Documentation/userspace-api/media/v4l/ext-ctrls-fm-tx.rst

Source file repositories/reference/linux-study-clean/Documentation/userspace-api/media/v4l/ext-ctrls-fm-tx.rst

File Facts

System
Linux kernel
Corpus path
Documentation/userspace-api/media/v4l/ext-ctrls-fm-tx.rst
Extension
.rst
Size
7219 bytes
Lines
176
Domain
Support Tooling And Documentation
Bucket
Documentation
Inferred role
Support Tooling And Documentation: documentation
Status
atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
.. c:namespace:: V4L

.. _fm-tx-controls:

********************************
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-id:

FM_TX Control IDs
=================

``V4L2_CID_FM_TX_CLASS (class)``
    The FM_TX class descriptor. Calling
    :ref:`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 :ref:`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.

``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 :ref:`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.

``V4L2_CID_RDS_TX_MONO_STEREO (boolean)``
    Sets the Mono/Stereo bit of the Decoder Identification code. If set,
    then the audio was recorded as stereo.

``V4L2_CID_RDS_TX_ARTIFICIAL_HEAD (boolean)``
    Sets the
    `Artificial Head <http://en.wikipedia.org/wiki/Artificial_head>`__

Annotation

Implementation Notes