From 849369d6c66d3054688672f97d31fceb8e8230fb Mon Sep 17 00:00:00 2001 From: root Date: Fri, 25 Dec 2015 04:40:36 +0000 Subject: initial_commit --- Documentation/DocBook/v4l/controls.xml | 2103 ++++++++++++++++++++++++++++++++ 1 file changed, 2103 insertions(+) create mode 100644 Documentation/DocBook/v4l/controls.xml (limited to 'Documentation/DocBook/v4l/controls.xml') diff --git a/Documentation/DocBook/v4l/controls.xml b/Documentation/DocBook/v4l/controls.xml new file mode 100644 index 00000000..a920ee80 --- /dev/null +++ b/Documentation/DocBook/v4l/controls.xml @@ -0,0 +1,2103 @@ +
+ User Controls + + Devices typically have a number of user-settable controls +such as brightness, saturation and so on, which would be presented to +the user on a graphical user interface. But, different devices +will have different controls available, and furthermore, the range of +possible values, and the default value will vary from device to +device. The control ioctls provide the information and a mechanism to +create a nice user interface for these controls that will work +correctly with any device. + + All controls are accessed using an ID value. V4L2 defines +several IDs for specific purposes. Drivers can also implement their +own custom controls using V4L2_CID_PRIVATE_BASE +and higher values. The pre-defined control IDs have the prefix +V4L2_CID_, and are listed in . The ID is used when querying the attributes of +a control, and when getting or setting the current value. + + Generally applications should present controls to the user +without assumptions about their purpose. Each control comes with a +name string the user is supposed to understand. When the purpose is +non-intuitive the driver writer should provide a user manual, a user +interface plug-in or a driver specific panel application. Predefined +IDs were introduced to change a few controls programmatically, for +example to mute a device during a channel switch. + + Drivers may enumerate different controls after switching +the current video input or output, tuner or modulator, or audio input +or output. Different in the sense of other bounds, another default and +current value, step size or other menu items. A control with a certain +custom ID can also change name and +type. + It will be more convenient for applications if drivers +make use of the V4L2_CTRL_FLAG_DISABLED flag, but +that was never required. + Control values are stored globally, they do not +change when switching except to stay within the reported bounds. They +also do not change ⪚ when the device is opened or closed, when the +tuner radio frequency is changed or generally never without +application request. Since V4L2 specifies no event mechanism, panel +applications intended to cooperate with other panel applications (be +they built into a larger application, as a TV viewer) may need to +regularly poll control values to update their user +interface. + Applications could call an ioctl to request events. +After another process called &VIDIOC-S-CTRL; or another ioctl changing +shared properties the &func-select; function would indicate +readability until any ioctl (querying the properties) is +called. + + + + Control IDs + + &cs-def; + + + ID + Type + Description + + + + + V4L2_CID_BASE + + First predefined ID, equal to +V4L2_CID_BRIGHTNESS. + + + V4L2_CID_USER_BASE + + Synonym of V4L2_CID_BASE. + + + V4L2_CID_BRIGHTNESS + integer + Picture brightness, or more precisely, the black +level. + + + V4L2_CID_CONTRAST + integer + Picture contrast or luma gain. + + + V4L2_CID_SATURATION + integer + Picture color saturation or chroma gain. + + + V4L2_CID_HUE + integer + Hue or color balance. + + + V4L2_CID_AUDIO_VOLUME + integer + Overall audio volume. Note some drivers also +provide an OSS or ALSA mixer interface. + + + V4L2_CID_AUDIO_BALANCE + integer + Audio stereo balance. Minimum corresponds to all +the way left, maximum to right. + + + V4L2_CID_AUDIO_BASS + integer + Audio bass adjustment. + + + V4L2_CID_AUDIO_TREBLE + integer + Audio treble adjustment. + + + V4L2_CID_AUDIO_MUTE + boolean + Mute audio, &ie; set the volume to zero, however +without affecting V4L2_CID_AUDIO_VOLUME. Like +ALSA drivers, V4L2 drivers must mute at load time to avoid excessive +noise. Actually the entire device should be reset to a low power +consumption state. + + + V4L2_CID_AUDIO_LOUDNESS + boolean + Loudness mode (bass boost). + + + V4L2_CID_BLACK_LEVEL + integer + Another name for brightness (not a synonym of +V4L2_CID_BRIGHTNESS). This control is deprecated +and should not be used in new drivers and applications. + + + V4L2_CID_AUTO_WHITE_BALANCE + boolean + Automatic white balance (cameras). + + + V4L2_CID_DO_WHITE_BALANCE + button + This is an action control. When set (the value is +ignored), the device will do a white balance and then hold the current +setting. Contrast this with the boolean +V4L2_CID_AUTO_WHITE_BALANCE, which, when +activated, keeps adjusting the white balance. + + + V4L2_CID_RED_BALANCE + integer + Red chroma balance. + + + V4L2_CID_BLUE_BALANCE + integer + Blue chroma balance. + + + V4L2_CID_GAMMA + integer + Gamma adjust. + + + V4L2_CID_WHITENESS + integer + Whiteness for grey-scale devices. This is a synonym +for V4L2_CID_GAMMA. This control is deprecated +and should not be used in new drivers and applications. + + + V4L2_CID_EXPOSURE + integer + Exposure (cameras). [Unit?] + + + V4L2_CID_AUTOGAIN + boolean + Automatic gain/exposure control. + + + V4L2_CID_GAIN + integer + Gain control. + + + V4L2_CID_HFLIP + boolean + Mirror the picture horizontally. + + + V4L2_CID_VFLIP + boolean + Mirror the picture vertically. + + + V4L2_CID_HCENTER_DEPRECATED (formerly V4L2_CID_HCENTER) + integer + Horizontal image centering. This control is +deprecated. New drivers and applications should use the Camera class controls +V4L2_CID_PAN_ABSOLUTE, +V4L2_CID_PAN_RELATIVE and +V4L2_CID_PAN_RESET instead. + + + V4L2_CID_VCENTER_DEPRECATED + (formerly V4L2_CID_VCENTER) + integer + Vertical image centering. Centering is intended to +physically adjust cameras. For image cropping see +, for clipping . This +control is deprecated. New drivers and applications should use the +Camera class controls +V4L2_CID_TILT_ABSOLUTE, +V4L2_CID_TILT_RELATIVE and +V4L2_CID_TILT_RESET instead. + + + V4L2_CID_POWER_LINE_FREQUENCY + enum + Enables a power line frequency filter to avoid +flicker. Possible values for enum v4l2_power_line_frequency are: +V4L2_CID_POWER_LINE_FREQUENCY_DISABLED (0), +V4L2_CID_POWER_LINE_FREQUENCY_50HZ (1) and +V4L2_CID_POWER_LINE_FREQUENCY_60HZ (2). + + + V4L2_CID_HUE_AUTO + boolean + Enables automatic hue control by the device. The +effect of setting V4L2_CID_HUE while automatic +hue control is enabled is undefined, drivers should ignore such +request. + + + V4L2_CID_WHITE_BALANCE_TEMPERATURE + integer + This control specifies the white balance settings +as a color temperature in Kelvin. A driver should have a minimum of +2800 (incandescent) to 6500 (daylight). For more information about +color temperature see Wikipedia. + + + V4L2_CID_SHARPNESS + integer + Adjusts the sharpness filters in a camera. The +minimum value disables the filters, higher values give a sharper +picture. + + + V4L2_CID_BACKLIGHT_COMPENSATION + integer + Adjusts the backlight compensation in a camera. The +minimum value disables backlight compensation. + + + V4L2_CID_CHROMA_AGC + boolean + Chroma automatic gain control. + + + V4L2_CID_CHROMA_GAIN + integer + Adjusts the Chroma gain control (for use when chroma AGC + is disabled). + + + V4L2_CID_COLOR_KILLER + boolean + Enable the color killer (&ie; force a black & white image in case of a weak video signal). + + + V4L2_CID_COLORFX + enum + Selects a color effect. Possible values for +enum v4l2_colorfx are: +V4L2_COLORFX_NONE (0), +V4L2_COLORFX_BW (1), +V4L2_COLORFX_SEPIA (2), +V4L2_COLORFX_NEGATIVE (3), +V4L2_COLORFX_EMBOSS (4), +V4L2_COLORFX_SKETCH (5), +V4L2_COLORFX_SKY_BLUE (6), +V4L2_COLORFX_GRASS_GREEN (7), +V4L2_COLORFX_SKIN_WHITEN (8) and +V4L2_COLORFX_VIVID (9). + + + V4L2_CID_ROTATE + integer + Rotates the image by specified angle. Common angles are 90, + 270 and 180. Rotating the image to 90 and 270 will reverse the height + and width of the display window. It is necessary to set the new height and + width of the picture using the &VIDIOC-S-FMT; ioctl according to + the rotation angle selected. + + + V4L2_CID_BG_COLOR + integer + Sets the background color on the current output device. + Background color needs to be specified in the RGB24 format. The + supplied 32 bit value is interpreted as bits 0-7 Red color information, + bits 8-15 Green color information, bits 16-23 Blue color + information and bits 24-31 must be zero. + + + V4L2_CID_ILLUMINATORS_1 + V4L2_CID_ILLUMINATORS_2 + boolean + Switch on or off the illuminator 1 or 2 of the device + (usually a microscope). + + + V4L2_CID_LASTP1 + + End of the predefined control IDs (currently +V4L2_CID_ILLUMINATORS_2 + 1). + + + V4L2_CID_PRIVATE_BASE + + ID of the first custom (driver specific) control. +Applications depending on particular custom controls should check the +driver name and version, see . + + + +
+ + Applications can enumerate the available controls with the +&VIDIOC-QUERYCTRL; and &VIDIOC-QUERYMENU; ioctls, get and set a +control value with the &VIDIOC-G-CTRL; and &VIDIOC-S-CTRL; ioctls. +Drivers must implement VIDIOC_QUERYCTRL, +VIDIOC_G_CTRL and +VIDIOC_S_CTRL when the device has one or more +controls, VIDIOC_QUERYMENU when it has one or +more menu type controls. + + + Enumerating all controls + + +&v4l2-queryctrl; queryctrl; +&v4l2-querymenu; querymenu; + +static void +enumerate_menu (void) +{ + printf (" Menu items:\n"); + + memset (&querymenu, 0, sizeof (querymenu)); + querymenu.id = queryctrl.id; + + for (querymenu.index = queryctrl.minimum; + querymenu.index <= queryctrl.maximum; + querymenu.index++) { + if (0 == ioctl (fd, &VIDIOC-QUERYMENU;, &querymenu)) { + printf (" %s\n", querymenu.name); + } + } +} + +memset (&queryctrl, 0, sizeof (queryctrl)); + +for (queryctrl.id = V4L2_CID_BASE; + queryctrl.id < V4L2_CID_LASTP1; + queryctrl.id++) { + if (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &queryctrl)) { + if (queryctrl.flags & V4L2_CTRL_FLAG_DISABLED) + continue; + + printf ("Control %s\n", queryctrl.name); + + if (queryctrl.type == V4L2_CTRL_TYPE_MENU) + enumerate_menu (); + } else { + if (errno == EINVAL) + continue; + + perror ("VIDIOC_QUERYCTRL"); + exit (EXIT_FAILURE); + } +} + +for (queryctrl.id = V4L2_CID_PRIVATE_BASE;; + queryctrl.id++) { + if (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &queryctrl)) { + if (queryctrl.flags & V4L2_CTRL_FLAG_DISABLED) + continue; + + printf ("Control %s\n", queryctrl.name); + + if (queryctrl.type == V4L2_CTRL_TYPE_MENU) + enumerate_menu (); + } else { + if (errno == EINVAL) + break; + + perror ("VIDIOC_QUERYCTRL"); + exit (EXIT_FAILURE); + } +} + + + + + Changing controls + + +&v4l2-queryctrl; queryctrl; +&v4l2-control; control; + +memset (&queryctrl, 0, sizeof (queryctrl)); +queryctrl.id = V4L2_CID_BRIGHTNESS; + +if (-1 == ioctl (fd, &VIDIOC-QUERYCTRL;, &queryctrl)) { + if (errno != EINVAL) { + perror ("VIDIOC_QUERYCTRL"); + exit (EXIT_FAILURE); + } else { + printf ("V4L2_CID_BRIGHTNESS is not supported\n"); + } +} else if (queryctrl.flags & V4L2_CTRL_FLAG_DISABLED) { + printf ("V4L2_CID_BRIGHTNESS is not supported\n"); +} else { + memset (&control, 0, sizeof (control)); + control.id = V4L2_CID_BRIGHTNESS; + control.value = queryctrl.default_value; + + if (-1 == ioctl (fd, &VIDIOC-S-CTRL;, &control)) { + perror ("VIDIOC_S_CTRL"); + exit (EXIT_FAILURE); + } +} + +memset (&control, 0, sizeof (control)); +control.id = V4L2_CID_CONTRAST; + +if (0 == ioctl (fd, &VIDIOC-G-CTRL;, &control)) { + control.value += 1; + + /* The driver may clamp the value or return ERANGE, ignored here */ + + if (-1 == ioctl (fd, &VIDIOC-S-CTRL;, &control) + && errno != ERANGE) { + perror ("VIDIOC_S_CTRL"); + exit (EXIT_FAILURE); + } +/* Ignore if V4L2_CID_CONTRAST is unsupported */ +} else if (errno != EINVAL) { + perror ("VIDIOC_G_CTRL"); + exit (EXIT_FAILURE); +} + +control.id = V4L2_CID_AUDIO_MUTE; +control.value = TRUE; /* silence */ + +/* Errors ignored */ +ioctl (fd, VIDIOC_S_CTRL, &control); + + +
+ +
+ Extended Controls + +
+ Introduction + + The control mechanism as originally designed was meant +to be used for user settings (brightness, saturation, etc). However, +it turned out to be a very useful model for implementing more +complicated driver APIs where each driver implements only a subset of +a larger API. + + The MPEG encoding API was the driving force behind +designing and implementing this extended control mechanism: the MPEG +standard is quite large and the currently supported hardware MPEG +encoders each only implement a subset of this standard. Further more, +many parameters relating to how the video is encoded into an MPEG +stream are specific to the MPEG encoding chip since the MPEG standard +only defines the format of the resulting MPEG stream, not how the +video is actually encoded into that format. + + Unfortunately, the original control API lacked some +features needed for these new uses and so it was extended into the +(not terribly originally named) extended control API. + + Even though the MPEG encoding API was the first effort +to use the Extended Control API, nowadays there are also other classes +of Extended Controls, such as Camera Controls and FM Transmitter Controls. +The Extended Controls API as well as all Extended Controls classes are +described in the following text. +
+ +
+ The Extended Control API + + Three new ioctls are available: &VIDIOC-G-EXT-CTRLS;, +&VIDIOC-S-EXT-CTRLS; and &VIDIOC-TRY-EXT-CTRLS;. These ioctls act on +arrays of controls (as opposed to the &VIDIOC-G-CTRL; and +&VIDIOC-S-CTRL; ioctls that act on a single control). This is needed +since it is often required to atomically change several controls at +once. + + Each of the new ioctls expects a pointer to a +&v4l2-ext-controls;. This structure contains a pointer to the control +array, a count of the number of controls in that array and a control +class. Control classes are used to group similar controls into a +single class. For example, control class +V4L2_CTRL_CLASS_USER contains all user controls +(&ie; all controls that can also be set using the old +VIDIOC_S_CTRL ioctl). Control class +V4L2_CTRL_CLASS_MPEG contains all controls +relating to MPEG encoding, etc. + + All controls in the control array must belong to the +specified control class. An error is returned if this is not the +case. + + It is also possible to use an empty control array (count +== 0) to check whether the specified control class is +supported. + + The control array is a &v4l2-ext-control; array. The +v4l2_ext_control structure is very similar to +&v4l2-control;, except for the fact that it also allows for 64-bit +values and pointers to be passed. + + It is important to realize that due to the flexibility of +controls it is necessary to check whether the control you want to set +actually is supported in the driver and what the valid range of values +is. So use the &VIDIOC-QUERYCTRL; and &VIDIOC-QUERYMENU; ioctls to +check this. Also note that it is possible that some of the menu +indices in a control of type V4L2_CTRL_TYPE_MENU +may not be supported (VIDIOC_QUERYMENU will +return an error). A good example is the list of supported MPEG audio +bitrates. Some drivers only support one or two bitrates, others +support a wider range. +
+ +
+ Enumerating Extended Controls + + The recommended way to enumerate over the extended +controls is by using &VIDIOC-QUERYCTRL; in combination with the +V4L2_CTRL_FLAG_NEXT_CTRL flag: + + + +&v4l2-queryctrl; qctrl; + +qctrl.id = V4L2_CTRL_FLAG_NEXT_CTRL; +while (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &qctrl)) { + /* ... */ + qctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL; +} + + + + The initial control ID is set to 0 ORed with the +V4L2_CTRL_FLAG_NEXT_CTRL flag. The +VIDIOC_QUERYCTRL ioctl will return the first +control with a higher ID than the specified one. When no such controls +are found an error is returned. + + If you want to get all controls within a specific control +class, then you can set the initial +qctrl.id value to the control class and add +an extra check to break out of the loop when a control of another +control class is found: + + + +qctrl.id = V4L2_CTRL_CLASS_MPEG | V4L2_CTRL_FLAG_NEXT_CTRL; +while (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &qctrl)) { + if (V4L2_CTRL_ID2CLASS (qctrl.id) != V4L2_CTRL_CLASS_MPEG) + break; + /* ... */ + qctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL; + } + + + + The 32-bit qctrl.id value is +subdivided into three bit ranges: the top 4 bits are reserved for +flags (⪚ V4L2_CTRL_FLAG_NEXT_CTRL) and are not +actually part of the ID. The remaining 28 bits form the control ID, of +which the most significant 12 bits define the control class and the +least significant 16 bits identify the control within the control +class. It is guaranteed that these last 16 bits are always non-zero +for controls. The range of 0x1000 and up are reserved for +driver-specific controls. The macro +V4L2_CTRL_ID2CLASS(id) returns the control class +ID based on a control ID. + + If the driver does not support extended controls, then +VIDIOC_QUERYCTRL will fail when used in +combination with V4L2_CTRL_FLAG_NEXT_CTRL. In +that case the old method of enumerating control should be used (see +1.8). But if it is supported, then it is guaranteed to enumerate over +all controls, including driver-private controls. +
