t38_gateway.h File Reference

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## Classes

struct | t38_stats_t

## Macros

#define | T38_RX_BUF_LEN 2048
#define | T38_TX_HDLC_BUFS 256
#define | T38_MAX_HDLC_LEN 260

## Typedefs

typedef struct t38_gateway_state_s | t38_gateway_state_t
typedef void | t38_gateway_real_time_frame_handler_t(t38_gateway_state_t *s, void *user_data, int direction, const uint8_t *msg, int len)
| T.30 real time frame handler.

## Functions

t38_gateway_state_t * | t38_gateway_init (t38_gateway_state_t *s, t38_tx_packet_handler_t *tx_packet_handler, void *tx_packet_user_data)
| Initialise a gateway mode T.38 context.
int | t38_gateway_release (t38_gateway_state_t *s)
| Release a T.38 context.
int | t38_gateway_free (t38_gateway_state_t *s)
| Free a T.38 context.
| SPAN_DECLARE_NONSTD (int) t38_gateway_rx(t38_gateway_state_t *s
| Process a block of received FAX audio samples.
void | t38_gateway_set_ecm_capability (t38_gateway_state_t *s, int ecm_allowed)
| Control whether error correcting mode (ECM) is allowed.
void | t38_gateway_set_transmit_on_idle (t38_gateway_state_t *s, int transmit_on_idle)
| Select whether silent audio will be sent when transmit is idle.
void | t38_gateway_set_supported_modems (t38_gateway_state_t *s, int supported_modems)
| Specify supported modems.
void | t38_gateway_set_nsx_suppression (t38_gateway_state_t *s, const uint8_t *from_t38, int from_t38_len, const uint8_t *from_modem, int from_modem_len)
| Select whether NSC, NSF, and NSS should be suppressed.
void | t38_gateway_set_tep_mode (t38_gateway_state_t *s, int use_tep)
| Select whether TEP will be sent for the image modems.
void | t38_gateway_set_fill_bit_removal (t38_gateway_state_t *s, int remove)
| Select whether non-ECM fill bits are to be removed during transmission.
void | t38_gateway_get_transfer_statistics (t38_gateway_state_t *s, t38_stats_t *t)
| Get the current transfer statistics.
t38_core_state_t * | t38_gateway_get_t38_core_state (t38_gateway_state_t *s)
| Get a pointer to the T.38 core IFP packet engine associated with a T.38 context.
logging_state_t * | t38_gateway_get_logging_state (t38_gateway_state_t *s)
| Get a pointer to the logging context associated with a T.38 context.
void | t38_gateway_set_real_time_frame_handler (t38_gateway_state_t *s, t38_gateway_real_time_frame_handler_t *handler, void *user_data)
| Set a callback function for T.30 frame exchange monitoring.

## Variables

int16_t | amp []
int16_t int | len
int16_t int | max_len

## Macro Definition Documentation

## T38_MAX_HDLC_LEN

#define T38_MAX_HDLC_LEN 260

The maximum length of an HDLC frame buffer. This must be big enough for ECM frames.

## T38_RX_BUF_LEN

#define T38_RX_BUF_LEN 2048

The receive buffer length

## T38_TX_HDLC_BUFS

#define T38_TX_HDLC_BUFS 256

The number of HDLC transmit buffers

## Typedef Documentation

## t38_gateway_real_time_frame_handler_t

typedef void t38_gateway_real_time_frame_handler_t(t38_gateway_state_t *s, void *user_data, int direction, const uint8_t *msg, int len)

T.30 real time frame handler.

T.30 real time frame handler.

Parameters

  s | The T.30 context.
  user_data | An opaque pointer.
  direction | TRUE for incoming, FALSE for outgoing.
  msg | The HDLC message.
  len | The length of the message.

## Function Documentation

## SPAN_DECLARE_NONSTD()

SPAN_DECLARE_NONSTD | ( | int |  | ) |

Process a block of received FAX audio samples.

Get the next bit of data from a T.38 rate adapting non-ECM buffer context.

Get a bit of received non-ECM image data.

Get the next bit of a transmitted serial bit stream.

Generate a block of FAX audio samples.

Apply fake received audio processing.

Process a block of received FAX audio samples.

Parameters

  s | The T.38 context.
  amp | The audio sample buffer.
  len | The number of samples in the buffer.

