Conference Bridge
[Media Ports Framework]

Detailed Description

This describes the conference bridge implementation in PJMEDIA. The conference bridge provides powerful and very efficient mechanism to route the audio flow and mix the audio signal when required.

Some more information about the media flow when conference bridge is used is described in http://www.pjsip.org/trac/wiki/media-flow .

Define Documentation

#define PJMEDIA_CONF_BRIDGE_SIGNATURE PJMEDIA_PORT_SIGNATURE('C', 'O', 'N', 'F')

The conference bridge signature in pjmedia_port_info.

#define PJMEDIA_CONF_SWITCH_SIGNATURE PJMEDIA_PORT_SIGNATURE('A', 'S', 'W', 'I')

The audio switchboard signature in pjmedia_port_info.

Typedef Documentation

typedef struct pjmedia_conf pjmedia_conf

Opaque type for conference bridge.

Enumeration Type Documentation

enum pjmedia_conf_option

Conference port options. The values here can be combined in bitmask to be specified when the conference bridge is created.

Enumerator:

PJMEDIA_CONF_NO_MIC	Disable audio streams from the microphone device.
PJMEDIA_CONF_NO_DEVICE	Do not create sound device.
PJMEDIA_CONF_SMALL_FILTER	Use small filter table when resampling
PJMEDIA_CONF_USE_LINEAR	Use linear resampling instead of filter based.

Function Documentation

pj_status_t pjmedia_conf_create	(	pj_pool_t *	pool,
		unsigned	max_slots,
		unsigned	sampling_rate,
		unsigned	channel_count,
		unsigned	samples_per_frame,
		unsigned	bits_per_sample,
		unsigned	options,
		pjmedia_conf **	p_conf
	)

Create conference bridge with the specified parameters. The sampling rate, samples per frame, and bits per sample will be used for the internal operation of the bridge (e.g. when mixing audio frames). However, ports with different configuration may be connected to the bridge. In this case, the bridge is able to perform sampling rate conversion, and buffering in case the samples per frame is different.

For this version of PJMEDIA, only 16bits per sample is supported.

For this version of PJMEDIA, the channel count of the ports MUST match the channel count of the bridge.

Under normal operation (i.e. when PJMEDIA_CONF_NO_DEVICE option is NOT specified), the bridge internally create an instance of sound device and connect the sound device to port zero of the bridge.

If PJMEDIA_CONF_NO_DEVICE options is specified, no sound device will be created in the conference bridge. Application MUST acquire the port interface of the bridge by calling pjmedia_conf_get_master_port(), and connect this port interface to a sound device port by calling pjmedia_snd_port_connect(), or to a master port (pjmedia_master_port) if application doesn't want to instantiate any sound devices.

The sound device or master port are crucial for the bridge's operation, because it provides the bridge with necessary clock to process the audio frames periodically. Internally, the bridge runs when get_frame() to port zero is called.

Parameters:

	pool	Pool to use to allocate the bridge and additional buffers for the sound device.
	max_slots	Maximum number of slots/ports to be created in the bridge. Note that the bridge internally uses one port for the sound device, so the actual maximum number of ports will be less one than this value.
	sampling_rate	Set the sampling rate of the bridge. This value is also used to set the sampling rate of the sound device.
	channel_count	Number of channels in the PCM stream. Normally the value will be 1 for mono, but application may specify a value of 2 for stereo. Note that all ports that will be connected to the bridge MUST have the same number of channels as the bridge.
	samples_per_frame	Set the number of samples per frame. This value is also used to set the sound device.
	bits_per_sample	Set the number of bits per sample. This value is also used to set the sound device. Currently only 16bit per sample is supported.
	options	Bitmask options to be set for the bridge. The options are constructed from pjmedia_conf_option enumeration.
	p_conf	Pointer to receive the conference bridge instance.

Returns:: PJ_SUCCESS if conference bridge can be created.

pj_status_t pjmedia_conf_destroy ( pjmedia_conf * conf )

Destroy conference bridge.

Parameters:

conf

The conference bridge.

Returns:: PJ_SUCCESS on success.

pjmedia_port* pjmedia_conf_get_master_port ( pjmedia_conf * conf )

Get the master port interface of the conference bridge. The master port corresponds to the port zero of the bridge. This is only usefull when application wants to manage the sound device by itself, instead of allowing the bridge to automatically create a sound device implicitly.

This function will only return a port interface if PJMEDIA_CONF_NO_DEVICE option was specified when the bridge was created.

Application can connect the port returned by this function to a sound device by calling pjmedia_snd_port_connect().

Parameters:

conf

The conference bridge.

