FarsightStream

FarsightStream — A object that represents and manages a single real-time audio/video stream.

Synopsis




            FarsightStream;
enum        FarsightCandidateType;
enum        FarsightNetworkProtocol;
            FarsightTransportInfo;
enum        FarsightStreamDirection;
enum        FarsightStreamState;
enum        FarsightStreamError;
enum        FarsightStreamDTMFEvent;
void        farsight_stream_prepare_transports
                                            (FarsightStream *self);
void        farsight_stream_add_remote_candidate
                                            (FarsightStream *self,
                                             const GList *remote_candidate);
GList*      farsight_stream_get_native_candidate
                                            (FarsightStream *self,
                                             const gchar *candidate_id);
const GList* farsight_stream_get_native_candidate_list
                                            (FarsightStream *self);
void        farsight_stream_remove_remote_candidate
                                            (FarsightStream *self,
                                             const gchar *remote_candidate_id);
void        farsight_stream_set_remote_candidate_list
                                            (FarsightStream *self,
                                             const GList *remote_candidates);
gboolean    farsight_stream_set_active_candidate_pair
                                            (FarsightStream *self,
                                             const gchar *native_candidate_id,
                                             const gchar *remote_candidate_id);
void        farsight_stream_set_remote_codecs
                                            (FarsightStream *self,
                                             const GList *codecs);
gint        farsight_stream_get_active_codec
                                            (FarsightStream *self);
void        farsight_stream_set_active_codec
                                            (FarsightStream *self,
                                             gint id);
void        farsight_stream_set_codec_preference_list
                                            (FarsightStream *self,
                                             FarsightCodecPreference codec_pref[]);
const GList* farsight_stream_get_local_codecs
                                            (FarsightStream *self);
GList*      farsight_stream_get_codec_intersection
                                            (FarsightStream *self);
gboolean    farsight_stream_set_sink        (FarsightStream *self,
                                             GstElement *sink);
GstElement* farsight_stream_get_sink        (FarsightStream *self);
gboolean    farsight_stream_set_sink_filter (FarsightStream *self,
                                             GstCaps *filter);
gboolean    farsight_stream_set_source      (FarsightStream *self,
                                             GstElement *source);
GstElement* farsight_stream_get_source      (FarsightStream *self);
gboolean    farsight_stream_set_source_filter
                                            (FarsightStream *self,
                                             GstCaps *filter);
GstElement* farsight_stream_get_pipeline    (FarsightStream *self);
gboolean    farsight_stream_set_pipeline    (FarsightStream *self,
                                             GstElement *pipeline);
FarsightMediaType farsight_stream_get_media_type
                                            (FarsightStream *self);
gboolean    farsight_stream_start           (FarsightStream *self);
void        farsight_stream_stop            (FarsightStream *self);
FarsightStreamDirection farsight_stream_get_direction
                                            (FarsightStream *self);
FarsightStreamState farsight_stream_get_state
                                            (FarsightStream *self);
void        farsight_stream_signal_error    (FarsightStream *self,
                                             FarsightStreamError err,
                                             const gchar *mesg);
void        farsight_stream_signal_native_candidates_prepared
                                            (FarsightStream *self);
void        farsight_stream_signal_new_active_candidate_pair
                                            (FarsightStream *self,
                                             const gchar *native_candidate_id,
                                             const gchar *remote_candidate_id);
void        farsight_stream_signal_new_native_candidate
                                            (FarsightStream *self,
                                             const gchar *candidate_id);
void        farsight_stream_signal_codec_changed
                                            (FarsightStream *self,
                                             int codec_id);
void        farsight_stream_signal_state_changed
                                            (FarsightStream *self,
                                             FarsightStreamState state,
                                             FarsightStreamDirection direction);
gboolean    farsight_stream_start_telephony_event
                                            (FarsightStream *self,
                                             guint8 ev,
                                             guint8 volume);
gboolean    farsight_stream_stop_telephony_event
                                            (FarsightStream *self);

Object Hierarchy


  GObject
   +----FarsightStream

Properties


  "direction"            guint                 : Read / Write / Construct Only
  "media-type"           guint                 : Read / Write / Construct Only

