diff options
Diffstat (limited to '')
| -rw-r--r-- | Documentation/DocBook/media/v4l/controls.xml | 408 |
1 files changed, 334 insertions, 74 deletions
diff --git a/Documentation/DocBook/media/v4l/controls.xml b/Documentation/DocBook/media/v4l/controls.xml index 47198eef75a4..9f5ffd85560b 100644 --- a/Documentation/DocBook/media/v4l/controls.xml +++ b/Documentation/DocBook/media/v4l/controls.xml @@ -13,6 +13,19 @@ correctly with any device.</para> <para>All controls are accessed using an ID value. V4L2 defines several IDs for specific purposes. Drivers can also implement their own custom controls using <constant>V4L2_CID_PRIVATE_BASE</constant> +<footnote><para>The use of <constant>V4L2_CID_PRIVATE_BASE</constant> +is problematic because different drivers may use the same +<constant>V4L2_CID_PRIVATE_BASE</constant> ID for different controls. +This makes it hard to programatically set such controls since the meaning +of the control with that ID is driver dependent. In order to resolve this +drivers use unique IDs and the <constant>V4L2_CID_PRIVATE_BASE</constant> +IDs are mapped to those unique IDs by the kernel. Consider these +<constant>V4L2_CID_PRIVATE_BASE</constant> IDs as aliases to the real +IDs.</para> +<para>Many applications today still use the <constant>V4L2_CID_PRIVATE_BASE</constant> +IDs instead of using &VIDIOC-QUERYCTRL; with the <constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant> +flag to enumerate all IDs, so support for <constant>V4L2_CID_PRIVATE_BASE</constant> +is still around.</para></footnote> and higher values. The pre-defined control IDs have the prefix <constant>V4L2_CID_</constant>, and are listed in <xref linkend="control-id" />. The ID is used when querying the attributes of @@ -31,25 +44,22 @@ 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 <emphasis>custom</emphasis> ID can also change name and -type.<footnote> - <para>It will be more convenient for applications if drivers -make use of the <constant>V4L2_CTRL_FLAG_DISABLED</constant> flag, but -that was never required.</para> - </footnote> Control values are stored globally, they do not +type.</para> + + <para>If a control is not applicable to the current configuration +of the device (for example, it doesn't apply to the current video input) +drivers set the <constant>V4L2_CTRL_FLAG_INACTIVE</constant> flag.</para> + + <para>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.<footnote> - <para>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.</para> - </footnote></para> +application request.</para> + + <para>V4L2 specifies an event mechanism to notify applications +when controls change value (see &VIDIOC-SUBSCRIBE-EVENT;, event +<constant>V4L2_EVENT_CTRL</constant>), panel applications might want to make +use of that in order to always reflect the correct control value.</para> <para> All controls use machine endianness. @@ -398,14 +408,17 @@ to work.</entry> <row id="v4l2-alpha-component"> <entry><constant>V4L2_CID_ALPHA_COMPONENT</constant></entry> <entry>integer</entry> - <entry> Sets the alpha color component on the capture device or on - the capture buffer queue of a mem-to-mem device. When a mem-to-mem - device produces frame format that includes an alpha component + <entry>Sets the alpha color component. When a capture device (or + capture queue of a mem-to-mem device) produces a frame format that + includes an alpha component (e.g. <link linkend="rgb-formats">packed RGB image formats</link>) - and the alpha value is not defined by the mem-to-mem input data - this control lets you select the alpha component value of all - pixels. It is applicable to any pixel format that contains an alpha - component. + and the alpha value is not defined by the device or the mem-to-mem + input data this control lets you select the alpha component value of + all pixels. When an output device (or output queue of a mem-to-mem + device) consumes a frame format that doesn't include an alpha + component and the device supports alpha channel processing this + control lets you set the alpha component value of all pixels for + further processing in the device. </entry> </row> <row> @@ -434,127 +447,152 @@ Drivers must implement <constant>VIDIOC_QUERYCTRL</constant>, controls, <constant>VIDIOC_QUERYMENU</constant> when it has one or more menu type controls.