# FE_GET_PROPERTY/FE_SET_PROPERTY

    /* Reserved fields should be set to 0 */
    struct dtv_property {
    	__u32 cmd;
    	union {
    		__u32 data;
    		struct {
    			__u8 data[32];
    			__u32 len;
    			__u32 reserved1[3];
    			void *reserved2;
    		} buffer;
    	} u;
    	int result;
    } __attribute__ ((packed));

    /* num of properties cannot exceed DTV_IOCTL_MAX_MSGS per ioctl */
    #define DTV_IOCTL_MAX_MSGS 64

    struct dtv_properties {
    	__u32 num;
    	struct dtv_property *props;
    };

## FE_GET_PROPERTY

DESCRIPTION

This ioctl call returns one or more frontend properties. This call only requires read-only access to the device.

SYNOPSIS

int ioctl(int fd, int request = FE_GET_PROPERTY, dtv_properties ⋆props);

PARAMETERS

int fd | File descriptor returned by a previous call to open().
int num | Equals FE_GET_PROPERTY for this command.
struct dtv_property *props | Points to the location where the front-end property commands are stored.

ERRORS

EINVAL | Invalid parameter(s) received or number of parameters out of the range.
ENOMEM | Out of memory.
EFAULT | Failure while copying data from/to userspace.
EOPNOTSUPP | Property type not supported.

## FE_SET_PROPERTY

DESCRIPTION

This ioctl call sets one or more frontend properties. This call only requires read-only access to the device.

SYNOPSIS

int ioctl(int fd, int request = FE_SET_PROPERTY, dtv_properties ⋆props);

PARAMETERS

int fd | File descriptor returned by a previous call to open().
int num | Equals FE_SET_PROPERTY for this command.
struct dtv_property *props | Points to the location where the front-end property commands are stored.

ERRORS

EINVAL | Invalid parameter(s) received or number of parameters out of the range.
ENOMEM | Out of memory.
EFAULT | Failure while copying data from/to userspace.
EOPNOTSUPP | Property type not supported.

## Property types

On FE_GET_PROPERTY/FE_SET_PROPERTY, the actual action is determined by the dtv_property cmd/data pairs. With one single ioctl, is possible to get/set up to 64 properties. The actual meaning of each property is described on the next sections.

The available frontend property types are:

    #define DTV_UNDEFINED		0
    #define DTV_TUNE		1
    #define DTV_CLEAR		2
    #define DTV_FREQUENCY		3
    #define DTV_MODULATION		4
    #define DTV_BANDWIDTH_HZ	5
    #define DTV_INVERSION		6
    #define DTV_DISEQC_MASTER	7
    #define DTV_SYMBOL_RATE		8
    #define DTV_INNER_FEC		9
    #define DTV_VOLTAGE		10
    #define DTV_TONE		11
    #define DTV_PILOT		12
    #define DTV_ROLLOFF		13
    #define DTV_DISEQC_SLAVE_REPLY	14
    #define DTV_FE_CAPABILITY_COUNT	15
    #define DTV_FE_CAPABILITY	16
    #define DTV_DELIVERY_SYSTEM	17
    #define DTV_ISDBT_PARTIAL_RECEPTION	18
    #define DTV_ISDBT_SOUND_BROADCASTING	19
    #define DTV_ISDBT_SB_SUBCHANNEL_ID	20
    #define DTV_ISDBT_SB_SEGMENT_IDX	21
    #define DTV_ISDBT_SB_SEGMENT_COUNT	22
    #define DTV_ISDBT_LAYERA_FEC			23
    #define DTV_ISDBT_LAYERA_MODULATION		24
    #define DTV_ISDBT_LAYERA_SEGMENT_COUNT		25
    #define DTV_ISDBT_LAYERA_TIME_INTERLEAVING	26
    #define DTV_ISDBT_LAYERB_FEC			27
    #define DTV_ISDBT_LAYERB_MODULATION		28
    #define DTV_ISDBT_LAYERB_SEGMENT_COUNT		29
    #define DTV_ISDBT_LAYERB_TIME_INTERLEAVING	30
    #define DTV_ISDBT_LAYERC_FEC			31
    #define DTV_ISDBT_LAYERC_MODULATION		32
    #define DTV_ISDBT_LAYERC_SEGMENT_COUNT		33
    #define DTV_ISDBT_LAYERC_TIME_INTERLEAVING	34
    #define DTV_API_VERSION		35
    #define DTV_CODE_RATE_HP	36
    #define DTV_CODE_RATE_LP	37
    #define DTV_GUARD_INTERVAL	38
    #define DTV_TRANSMISSION_MODE	39
    #define DTV_HIERARCHY		40
    #define DTV_ISDBT_LAYER_ENABLED	41
    #define DTV_ISDBS_TS_ID		42

