8.42. ioctl VIDIOC_G_TUNER, VIDIOC_S_TUNER¶
8.42.1. Name¶
VIDIOC_G_TUNER - VIDIOC_S_TUNER - Get or set tuner attributes
8.42.2. Synopsis¶
-
int
ioctl
(int fd, int request, struct v4l2_tuner *argp)¶
-
int
ioctl
(int fd, int request, const struct v4l2_tuner *argp)¶
8.42.3. Arguments¶
fd
- File descriptor returned by open().
request
- VIDIOC_G_TUNER, VIDIOC_S_TUNER
argp
8.42.4. Description¶
To query the attributes of a tuner applications initialize the index
field and zero out the reserved
array of a struct
v4l2_tuner and call the VIDIOC_G_TUNER
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 tuners applications shall begin at index zero,
incrementing by one until the driver returns EINVAL
.
Tuners have two writable properties, the audio mode and the radio
frequency. To change the audio mode, applications initialize the
index
, audmode
and reserved
fields and call the
VIDIOC_S_TUNER
ioctl. This will not change the current tuner,
which is determined by the current video input. Drivers may choose a
different audio mode if the requested mode is invalid or unsupported.
Since this is a write-only ioctl, it does not return the actually
selected audio mode.
SDR specific tuner types are V4L2_TUNER_SDR
and
V4L2_TUNER_RF
. For SDR devices audmode
field must be initialized
to zero. The term ‘tuner’ means SDR receiver in this context.
To change the radio frequency the VIDIOC_S_FREQUENCY ioctl is available.
__u32 | index |
Identifies the tuner, set by the application. | |
__u8 | name [32] |
Name of the tuner, a NUL-terminated ASCII string. This information is intended for the user. |
|
__u32 | type |
Type of the tuner, see enum v4l2_tuner_type. | |
__u32 | capability |
Tuner capability flags, see Tuner and Modulator Capability Flags. Audio flags indicate the ability to decode audio subprograms. They will not change, for example with the current video standard. When the structure refers to a radio tuner the
If multiple frequency bands are supported, then |
|
__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, or if the capability flag V4L2_TUNER_CAP_1HZ
is set, in units of 1 Hz. If multiple frequency bands are
supported, then rangelow is the lowest frequency of all the
frequency bands. |
|
__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, or if the capability flag
V4L2_TUNER_CAP_1HZ is set, in units of 1 Hz. If multiple
frequency bands are supported, then rangehigh is the highest
frequency of all the frequency bands. |
|
__u32 | rxsubchans |
Some tuners or audio decoders can determine the received audio subprograms by analyzing audio carriers, pilot tones or other indicators. To pass this information drivers set flags defined in Tuner Audio Reception Flags in this field. For example: |
|
V4L2_TUNER_SUB_MONO |
receiving mono audio | ||
STEREO | SAP |
receiving stereo audio and a secondary audio program | ||
MONO | STEREO |
receiving mono or stereo audio, the hardware cannot distinguish | ||
LANG1 | LANG2 |
receiving bilingual audio | ||
MONO | STEREO | LANG1 | LANG2 |
receiving mono, stereo or bilingual audio | ||
When the This field is valid only if this is the tuner of the current video input, or when the structure refers to a radio tuner. |
|||
__u32 | audmode |
The selected audio mode, see Tuner Audio Modes for valid values. The audio mode does not affect audio subprogram detection, and like a User Controls it does not automatically change unless the requested mode is invalid or unsupported. See Tuner Audio Matrix for possible results when the selected and received audio programs do not match. Currently this is the only field of struct struct v4l2_tuner applications can change. |
|
__u32 | signal |
The signal strength if known, ranging from 0 to 65535. Higher values indicate a better signal. | |
__s32 | afc |
Automatic frequency control: When the afc value
is negative, the frequency is too low, when positive too high. |
|
__u32 | reserved [4] |
Reserved for future extensions. Drivers and applications must set the array to zero. |
V4L2_TUNER_RADIO |
1 | |
V4L2_TUNER_ANALOG_TV |
2 | |
V4L2_TUNER_SDR |
4 | |
V4L2_TUNER_RF |
5 |
V4L2_TUNER_CAP_LOW |
0x0001 | When set, tuning frequencies are expressed in units of 62.5 Hz instead of 62.5 kHz. |
V4L2_TUNER_CAP_NORM |
0x0002 | This is a multi-standard tuner; the video standard can or must be
switched. (B/G PAL tuners for example are typically not considered
multi-standard because the video standard is automatically
determined from the frequency band.) The set of supported video
standards is available from the struct
v4l2_input pointing to this tuner, see the
description of ioctl ioctl VIDIOC_ENUMINPUT
for details. Only V4L2_TUNER_ANALOG_TV tuners can have this
capability. |
V4L2_TUNER_CAP_HWSEEK_BOUNDED |
0x0004 | If set, then this tuner supports the hardware seek functionality where the seek stops when it reaches the end of the frequency range. |
V4L2_TUNER_CAP_HWSEEK_WRAP |
0x0008 | If set, then this tuner supports the hardware seek functionality where the seek wraps around when it reaches the end of the frequency range. |
V4L2_TUNER_CAP_STEREO |
0x0010 | Stereo audio reception is supported. |
V4L2_TUNER_CAP_LANG1 |
0x0040 | Reception of the primary language of a bilingual audio program is
supported. Bilingual audio is a feature of two-channel systems,
transmitting the primary language monaural on the main audio
carrier and a secondary language monaural on a second carrier.
