7.17. ioctl VIDIOC_ENUM_FREQ_BANDS¶
7.17.1. Name¶
VIDIOC_ENUM_FREQ_BANDS - Enumerate supported frequency bands
7.17.2. Synopsis¶
-
int
ioctl
(int fd, VIDIOC_ENUM_FREQ_BANDS, struct v4l2_frequency_band *argp)¶
7.17.3. Arguments¶
fd
- File descriptor returned by open().
argp
- Pointer to struct
v4l2_frequency_band
.
7.17.4. Description¶
Enumerates the frequency bands that a tuner or modulator supports. To do
this applications initialize the tuner
, type
and index
fields, and zero out the reserved
array of a struct
v4l2_frequency_band
and call the
ioctl VIDIOC_ENUM_FREQ_BANDS ioctl with a pointer to this structure.
This ioctl is supported if the V4L2_TUNER_CAP_FREQ_BANDS
capability
of the corresponding tuner/modulator is set.
-
v4l2_frequency_band
¶
__u32 | tuner |
The tuner or modulator index number. This is the same value as in
the struct v4l2_input tuner field and
the struct v4l2_tuner index field, or
the struct v4l2_output modulator field
and the struct v4l2_modulator index
field. |
||
__u32 | type |
The tuner type. This is the same value as in the struct
v4l2_tuner type field. The type must be
set to V4L2_TUNER_RADIO for /dev/radioX device nodes, and
to V4L2_TUNER_ANALOG_TV for all others. Set this field to
V4L2_TUNER_RADIO for modulators (currently only radio
modulators are supported). See v4l2_tuner_type |
||
__u32 | index |
Identifies the frequency band, set by the application. | ||
__u32 | capability |
The tuner/modulator capability flags for this
frequency band, see Tuner and Modulator Capability Flags. The
V4L2_TUNER_CAP_LOW or V4L2_TUNER_CAP_1HZ capability must
be the same for all frequency bands of the selected
tuner/modulator. So either all bands have that capability set, or
none of them have that capability. |
||
__u32 | rangelow |
The lowest tunable frequency in units of 62.5 kHz, or
if the capability flag V4L2_TUNER_CAP_LOW is set, in units
of 62.5 Hz, for this frequency band. A 1 Hz unit is used when the
capability flag V4L2_TUNER_CAP_1HZ is set. |
||
__u32 | rangehigh |
The highest tunable frequency in units of 62.5 kHz,
or if the capability flag V4L2_TUNER_CAP_LOW is set, in
units of 62.5 Hz, for this frequency band. A 1 Hz unit is used
when the capability flag V4L2_TUNER_CAP_1HZ is set. |
||
__u32 | modulation |
The supported modulation systems of this frequency band. See Band Modulation Systems. Note Currently only one modulation system per frequency band is supported. More work will need to be done if multiple modulation systems are possible. Contact the linux-media mailing list (https://linuxtv.org/lists.php) if you need such functionality. |
||
__u32 | reserved [9] |
Reserved for future extensions. Applications and drivers must set the array to zero. |
V4L2_BAND_MODULATION_VSB |
0x02 | Vestigial Sideband modulation, used for analog TV. |
V4L2_BAND_MODULATION_FM |
0x04 | Frequency Modulation, commonly used for analog radio. |
V4L2_BAND_MODULATION_AM |
0x08 | Amplitude Modulation, commonly used for analog radio. |
7.17.5. Return Value¶
On success 0 is returned, on error -1 and the errno
variable is set
appropriately. The generic error codes are described at the
Generic Error Codes chapter.
- EINVAL
- The
tuner
orindex
is out of bounds or thetype
field is wrong.