## Parameters that are common to all Digital TV standards

### `DTV_FREQUENCY`

Central frequency of the channel, in HZ.

Notes:

1)For ISDB-T, the channels are usually transmitted with an offset of 143kHz. E.g. a valid frequncy could be 474143 kHz. The stepping is bound to the bandwidth of the channel which is 6MHz.

2)As in ISDB-Tsb the channel consists of only one or three segments the frequency step is 429kHz, 3*429 respectively. As for ISDB-T the central frequency of the channel is expected.

### `DTV_BANDWIDTH_HZ`

Bandwidth for the channel, in HZ.

Possible values: `1712000`, `5000000`, `6000000`, `7000000`, `8000000`, `10000000`.

Notes:

1) For ISDB-T it should be always 6000000Hz (6MHz)

2) For ISDB-Tsb it can vary depending on the number of connected segments

3) Bandwidth doesn't apply for DVB-C transmissions, as the bandwidth for DVB-C depends on the symbol rate

4) Bandwidth in ISDB-T is fixed (6MHz) or can be easily derived from other parameters (DTV_ISDBT_SB_SEGMENT_IDX, DTV_ISDBT_SB_SEGMENT_COUNT).

5) DVB-T supports 6, 7 and 8MHz.

6) In addition, DVB-T2 supports 1.172, 5 and 10MHz.

### `DTV_DELIVERY_SYSTEM`

Specifies the type of Delivery system

Possible values:

    typedef enum fe_delivery_system {
    	SYS_UNDEFINED,
    	SYS_DVBC_ANNEX_AC,
    	SYS_DVBC_ANNEX_B,
    	SYS_DVBT,
    	SYS_DSS,
    	SYS_DVBS,
    	SYS_DVBS2,
    	SYS_DVBH,
    	SYS_ISDBT,
    	SYS_ISDBS,
    	SYS_ISDBC,
    	SYS_ATSC,
    	SYS_ATSCMH,
    	SYS_DMBTH,
    	SYS_CMMB,
    	SYS_DAB,
    	SYS_DVBT2,
    } fe_delivery_system_t;

### `DTV_TRANSMISSION_MODE`

Specifies the number of carriers used by the standard

Possible values are:

    typedef enum fe_transmit_mode {
    	TRANSMISSION_MODE_2K,
    	TRANSMISSION_MODE_8K,
    	TRANSMISSION_MODE_AUTO,
    	TRANSMISSION_MODE_4K,
    	TRANSMISSION_MODE_1K,
    	TRANSMISSION_MODE_16K,
    	TRANSMISSION_MODE_32K,
    } fe_transmit_mode_t;

Notes:

1) ISDB-T supports three carrier/symbol-size: 8K, 4K, 2K. It is called 'mode' in the standard: Mode 1 is 2K, mode 2 is 4K, mode 3 is 8K

2) If `DTV_TRANSMISSION_MODE` is set the `TRANSMISSION_MODE_AUTO` the hardware will try to find the correct FFT-size (if capable) and will use TMCC to fill in the missing parameters.

3) DVB-T specifies 2K and 8K as valid sizes.

4) DVB-T2 specifies 1K, 2K, 4K, 8K, 16K and 32K.