Returns:: The port interface of port zero of the bridge, only when PJMEDIA_CONF_NO_DEVICE options was specified when the bridge was created.

pj_status_t pjmedia_conf_set_port0_name	(	pjmedia_conf *	conf,
		const pj_str_t *	name
	)

Set master port name.

Parameters:

	conf	The conference bridge.
	name	Name to be assigned.

Returns:: PJ_SUCCESS on success.

pj_status_t pjmedia_conf_add_port	(	pjmedia_conf *	conf,
		pj_pool_t *	pool,
		pjmedia_port *	strm_port,
		const pj_str_t *	name,
		unsigned *	p_slot
	)

Add media port to the conference bridge.

By default, the new conference port will have both TX and RX enabled, but it is not connected to any other ports. Application SHOULD call pjmedia_conf_connect_port() to enable audio transmission and receipt to/from this port.

Once the media port is connected to other port(s) in the bridge, the bridge will continuosly call get_frame() and put_frame() to the port, allowing media to flow to/from the port.

Parameters:

	conf	The conference bridge.
	pool	Pool to allocate buffers for this port.
	strm_port	Stream port interface.
	name	Optional name for the port. If this value is NULL, the name will be taken from the name in the port info.
	p_slot	Pointer to receive the slot index of the port in the conference bridge.

Returns:: PJ_SUCCESS on success.

pj_status_t pjmedia_conf_add_passive_port	(	pjmedia_conf *	conf,
		pj_pool_t *	pool,
		const pj_str_t *	name,
		unsigned	clock_rate,
		unsigned	channel_count,
		unsigned	samples_per_frame,
		unsigned	bits_per_sample,
		unsigned	options,
		unsigned *	p_slot,
		pjmedia_port **	p_port
	)

Warning: This API has been deprecated since 1.3 and will be removed in the future release, use PJMEDIA_SPLITCOMB instead.

Create and add a passive media port to the conference bridge. Unlike "normal" media port that is added with pjmedia_conf_add_port(), media port created with this function will not have its get_frame() and put_frame() called by the bridge; instead, application MUST continuosly call these functions to the port, to allow media to flow from/to the port.

Upon return of this function, application will be given two objects: the slot number of the port in the bridge, and pointer to the media port where application MUST start calling get_frame() and put_frame() to the port.

Parameters:

	conf	The conference bridge.
	pool	Pool to allocate buffers etc for this port.
	name	Name to be assigned to the port.
	clock_rate	Clock rate/sampling rate.
	channel_count	Number of channels.
	samples_per_frame	Number of samples per frame.
	bits_per_sample	Number of bits per sample.
	options	Options (should be zero at the moment).
	p_slot	Pointer to receive the slot index of the port in the conference bridge.
	p_port	Pointer to receive the port instance.

Returns:: PJ_SUCCESS on success, or the appropriate error code.

pj_status_t pjmedia_conf_configure_port	(	pjmedia_conf *	conf,
		unsigned	slot,
		pjmedia_port_op	tx,
		pjmedia_port_op	rx
	)

Change TX and RX settings for the port.

Parameters:

	conf	The conference bridge.
	slot	Port number/slot in the conference bridge.
	tx	Settings for the transmission TO this port.
	rx	Settings for the receipt FROM this port.

Returns:: PJ_SUCCESS on success.

pj_status_t pjmedia_conf_connect_port	(	pjmedia_conf *	conf,
		unsigned	src_slot,
		unsigned	sink_slot,
		int	level
	)

Enable unidirectional audio from the specified source slot to the specified sink slot.

Parameters:

	conf	The conference bridge.
	src_slot	Source slot.
	sink_slot	Sink slot.
	level	This argument is reserved for future improvements where it is possible to adjust the level of signal transmitted in a specific connection. For now, this argument MUST be zero.

Returns:: PJ_SUCCES on success.

pj_status_t pjmedia_conf_disconnect_port	(	pjmedia_conf *	conf,
		unsigned	src_slot,
		unsigned	sink_slot
	)

Disconnect unidirectional audio from the specified source to the specified sink slot.

Parameters:

	conf	The conference bridge.
	src_slot	Source slot.
	sink_slot	Sink slot.

Returns:: PJ_SUCCESS on success.

unsigned pjmedia_conf_get_port_count ( pjmedia_conf * conf )

Get number of ports currently registered to the conference bridge.

Parameters:

conf

The conference bridge.

Returns:: Number of ports currently registered to the conference bridge.

unsigned pjmedia_conf_get_connect_count ( pjmedia_conf * conf )

Get total number of ports connections currently set up in the bridge.

