frontend_scan man page

frontend_scan — Digital TV frontend scan

Files

file dvb-scan.h
Provides interfaces to scan programs inside MPEG-TS digital TV streams.

Data Structures

struct dvb_v5_descriptors_program
Associates PMT with PAT tables.
struct dvb_v5_descriptors
Contains the descriptors needed to scan the Service ID and other relevant info at a MPEG-TS Digital TV stream.
struct dvb_table_filter
Describes the PES filters used by DVB scan.

Typedefs

typedef int( check_frontend_t) (void *args, struct dvb_v5_fe_parms *parms)
Callback for the application to show the frontend status.

Functions

void dvb_table_filter_free (struct dvb_table_filter *sect)
deallocates all data associated with a table filter
int dvb_read_section (struct dvb_v5_fe_parms *parms, int dmx_fd, unsigned char tid, uint16_t pid, void **table, unsigned timeout)
read MPEG-TS tables that comes from a DTV card
int dvb_read_section_with_id (struct dvb_v5_fe_parms *parms, int dmx_fd, unsigned char tid, uint16_t pid, int ts_id, void **table, unsigned timeout)
read MPEG-TS tables that comes from a DTV card with an specific table section ID
int dvb_read_sections (struct dvb_v5_fe_parms *parms, int dmx_fd, struct dvb_table_filter *sect, unsigned timeout)
read MPEG-TS tables that comes from a DTV card
struct dvb_v5_descriptors * dvb_scan_alloc_handler_table (uint32_t delivery_system)
allocates a struct dvb_v5_descriptors
void dvb_scan_free_handler_table (struct dvb_v5_descriptors *dvb_scan_handler)
frees a struct dvb_v5_descriptors
struct dvb_v5_descriptors * dvb_get_ts_tables (struct dvb_v5_fe_parms *parms, int dmx_fd, uint32_t delivery_system, unsigned other_nit, unsigned timeout_multiply)
Scans a DVB stream, looking for the tables needed to identify the programs inside a MPEG-TS.
void dvb_free_ts_tables (struct dvb_v5_descriptors *dvb_desc)
frees a struct dvb_v5_descriptors
struct dvb_v5_descriptors * dvb_scan_transponder (struct dvb_v5_fe_parms *parms, struct dvb_entry *entry, int dmx_fd, check_frontend_t *check_frontend, void *args, unsigned other_nit, unsigned timeout_multiply)
Scans a DVB dvb_add_scaned_transponder.
void dvb_add_scaned_transponders (struct dvb_v5_fe_parms *parms, struct dvb_v5_descriptors *dvb_scan_handler, struct dvb_entry *first_entry, struct dvb_entry *entry)
Add new transponders to a dvb_file.

Typedef Documentation

typedef int( check_frontend_t) (void *args, struct dvb_v5_fe_parms *parms)

Callback for the application to show the frontend status.

Parameters:

args a pointer, opaque to libdvbv5, to be used by the application if needed.
parms pointer to struct dvb_v5_fe_parms created when the frontend is opened

Definition at line 278 of file dvb-scan.h.

Function Documentation

void dvb_add_scaned_transponders (struct dvb_v5_fe_parms * parms, struct dvb_v5_descriptors * dvb_scan_handler, struct dvb_entry * first_entry, struct dvb_entry * entry)

Add new transponders to a dvb_file.

Parameters:

parms pointer to struct dvb_v5_fe_parms created when the frontend is opened
dvb_scan_handler pointer to a struct dvb_v5_descriptors containing scaned MPEG-TS
first_entry first entry of a DVB file struct
entry current entry on a DVB file struct

When the NIT table is parsed, some new transponders could be described inside. This function adds new entries to a dvb_file struct, pointing to those new transponders. It is used inside the scan loop, as shown at the dvb_scan_transponder(), to add new channels.

Example:

1 for (entry = dvb_file->first_entry; entry != NULL; entry = entry->next) {
2      struct dvb_v5_descriptors *dvb_scan_handler = NULL;
3 
4      dvb_scan_handler = dvb_scan_transponder(parms, entry, dmx_fd,
5                                         &check_frontend, args,
6                                         args->other_nit,
7                                         args->timeout_multiply);
8      if (parms->abort) {
9         dvb_scan_free_handler_table(dvb_scan_handler);
10         break;
11      }
12      if (dvb_scan_handler) {
13         dvb_store_channel(&dvb_file_new, parms, dvb_scan_handler,
14                           args->get_detected, args->get_nit);
15         dvb_scan_free_handler_table(dvb_scan_handler);
16 
17         dvb_add_scaned_transponders(parms, dvb_scan_handler,
18                                     dvb_file->first_entry, entry);
19 
20         dvb_scan_free_handler_table(dvb_scan_handler);
21         }
22 }

Examples: dvbv5-scan.c.

void dvb_free_ts_tables (struct dvb_v5_descriptors * dvb_desc)

frees a struct dvb_v5_descriptors

Parameters:

dvb_desc pointed to the structure to be freed.

This function recursively frees everything that is allocated by dvb_get_ts_tables() and stored at dvb_desc, including dvb_desc itself.

struct dvb_v5_descriptors* dvb_get_ts_tables (struct dvb_v5_fe_parms * parms, int dmx_fd, uint32_t delivery_system, unsigned other_nit, unsigned timeout_multiply)

Scans a DVB stream, looking for the tables needed to identify the programs inside a MPEG-TS.

Parameters:

parms pointer to struct dvb_v5_fe_parms created when the frontend is opened
dmx_fd an opened demux file descriptor
delivery_system delivery system to be scanned
other_nit use alternate table IDs for NIT and other tables
timeout_multiply improves the timeout for each table reception by using a value that will multiply the wait time.

