1.. Permission is granted to copy, distribute and/or modify this 2.. document under the terms of the GNU Free Documentation License, 3.. Version 1.1 or any later version published by the Free Software 4.. Foundation, with no Invariant Sections, no Front-Cover Texts 5.. and no Back-Cover Texts. A copy of the license is included at 6.. Documentation/userspace-api/media/fdl-appendix.rst. 7.. 8.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections 9 10.. _VIDIOC_G_MODULATOR: 11 12******************************************** 13ioctl VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR 14******************************************** 15 16Name 17==== 18 19VIDIOC_G_MODULATOR - VIDIOC_S_MODULATOR - Get or set modulator attributes 20 21 22Synopsis 23======== 24 25.. c:function:: int ioctl( int fd, VIDIOC_G_MODULATOR, struct v4l2_modulator *argp ) 26 :name: VIDIOC_G_MODULATOR 27 28.. c:function:: int ioctl( int fd, VIDIOC_S_MODULATOR, const struct v4l2_modulator *argp ) 29 :name: VIDIOC_S_MODULATOR 30 31 32Arguments 33========= 34 35``fd`` 36 File descriptor returned by :ref:`open() <func-open>`. 37 38``argp`` 39 Pointer to struct :c:type:`v4l2_modulator`. 40 41 42Description 43=========== 44 45To query the attributes of a modulator applications initialize the 46``index`` field and zero out the ``reserved`` array of a struct 47:c:type:`v4l2_modulator` and call the 48:ref:`VIDIOC_G_MODULATOR <VIDIOC_G_MODULATOR>` ioctl with a pointer to this structure. Drivers 49fill the rest of the structure or return an ``EINVAL`` error code when the 50index is out of bounds. To enumerate all modulators applications shall 51begin at index zero, incrementing by one until the driver returns 52EINVAL. 53 54Modulators have two writable properties, an audio modulation set and the 55radio frequency. To change the modulated audio subprograms, applications 56initialize the ``index`` and ``txsubchans`` fields and the ``reserved`` 57array and call the :ref:`VIDIOC_S_MODULATOR <VIDIOC_G_MODULATOR>` ioctl. Drivers may choose a 58different audio modulation if the request cannot be satisfied. However 59this is a write-only ioctl, it does not return the actual audio 60modulation selected. 61 62:ref:`SDR <sdr>` specific modulator types are ``V4L2_TUNER_SDR`` and 63``V4L2_TUNER_RF``. For SDR devices ``txsubchans`` field must be 64initialized to zero. The term 'modulator' means SDR transmitter in this 65context. 66 67To change the radio frequency the 68:ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctl is available. 69 70 71.. tabularcolumns:: |p{2.9cm}|p{2.9cm}|p{5.8cm}|p{2.9cm}|p{3.0cm}| 72 73.. c:type:: v4l2_modulator 74 75.. flat-table:: struct v4l2_modulator 76 :header-rows: 0 77 :stub-columns: 0 78 :widths: 1 1 2 1 1 79 80 * - __u32 81 - ``index`` 82 - Identifies the modulator, set by the application. 83 * - __u8 84 - ``name``\ [32] 85 - Name of the modulator, a NUL-terminated ASCII string. 86 87 This information is intended for the user. 88 * - __u32 89 - ``capability`` 90 - Modulator capability flags. No flags are defined for this field, 91 the tuner flags in struct :c:type:`v4l2_tuner` are 92 used accordingly. The audio flags indicate the ability to encode 93 audio subprograms. They will *not* change for example with the 94 current video standard. 95 * - __u32 96 - ``rangelow`` 97 - The lowest tunable frequency in units of 62.5 KHz, or if the 98 ``capability`` flag ``V4L2_TUNER_CAP_LOW`` is set, in units of 99 62.5 Hz, or if the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is 100 set, in units of 1 Hz. 101 * - __u32 102 - ``rangehigh`` 103 - The highest tunable frequency in units of 62.5 KHz, or if the 104 ``capability`` flag ``V4L2_TUNER_CAP_LOW`` is set, in units of 105 62.5 Hz, or if the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is 106 set, in units of 1 Hz. 107 * - __u32 108 - ``txsubchans`` 109 - With this field applications can determine how audio sub-carriers 110 shall be modulated. It contains a set of flags as defined in 111 :ref:`modulator-txsubchans`. 