Signals


"codec-changed"
            void        user_function      (FarsightStream *self,
                                            gint            codec_id,
                                            gpointer        user_data)      : Run last
"error"     void        user_function      (FarsightStream *self,
                                            gint            type,
                                            gchar          *message,
                                            gpointer        user_data)      : Run last
"native-candidates-prepared"
            void        user_function      (FarsightStream *self,
                                            gpointer        user_data)      : Run last
"new-active-candidate-pair"
            void        user_function      (FarsightStream *self,
                                            gchar          *native_candidate_id,
                                            gchar          *remote_candidate_id,
                                            gpointer        user_data)                : Run last
"new-native-candidate"
            void        user_function      (FarsightStream *self,
                                            gchar          *candidate_id,
                                            gpointer        user_data)         : Run last
"sink-pad-ready"
            void        user_function      (FarsightStream *self,
                                            gpointer        pad,
                                            gpointer        user_data)      : Run last
"state-changed"
            void        user_function      (FarsightStream *self,
                                            gint            state,
                                            gint            direction,
                                            gpointer        user_data)      : Run last

Description

Details

FarsightStream

typedef struct _FarsightStream FarsightStream;

A object that represents and manages a single real-time audio/video stream.


enum FarsightCandidateType

typedef enum
{
  FARSIGHT_CANDIDATE_TYPE_LOCAL,   /* A local address */
  FARSIGHT_CANDIDATE_TYPE_DERIVED, /* An address derived by some method such as 
                                    * STUN which should reach the local client
                                    */
  FARSIGHT_CANDIDATE_TYPE_RELAY    /* An external stream relay */
} FarsightCandidateType;

An enum for the type of candidate used/reported

FARSIGHT_CANDIDATE_TYPE_LOCAL A local address
FARSIGHT_CANDIDATE_TYPE_DERIVED An address derived by some method such as STUN which should reach the local client
FARSIGHT_CANDIDATE_TYPE_RELAY An external stream relay

enum FarsightNetworkProtocol

typedef enum
{
  FARSIGHT_NETWORK_PROTOCOL_UDP,
  FARSIGHT_NETWORK_PROTOCOL_TCP
} FarsightNetworkProtocol;

An enum for the base IP protocol used for a FarsightStream

FARSIGHT_NETWORK_PROTOCOL_UDP A UDP based protocol
FARSIGHT_NETWORK_PROTOCOL_TCP A TCP based protocol

FarsightTransportInfo

typedef struct {
  const gchar *candidate_id;
  guint component;
  const gchar *ip;
  guint16 port;
  FarsightNetworkProtocol proto;
  const gchar *proto_subtype;
  const gchar *proto_profile;
  float preference;
  FarsightCandidateType type;
  const gchar *username;
  const gchar *password;
} FarsightTransportInfo;

Struct to hold information about a possible stream network transport.

const gchar *candidate_id; string identifier of the candidate of which this transport is a part.
guint component; number indicating which component of the candidate is formed by this transport
const gchar *ip; IP in dotted format
guint16 port; Port to use
FarsightNetworkProtocol proto; FarsightNetworkProtocol for ip protocol to use as transport
const gchar *proto_subtype; a string specifying subtype of this protocol type if needed
const gchar *proto_profile; a string specifying a profile type for this protocol, if applicable
float preference; Value between
FarsightCandidateType type; Type of candidate
const gchar *username; Username to use to connect to client if necessary, NULL otherwise
const gchar *password; Username to use to connect to client if necessary, NULL otherwise

enum FarsightStreamDirection

typedef enum
{
  FARSIGHT_STREAM_DIRECTION_NONE,
  FARSIGHT_STREAM_DIRECTION_SENDONLY,
  FARSIGHT_STREAM_DIRECTION_RECEIVEONLY,
  FARSIGHT_STREAM_DIRECTION_BOTH,
  FARSIGHT_STREAM_DIRECTION_LAST
} FarsightStreamDirection;

Enum for the direction of a FarsightStream

FARSIGHT_STREAM_DIRECTION_NONE No stream direction defined.
FARSIGHT_STREAM_DIRECTION_SENDONLY Stream only sends to the other client.
FARSIGHT_STREAM_DIRECTION_RECEIVEONLY Stream only recives from the other client
FARSIGHT_STREAM_DIRECTION_BOTH Stream is bidirectional.
FARSIGHT_STREAM_DIRECTION_LAST

enum FarsightStreamState

typedef enum
{
  FARSIGHT_STREAM_STATE_DISCONNECTED,
  FARSIGHT_STREAM_STATE_CONNECTING,
  FARSIGHT_STREAM_STATE_CONNECTED
} FarsightStreamState;

An enum used to signal the state of a FarsightStream

FARSIGHT_STREAM_STATE_DISCONNECTED The stream is not connected
FARSIGHT_STREAM_STATE_CONNECTING The stream is trying to establish a connection
FARSIGHT_STREAM_STATE_CONNECTED The stream is connected and can start streaming.

