7.17. ioctl VIDIOC_ENUM_FREQ_BANDS¶

7.17.1. Name¶

VIDIOC_ENUM_FREQ_BANDS - Enumerate supported frequency bands

7.17.2. Synopsis¶

VIDIOC_ENUM_FREQ_BANDS¶

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.

type v4l2_frequency_band¶

struct 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.

Band Modulation Systems¶
`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 or index is out of bounds or the type field is wrong.