+ +
+ Creating Control Panels + + It is possible to create control panels for a graphical +user interface where the user can select the various controls. +Basically you will have to iterate over all controls using the method +described above. Each control class starts with a control of type +V4L2_CTRL_TYPE_CTRL_CLASS. +VIDIOC_QUERYCTRL will return the name of this +control class which can be used as the title of a tab page within a +control panel. + + The flags field of &v4l2-queryctrl; also contains hints on +the behavior of the control. See the &VIDIOC-QUERYCTRL; documentation +for more details. +
+ +
+ MPEG Control Reference + + Below all controls within the MPEG control class are +described. First the generic controls, then controls specific for +certain hardware. + +
+ Generic MPEG Controls + + + MPEG Control IDs + + + + + + + + + + ID + Type + Description + + + + + + V4L2_CID_MPEG_CLASS  + class + The MPEG class +descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a +description of this control class. This description can be used as the +caption of a Tab page in a GUI, for example. + + + + V4L2_CID_MPEG_STREAM_TYPE  + enum v4l2_mpeg_stream_type + The MPEG-1, -2 or -4 +output stream type. One cannot assume anything here. Each hardware +MPEG encoder tends to support different subsets of the available MPEG +stream types. The currently defined stream types are: + + + + + + V4L2_MPEG_STREAM_TYPE_MPEG2_PS  + MPEG-2 program stream + + + V4L2_MPEG_STREAM_TYPE_MPEG2_TS  + MPEG-2 transport stream + + + V4L2_MPEG_STREAM_TYPE_MPEG1_SS  + MPEG-1 system stream + + + V4L2_MPEG_STREAM_TYPE_MPEG2_DVD  + MPEG-2 DVD-compatible stream + + + V4L2_MPEG_STREAM_TYPE_MPEG1_VCD  + MPEG-1 VCD-compatible stream + + + V4L2_MPEG_STREAM_TYPE_MPEG2_SVCD  + MPEG-2 SVCD-compatible stream + + + + + + + V4L2_CID_MPEG_STREAM_PID_PMT  + integer + Program Map Table +Packet ID for the MPEG transport stream (default 16) + + + + V4L2_CID_MPEG_STREAM_PID_AUDIO  + integer + Audio Packet ID for +the MPEG transport stream (default 256) + + + + V4L2_CID_MPEG_STREAM_PID_VIDEO  + integer + Video Packet ID for +the MPEG transport stream (default 260) + + + + V4L2_CID_MPEG_STREAM_PID_PCR  + integer + Packet ID for the +MPEG transport stream carrying PCR fields (default 259) + + + + V4L2_CID_MPEG_STREAM_PES_ID_AUDIO  + integer + Audio ID for MPEG +PES + + + + V4L2_CID_MPEG_STREAM_PES_ID_VIDEO  + integer + Video ID for MPEG +PES + + + + V4L2_CID_MPEG_STREAM_VBI_FMT  + enum v4l2_mpeg_stream_vbi_fmt + Some cards can embed +VBI data (⪚ Closed Caption, Teletext) into the MPEG stream. This +control selects whether VBI data should be embedded, and if so, what +embedding method should be used. The list of possible VBI formats +depends on the driver. The currently defined VBI format types +are: + + + + + + V4L2_MPEG_STREAM_VBI_FMT_NONE  + No VBI in the MPEG stream + + + V4L2_MPEG_STREAM_VBI_FMT_IVTV  + VBI in private packets, IVTV format (documented +in the kernel sources in the file Documentation/video4linux/cx2341x/README.vbi) + + + + + + + V4L2_CID_MPEG_AUDIO_SAMPLING_FREQ  + enum v4l2_mpeg_audio_sampling_freq + MPEG Audio sampling +frequency. Possible values are: + + + + + + V4L2_MPEG_AUDIO_SAMPLING_FREQ_44100  + 44.1 kHz + + + V4L2_MPEG_AUDIO_SAMPLING_FREQ_48000  + 48 kHz + + + V4L2_MPEG_AUDIO_SAMPLING_FREQ_32000  + 32 kHz + + + + + + + V4L2_CID_MPEG_AUDIO_ENCODING  + enum v4l2_mpeg_audio_encoding + MPEG Audio encoding. +Possible values are: + + + + + + V4L2_MPEG_AUDIO_ENCODING_LAYER_1  + MPEG-1/2 Layer I encoding + + + V4L2_MPEG_AUDIO_ENCODING_LAYER_2  + MPEG-1/2 Layer II encoding + + + V4L2_MPEG_AUDIO_ENCODING_LAYER_3  + MPEG-1/2 Layer III encoding + + + V4L2_MPEG_AUDIO_ENCODING_AAC  + MPEG-2/4 AAC (Advanced Audio Coding) + + + V4L2_MPEG_AUDIO_ENCODING_AC3  + AC-3 aka ATSC A/52 encoding + + + + + + + V4L2_CID_MPEG_AUDIO_L1_BITRATE  + enum v4l2_mpeg_audio_l1_bitrate + MPEG-1/2 Layer I bitrate. +Possible values are: + + + + + + V4L2_MPEG_AUDIO_L1_BITRATE_32K  + 32 kbit/s + + V4L2_MPEG_AUDIO_L1_BITRATE_64K  + 64 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_96K  + 96 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_128K  + 128 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_160K  + 160 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_192K  + 192 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_224K  + 224 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_256K  + 256 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_288K  + 288 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_320K  + 320 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_352K  + 352 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_384K  + 384 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_416K  + 416 kbit/s + + + V4L2_MPEG_AUDIO_L1_BITRATE_448K  + 448 kbit/s + + + + + + + V4L2_CID_MPEG_AUDIO_L2_BITRATE  + enum v4l2_mpeg_audio_l2_bitrate + MPEG-1/2 Layer II bitrate. +Possible values are: + + + + + + V4L2_MPEG_AUDIO_L2_BITRATE_32K  + 32 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_48K  + 48 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_56K  + 56 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_64K  + 64 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_80K  + 80 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_96K  + 96 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_112K  + 112 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_128K  + 128 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_160K  + 160 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_192K  + 192 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_224K  + 224 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_256K  + 256 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_320K  + 320 kbit/s + + + V4L2_MPEG_AUDIO_L2_BITRATE_384K  + 384 kbit/s + + + + + + + V4L2_CID_MPEG_AUDIO_L3_BITRATE  + enum v4l2_mpeg_audio_l3_bitrate + MPEG-1/2 Layer III bitrate. +Possible values are: + + + + + + V4L2_MPEG_AUDIO_L3_BITRATE_32K  + 32 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_40K  + 40 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_48K  + 48 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_56K  + 56 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_64K  + 64 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_80K  + 80 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_96K  + 96 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_112K  + 112 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_128K  + 128 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_160K  + 160 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_192K  + 192 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_224K  + 224 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_256K  + 256 kbit/s + + + V4L2_MPEG_AUDIO_L3_BITRATE_320K  + 320 kbit/s + + + + + + + V4L2_CID_MPEG_AUDIO_AAC_BITRATE  + integer + AAC bitrate in bits per second. + + + + V4L2_CID_MPEG_AUDIO_AC3_BITRATE  + enum v4l2_mpeg_audio_ac3_bitrate + AC-3 bitrate. +Possible values are: + + + + + + V4L2_MPEG_AUDIO_AC3_BITRATE_32K  + 32 kbit/s + + + V4L2_MPEG_AUDIO_AC3_BITRATE_40K  + 40 kbit/s + + + V4L2_MPEG_AUDIO_AC3_BITRATE_48K  + 48 kbit/s + + + V4L2_MPEG_AUDIO_AC3_BITRATE_56K  + 56 kbit/s + + + V4L2_MPEG_AUDIO_AC3_BITRATE_64K  + 64 kbit/s + + + V4L2_MPEG_AUDIO_AC3_BITRATE_80K  + 80 kbit/s + + + V4L2_MPEG_AUDIO_AC3_BITRATE_96K  + 96 kbit/s + + + V4L2_MPEG_AUDIO_AC3_BITRATE_112K  + 112 kbit/s + + + V4L2_MPEG_AUDIO_AC3_BITRATE_128K  + 128 kbit/s + + + V4L2_MPEG_AUDIO_AC3_BITRATE_160K  + 160 kbit/s + + + V4L2_MPEG_AUDIO_AC3_BITRATE_192K  + 192 kbit/s + + + V4L2_MPEG_AUDIO_AC3_BITRATE_224K  + 224 kbit/s + + + V4L2_MPEG_AUDIO_AC3_BITRATE_256K  + 256 kbit/s + + + V4L2_MPEG_AUDIO_AC3_BITRATE_320K  + 320 kbit/s + + + V4L2_MPEG_AUDIO_AC3_BITRATE_384K  + 384 kbit/s + + + V4L2_MPEG_AUDIO_AC3_BITRATE_448K  + 448 kbit/s + + + V4L2_MPEG_AUDIO_AC3_BITRATE_512K  + 512 kbit/s + + + V4L2_MPEG_AUDIO_AC3_BITRATE_576K  + 576 kbit/s + + + V4L2_MPEG_AUDIO_AC3_BITRATE_640K  + 640 kbit/s + + + + + + + V4L2_CID_MPEG_AUDIO_MODE  + enum v4l2_mpeg_audio_mode + MPEG Audio mode. +Possible values are: + + + + + + V4L2_MPEG_AUDIO_MODE_STEREO  + Stereo + + + V4L2_MPEG_AUDIO_MODE_JOINT_STEREO  + Joint Stereo + + + V4L2_MPEG_AUDIO_MODE_DUAL  + Bilingual + + + V4L2_MPEG_AUDIO_MODE_MONO  + Mono + + + + + + + V4L2_CID_MPEG_AUDIO_MODE_EXTENSION  + enum v4l2_mpeg_audio_mode_extension + Joint Stereo +audio mode extension. In Layer I and II they indicate which subbands +are in intensity stereo. All other subbands are coded in stereo. Layer +III is not (yet) supported. Possible values +are: + + + + + + V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_4  + Subbands 4-31 in intensity stereo + + + V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_8  + Subbands 8-31 in intensity stereo + + + V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_12  + Subbands 12-31 in intensity stereo + + + V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_16  + Subbands 16-31 in intensity stereo + + + + + + + V4L2_CID_MPEG_AUDIO_EMPHASIS  + enum v4l2_mpeg_audio_emphasis + Audio Emphasis. +Possible values are: + + + + + + V4L2_MPEG_AUDIO_EMPHASIS_NONE  + None + + + V4L2_MPEG_AUDIO_EMPHASIS_50_DIV_15_uS  + 50/15 microsecond emphasis + + + V4L2_MPEG_AUDIO_EMPHASIS_CCITT_J17  + CCITT J.17 + + + + + + + V4L2_CID_MPEG_AUDIO_CRC  + enum v4l2_mpeg_audio_crc + CRC method. Possible +values are: + + + + + + V4L2_MPEG_AUDIO_CRC_NONE  + None + + + V4L2_MPEG_AUDIO_CRC_CRC16  + 16 bit parity check + + + + + + + V4L2_CID_MPEG_AUDIO_MUTE  + boolean + Mutes the audio when +capturing. This is not done by muting audio hardware, which can still +produce a slight hiss, but in the encoder itself, guaranteeing a fixed +and reproducible audio bitstream. 