7.35. ioctl VIDIOC_G_MODULATOR, VIDIOC_S_MODULATOR¶
VIDIOC_G_MODULATOR - VIDIOC_S_MODULATOR - Get or set modulator attributes
int ioctl(int fd, VIDIOC_G_MODULATOR, struct v4l2_modulator *argp)
int ioctl(int fd, VIDIOC_S_MODULATOR, const struct v4l2_modulator *argp)
- File descriptor returned by
- Pointer to struct
To query the attributes of a modulator applications initialize the
index field and zero out the
reserved array of a struct
v4l2_modulator and call the
VIDIOC_G_MODULATOR ioctl with a pointer to this structure. Drivers
fill the rest of the structure or return an
EINVAL error code when the
index is out of bounds. To enumerate all modulators applications shall
begin at index zero, incrementing by one until the driver returns
Modulators have two writable properties, an audio modulation set and the
radio frequency. To change the modulated audio subprograms, applications
txsubchans fields and the
array and call the VIDIOC_S_MODULATOR ioctl. Drivers may choose a
different audio modulation if the request cannot be satisfied. However
this is a write-only ioctl, it does not return the actual audio
SDR specific modulator types are
V4L2_TUNER_RF. For SDR devices
txsubchans field must be
initialized to zero. The term ‘modulator’ means SDR transmitter in this
To change the radio frequency the VIDIOC_S_FREQUENCY ioctl is available.
||Identifies the modulator, set by the application.|
Name of the modulator, a NUL-terminated ASCII string.
This information is intended for the user.
||Modulator capability flags. No flags are defined for this field,
the tuner flags in struct
||The lowest tunable frequency in units of 62.5 KHz, or if the
||The highest tunable frequency in units of 62.5 KHz, or if the
With this field applications can determine how audio sub-carriers shall be modulated. It contains a set of flags as defined in Modulator Audio Transmission Flags.
|| Type of the modulator, see
Reserved for future extensions.
Drivers and applications must set the array to zero.
||0x0001||Modulate channel 1 as mono audio, when the input has more
channels, a down-mix of channel 1 and 2. This flag does not
||0x0002||Modulate channel 1 and 2 as left and right channel of a stereo
audio signal. When the input has only one channel or two channels
||0x0008||Modulate channel 1 and 2 as primary and secondary language of a
bilingual audio signal. When the input has only one channel it is
used for both languages. It is not possible to encode the primary
or secondary language only. This flag does not combine with
||0x0004||Same effect as
||0x0004||When combined with
||0x0010||Enable the RDS encoder for a radio FM transmitter.|