Returns
  The number of samples unprocessed.

Apply fake processing when a block of audio samples is missing (e.g due to packet loss).

Parameters

  s | The T.38 context.
  len | The number of samples to fake.

Returns
  The number of samples unprocessed. This should only be non-zero if the software has reached the end of the FAX call.

Generate a block of FAX audio samples.

Parameters

  s | The T.38 context.
  amp | The audio sample buffer.
  max_len | The number of samples to be generated.

Returns
  The number of samples actually generated.

## t38_gateway_free()

int t38_gateway_free | ( | t38_gateway_state_t * | s | ) |

Free a T.38 context.

Free a gateway mode T.38 context.

Parameters

  s | The T.38 context.

Returns
  0 for OK, else -1.

## t38_gateway_get_logging_state()

logging_state_t * t38_gateway_get_logging_state | ( | t38_gateway_state_t * | s | ) |

Get a pointer to the logging context associated with a T.38 context.

Get a pointer to the logging context associated with a T.38 context.

Parameters

  s | The T.38 context.

Returns
  A pointer to the logging context, or NULL.

References t38_gateway_state_s::logging.

## t38_gateway_get_t38_core_state()

t38_core_state_t * t38_gateway_get_t38_core_state | ( | t38_gateway_state_t * | s | ) |

Get a pointer to the T.38 core IFP packet engine associated with a T.38 context.

Get a pointer to the T.38 core IFP packet engine associated with a gateway mode T.38 context.

Parameters

  s | The T.38 context.

Returns
  A pointer to the T.38 core context, or NULL.

References t38_gateway_t38_state_t::t38, and t38_gateway_state_s::t38x.

## t38_gateway_get_transfer_statistics()

void t38_gateway_get_transfer_statistics | ( | t38_gateway_state_t * | s,
|  | t38_stats_t * | t )

Get the current transfer statistics.

Get the current transfer statistics for the current T.38 session.

Parameters

  s | The T.38 context.
  t | A pointer to a buffer for the statistics.

References t38_stats_t::bit_rate, t38_gateway_state_s::core, t38_gateway_core_state_t::ecm_mode, t38_stats_t::error_correcting_mode, t38_gateway_core_state_t::fast_bit_rate, t38_gateway_core_state_t::pages_confirmed, and t38_stats_t::pages_transferred.

## t38_gateway_init()

t38_gateway_state_t * t38_gateway_init | ( | t38_gateway_state_t * | s,
|  | t38_tx_packet_handler_t * | tx_packet_handler,
|  | void * | tx_packet_user_data )

Initialise a gateway mode T.38 context.

Parameters

  s | The T.38 context.
  tx_packet_handler | A callback routine to encapsulate and transmit T.38 packets.
  tx_packet_user_data | An opaque pointer passed to the tx_packet_handler routine.

Returns
  A pointer to the termination mode T.38 context, or NULL if there was a problem.

References t38_gateway_state_s::audio, fax_modems_state_s::audio_rx_log, fax_modems_state_s::audio_tx_log, t38_gateway_state_s::core, t38_gateway_core_state_t::ecm_allowed, t38_gateway_state_s::logging, t38_gateway_audio_state_t::modems, t38_gateway_core_state_t::non_ecm_to_modem, t38_gateway_to_t38_state_t::octets_per_data_packet, t38_gateway_core_state_t::samples_to_timeout, T30_SUPPORT_V17, T30_SUPPORT_V27TER, T30_SUPPORT_V29, t38_gateway_set_nsx_suppression(), t38_gateway_set_supported_modems(), t38_non_ecm_buffer_init(), t38_gateway_core_state_t::timed_mode, and t38_gateway_core_state_t::to_t38.

## t38_gateway_release()

int t38_gateway_release | ( | t38_gateway_state_t * | s | ) |

Release a T.38 context.

Release a gateway mode T.38 context.

Parameters

  s | The T.38 context.

Returns
  0 for OK, else -1.

## t38_gateway_set_ecm_capability()

void t38_gateway_set_ecm_capability | ( | t38_gateway_state_t * | s,
|  | int | ecm_allowed )

Control whether error correcting mode (ECM) is allowed.

Control whether error correcting mode (ECM) is allowed.