0 = unmuted, 1 = muted. + + + + V4L2_CID_MPEG_VIDEO_ENCODING  + enum v4l2_mpeg_video_encoding + MPEG Video encoding +method. Possible values are: + + + + + + V4L2_MPEG_VIDEO_ENCODING_MPEG_1  + MPEG-1 Video encoding + + + V4L2_MPEG_VIDEO_ENCODING_MPEG_2  + MPEG-2 Video encoding + + + V4L2_MPEG_VIDEO_ENCODING_MPEG_4_AVC  + MPEG-4 AVC (H.264) Video encoding + + + + + + + V4L2_CID_MPEG_VIDEO_ASPECT  + enum v4l2_mpeg_video_aspect + Video aspect. +Possible values are: + + + + + + V4L2_MPEG_VIDEO_ASPECT_1x1  + + + V4L2_MPEG_VIDEO_ASPECT_4x3  + + + V4L2_MPEG_VIDEO_ASPECT_16x9  + + + V4L2_MPEG_VIDEO_ASPECT_221x100  + + + + + + + V4L2_CID_MPEG_VIDEO_B_FRAMES  + integer + Number of B-Frames +(default 2) + + + + V4L2_CID_MPEG_VIDEO_GOP_SIZE  + integer + GOP size (default +12) + + + + V4L2_CID_MPEG_VIDEO_GOP_CLOSURE  + boolean + GOP closure (default +1) + + + + V4L2_CID_MPEG_VIDEO_PULLDOWN  + boolean + Enable 3:2 pulldown +(default 0) + + + + V4L2_CID_MPEG_VIDEO_BITRATE_MODE  + enum v4l2_mpeg_video_bitrate_mode + Video bitrate mode. +Possible values are: + + + + + + V4L2_MPEG_VIDEO_BITRATE_MODE_VBR  + Variable bitrate + + + V4L2_MPEG_VIDEO_BITRATE_MODE_CBR  + Constant bitrate + + + + + + + V4L2_CID_MPEG_VIDEO_BITRATE  + integer + Video bitrate in bits +per second. + + + + V4L2_CID_MPEG_VIDEO_BITRATE_PEAK  + integer + Peak video bitrate in +bits per second. Must be larger or equal to the average video bitrate. +It is ignored if the video bitrate mode is set to constant +bitrate. + + + + V4L2_CID_MPEG_VIDEO_TEMPORAL_DECIMATION  + integer + For every captured +frame, skip this many subsequent frames (default 0). + + + + V4L2_CID_MPEG_VIDEO_MUTE  + boolean + + "Mutes" the video to a +fixed color when capturing. This is useful for testing, to produce a +fixed video bitstream. 0 = unmuted, 1 = muted. + + + + V4L2_CID_MPEG_VIDEO_MUTE_YUV  + integer + Sets the "mute" color +of the video. The supplied 32-bit integer is interpreted as follows (bit +0 = least significant bit): + + + + + + Bit 0:7 + V chrominance information + + + Bit 8:15 + U chrominance information + + + Bit 16:23 + Y luminance information + + + Bit 24:31 + Must be zero. + + + + + + +
+
+ +
+ CX2341x MPEG Controls + + The following MPEG class controls deal with MPEG +encoding settings that are specific to the Conexant CX23415 and +CX23416 MPEG encoding chips. + + + CX2341x Control IDs + + + + + + + + + + ID + Type + Description + + + + + + V4L2_CID_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE  + enum v4l2_mpeg_cx2341x_video_spatial_filter_mode + Sets the Spatial +Filter mode (default MANUAL). Possible values +are: + + + + + + V4L2_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE_MANUAL  + Choose the filter manually + + + V4L2_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE_AUTO  + Choose the filter automatically + + + + + + + V4L2_CID_MPEG_CX2341X_VIDEO_SPATIAL_FILTER  + integer (0-15) + The setting for the +Spatial Filter. 0 = off, 15 = maximum. (Default is 0.) + + + + V4L2_CID_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE  + enum v4l2_mpeg_cx2341x_video_luma_spatial_filter_type + Select the algorithm +to use for the Luma Spatial Filter (default +1D_HOR). Possible values: + + + + + + V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_OFF  + No filter + + + V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_1D_HOR  + One-dimensional horizontal + + + V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_1D_VERT  + One-dimensional vertical + + + V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_2D_HV_SEPARABLE  + Two-dimensional separable + + + V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_2D_SYM_NON_SEPARABLE  + Two-dimensional symmetrical +non-separable + + + + + + + V4L2_CID_MPEG_CX2341X_VIDEO_CHROMA_SPATIAL_FILTER_TYPE  + enum v4l2_mpeg_cx2341x_video_chroma_spatial_filter_type + Select the algorithm +for the Chroma Spatial Filter (default 1D_HOR). +Possible values are: + + + + + + V4L2_MPEG_CX2341X_VIDEO_CHROMA_SPATIAL_FILTER_TYPE_OFF  + No filter + + + V4L2_MPEG_CX2341X_VIDEO_CHROMA_SPATIAL_FILTER_TYPE_1D_HOR  + One-dimensional horizontal + + + + + + + V4L2_CID_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER_MODE  + enum v4l2_mpeg_cx2341x_video_temporal_filter_mode + Sets the Temporal +Filter mode (default MANUAL). Possible values +are: + + + + + + V4L2_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER_MODE_MANUAL  + Choose the filter manually + + + V4L2_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER_MODE_AUTO  + Choose the filter automatically + + + + + + + V4L2_CID_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER  + integer (0-31) + The setting for the +Temporal Filter. 0 = off, 31 = maximum. (Default is 8 for full-scale +capturing and 0 for scaled capturing.) + + + + V4L2_CID_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE  + enum v4l2_mpeg_cx2341x_video_median_filter_type + Median Filter Type +(default OFF). Possible values are: + + + + + + V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_OFF  + No filter + + + V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_HOR  + Horizontal filter + + + V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_VERT  + Vertical filter + + + V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_HOR_VERT  + Horizontal and vertical filter + + + V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_DIAG  + Diagonal filter + + + + + + + V4L2_CID_MPEG_CX2341X_VIDEO_LUMA_MEDIAN_FILTER_BOTTOM  + integer (0-255) + Threshold above which +the luminance median filter is enabled (default 0) + + + + V4L2_CID_MPEG_CX2341X_VIDEO_LUMA_MEDIAN_FILTER_TOP  + integer (0-255) + Threshold below which +the luminance median filter is enabled (default 255) + + + + V4L2_CID_MPEG_CX2341X_VIDEO_CHROMA_MEDIAN_FILTER_BOTTOM  + integer (0-255) + Threshold above which +the chroma median filter is enabled (default 0) + + + + V4L2_CID_MPEG_CX2341X_VIDEO_CHROMA_MEDIAN_FILTER_TOP  + integer (0-255) + Threshold below which +the chroma median filter is enabled (default 255) + + + + V4L2_CID_MPEG_CX2341X_STREAM_INSERT_NAV_PACKETS  + boolean + + The CX2341X MPEG encoder +can insert one empty MPEG-2 PES packet into the stream between every +four video frames. The packet size is 2048 bytes, including the +packet_start_code_prefix and stream_id fields. The stream_id is 0xBF +(private stream 2). The payload consists of 0x00 bytes, to be filled +in by the application. 0 = do not insert, 1 = insert packets. + + + +