### `DTV_GUARD_INTERVAL`

Possible values are:

    typedef enum fe_guard_interval {
    	GUARD_INTERVAL_1_32,
    	GUARD_INTERVAL_1_16,
    	GUARD_INTERVAL_1_8,
    	GUARD_INTERVAL_1_4,
    	GUARD_INTERVAL_AUTO,
    	GUARD_INTERVAL_1_128,
    	GUARD_INTERVAL_19_128,
    	GUARD_INTERVAL_19_256,
    } fe_guard_interval_t;

Notes:

1) If `DTV_GUARD_INTERVAL` is set the `GUARD_INTERVAL_AUTO` the hardware will try to find the correct guard interval (if capable) and will use TMCC to fill in the missing parameters.

2) Intervals 1/128, 19/128 and 19/256 are used only for DVB-T2 at present

## ISDB-T frontend

This section describes shortly what are the possible parameters in the Linux DVB-API called "S2API" and now DVB API 5 in order to tune an ISDB-T/ISDB-Tsb demodulator:

This ISDB-T/ISDB-Tsb API extension should reflect all information needed to tune any ISDB-T/ISDB-Tsb hardware. Of course it is possible that some very sophisticated devices won't need certain parameters to tune.

The information given here should help application writers to know how to handle ISDB-T and ISDB-Tsb hardware using the Linux DVB-API.

The details given here about ISDB-T and ISDB-Tsb are just enough to basically show the dependencies between the needed parameter values, but surely some information is left out. For more detailed information see the following documents:

ARIB STD-B31 - "Transmission System for Digital Terrestrial Television Broadcasting" and

ARIB TR-B14 - "Operational Guidelines for Digital Terrestrial Television Broadcasting".

In order to read this document one has to have some knowledge the channel structure in ISDB-T and ISDB-Tsb. I.e. it has to be known to the reader that an ISDB-T channel consists of 13 segments, that it can have up to 3 layer sharing those segments, and things like that.

Parameters used by ISDB-T and ISDB-Tsb.

### ISDB-T only parameters

#### `DTV_ISDBT_PARTIAL_RECEPTION`

`If DTV_ISDBT_SOUND_BROADCASTING` is '0' this bit-field represents whether the channel is in partial reception mode or not.

If '1' `DTV_ISDBT_LAYERA_*` values are assigned to the center segment and `DTV_ISDBT_LAYERA_SEGMENT_COUNT` has to be '1'.

If in addition `DTV_ISDBT_SOUND_BROADCASTING` is '1' `DTV_ISDBT_PARTIAL_RECEPTION` represents whether this ISDB-Tsb channel is consisting of one segment and layer or three segments and two layers.

Possible values: 0, 1, -1 (AUTO)

#### `DTV_ISDBT_SOUND_BROADCASTING`

This field represents whether the other DTV_ISDBT_*-parameters are referring to an ISDB-T and an ISDB-Tsb channel. (See also `DTV_ISDBT_PARTIAL_RECEPTION`).

Possible values: 0, 1, -1 (AUTO)

#### `DTV_ISDBT_SB_SUBCHANNEL_ID`

This field only applies if `DTV_ISDBT_SOUND_BROADCASTING` is '1'.

(Note of the author: This might not be the correct description of the `SUBCHANNEL-ID` in all details, but it is my understanding of the technical background needed to program a device)

An ISDB-Tsb channel (1 or 3 segments) can be broadcasted alone or in a set of connected ISDB-Tsb channels. In this set of channels every channel can be received independently. The number of connected ISDB-Tsb segment can vary, e.g. depending on the frequency spectrum bandwidth available.

Example: Assume 8 ISDB-Tsb connected segments are broadcasted. The broadcaster has several possibilities to put those channels in the air: Assuming a normal 13-segment ISDB-T spectrum he can align the 8 segments from position 1-8 to 5-13 or anything in between.

The underlying layer of segments are subchannels: each segment is consisting of several subchannels with a predefined IDs. A sub-channel is used to help the demodulator to synchronize on the channel.

An ISDB-T channel is always centered over all sub-channels. As for the example above, in ISDB-Tsb it is no longer as simple as that.

`The DTV_ISDBT_SB_SUBCHANNEL_ID` parameter is used to give the sub-channel ID of the segment to be demodulated.

Possible values: 0 .. 41, -1 (AUTO)

#### `DTV_ISDBT_SB_SEGMENT_IDX`

This field only applies if `DTV_ISDBT_SOUND_BROADCASTING` is '1'.