Given an opened frontend and demux, this function seeks for all programs available at the transport stream, and parses the following tables: PAT, PMT, NIT, SDT (and VCT, if the delivery system is ATSC).

On sucess, it returns a pointer to a struct dvb_v5_descriptors, that can either be used to tune into a service or to be stored inside a file.

int dvb_read_section (struct dvb_v5_fe_parms * parms, int dmx_fd, unsigned char tid, uint16_t pid, void ** table, unsigned timeout)

read MPEG-TS tables that comes from a DTV card

Parameters:

parms pointer to struct dvb_v5_fe_parms created when the frontend is opened
dmx_fd an opened demux file descriptor
tid Table ID
pid Program ID
table pointer to a pointer for the table struct to be filled
timeout Limit, in seconds, to read a MPEG-TS table

This function is used to read the DVB tables by specifying a table ID and a program ID. The libdvbv5 should have a parser for the descriptors of the table type that should be parsed. The table will be automatically allocated on success. The function will read on the specified demux and return when reading is done or an error has occurred. If table is not NULL after the call, it has to be freed with the apropriate free table function (even if an error has occurred).

If the application wants to abort the read operation, it can change the value of parms->p.abort to 1.

Returns 0 on success or a negative error code.

Example usage:

1 struct dvb_table_pat *pat;
2 int r = dvb_read_section( parms, dmx_fd, DVB_TABLE_PAT, DVB_TABLE_PAT_PID,
3                     (void **) &pat, 5 );
4 if (r < 0)
5      dvb_logerr("error reading PAT table");
6 else {
7      // do something with pat
8 }
9 if (pat)
10      dvb_table_pat_free( pat );

int dvb_read_section_with_id (struct dvb_v5_fe_parms * parms, int dmx_fd, unsigned char tid, uint16_t pid, int ts_id, void ** table, unsigned timeout)

read MPEG-TS tables that comes from a DTV card with an specific table section ID

Parameters:

parms pointer to struct dvb_v5_fe_parms created when the frontend is opened
dmx_fd an opened demux file descriptor
tid Table ID
pid Program ID
ts_id Table section ID (for multisession filtering). If no specific table section is needed, -1 should be used
table pointer to a pointer for the table struct to be filled
timeout limit, in seconds, to read a MPEG-TS table

This is a variant of dvb_read_section() that also seeks for an specific table section ID given by ts_id.

int dvb_read_sections (struct dvb_v5_fe_parms * parms, int dmx_fd, struct dvb_table_filter * sect, unsigned timeout)

read MPEG-TS tables that comes from a DTV card

Parameters:

parms pointer to struct dvb_v5_fe_parms created when the frontend is opened
dmx_fd an opened demux file descriptor
sect section filter pointer
timeout limit, in seconds, to read a MPEG-TS table

This is a variant of dvb_read_section() that uses a struct dvb_table_filter to specify the filter to use.

struct dvb_v5_descriptors* dvb_scan_alloc_handler_table (uint32_t delivery_system)

allocates a struct dvb_v5_descriptors

Parameters:

delivery_system Delivery system to be used on the table

At success, returns a pointer. NULL otherwise.

void dvb_scan_free_handler_table (struct dvb_v5_descriptors * dvb_scan_handler)

frees a struct dvb_v5_descriptors

Parameters:

dvb_scan_handler pointer to the struct to be freed.

Examples: dvbv5-scan.c.

struct dvb_v5_descriptors* dvb_scan_transponder (struct dvb_v5_fe_parms * parms, struct dvb_entry * entry, int dmx_fd, check_frontend_t * check_frontend, void * args, unsigned other_nit, unsigned timeout_multiply)

Scans a DVB dvb_add_scaned_transponder.

Parameters:

parms pointer to struct dvb_v5_fe_parms created when the frontend is opened
entry DVB file entry that corresponds to a transponder to be tuned
dmx_fd an opened demux file descriptor
check_frontend a pointer to a function that will show the frontend status while tuning into a transponder
args a pointer, opaque to libdvbv5, that will be used when calling check_frontend. It should contain any parameters that could be needed by check_frontend.
other_nit Use alternate table IDs for NIT and other tables
timeout_multiply Improves the timeout for each table reception, by

This is the function that applications should use when doing a transponders scan. It does everything needed to fill the entries with DVB programs (virtual channels) and detect the PIDs associated with them.

A typical usage is to after open a channel file, open a dmx_fd and open a frontend. Then, seek for the MPEG tables on all the transponder frequencies with:

1 for (entry = dvb_file->first_entry; entry != NULL; entry = entry->next) {
2      struct dvb_v5_descriptors *dvb_scan_handler = NULL;
3 
4      dvb_scan_handler = dvb_scan_transponder(parms, entry, dmx_fd,
5                                         &check_frontend, args,
6                                         args->other_nit,
7                                         args->timeout_multiply);
8      if (parms->abort) {
9         dvb_scan_free_handler_table(dvb_scan_handler);
10         break;
11      }
12      if (dvb_scan_handler) {
13         dvb_store_channel(&dvb_file_new, parms, dvb_scan_handler,
14                           args->get_detected, args->get_nit);
15         dvb_scan_free_handler_table(dvb_scan_handler);
16         }
17 }

Examples: dvbv5-scan.c.

void dvb_table_filter_free (struct dvb_table_filter * sect)

deallocates all data associated with a table filter

Parameters:

sect table filter pointer

Author

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Info

Tue Mar 1 2016 Version 1.10.0 libdvbv5