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 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.

Apply T.30 receive processing to a block of audio samples.

Process a block of received V.8 audio samples.

Fake processing of a missing block of received V.29 modem audio samples.

Fake processing of a missing block of received V.27ter modem audio samples.

Generate a block of V.22bis modem audio samples.

Fake processing of a missing block of received V.22bis modem audio samples.

Process a block of received V.18 audio samples.

Fake processing of a missing block of received V.17 modem audio samples.

Generate a block of FAX audio samples.

Apply fake received audio processing.

Process a received T.38 IFP packet from a reliable stream (e.g. TCP).

Generate a block of T.31 modem audio samples.

Fake processing of a missing block of received T.31 modem audio samples.

Dummy receive fillin callback.

Dummy receive callback.

Process a block of samples through an instance of the modem connect tones detector.

Get the next sequence of bytes for transmission.

Get the next byte for transmission.

Fake processing of a missing block of received FSK modem audio samples.

Process a block of received FSK modem audio samples.

Apply T.30 transmit processing to generate a block of audio samples.

Apply fake T.30 receive processing.

Get the next bit of a transmitted serial bit stream.

Parameters

user_data

An opaque point which must point to a transmitter context.

Returns

the next bit, or PUTBIT_END_OF_DATA to indicate the data stream has ended.

Apply fake T.30 receive processing when a block of audio samples is missing (e.g due to packet loss).

Parameters

s	The FAX 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.

Apply T.30 transmit processing to generate a block of audio samples.

Parameters

s	The FAX context.
amp	The audio sample buffer.
max_len	The number of samples to be generated.

Returns

The number of samples actually generated. This will be zero when there is nothing to send.

Process a block of received FSK modem audio samples.

Parameters

s	The modem context.
amp	The audio sample buffer.
len	The number of samples in the buffer.

Returns

The number of samples unprocessed.

Fake processing of a missing block of received FSK modem audio samples (e.g due to packet loss).

Parameters

s	The modem context.
len	The number of samples to fake.

Returns

The number of samples unprocessed.

Parameters

s	A pointer to an HDLC transmitter context.

Returns

The next byte for transmission.

Parameters

s	A pointer to an HDLC transmitter context.
buf	The buffer for the data.
max_len	The number of bytes to get.

Returns

The number of bytes actually got.

Parameters

s	The context.
amp	An array of signal samples.
len	The number of samples in the array.

Returns

The number of unprocessed samples.

A dummy routine to use as a receive callback, when we aren't really trying to process what is received. It just absorbs and ignores the data.

Parameters

user_data	The context.
amp	The signal.buffer
len	The length of the signal buffer

Returns

0.

A dummy routine to use as a receive fillin callback, when we aren't really trying to process what is received. It just absorbs and ignores the request.

Parameters

user_data	The context.
len	The length of the signal buffer

Returns

0.

Fake processing of a missing block of received T.31 modem audio samples (e.g due to packet loss).

Parameters

s	The T.31 modem context.
len	The number of samples to fake.

Returns

The number of samples unprocessed.

Generate a block of T.31 modem audio samples.

Parameters

s	The T.31 modem context.
amp	The audio sample buffer.
max_len	The number of samples to be generated.

Returns

The number of samples actually generated.

Parameters

s	The T.38 context.
buf	The packet contents.
len	The length of the packet contents.
seq_no	The packet sequence number, used for logging purposes.

Returns

The length of the packet processed, or -1 if there is an error in the packet, or too few bytes of data to complete it.

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.

Fake processing of a missing block of received V.17 modem audio samples. (e.g due to packet loss).

Parameters

s	The modem context.
len	The number of samples to fake.

Returns

The number of samples unprocessed.

Process a block of received V.18 audio samples.

Parameters

s	The V.18 context.
amp	The audio sample buffer.
len	The number of samples in the buffer.

Fake processing of a missing block of received V.22bis modem audio samples. (e.g due to packet loss).

Parameters

s	The modem context.
len	The number of samples to fake.

Returns

The number of samples unprocessed.

Generate a block of V.22bis modem audio samples.

Parameters

s	The modem context.
amp	The audio sample buffer.
len	The number of samples to be generated.

Returns

The number of samples actually generated.

Fake processing of a missing block of received V.27ter modem audio samples. (e.g due to packet loss).

Parameters

s	The modem context.
len	The number of samples to fake.

Returns

The number of samples unprocessed.

Fake processing of a missing block of received V.29 modem audio samples. (e.g due to packet loss).

Parameters

s	The modem context.
len	The number of samples to fake.

Returns

The number of samples unprocessed.

Process a block of received V.8 audio samples.

Parameters

s	The V.8 context.
amp	The audio sample buffer.
len	The number of samples in the buffer.

Get the next bit of a transmitted serial bit stream.

Apply T.30 transmit processing to generate a block of audio samples.

Apply fake T.30 receive processing.

Apply T.30 receive processing to a block of audio samples.

Parameters

s	The FAX context.
amp	The audio sample buffer.
len	The number of samples in the buffer.

Returns

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

Apply fake T.30 receive processing when a block of audio samples is missing (e.g due to packet loss).

Parameters

s	The FAX 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.

Apply T.30 transmit processing to generate a block of audio samples.

Parameters

s	The FAX context.
amp	The audio sample buffer.
max_len	The number of samples to be generated.

Returns

The number of samples actually generated. This will be zero when there is nothing to send.

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.