Only V4L2_TUNER_ANALOG_TV tuners can have this capability. |
V4L2_TUNER_CAP_LANG2 |
0x0020 | Reception of the secondary language of a bilingual audio program
is supported. Only V4L2_TUNER_ANALOG_TV tuners can have this
capability. |
V4L2_TUNER_CAP_SAP |
0x0020 | Reception of a secondary audio program is supported. This is a
feature of the BTSC system which accompanies the NTSC video
standard. Two audio carriers are available for mono or stereo
transmissions of a primary language, and an independent third
carrier for a monaural secondary language. Only
Note The |
V4L2_TUNER_CAP_RDS |
0x0080 | RDS capture is supported. This capability is only valid for radio tuners. |
V4L2_TUNER_CAP_RDS_BLOCK_IO |
0x0100 | The RDS data is passed as unparsed RDS blocks. |
V4L2_TUNER_CAP_RDS_CONTROLS |
0x0200 | The RDS data is parsed by the hardware and set via controls. |
V4L2_TUNER_CAP_FREQ_BANDS |
0x0400 | The ioctl VIDIOC_ENUM_FREQ_BANDS ioctl can be used to enumerate the available frequency bands. |
V4L2_TUNER_CAP_HWSEEK_PROG_LIM |
0x0800 | The range to search when using the hardware seek functionality is programmable, see ioctl VIDIOC_S_HW_FREQ_SEEK for details. |
V4L2_TUNER_CAP_1HZ |
0x1000 | When set, tuning frequencies are expressed in units of 1 Hz instead of 62.5 kHz. |
V4L2_TUNER_SUB_MONO |
0x0001 | The tuner receives a mono audio signal. |
V4L2_TUNER_SUB_STEREO |
0x0002 | The tuner receives a stereo audio signal. |
V4L2_TUNER_SUB_LANG1 |
0x0008 | The tuner receives the primary language of a bilingual audio
signal. Drivers must clear this flag when the current video
standard is V4L2_STD_NTSC_M . |
V4L2_TUNER_SUB_LANG2 |
0x0004 | The tuner receives the secondary language of a bilingual audio signal (or a second audio program). |
V4L2_TUNER_SUB_SAP |
0x0004 | The tuner receives a Second Audio Program. Note The |
V4L2_TUNER_SUB_RDS |
0x0010 | The tuner receives an RDS channel. |
V4L2_TUNER_MODE_MONO |
0 | Play mono audio. When the tuner receives a stereo signal this a down-mix of the left and right channel. When the tuner receives a bilingual or SAP signal this mode selects the primary language. |
V4L2_TUNER_MODE_STEREO |
1 | Play stereo audio. When the tuner receives bilingual audio it may play different languages on the left and right channel or the primary language is played on both channels. Playing different languages in this mode is deprecated. New
drivers should do this only in When the tuner receives no stereo signal or does not support
stereo reception the driver shall fall back to |
V4L2_TUNER_MODE_LANG1 |
3 | Play the primary language, mono or stereo. Only
V4L2_TUNER_ANALOG_TV tuners support this mode. |
V4L2_TUNER_MODE_LANG2 |
2 | Play the secondary language, mono. When the tuner receives no
bilingual audio or SAP, or their reception is not supported the
driver shall fall back to mono or stereo mode. Only
V4L2_TUNER_ANALOG_TV tuners support this mode. |
V4L2_TUNER_MODE_SAP |
2 | Play the Second Audio Program. When the tuner receives no
bilingual audio or SAP, or their reception is not supported the
driver shall fall back to mono or stereo mode. Only
Note The |
V4L2_TUNER_MODE_LANG1_LANG2 |
4 | Play the primary language on the left channel, the secondary
language on the right channel. When the tuner receives no
bilingual audio or SAP, it shall fall back to MODE_LANG1 or
MODE_MONO . Only V4L2_TUNER_ANALOG_TV tuners support this
mode. |
Selected V4L2_TUNER_MODE_ |
||||||
---|---|---|---|---|---|---|
Received V4L2_TUNER_SUB_ |
MONO |
STEREO |
LANG1 |
LANG2 = SAP |
LANG1_LANG2 [1] |
|
MONO |
Mono | Mono/Mono | Mono | Mono | Mono/Mono | |
MONO | SAP |
Mono | Mono/Mono | Mono | SAP | Mono/SAP (preferred) or Mono/Mono | |
STEREO |
L+R | L/R | Stereo L/R (preferred) or Mono L+R | Stereo L/R (preferred) or Mono L+R | L/R (preferred) or L+R/L+R | |
STEREO | SAP |
L+R | L/R | Stereo L/R (preferred) or Mono L+R | SAP | L+R/SAP (preferred) or L/R or L+R/L+R | |
LANG1 | LANG2 |
Language 1 | Lang1/Lang2 (deprecated [2]) or Lang1/Lang1 | Language 1 | Language 2 | Lang1/Lang2 (preferred) or Lang1/Lang1 |
8.42.5. 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 struct v4l2_tuner
index
is out of bounds.
[1] | This mode has been added in Linux 2.6.17 and may not be supported by older drivers. |
[2] | Playback of both languages in MODE_STEREO is deprecated. In the
future drivers should produce only the primary language in this mode.
Applications should request MODE_LANG1_LANG2 to record both
languages or a stereo signal. |