€•JŒsphinx.addnodes”Œdocument”“”)”}”(Œ rawsource”Œ”Œchildren”]”(Œtranslations”Œ LanguagesNode”“”)”}”(hhh]”(hŒpending_xref”“”)”}”(hhh]”Œdocutils.nodes”ŒText”“”ŒChinese (Simplified)”…””}”Œparent”hsbaŒ attributes”}”(Œids”]”Œclasses”]”Œnames”]”Œdupnames”]”Œbackrefs”]”Œ refdomain”Œstd”Œreftype”Œdoc”Œ reftarget”Œ7/translations/zh_CN/userspace-api/media/v4l/dev-overlay”Œmodname”NŒ classname”NŒrefexplicit”ˆuŒtagname”hhhubh)”}”(hhh]”hŒChinese (Traditional)”…””}”hh2sbah}”(h]”h ]”h"]”h$]”h&]”Œ refdomain”h)Œreftype”h+Œ reftarget”Œ7/translations/zh_TW/userspace-api/media/v4l/dev-overlay”Œmodname”NŒ classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ refdomain”h)Œreftype”h+Œ reftarget”Œ7/translations/it_IT/userspace-api/media/v4l/dev-overlay”Œmodname”NŒ classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ refdomain”h)Œreftype”h+Œ reftarget”Œ7/translations/ja_JP/userspace-api/media/v4l/dev-overlay”Œmodname”NŒ classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ refdomain”h)Œreftype”h+Œ reftarget”Œ7/translations/ko_KR/userspace-api/media/v4l/dev-overlay”Œmodname”NŒ classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ refdomain”h)Œreftype”h+Œ reftarget”Œ7/translations/sp_SP/userspace-api/media/v4l/dev-overlay”Œmodname”NŒ classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h hhŒ _document”hŒsource”NŒline”NubhŒcomment”“”)”}”(hŒ8SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later”h]”hŒ8SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later”…””}”hh£sbah}”(h]”h ]”h"]”h$]”h&]”Œ xml:space”Œpreserve”uh1h¡hhhžhhŸŒQ/var/lib/git/docbuild/linux/Documentation/userspace-api/media/v4l/dev-overlay.rst”h KubhŒtarget”“”)”}”(hŒ.. _overlay:”h]”h}”(h]”h ]”h"]”h$]”h&]”Œrefid”Œoverlay”uh1h´h KhhhžhhŸh³ubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒVideo Overlay Interface”h]”hŒVideo Overlay Interface”…””}”(hhÉhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÇhhÄhžhhŸh³h KubhŒ paragraph”“”)”}”(hŒ4**Also known as Framebuffer Overlay or Previewing.**”h]”hŒstrong”“”)”}”(hhÛh]”hŒ0Also known as Framebuffer Overlay or Previewing.”…””}”(hhßhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÝhhÙubah}”(h]”h ]”h"]”h$]”h&]”uh1h×hŸh³h K hhÄhžhubhØ)”}”(hX³Video overlay devices have the ability to genlock (TV-)video into the (VGA-)video signal of a graphics card, or to store captured images directly in video memory of a graphics card, typically with clipping. This can be considerable more efficient than capturing images and displaying them by other means. In the old days when only nuclear power plants needed cooling towers this used to be the only way to put live video into a window.”h]”hX³Video overlay devices have the ability to genlock (TV-)video into the (VGA-)video signal of a graphics card, or to store captured images directly in video memory of a graphics card, typically with clipping. This can be considerable more efficient than capturing images and displaying them by other means. In the old days when only nuclear power plants needed cooling towers this used to be the only way to put live video into a window.”