Parameters:

conf

The conference bridge.

Returns:: PJ_SUCCESS on success.

pj_status_t pjmedia_conf_remove_port	(	pjmedia_conf *	conf,
		unsigned	slot
	)

Remove the specified port from the conference bridge.

Parameters:

	conf	The conference bridge.
	slot	The port index to be removed.

Returns:: PJ_SUCCESS on success.

pj_status_t pjmedia_conf_enum_ports	(	pjmedia_conf *	conf,
		unsigned	ports[],
		unsigned *	count
	)

Enumerate occupied ports in the bridge.

Parameters:

	conf	The conference bridge.
	ports	Array of port numbers to be filled in.
	count	On input, specifies the maximum number of ports in the array. On return, it will be filled with the actual number of ports.

Returns:: PJ_SUCCESS on success.

pj_status_t pjmedia_conf_get_port_info	(	pjmedia_conf *	conf,
		unsigned	slot,
		pjmedia_conf_port_info *	info
	)

Get port info.

Parameters:

	conf	The conference bridge.
	slot	Port index.
	info	Pointer to receive the info.

Returns:: PJ_SUCCESS on success.

pj_status_t pjmedia_conf_get_ports_info	(	pjmedia_conf *	conf,
		unsigned *	size,
		pjmedia_conf_port_info	info[]
	)

Get occupied ports info.

Parameters:

	conf	The conference bridge.
	size	On input, contains maximum number of infos to be retrieved. On output, contains the actual number of infos that have been copied.
	info	Array of info.

Returns:: PJ_SUCCESS on success.

pj_status_t pjmedia_conf_get_signal_level	(	pjmedia_conf *	conf,
		unsigned	slot,
		unsigned *	tx_level,
		unsigned *	rx_level
	)

Get last signal level transmitted to or received from the specified port. This will retrieve the "real-time" signal level of the audio as they are transmitted or received by the specified port. Application may call this function periodically to display the signal level to a VU meter.

The signal level is an integer value in zero to 255, with zero indicates no signal, and 255 indicates the loudest signal level.

Parameters:

	conf	The conference bridge.
	slot	Slot number.
	tx_level	Optional argument to receive the level of signal transmitted to the specified port (i.e. the direction is from the bridge to the port).
	rx_level	Optional argument to receive the level of signal received from the port (i.e. the direction is from the port to the bridge).

Returns:: PJ_SUCCESS on success.

pj_status_t pjmedia_conf_adjust_rx_level	(	pjmedia_conf *	conf,
		unsigned	slot,
		int	adj_level
	)

Adjust the level of signal received from the specified port. Application may adjust the level to make signal received from the port either louder or more quiet. The level adjustment is calculated with this formula: output = input * (adj_level+128) / 128. Using this, zero indicates no adjustment, the value -128 will mute the signal, and the value of +128 will make the signal 100% louder, +256 will make it 200% louder, etc.

The level adjustment value will stay with the port until the port is removed from the bridge or new adjustment value is set. The current level adjustment value is reported in the media port info when the pjmedia_conf_get_port_info() function is called.

Parameters:

	conf	The conference bridge.
	slot	Slot number of the port.
	adj_level	Adjustment level, which must be greater than or equal to -128. A value of zero means there is no level adjustment to be made, the value -128 will mute the signal, and the value of +128 will make the signal 100% louder, +256 will make it 200% louder, etc. See the function description for the formula.

Returns:: PJ_SUCCESS on success.

pj_status_t pjmedia_conf_adjust_tx_level	(	pjmedia_conf *	conf,
		unsigned	slot,
		int	adj_level
	)

Adjust the level of signal to be transmitted to the specified port. Application may adjust the level to make signal transmitted to the port either louder or more quiet. The level adjustment is calculated with this formula: output = input * (adj_level+128) / 128. Using this, zero indicates no adjustment, the value -128 will mute the signal, and the value of +128 will make the signal 100% louder, +256 will make it 200% louder, etc.

Parameters:

	conf	The conference bridge.
	slot	Slot number of the port.
	adj_level	Adjustment level, which must be greater than or equal to -128. A value of zero means there is no level adjustment to be made, the value -128 will mute the signal, and the value of +128 will make the signal 100% louder, +256 will make it 200% louder, etc. See the function description for the formula.

Returns:: PJ_SUCCESS on success.

Conference Bridge [Media Ports Framework]

Detailed Description

Data Structures

Defines

Typedefs

Enumerations

Functions

Define Documentation

Typedef Documentation

Enumeration Type Documentation

Function Documentation

Conference Bridge
[Media Ports Framework]