</para> - <example> - <title>Enumerating all controls</title> + <example id="enum_all_controls"> + <title>Enumerating all user controls</title> <programlisting> &v4l2-queryctrl; queryctrl; &v4l2-querymenu; querymenu; -static void -enumerate_menu (void) +static void enumerate_menu(void) { - printf (" Menu items:\n"); + printf(" Menu items:\n"); - memset (&querymenu, 0, sizeof (querymenu)); + 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); + querymenu.index++) { + if (0 == ioctl(fd, &VIDIOC-QUERYMENU;, &querymenu)) { + printf(" %s\n", querymenu.name); } } } -memset (&queryctrl, 0, sizeof (queryctrl)); +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 (0 == ioctl(fd, &VIDIOC-QUERYCTRL;, &queryctrl)) { if (queryctrl.flags & V4L2_CTRL_FLAG_DISABLED) continue; - printf ("Control %s\n", queryctrl.name); + printf("Control %s\n", queryctrl.name); if (queryctrl.type == V4L2_CTRL_TYPE_MENU) - enumerate_menu (); + enumerate_menu(); } else { if (errno == EINVAL) continue; - perror ("VIDIOC_QUERYCTRL"); - exit (EXIT_FAILURE); + perror("VIDIOC_QUERYCTRL"); + exit(EXIT_FAILURE); } } for (queryctrl.id = V4L2_CID_PRIVATE_BASE;; queryctrl.id++) { - if (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &queryctrl)) { + if (0 == ioctl(fd, &VIDIOC-QUERYCTRL;, &queryctrl)) { if (queryctrl.flags & V4L2_CTRL_FLAG_DISABLED) continue; - printf ("Control %s\n", queryctrl.name); + printf("Control %s\n", queryctrl.name); if (queryctrl.type == V4L2_CTRL_TYPE_MENU) - enumerate_menu (); + enumerate_menu(); } else { if (errno == EINVAL) break; - perror ("VIDIOC_QUERYCTRL"); - exit (EXIT_FAILURE); + perror("VIDIOC_QUERYCTRL"); + exit(EXIT_FAILURE); } } </programlisting> </example> <example> + <title>Enumerating all user controls (alternative)</title> + <programlisting> +memset(&queryctrl, 0, sizeof(queryctrl)); + +queryctrl.id = V4L2_CTRL_CLASS_USER | V4L2_CTRL_FLAG_NEXT_CTRL; +while (0 == ioctl(fd, &VIDIOC-QUERYCTRL;, &queryctrl)) { + if (V4L2_CTRL_ID2CLASS(queryctrl.id) != V4L2_CTRL_CLASS_USER) + break; + if (queryctrl.flags & V4L2_CTRL_FLAG_DISABLED) + continue; + + printf("Control %s\n", queryctrl.name); + + if (queryctrl.type == V4L2_CTRL_TYPE_MENU) + enumerate_menu(); + + queryctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL; +} +if (errno != EINVAL) { + perror("VIDIOC_QUERYCTRL"); + exit(EXIT_FAILURE); +} +</programlisting> + </example> + + <example> <title>Changing controls</title> <programlisting> &v4l2-queryctrl; queryctrl; &v4l2-control; control; -memset (&queryctrl, 0, sizeof (queryctrl)); +memset(&queryctrl, 0, sizeof(queryctrl)); queryctrl.id = V4L2_CID_BRIGHTNESS; -if (-1 == ioctl (fd, &VIDIOC-QUERYCTRL;, &queryctrl)) { +if (-1 == ioctl(fd, &VIDIOC-QUERYCTRL;, &queryctrl)) { if (errno != EINVAL) { - perror ("VIDIOC_QUERYCTRL"); - exit (EXIT_FAILURE); + perror("VIDIOC_QUERYCTRL"); + exit(EXIT_FAILURE); } else { - printf ("V4L2_CID_BRIGHTNESS is not supported\n"); + printf("V4L2_CID_BRIGHTNESS is not supported\n"); } } else if (queryctrl.flags & V4L2_CTRL_FLAG_DISABLED) { - printf ("V4L2_CID_BRIGHTNESS is not supported\n"); + printf("V4L2_CID_BRIGHTNESS is not supported\n"); } else { - memset (&control, 0, sizeof (control)); + 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); + if (-1 == ioctl(fd, &VIDIOC-S-CTRL;, &control)) { + perror("VIDIOC_S_CTRL"); + exit(EXIT_FAILURE); } } -memset (&control, 0, sizeof (control)); +memset(&control, 0, sizeof(control)); control.id = V4L2_CID_CONTRAST; -if (0 == ioctl (fd, &VIDIOC-G-CTRL;, &control)) { +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) + if (-1 == ioctl(fd, &VIDIOC-S-CTRL;, &control) && errno != ERANGE) { - perror ("VIDIOC_S_CTRL"); - exit (EXIT_FAILURE); + 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); + perror("VIDIOC_G_CTRL"); + exit(EXIT_FAILURE); } control.id = V4L2_CID_AUDIO_MUTE; -control.value = TRUE; /* silence */ +control.value = 1; /* silence */ /* Errors ignored */ -ioctl (fd, VIDIOC_S_CTRL, &control); +ioctl(fd, VIDIOC_S_CTRL, &control); </programlisting> </example> </section> @@ -625,16 +663,29 @@ supported.</para> &v4l2-control;, except for the fact that it also allows for 64-bit values and pointers to be passed.</para> + <para>Since the &v4l2-ext-control; supports pointers it is now +also possible to have controls with compound types such as N-dimensional arrays +and/or structures. You need to specify the <constant>V4L2_CTRL_FLAG_NEXT_COMPOUND</constant> +when enumerating controls to actually be able to see such compound controls. +In other words, these controls with compound types should only be used +programmatically.</para> + + <para>Since such compound controls need to expose more information +about themselves than is possible with &VIDIOC-QUERYCTRL; the +&VIDIOC-QUERY-EXT-CTRL; ioctl was added. In particular, this ioctl gives +the dimensions of the N-dimensional array if this control consists of more than +one element.</para> + <para>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 <constant>V4L2_CTRL_TYPE_MENU</constant> -may not be supported (<constant>VIDIOC_QUERYMENU</constant> 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.</para> +is. So use the &VIDIOC-QUERYCTRL; (or &VIDIOC-QUERY-EXT-CTRL;) and +&VIDIOC-QUERYMENU; ioctls to check this. Also note that it is possible +that some of the menu indices in a control of type +<constant>V4L2_CTRL_TYPE_MENU</constant> may not be supported +(<constant>VIDIOC_QUERYMENU</constant> 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.</para> <para> All controls use machine endianness. @@ -675,12 +726,12 @@ control class is found:</para> <informalexample> <programlisting> 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) +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; - } + qctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL; +} </programlisting> </informalexample> @@ -700,7 +751,7 @@ ID based on a control ID.</para> <constant>VIDIOC_QUERYCTRL</constant> will fail when used in combination with <constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant>. 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 +<xref linkend="enum_all_controls" />). But if it is supported, then it is guaranteed to enumerate over all controls, including driver-private controls.</para> </section> @@ -4000,6 +4051,68 @@ to find receivers which can scroll strings sized as 32 x N or 64 x N characters. with steps of 32 or 64 characters. The result is it must always contain a string with size multiple of 32 or 64. </entry> </row> <row> + <entry spanname="id"><constant>V4L2_CID_RDS_TX_MONO_STEREO</constant> </entry> + <entry>boolean</entry> + </row> + <row><entry spanname="descr">Sets the Mono/Stereo bit of the Decoder Identification code. If set, +then the audio was recorded as stereo.</entry> + </row> + <row> + <entry spanname="id"><constant>V4L2_CID_RDS_TX_ARTIFICIAL_HEAD</constant> </entry> + <entry>boolean</entry> + </row> + <row><entry spanname="descr">Sets the +<ulink url="http://en.wikipedia.org/wiki/Artificial_head">Artificial Head</ulink> bit of the Decoder +Identification code. If set, then the audio was recorded using an artificial head.</entry> + </row> + <row> + <entry spanname="id"><constant>V4L2_CID_RDS_TX_COMPRESSED</constant> </entry> + <entry>boolean</entry> + </row> + <row><entry spanname="descr">Sets the Compressed bit of the Decoder Identification code. If set, +then the audio is compressed.