HDMI and |
|
DisplayPort connectors. |
|
|
|
``V4L2_CID_DV_RX_RGB_RANGE`` |
|
(enum) |
|
|
|
enum v4l2_dv_rgb_range - |
|
Select the quantization range for RGB input. V4L2_DV_RANGE_AUTO |
|
follows the RGB quantization range specified in the standard for the |
|
video interface (ie. :ref:`cea861` for HDMI). |
|
V4L2_DV_RANGE_LIMITED and V4L2_DV_RANGE_FULL override the |
|
standard to be compatible with sources that have not implemented the |
|
standard correctly (unfortunately quite common for HDMI and DVI-D). |
|
Full range allows all possible values to be used whereas limited |
|
range sets the range to (16 << (N-8)) - (235 << (N-8)) where N is |
|
the number of bits per component. This control is applicable to VGA, |
|
DVI-A/D, HDMI and DisplayPort connectors. |
|
|
|
``V4L2_CID_DV_RX_IT_CONTENT_TYPE`` |
|
(enum) |
|
|
|
enum v4l2_dv_it_content_type - |
|
Reads the IT Content Type of the received video. This information is |
|
sent over HDMI and DisplayPort connectors as part of the AVI |
|
InfoFrame. The term 'IT Content' is used for content that originates |
|
from a computer as opposed to content from a TV broadcast or an |
|
analog source. See ``V4L2_CID_DV_TX_IT_CONTENT_TYPE`` for the |
|
available content types.
|
|
|