ioctl VIDIOC_G_TUNER, VIDIOC_S_TUNER &manvol; VIDIOC_G_TUNER VIDIOC_S_TUNER Get or set tuner attributes int ioctl int fd int request struct v4l2_tuner *argp int ioctl int fd int request const struct v4l2_tuner *argp fd &fd; request VIDIOC_G_TUNER, VIDIOC_S_TUNER argp To query the attributes of a tuner applications initialize the index field and zero out the reserved array of a &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; 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. 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. &v4l2-tuner-type; type Type of the tuner, see . __u32 capability Tuner capability flags, see . 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 only the V4L2_TUNER_CAP_LOW, V4L2_TUNER_CAP_STEREO and V4L2_TUNER_CAP_RDS flags can be set. __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. __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. __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 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 V4L2_TUNER_CAP_STEREO, _LANG1, _LANG2 or _SAP flag is cleared in the capability field, the corresponding V4L2_TUNER_SUB_ flag must not be set here.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 for valid values. The audio mode does not affect audio subprogram detection, and like a control it does not automatically change unless the requested mode is invalid or unsupported. See for possible results when the selected and received audio programs do not match.Currently this is the only field of 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. &cs-def; V4L2_TUNER_RADIO 1 V4L2_TUNER_ANALOG_TV 2 &cs-def; V4L2_TUNER_CAP_LOW 0x0001 When set, tuning frequencies are expressed in units of 62.5 Hz, otherwise in units 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 &v4l2-input; pointing to this tuner, see the description of ioctl &VIDIOC-ENUMINPUT; for details. Only V4L2_TUNER_ANALOG_TV tuners can have this capability. 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 V4L2_TUNER_ANALOG_TV tuners can have this capability.Note the V4L2_TUNER_CAP_LANG2 and V4L2_TUNER_CAP_SAP flags are synonyms. V4L2_TUNER_CAP_SAP applies when the tuner supports the V4L2_STD_NTSC_M video standard. 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. &cs-def; 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_LANG2 and V4L2_TUNER_SUB_SAP flags are synonyms. The V4L2_TUNER_SUB_SAP flag applies when the current video standard is V4L2_STD_NTSC_M. V4L2_TUNER_SUB_RDS 0x0010 The tuner receives an RDS channel. &cs-def; 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 MODE_LANG1_LANG2.When the tuner receives no stereo signal or does not support stereo reception the driver shall fall back to MODE_MONO. 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 V4L2_TUNER_ANALOG_TV tuners support this mode. Note the V4L2_TUNER_MODE_LANG2 and V4L2_TUNER_MODE_SAP are synonyms. 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_LANG2This mode has been added in Linux 2.6.17 and may not be supported by older drivers. 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 (deprecatedPlayback 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.) or Lang1/Lang1 Language 1 Language 2 Lang1/Lang2 (preferred) or Lang1/Lang1 &return-value; EINVAL The &v4l2-tuner; index is out of bounds.