…””}”(hhòhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h×hŸh³h KhhÄhžhubhØ)”}”(hŒvVideo overlay devices are accessed through the same character special files as :ref:`video capture ` devices.”h]”(hŒOVideo overlay devices are accessed through the same character special files as ”…””}”(hjhžhhŸNh Nubh)”}”(hŒ:ref:`video capture `”h]”hŒinline”“”)”}”(hj h]”hŒ video capture”…””}”(hjhžhhŸNh Nubah}”(h]”h ]”(Œxref”Œstd”Œstd-ref”eh"]”h$]”h&]”uh1jhjubah}”(h]”h ]”h"]”h$]”h&]”Œrefdoc”Œ#userspace-api/media/v4l/dev-overlay”Œ refdomain”jŒreftype”Œref”Œrefexplicit”ˆŒrefwarn”ˆŒ reftarget”Œcapture”uh1hhŸh³h KhjubhŒ devices.”…””}”(hjhžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h×hŸh³h KhhÄhžhubhŒnote”“”)”}”(hŒ¦The default function of a ``/dev/video`` device is video capturing. The overlay function is only available after calling the :ref:`VIDIOC_S_FMT ` ioctl.”h]”hØ)”}”(hŒ¦The default function of a ``/dev/video`` device is video capturing. The overlay function is only available after calling the :ref:`VIDIOC_S_FMT ` ioctl.”h]”(hŒThe default function of a ”…””}”(hj=hžhhŸNh NubhŒliteral”“”)”}”(hŒ``/dev/video``”h]”hŒ /dev/video”…””}”(hjGhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jEhj=ubhŒU device is video capturing. The overlay function is only available after calling the ”…””}”(hj=hžhhŸNh Nubh)”}”(hŒ":ref:`VIDIOC_S_FMT `”h]”j )”}”(hj[h]”hŒVIDIOC_S_FMT”…””}”(hj]hžhhŸNh Nubah}”(h]”h ]”(jŒstd”Œstd-ref”eh"]”h$]”h&]”uh1jhjYubah}”(h]”h ]”h"]”h$]”h&]”Œrefdoc”j%Œ refdomain”jgŒreftype”Œref”Œrefexplicit”ˆŒrefwarn”ˆj+Œvidioc_g_fmt”uh1hhŸh³h Khj=ubhŒ ioctl.”…””}”(hj=hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h×hŸh³h Khj9ubah}”(h]”h ]”h"]”h$]”h&]”uh1j7hhÄhžhhŸh³h NubhØ)”}”(hXXThe driver may support simultaneous overlay and capturing using the read/write and streaming I/O methods. If so, operation at the nominal frame rate of the video standard is not guaranteed. Frames may be directed away from overlay to capture, or one field may be used for overlay and the other for capture if the capture parameters permit this.”h]”hXXThe driver may support simultaneous overlay and capturing using the read/write and streaming I/O methods. If so, operation at the nominal frame rate of the video standard is not guaranteed. Frames may be directed away from overlay to capture, or one field may be used for overlay and the other for capture if the capture parameters permit this.”…””}”(hj‰hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h×hŸh³h KhhÄhžhubhØ)”}”(hX?Applications should use different file descriptors for capturing and overlay. This must be supported by all drivers capable of simultaneous capturing and overlay. Optionally these drivers may also permit capturing and overlay with a single file descriptor for compatibility with V4L and earlier versions of V4L2. [#f1]_”h]”(hX9Applications should use different file descriptors for capturing and overlay. This must be supported by all drivers capable of simultaneous capturing and overlay. Optionally