enum FarsightStreamError

typedef enum
{
  FARSIGHT_STREAM_ERROR_EOS,
  FARSIGHT_STREAM_UNKNOWN_ERROR,
  FARSIGHT_STREAM_ERROR_UNKNOWN = FARSIGHT_STREAM_UNKNOWN_ERROR,
  FARSIGHT_STREAM_ERROR_TIMEOUT,
  FARSIGHT_STREAM_ERROR_NETWORK,
  FARSIGHT_STREAM_ERROR_PIPELINE_SETUP,
  FARSIGHT_STREAM_ERROR_RESOURCE,
  FARSIGHT_STREAM_ERROR_LAST = FARSIGHT_STREAM_ERROR_RESOURCE
} FarsightStreamError;

An enum used to signal errors that occur on a FarsightStream

FARSIGHT_STREAM_ERROR_EOS The stream was erronously ended
FARSIGHT_STREAM_UNKNOWN_ERROR An unknown error has occured (depricated)
FARSIGHT_STREAM_ERROR_UNKNOWN An unknown error has occured
FARSIGHT_STREAM_ERROR_TIMEOUT Timed out on attempt to establish a connection
FARSIGHT_STREAM_ERROR_NETWORK A network error has occured
FARSIGHT_STREAM_ERROR_PIPELINE_SETUP An error has occured while setting up the required pipeline
FARSIGHT_STREAM_ERROR_RESOURCE An error has occured on a required resource
FARSIGHT_STREAM_ERROR_LAST

enum FarsightStreamDTMFEvent

typedef enum
{
  FARSIGHT_DTMF_EVENT_0 = 0,
  FARSIGHT_DTMF_EVENT_1 = 1,
  FARSIGHT_DTMF_EVENT_2 = 2,
  FARSIGHT_DTMF_EVENT_3 = 3,
  FARSIGHT_DTMF_EVENT_4 = 4,
  FARSIGHT_DTMF_EVENT_5 = 5,
  FARSIGHT_DTMF_EVENT_6 = 6,
  FARSIGHT_DTMF_EVENT_7 = 7,
  FARSIGHT_DTMF_EVENT_8 = 8,
  FARSIGHT_DTMF_EVENT_9 = 9,
  FARSIGHT_DTMF_EVENT_STAR = 10,
  FARSIGHT_DTMF_EVENT_POUND = 11,
  FARSIGHT_DTMF_EVENT_A = 12,
  FARSIGHT_DTMF_EVENT_B = 13,
  FARSIGHT_DTMF_EVENT_C = 14,
  FARSIGHT_DTMF_EVENT_D = 15
} FarsightStreamDTMFEvent;

An enum that represents the different DTMF event that can be sent to a FarsightStream. The values corresponds those those defined in RFC 4733 The rest of the possibles values are in the IANA registry at: http://www.iana.org/assignments/audio-telephone-event-registry


farsight_stream_prepare_transports ()

void        farsight_stream_prepare_transports
                                            (FarsightStream *self);

Prepare a stream for connection. This function should enumerate local interfaces, open any ports and determine external ip/ports (STUN), start relay server (TURN).

It should also set a callback function for taking appropriate action when a new local interface has been detected by connecting to signal new-native-candiate.

self : a FarsightStream

farsight_stream_add_remote_candidate ()

void        farsight_stream_add_remote_candidate
                                            (FarsightStream *self,
                                             const GList *remote_candidate);

Adds the given list of transports (forming one candidate) to the list of remote candidates

self : a FarsightStream
remote_candidate : a GList of FarsightTransportInfo

farsight_stream_get_native_candidate ()

GList*      farsight_stream_get_native_candidate
                                            (FarsightStream *self,
                                             const gchar *candidate_id);

Returns a specific native candidate

self : a FarsightStream
candidate_id : a string indicating the candidate id
Returns : a GList of FarsightTransportInfo for the given native candidate. This GList must be freed using farsight_transport_list_destroy when not needed anymore.

farsight_stream_get_native_candidate_list ()

const GList* farsight_stream_get_native_candidate_list
                                            (FarsightStream *self);

Get list of native candidates for this stream

self : a FarsightStream
Returns : GList of FarsightTransportInfo

farsight_stream_remove_remote_candidate ()

void        farsight_stream_remove_remote_candidate
                                            (FarsightStream *self,
                                             const gchar *remote_candidate_id);

Removes the given remote candidate from the remote candidate list

self : a FarsightStream
remote_candidate_id : a string representing a remote candidate id

farsight_stream_set_remote_candidate_list ()

void        farsight_stream_set_remote_candidate_list
                                            (FarsightStream *self,
                                             const GList *remote_candidates);