`DTV_ISDBT_SB_SEGMENT_IDX` gives the index of the segment to be demodulated for an ISDB-Tsb channel where several of them are transmitted in the connected manner.

Possible values: 0 .. `DTV_ISDBT_SB_SEGMENT_COUNT` - 1

Note: This value cannot be determined by an automatic channel search.

#### `DTV_ISDBT_SB_SEGMENT_COUNT`

This field only applies if `DTV_ISDBT_SOUND_BROADCASTING` is '1'.

`DTV_ISDBT_SB_SEGMENT_COUNT` gives the total count of connected ISDB-Tsb channels.

Possible values: 1 .. 13

Note: This value cannot be determined by an automatic channel search.

#### Hierarchical layers

ISDB-T channels can be coded hierarchically. As opposed to DVB-T in ISDB-T hierarchical layers can be decoded simultaneously. For that reason a ISDB-T demodulator has 3 viterbi and 3 reed-solomon-decoders.

ISDB-T has 3 hierarchical layers which each can use a part of the available segments. The total number of segments over all layers has to 13 in ISDB-T.

##### `DTV_ISDBT_LAYER_ENABLED`

Hierarchical reception in ISDB-T is achieved by enabling or disabling layers in the decoding process. Setting all bits of `DTV_ISDBT_LAYER_ENABLED` to '1' forces all layers (if applicable) to be demodulated. This is the default.

If the channel is in the partial reception mode (`DTV_ISDBT_PARTIAL_RECEPTION` = 1) the central segment can be decoded independently of the other 12 segments. In that mode layer A has to have a `SEGMENT_COUNT` of 1.

In ISDB-Tsb only layer A is used, it can be 1 or 3 in ISDB-Tsb according to `DTV_ISDBT_PARTIAL_RECEPTION`. `SEGMENT_COUNT` must be filled accordingly.

Possible values: 0x1, 0x2, 0x4 (|-able)

`DTV_ISDBT_LAYER_ENABLED[0:0]` - layer A

`DTV_ISDBT_LAYER_ENABLED[1:1]` - layer B

`DTV_ISDBT_LAYER_ENABLED[2:2]` - layer C

`DTV_ISDBT_LAYER_ENABLED[31:3]` unused

##### `DTV_ISDBT_LAYER*_FEC`

Possible values: `FEC_AUTO`, `FEC_1_2`, `FEC_2_3`, `FEC_3_4`, `FEC_5_6`, `FEC_7_8`

##### `DTV_ISDBT_LAYER*_MODULATION`

Possible values: `QAM_AUTO`, QP`SK, QAM_16`, `QAM_64`, `DQPSK`

Note: If layer C is `DQPSK` layer B has to be `DQPSK`. If layer B is `DQPSK` and `DTV_ISDBT_PARTIAL_RECEPTION`=0 layer has to be `DQPSK`.

##### `DTV_ISDBT_LAYER*_SEGMENT_COUNT`

Possible values: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, -1 (AUTO)

Note: Truth table for `DTV_ISDBT_SOUND_BROADCASTING` and `DTV_ISDBT_PARTIAL_RECEPTION` and `LAYER`*_SEGMENT_COUNT

PR | SB | Layer A width | Layer B width | Layer C width | total width
0 | 0 | 1 .. 13 | 1 .. 13 | 1 .. 13 | 13
1 | 0 | 1 | 1 .. 13 | 1 .. 13 | 13
0 | 1 | 1 | 0 | 0 | 1
1 | 1 | 1 | 2 | 0 | 13

##### `DTV_ISDBT_LAYER*_TIME_INTERLEAVING`

Possible values: 0, 1, 2, 3, -1 (AUTO)

Note: The real inter-leaver depth-names depend on the mode (fft-size); the values here are referring to what can be found in the TMCC-structure - independent of the mode.

### DVB-T2 parameters

This section covers parameters that apply only to the DVB-T2 delivery method. DVB-T2 support is currently in the early stages development so expect this section to grow and become more detailed with time.

#### `DTV_DVBT2_PLP_ID`

DVB-T2 supports Physical Layer Pipes (PLP) to allow transmission of many data types via a single multiplex. The API will soon support this at which point this section will be expanded.