+
+
+ +
+ Camera Control Reference + + The Camera class includes controls for mechanical (or +equivalent digital) features of a device such as controllable lenses +or sensors. + + + Camera Control IDs + + + + + + + + + + ID + Type + Description + + + + + + V4L2_CID_CAMERA_CLASS  + class + The Camera class +descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a +description of this control class. + + + + + V4L2_CID_EXPOSURE_AUTO  + enum v4l2_exposure_auto_type + Enables automatic +adjustments of the exposure time and/or iris aperture. The effect of +manual changes of the exposure time or iris aperture while these +features are enabled is undefined, drivers should ignore such +requests. Possible values are: + + + + + + V4L2_EXPOSURE_AUTO  + Automatic exposure time, automatic iris +aperture. + + + V4L2_EXPOSURE_MANUAL  + Manual exposure time, manual iris. + + + V4L2_EXPOSURE_SHUTTER_PRIORITY  + Manual exposure time, auto iris. + + + V4L2_EXPOSURE_APERTURE_PRIORITY  + Auto exposure time, manual iris. + + + + + + + + V4L2_CID_EXPOSURE_ABSOLUTE  + integer + Determines the exposure +time of the camera sensor. The exposure time is limited by the frame +interval. Drivers should interpret the values as 100 µs units, +where the value 1 stands for 1/10000th of a second, 10000 for 1 second +and 100000 for 10 seconds. + + + + + V4L2_CID_EXPOSURE_AUTO_PRIORITY  + boolean + When +V4L2_CID_EXPOSURE_AUTO is set to +AUTO or APERTURE_PRIORITY, +this control determines if the device may dynamically vary the frame +rate. By default this feature is disabled (0) and the frame rate must +remain constant. + + + + + V4L2_CID_PAN_RELATIVE  + integer + This control turns the +camera horizontally by the specified amount. The unit is undefined. A +positive value moves the camera to the right (clockwise when viewed +from above), a negative value to the left. A value of zero does not +cause motion. This is a write-only control. + + + + + V4L2_CID_TILT_RELATIVE  + integer + This control turns the +camera vertically by the specified amount. The unit is undefined. A +positive value moves the camera up, a negative value down. A value of +zero does not cause motion. This is a write-only control. + + + + + V4L2_CID_PAN_RESET  + button + When this control is set, +the camera moves horizontally to the default position. + + + + + V4L2_CID_TILT_RESET  + button + When this control is set, +the camera moves vertically to the default position. + + + + + V4L2_CID_PAN_ABSOLUTE  + integer + This control +turns the camera horizontally to the specified position. Positive +values move the camera to the right (clockwise when viewed from above), +negative values to the left. Drivers should interpret the values as arc +seconds, with valid values between -180 * 3600 and +180 * 3600 +inclusive. + + + + + V4L2_CID_TILT_ABSOLUTE  + integer + This control +turns the camera vertically to the specified position. Positive values +move the camera up, negative values down. Drivers should interpret the +values as arc seconds, with valid values between -180 * 3600 and +180 +* 3600 inclusive. + + + + + V4L2_CID_FOCUS_ABSOLUTE  + integer + This control sets the +focal point of the camera to the specified position. The unit is +undefined. Positive values set the focus closer to the camera, +negative values towards infinity. + + + + + V4L2_CID_FOCUS_RELATIVE  + integer + This control moves the +focal point of the camera by the specified amount. The unit is +undefined. Positive values move the focus closer to the camera, +negative values towards infinity. This is a write-only control. + + + + + V4L2_CID_FOCUS_AUTO  + boolean + Enables automatic focus +adjustments. The effect of manual focus adjustments while this feature +is enabled is undefined, drivers should ignore such requests. + + + + + V4L2_CID_ZOOM_ABSOLUTE  + integer + Specify the objective lens +focal length as an absolute value. The zoom unit is driver-specific and its +value should be a positive integer. + + + + + V4L2_CID_ZOOM_RELATIVE  + integer + Specify the objective lens +focal length relatively to the current value. Positive values move the zoom +lens group towards the telephoto direction, negative values towards the +wide-angle direction. The zoom unit is driver-specific. This is a write-only control. + + + + + V4L2_CID_ZOOM_CONTINUOUS  + integer + Move the objective lens group +at the specified speed until it reaches physical device limits or until an +explicit request to stop the movement. A positive value moves the zoom lens +group towards the telephoto direction. A value of zero stops the zoom lens +group movement. A negative value moves the zoom lens group towards the +wide-angle direction. The zoom speed unit is driver-specific. + + + + + V4L2_CID_IRIS_ABSOLUTE  + integer + This control sets the +camera's aperture to the specified value. The unit is undefined. +Larger values open the iris wider, smaller values close it. + + + + + V4L2_CID_IRIS_RELATIVE  + integer + This control modifies the +camera's aperture by the specified amount. The unit is undefined. +Positive values open the iris one step further, negative values close +it one step further. This is a write-only control. + + + + + V4L2_CID_PRIVACY  + boolean + Prevent video from being acquired +by the camera. When this control is set to TRUE (1), no +image can be captured by the camera. Common means to enforce privacy are +mechanical obturation of the sensor and firmware image processing, but the +device is not restricted to these methods. Devices that implement the privacy +control must support read access and may support write access. + + + + V4L2_CID_BAND_STOP_FILTER  + integer + Switch the band-stop filter of a +camera sensor on or off, or specify its strength. Such band-stop filters can +be used, for example, to filter out the fluorescent light component. + + + + +