Sets a list of remote candidates

self : a FarsightStream
remote_candidates : a GList of FarsightTransportInfo

farsight_stream_set_active_candidate_pair ()

gboolean    farsight_stream_set_active_candidate_pair
                                            (FarsightStream *self,
                                             const gchar *native_candidate_id,
                                             const gchar *remote_candidate_id);

Sets the given candidate pair as the active candidate pair, and emits the "new-active-candidate-pair" signal.

self : a FarsightStream
native_candidate_id : a string representing a native candidate id
remote_candidate_id : a string representing a remote candidate id
Returns : TRUE if sucessfully set the active candidate pair

farsight_stream_set_remote_codecs ()

void        farsight_stream_set_remote_codecs
                                            (FarsightStream *self,
                                             const GList *codecs);

Set the selection of codecs that the remote end claims to understand

self : a FarsightStream
codecs : GList of FarsightCodec

farsight_stream_get_active_codec ()

gint        farsight_stream_get_active_codec
                                            (FarsightStream *self);

Get the codec to use for this stream.

self : a FarsightStream
Returns : the id of the codec currently in use, -1 if unset

farsight_stream_set_active_codec ()

void        farsight_stream_set_active_codec
                                            (FarsightStream *self,
                                             gint id);

Set the codec to use for this stream. There should now be enough information to build the pipeline.

self : a FarsightStream
id : id of codec to use

farsight_stream_set_codec_preference_list ()

void        farsight_stream_set_codec_preference_list
                                            (FarsightStream *self,
                                             FarsightCodecPreference codec_pref[]);

Set a list of prefered codecs (optional)

self : a FarsightStream
codec_pref : an array of FarsightCodecPreference

farsight_stream_get_local_codecs ()

const GList* farsight_stream_get_local_codecs
                                            (FarsightStream *self);

Get the selection of local codec ids to restrict this stream to using

self : a FarsightStream
Returns : : a GList of codec ids

farsight_stream_get_codec_intersection ()

GList*      farsight_stream_get_codec_intersection
                                            (FarsightStream *self);

Get the intersection of local and remote codecs.

self : a FarsightStream
Returns : a GList of FarsightCodec. The caller is responsible for freeing the list and individual items when it's done with it.

farsight_stream_set_sink ()

gboolean    farsight_stream_set_sink        (FarsightStream *self,
                                             GstElement *sink);

Set the GStreamer sink for this stream. If sink is NULL it will block the incoming stream and remove the old sink. If called with a new sink it will replace the old one. If there is a user specified pipeline, the sink won't be added into the Farsight bin.

self : a FarsightStream
sink : a GstElement to use as the sink
Returns : TRUE if sucessful

farsight_stream_get_sink ()

GstElement* farsight_stream_get_sink        (FarsightStream *self);

Get the GStreamer sink for this stream

self : a FarsightStream
Returns : A GstElement for the current stream sink

farsight_stream_set_sink_filter ()

gboolean    farsight_stream_set_sink_filter (FarsightStream *self,
                                             GstCaps *filter);

Set the GStreamer sink link filter for this stream

self : a FarsightStream
filter : a GstCaps to use as a filter
Returns : TRUE if sucessful

farsight_stream_set_source ()

gboolean    farsight_stream_set_source      (FarsightStream *self,
                                             GstElement *source);

Set the GStreamer source for this stream. If the element does not have a parent, it will be added into the Farsight stream bin. So if you need to set a parent for the source, do it before calling this function.

self : a FarsightStream
source : a GstElement to use as the source
Returns : TRUE if sucessful

farsight_stream_get_source ()

GstElement* farsight_stream_get_source      (FarsightStream *self);

Get the GStreamer source for this stream

self : a FarsightStream
Returns : A GstElement for the current stream source

farsight_stream_set_source_filter ()

gboolean    farsight_stream_set_source_filter
                                            (FarsightStream *self,
                                             GstCaps *filter);

Set the GStreamer source link filter for this stream

self : a FarsightStream
filter : a GstCaps to use as a filter
Returns : TRUE if sucessful

farsight_stream_get_pipeline ()

GstElement* farsight_stream_get_pipeline    (FarsightStream *self);

Get the FarsightStream working pipeline. This will return the pipeline set by the user or the pipeline created by Farsight if not set by the user.

self : a FarsightStream
Returns : GstElement or NULL if pipeline not available yet

farsight_stream_set_pipeline ()

gboolean    farsight_stream_set_pipeline    (FarsightStream *self,
                                             GstElement *pipeline);

This function is used if the user wants to create the GstPipeline himself. This means Farsight will use this pipeline instead of creating it's own. It will create a GstBin and insert it into the given pipeline. This is usefull when the user wants all the different Farsight streams to be part of the same global pipeline (i.e. Tee the same source to various streams) If the pipeline is set by the user, the sources will not be added into the Farsight bin.