</entry> + </row> + <row> + <entry spanname="id"><constant>V4L2_CID_RDS_TX_DYNAMIC_PTY</constant> </entry> + <entry>boolean</entry> + </row> + <row><entry spanname="descr">Sets the Dynamic PTY bit of the Decoder Identification code. If set, +then the PTY code is dynamically switched.</entry> + </row> + <row> + <entry spanname="id"><constant>V4L2_CID_RDS_TX_TRAFFIC_ANNOUNCEMENT</constant> </entry> + <entry>boolean</entry> + </row> + <row><entry spanname="descr">If set, then a traffic announcement is in progress.</entry> + </row> + <row> + <entry spanname="id"><constant>V4L2_CID_RDS_TX_TRAFFIC_PROGRAM</constant> </entry> + <entry>boolean</entry> + </row> + <row><entry spanname="descr">If set, then the tuned programme carries traffic announcements.</entry> + </row> + <row> + <entry spanname="id"><constant>V4L2_CID_RDS_TX_MUSIC_SPEECH</constant> </entry> + <entry>boolean</entry> + </row> + <row><entry spanname="descr">If set, then this channel broadcasts music. If cleared, then it +broadcasts speech. If the transmitter doesn't make this distinction, then it should be set.</entry> + </row> + <row> + <entry spanname="id"><constant>V4L2_CID_RDS_TX_ALT_FREQS_ENABLE</constant> </entry> + <entry>boolean</entry> + </row> + <row><entry spanname="descr">If set, then transmit alternate frequencies.</entry> + </row> + <row> + <entry spanname="id"><constant>V4L2_CID_RDS_TX_ALT_FREQS</constant> </entry> + <entry>__u32 array</entry> + </row> + <row><entry spanname="descr">The alternate frequencies in kHz units. The RDS standard allows +for up to 25 frequencies to be defined. Drivers may support fewer frequencies so check +the array size.</entry> + </row> + <row> <entry spanname="id"><constant>V4L2_CID_AUDIO_LIMITER_ENABLED</constant> </entry> <entry>boolean</entry> </row> @@ -4976,6 +5089,57 @@ description of this control class.</entry> </row><row><entry spanname="descr">Enables/disables RDS reception by the radio tuner</entry> </row> + <row> + <entry spanname="id"><constant>V4L2_CID_RDS_RX_PTY</constant> </entry> + <entry>integer</entry> + </row> + <row><entry spanname="descr">Gets RDS Programme Type field. +This encodes up to 31 pre-defined programme types.</entry> + </row> + <row> + <entry spanname="id"><constant>V4L2_CID_RDS_RX_PS_NAME</constant> </entry> + <entry>string</entry> + </row> + <row><entry spanname="descr">Gets the Programme Service name (PS_NAME). +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 <xref linkend="iec62106" />, 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.</entry> + </row> + <row> + <entry spanname="id"><constant>V4L2_CID_RDS_RX_RADIO_TEXT</constant> </entry> + <entry>string</entry> + </row> + <row><entry spanname="descr">Gets the Radio Text info. 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 can be used in addition to +<constant>V4L2_CID_RDS_RX_PS_NAME</constant>. The encoding for Radio Text strings is also fully described +in Annex E of <xref linkend="iec62106" />. 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. </entry> + </row> + <row> + <entry spanname="id"><constant>V4L2_CID_RDS_RX_TRAFFIC_ANNOUNCEMENT</constant> </entry> + <entry>boolean</entry> + </row> + <row><entry spanname="descr">If set, then a traffic announcement is in progress.</entry> + </row> + <row> + <entry spanname="id"><constant>V4L2_CID_RDS_RX_TRAFFIC_PROGRAM</constant> </entry> + <entry>boolean</entry> + </row> + <row><entry spanname="descr">If set, then the tuned programme carries traffic announcements.</entry> + </row> + <row> + <entry spanname="id"><constant>V4L2_CID_RDS_RX_MUSIC_SPEECH</constant> </entry> + <entry>boolean</entry> + </row> + <row><entry spanname="descr">If set, then this channel broadcasts music. If cleared, then it +broadcasts speech. If the transmitter doesn't make this distinction, then it will be set.