112 113 .. note:: 114 115 The tuner ``rxsubchans`` flags are reused, but the 116 semantics are different. Video output devices 117 are assumed to have an analog or PCM audio input with 1-3 118 channels. The ``txsubchans`` flags select one or more channels 119 for modulation, together with some audio subprogram indicator, 120 for example, a stereo pilot tone. 121 * - __u32 122 - ``type`` 123 - :cspan:`2` Type of the modulator, see :c:type:`v4l2_tuner_type`. 124 * - __u32 125 - ``reserved``\ [3] 126 - Reserved for future extensions. 127 128 Drivers and applications must set the array to zero. 129 130 131 132.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}| 133 134.. _modulator-txsubchans: 135 136.. flat-table:: Modulator Audio Transmission Flags 137 :header-rows: 0 138 :stub-columns: 0 139 :widths: 3 1 4 140 141 * - ``V4L2_TUNER_SUB_MONO`` 142 - 0x0001 143 - Modulate channel 1 as mono audio, when the input has more 144 channels, a down-mix of channel 1 and 2. This flag does not 145 combine with ``V4L2_TUNER_SUB_STEREO`` or 146 ``V4L2_TUNER_SUB_LANG1``. 147 * - ``V4L2_TUNER_SUB_STEREO`` 148 - 0x0002 149 - Modulate channel 1 and 2 as left and right channel of a stereo 150 audio signal. When the input has only one channel or two channels 151 and ``V4L2_TUNER_SUB_SAP`` is also set, channel 1 is encoded as 152 left and right channel. This flag does not combine with 153 ``V4L2_TUNER_SUB_MONO`` or ``V4L2_TUNER_SUB_LANG1``. When the 154 driver does not support stereo audio it shall fall back to mono. 155 * - ``V4L2_TUNER_SUB_LANG1`` 156 - 0x0008 157 - Modulate channel 1 and 2 as primary and secondary language of a 158 bilingual audio signal. When the input has only one channel it is 159 used for both languages. It is not possible to encode the primary 160 or secondary language only. This flag does not combine with 161 ``V4L2_TUNER_SUB_MONO``, ``V4L2_TUNER_SUB_STEREO`` or 162 ``V4L2_TUNER_SUB_SAP``. If the hardware does not support the 163 respective audio matrix, or the current video standard does not 164 permit bilingual audio the :ref:`VIDIOC_S_MODULATOR <VIDIOC_G_MODULATOR>` ioctl shall 165 return an ``EINVAL`` error code and the driver shall fall back to mono 166 or stereo mode. 167 * - ``V4L2_TUNER_SUB_LANG2`` 168 - 0x0004 169 - Same effect as ``V4L2_TUNER_SUB_SAP``. 170 * - ``V4L2_TUNER_SUB_SAP`` 171 - 0x0004 172 - When combined with ``V4L2_TUNER_SUB_MONO`` the first channel is 173 encoded as mono audio, the last channel as Second Audio Program. 174 When the input has only one channel it is used for both audio 175 tracks. When the input has three channels the mono track is a 176 down-mix of channel 1 and 2. When combined with 177 ``V4L2_TUNER_SUB_STEREO`` channel 1 and 2 are encoded as left and 178 right stereo audio, channel 3 as Second Audio Program. When the 179 input has only two channels, the first is encoded as left and 180 right channel and the second as SAP. When the input has only one 181 channel it is used for all audio tracks. It is not possible to 182 encode a Second Audio Program only. This flag must combine with 183 ``V4L2_TUNER_SUB_MONO`` or ``V4L2_TUNER_SUB_STEREO``. If the 184 hardware does not support the respective audio matrix, or the 185 current video standard does not permit SAP the 186 :ref:`VIDIOC_S_MODULATOR <VIDIOC_G_MODULATOR>` ioctl shall return an ``EINVAL`` error code and 187 driver shall fall back to mono or stereo mode. 188 * - ``V4L2_TUNER_SUB_RDS`` 189 - 0x0010 190 - Enable the RDS encoder for a radio FM transmitter. 191 192 193Return Value 194============ 195 196On success 0 is returned, on error -1 and the ``errno`` variable is set 197appropriately. The generic error codes are described at the 198:ref:`Generic Error Codes <gen-errors>` chapter. 199 200EINVAL 201 The struct :c:type:`v4l2_modulator` ``index`` is 202 out of bounds. 203