+
+ +
+ FM Transmitter Control Reference + + The FM Transmitter (FM_TX) class includes controls for common features of +FM transmissions capable devices. Currently this class includes parameters for audio +compression, pilot tone generation, audio deviation limiter, RDS transmission and +tuning power features. + + + FM_TX Control IDs + + + + + + + + + + + ID + Type + Description + + + + + + V4L2_CID_FM_TX_CLASS  + class + The FM_TX class +descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a +description of this control class. + + + V4L2_CID_RDS_TX_DEVIATION  + integer + + Configures RDS signal frequency deviation level in Hz. +The range and step are driver-specific. + + + V4L2_CID_RDS_TX_PI  + integer + + Sets the RDS Programme Identification field +for transmission. + + + V4L2_CID_RDS_TX_PTY  + integer + + Sets the RDS Programme Type field for transmission. +This encodes up to 31 pre-defined programme types. + + + V4L2_CID_RDS_TX_PS_NAME  + string + + Sets the Programme Service name (PS_NAME) for transmission. +It is intended for static display on a receiver. It is the primary aid to listeners in programme service +identification and selection. In Annex E of , the RDS specification, +there is a full description of the correct character encoding for Programme Service name strings. +Also from RDS specification, PS is usually a single eight character text. However, it is also possible +to find receivers which can scroll strings sized as 8 x N characters. So, this control must be configured +with steps of 8 characters. The result is it must always contain a string with size multiple of 8. + + + V4L2_CID_RDS_TX_RADIO_TEXT  + string + + Sets the Radio Text info for transmission. It is a textual description of +what is being broadcasted. RDS Radio Text can be applied when broadcaster wishes to transmit longer PS names, +programme-related information or any other text. In these cases, RadioText should be used in addition to +V4L2_CID_RDS_TX_PS_NAME. The encoding for Radio Text strings is also fully described +in Annex E of . The length of Radio Text strings depends on which RDS Block is being +used to transmit it, either 32 (2A block) or 64 (2B block). However, it is also possible +to find receivers which can scroll strings sized as 32 x N or 64 x N characters. So, this control must be configured +with steps of 32 or 64 characters. The result is it must always contain a string with size multiple of 32 or 64. + + + V4L2_CID_AUDIO_LIMITER_ENABLED  + boolean + + Enables or disables the audio deviation limiter feature. +The limiter is useful when trying to maximize the audio volume, minimize receiver-generated +distortion and prevent overmodulation. + + + + V4L2_CID_AUDIO_LIMITER_RELEASE_TIME  + integer + + Sets the audio deviation limiter feature release time. +Unit is in useconds. Step and range are driver-specific. + + + V4L2_CID_AUDIO_LIMITER_DEVIATION  + integer + + Configures audio frequency deviation level in Hz. +The range and step are driver-specific. + + + V4L2_CID_AUDIO_COMPRESSION_ENABLED  + boolean + + Enables or disables the audio compression feature. +This feature amplifies signals below the threshold by a fixed gain and compresses audio +signals above the threshold by the ratio of Threshold/(Gain + Threshold). + + + V4L2_CID_AUDIO_COMPRESSION_GAIN  + integer + + Sets the gain for audio compression feature. It is +a dB value. The range and step are driver-specific. + + + V4L2_CID_AUDIO_COMPRESSION_THRESHOLD  + integer + + Sets the threshold level for audio compression freature. +It is a dB value. The range and step are driver-specific. + + + V4L2_CID_AUDIO_COMPRESSION_ATTACK_TIME  + integer + + Sets the attack time for audio compression feature. +It is a useconds value. The range and step are driver-specific. + + + V4L2_CID_AUDIO_COMPRESSION_RELEASE_TIME  + integer + + Sets the release time for audio compression feature. +It is a useconds value. The range and step are driver-specific. + + + V4L2_CID_PILOT_TONE_ENABLED  + boolean + + Enables or disables the pilot tone generation feature. + + + V4L2_CID_PILOT_TONE_DEVIATION  + integer + + Configures pilot tone frequency deviation level. Unit is +in Hz. The range and step are driver-specific. + + + V4L2_CID_PILOT_TONE_FREQUENCY  + integer + + Configures pilot tone frequency value. Unit is +in Hz. The range and step are driver-specific. + + + V4L2_CID_TUNE_PREEMPHASIS  + integer + + Configures the pre-emphasis value for broadcasting. +A pre-emphasis filter is applied to the broadcast to accentuate the high audio frequencies. +Depending on the region, a time constant of either 50 or 75 useconds is used. The enum v4l2_preemphasis +defines possible values for pre-emphasis. Here they are: + + + + + V4L2_PREEMPHASIS_DISABLED  + No pre-emphasis is applied. + + + V4L2_PREEMPHASIS_50_uS  + A pre-emphasis of 50 uS is used. + + + V4L2_PREEMPHASIS_75_uS  + A pre-emphasis of 75 uS is used. + + + + + + + V4L2_CID_TUNE_POWER_LEVEL  + integer + + Sets the output power level for signal transmission. +Unit is in dBuV. Range and step are driver-specific. + + + V4L2_CID_TUNE_ANTENNA_CAPACITOR  + integer + + This selects the value of antenna tuning capacitor +manually or automatically if set to zero. Unit, range and step are driver-specific. + + + + +
+ +For more details about RDS specification, refer to + document, from CENELEC. +
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