Parameters

  s | The T.38 context.
  ecm_allowed | TRUE is ECM is to be allowed.

References t38_gateway_state_s::core, and t38_gateway_core_state_t::ecm_allowed.

## t38_gateway_set_fill_bit_removal()

void t38_gateway_set_fill_bit_removal | ( | t38_gateway_state_t * | s,
|  | int | remove )

Select whether non-ECM fill bits are to be removed during transmission.

Select whether non-ECM fill bits are to be removed during transmission.

Parameters

  s | The T.38 context.
  remove | TRUE if fill bits are to be removed.

References t38_gateway_state_s::core, t38_gateway_to_t38_state_t::fill_bit_removal, and t38_gateway_core_state_t::to_t38.

## t38_gateway_set_nsx_suppression()

void t38_gateway_set_nsx_suppression | ( | t38_gateway_state_t * | s,
|  | const uint8_t * | from_t38,
|  | int | from_t38_len,
|  | const uint8_t * | from_modem,
|  | int | from_modem_len )

Select whether NSC, NSF, and NSS should be suppressed.

Select whether NSC, NSF, and NSS should be suppressed. It selected, the contents of these messages are forced to zero for all octets beyond the message type. This makes them look like manufacturer specific messages, from a manufacturer which does not exist.

Parameters

  s | The T.38 context.
  from_t38 | A string of bytes to overwrite the header of any NSC, NSF, and NSS frames passing through the gateway from T.38 the the modem.
  from_t38_len | The length of the overwrite string.
  from_modem | A string of bytes to overwrite the header of any NSC, NSF, and NSS frames passing through the gateway from the modem to T.38.
  from_modem_len | The length of the overwrite string.

References MAX_NSX_SUPPRESSION, t38_gateway_t38_state_t::suppress_nsx_len, and t38_gateway_state_s::t38x.

Referenced by t38_gateway_init().

## t38_gateway_set_real_time_frame_handler()

void t38_gateway_set_real_time_frame_handler | ( | t38_gateway_state_t * | s,
|  | t38_gateway_real_time_frame_handler_t * | handler,
|  | void * | user_data )

Set a callback function for T.30 frame exchange monitoring.

Set a callback function for T.30 frame exchange monitoring. This is called from the heart of the signal processing, so don't take too long in the handler routine.

Parameters

  s | The T.30 context.
  handler | The callback function.
  user_data | An opaque pointer passed to the callback function.

References t38_gateway_state_s::core, t38_gateway_core_state_t::real_time_frame_handler, and t38_gateway_core_state_t::real_time_frame_user_data.

## t38_gateway_set_supported_modems()

void t38_gateway_set_supported_modems | ( | t38_gateway_state_t * | s,
|  | int | supported_modems )

Specify supported modems.

Specify which modem types are supported by a T.30 context.

Parameters

  s | The T.38 context.
  supported_modems | Bit field list of the supported modems.

References t38_gateway_state_s::core, t38_gateway_core_state_t::supported_modems, T30_SUPPORT_V17, T30_SUPPORT_V29, t38_gateway_t38_state_t::t38, and t38_gateway_state_s::t38x.

Referenced by t38_gateway_init().

## t38_gateway_set_tep_mode()

void t38_gateway_set_tep_mode | ( | t38_gateway_state_t * | s,
|  | int | use_tep )

Select whether TEP will be sent for the image modems.

Select whether talker echo protection tone will be sent for the image modems.

Parameters

  s | The T.38 context.
  use_tep | TRUE if TEP should be sent.

References t38_gateway_state_s::audio, t38_gateway_audio_state_t::modems, and fax_modems_state_s::use_tep.

## t38_gateway_set_transmit_on_idle()

void t38_gateway_set_transmit_on_idle | ( | t38_gateway_state_t * | s,
|  | int | transmit_on_idle )

Select whether silent audio will be sent when transmit is idle.

Select whether silent audio will be sent when transmit is idle.

Parameters

  s | The T.38 context.
  transmit_on_idle | TRUE if silent audio should be output when the FAX transmitter is idle. FALSE to transmit zero length audio when the FAX transmitter is idle. The default behaviour is FALSE.

References t38_gateway_state_s::audio, t38_gateway_audio_state_t::modems, and fax_modems_state_s::transmit_on_idle.