these drivers may also permit capturing and overlay with a single file descriptor for compatibility with V4L and earlier versions of V4L2. ”…””}”(hj—hžhhŸNh NubhŒfootnote_reference”“”)”}”(hŒ[#f1]_”h]”hŒ1”…””}”(hj¡hžhhŸNh Nubah}”(h]”Œid1”ah ]”h"]”h$]”h&]”Œauto”KhÀŒf1”Œdocname”j%uh1jŸhj—Œresolved”Kubeh}”(h]”h ]”h"]”h$]”h&]”uh1h×hŸh³h K"hhÄhžhubhØ)”}”(hŒàA common application of two file descriptors is the X11 :ref:`Xv/V4L ` interface driver and a V4L2 application. While the X server controls video overlay, the application can take advantage of memory mapping and DMA.”h]”(hŒ8A common application of two file descriptors is the X11 ”…””}”(hjºhžhhŸNh Nubh)”}”(hŒ:ref:`Xv/V4L `”h]”j )”}”(hjÄh]”hŒXv/V4L”…””}”(hjÆhžhhŸNh Nubah}”(h]”h ]”(jŒstd”Œstd-ref”eh"]”h$]”h&]”uh1jhjÂubah}”(h]”h ]”h"]”h$]”h&]”Œrefdoc”j%Œ refdomain”jÐŒreftype”Œref”Œrefexplicit”ˆŒrefwarn”ˆj+Œxvideo”uh1hhŸh³h K(hjºubhŒ’ interface driver and a V4L2 application. While the X server controls video overlay, the application can take advantage of memory mapping and DMA.”…””}”(hjºhžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h×hŸh³h K(hhÄhžhubhÃ)”}”(hhh]”(hÈ)”}”(hŒQuerying Capabilities”h]”hŒQuerying Capabilities”…””}”(hjïhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÇhjìhžhhŸh³h K.ubhØ)”}”(hX&Devices supporting the video overlay interface set the ``V4L2_CAP_VIDEO_OVERLAY`` flag in the ``capabilities`` field of struct :c:type:`v4l2_capability` returned by the :ref:`VIDIOC_QUERYCAP` ioctl. The overlay I/O method specified below must be supported. Tuners and audio inputs are optional.”h]”(hŒ7Devices supporting the video overlay interface set the ”…””}”(hjýhžhhŸNh NubjF)”}”(hŒ``V4L2_CAP_VIDEO_OVERLAY``”h]”hŒV4L2_CAP_VIDEO_OVERLAY”…””}”(hjhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jEhjýubhŒ flag in the ”…””}”(hjýhžhhŸNh NubjF)”}”(hŒ``capabilities``”h]”hŒcapabilities”…””}”(hjhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jEhjýubhŒ field of struct ”…””}”(hjýhžhhŸNh Nubh)”}”(hŒ:c:type:`v4l2_capability`”h]”jF)”}”(hj+h]”hŒv4l2_capability”…””}”(hj-hžhhŸNh Nubah}”(h]”h ]”(jŒc”Œc-type”eh"]”h$]”h&]”uh1jEhj)ubah}”(h]”h ]”h"]”h$]”h&]”Œrefdoc”j%Œ refdomain”j7Œreftype”Œtype”Œrefexplicit”‰Œrefwarn”‰j+Œv4l2_capability”uh1hhŸh³h K0hjýubhŒ returned by the ”…””}”(hjýhžhhŸNh Nubh)”}”(hŒ:ref:`VIDIOC_QUERYCAP`”h]”j )”}”(hjOh]”hŒVIDIOC_QUERYCAP”…””}”(hjQhžhhŸNh Nubah}”(h]”h ]”(jŒstd”Œstd-ref”eh"]”h$]”h&]”uh1jhjMubah}”(h]”h ]”h"]”h$]”h&]”Œrefdoc”j%Œ refdomain”j[Œreftype”Œref”Œrefexplicit”‰Œrefwarn”ˆj+Œvidioc_querycap”uh1hhŸh³h K0hjýubhŒg ioctl. The overlay I/O method specified below must be supported. Tuners and audio inputs are optional.”…””}”(hjýhžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h×hŸh³h K0hjìhžhubeh}”(h]”Œquerying-capabilities”ah ]”h"]”Œquerying capabilities”ah$]”h&]”uh1hÂhhÄhžhhŸh³h K.ubhÃ)”}”(hhh]”(hÈ)”}”(hŒSupplemental Functions”h]”hŒSupplemental Functions”…””}”(hj‚hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÇhjhžhhŸh³h K9ubhØ)”}”(hXGVideo overlay devices shall support :ref:`audio input