</entry> + </row> <row> <entry spanname="id"><constant>V4L2_CID_TUNE_DEEMPHASIS</constant> </entry> <entry>enum v4l2_deemphasis</entry> @@ -5007,6 +5171,102 @@ defines possible values for de-emphasis. Here they are:</entry> </tbody> </tgroup> </table> + </section> + + <section id="detect-controls"> + <title>Detect Control Reference</title> + + <para>The Detect class includes controls for common features of + various motion or object detection capable devices.</para> + + <table pgwide="1" frame="none" id="detect-control-id"> + <title>Detect Control IDs</title> + + <tgroup cols="4"> + <colspec colname="c1" colwidth="1*" /> + <colspec colname="c2" colwidth="6*" /> + <colspec colname="c3" colwidth="2*" /> + <colspec colname="c4" colwidth="6*" /> + <spanspec namest="c1" nameend="c2" spanname="id" /> + <spanspec namest="c2" nameend="c4" spanname="descr" /> + <thead> + <row> + <entry spanname="id" align="left">ID</entry> + <entry align="left">Type</entry> + </row><row rowsep="1"><entry spanname="descr" align="left">Description</entry> + </row> + </thead> + <tbody valign="top"> + <row><entry></entry></row> + <row> + <entry spanname="id"><constant>V4L2_CID_DETECT_CLASS</constant> </entry> + <entry>class</entry> + </row><row><entry spanname="descr">The Detect class +descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a +description of this control class.</entry> + </row> + <row> + <entry spanname="id"><constant>V4L2_CID_DETECT_MD_MODE</constant> </entry> + <entry>menu</entry> + </row><row><entry spanname="descr">Sets the motion detection mode.</entry> + </row> + <row> + <entrytbl spanname="descr" cols="2"> + <tbody valign="top"> + <row> + <entry><constant>V4L2_DETECT_MD_MODE_DISABLED</constant> + </entry><entry>Disable motion detection.</entry> + </row> + <row> + <entry><constant>V4L2_DETECT_MD_MODE_GLOBAL</constant> + </entry><entry>Use a single motion detection threshold.</entry> + </row> + <row> + <entry><constant>V4L2_DETECT_MD_MODE_THRESHOLD_GRID</constant> + </entry><entry>The image is divided into a grid, each cell with its own + motion detection threshold. These thresholds are set through the + <constant>V4L2_CID_DETECT_MD_THRESHOLD_GRID</constant> matrix control.</entry> + </row> + <row> + <entry><constant>V4L2_DETECT_MD_MODE_REGION_GRID</constant> + </entry><entry>The image is divided into a grid, each cell with its own + region value that specifies which per-region motion detection thresholds + should be used. Each region has its own thresholds. How these per-region + thresholds are set up is driver-specific. The region values for the grid are set + through the <constant>V4L2_CID_DETECT_MD_REGION_GRID</constant> matrix + control.</entry> + </row> + </tbody> + </entrytbl> + </row> + <row> + <entry spanname="id"><constant>V4L2_CID_DETECT_MD_GLOBAL_THRESHOLD</constant> </entry> + <entry>integer</entry> + </row> + <row><entry spanname="descr">Sets the global motion detection threshold to be + used with the <constant>V4L2_DETECT_MD_MODE_GLOBAL</constant> motion detection mode.</entry> + </row> + <row> + <entry spanname="id"><constant>V4L2_CID_DETECT_MD_THRESHOLD_GRID</constant> </entry> + <entry>__u16 matrix</entry> + </row> + <row><entry spanname="descr">Sets the motion detection thresholds for each cell in the grid. + To be used with the <constant>V4L2_DETECT_MD_MODE_THRESHOLD_GRID</constant> + motion detection mode. Matrix element (0, 0) represents the cell at the top-left of the + grid.</entry> + </row> + <row> + <entry spanname="id"><constant>V4L2_CID_DETECT_MD_REGION_GRID</constant> </entry> + <entry>__u8 matrix</entry> + </row> + <row><entry spanname="descr">Sets the motion detection region value for each cell in the grid. + To be used with the <constant>V4L2_DETECT_MD_MODE_REGION_GRID</constant> + motion detection mode. Matrix element (0, 0) represents the cell at the top-left of the + grid.</entry> + </row> + </tbody> + </tgroup> + </table> </section> |