NOTE: This has to be called before farsight_stream_prepare_transports() in order to be used.

self : a FarsightStream
pipeline : a GstElement that is a pipeline
Returns : TRUE if successful

farsight_stream_get_media_type ()

FarsightMediaType farsight_stream_get_media_type
                                            (FarsightStream *self);

Get the FarsightStream direction

self : a FarsightStream
Returns : FarsightMediaType media type

farsight_stream_start ()

gboolean    farsight_stream_start           (FarsightStream *self);

Start the FarsightStream streaming to the network

self : a FarsightStream
Returns : TRUE if sucessful

farsight_stream_stop ()

void        farsight_stream_stop            (FarsightStream *self);

Stop the FarsightStream streaming to the network

self : a FarsightStream

farsight_stream_get_direction ()

FarsightStreamDirection farsight_stream_get_direction
                                            (FarsightStream *self);

Get the FarsightStream direction

self : a FarsightStream
Returns : FarsightStreamState direction

farsight_stream_get_state ()

FarsightStreamState farsight_stream_get_state
                                            (FarsightStream *self);

Get the current FarsightStream state

self : a FarsightStream
Returns : FarsightStreamState state

farsight_stream_signal_error ()

void        farsight_stream_signal_error    (FarsightStream *self,
                                             FarsightStreamError err,
                                             const gchar *mesg);

Used by subclasses of FarsightStream to emit an error signal

self : a FarsightStream
err : FarsightStreamError value
mesg : a string

farsight_stream_signal_native_candidates_prepared ()

void        farsight_stream_signal_native_candidates_prepared
                                            (FarsightStream *self);

Used by subclasses of FarsightStream to emit an native-candidates-prepared signal

self : a FarsightStream

farsight_stream_signal_new_active_candidate_pair ()

void        farsight_stream_signal_new_active_candidate_pair
                                            (FarsightStream *self,
                                             const gchar *native_candidate_id,
                                             const gchar *remote_candidate_id);

Used by subclasses of FarsightStream to emit an new-active-candidate-pair signal

self : a FarsightStream
native_candidate_id : string identifier of native candidate that is now active
remote_candidate_id : string identifier of remote candidate that is now active

farsight_stream_signal_new_native_candidate ()

void        farsight_stream_signal_new_native_candidate
                                            (FarsightStream *self,
                                             const gchar *candidate_id);

Used by subclasses of FarsightStream to emit an new-native-candidate signal

self : a FarsightStream
candidate_id : Identifier of newly discovered native candidate

farsight_stream_signal_codec_changed ()

void        farsight_stream_signal_codec_changed
                                            (FarsightStream *self,
                                             int codec_id);

Used by subclasses of FarsightStream to emit an codec-changed signal

self : a FarsightStream
codec_id : id of new codec in use

farsight_stream_signal_state_changed ()

void        farsight_stream_signal_state_changed
                                            (FarsightStream *self,
                                             FarsightStreamState state,
                                             FarsightStreamDirection direction);

Used by subclasses of FarsightStream to emit an state-changed signal

self : a FarsightStream
state : FarsightStreamState of new state
direction : FarsightStreamDirection for directions in

farsight_stream_start_telephony_event ()

gboolean    farsight_stream_start_telephony_event
                                            (FarsightStream *self,
                                             guint8 ev,
                                             guint8 volume);

This function will start sending a telephony event (such as a DTMF tone) on the FarsightStream, you have to call the function farsight_stream_stop_telephony_event() to stop it.

self : a FarsightStream
ev : A FarsightStreamDTMFEvent or another number defined at http://www.iana.org/assignments/audio-telephone-event-registry
volume : The volume in dBm0 without the negative sign. Should be between 0 and 36. Higher values mean lower volume
Returns : TRUE if sucessful, it can return FALSE if the FarsightStream does not support this telephony event.

farsight_stream_stop_telephony_event ()

gboolean    farsight_stream_stop_telephony_event
                                            (FarsightStream *self);

This function will stop sending a telephony event started by farsight_stream_start_telephony_event(). If the event was being sent for less than 50ms, it will be sent for 50ms minimum. If the duration was a positive and the event is not over, it will cut it short.

self : a FarsightStream
Returns : TRUE if sucessful, it can return FALSE if the FarsightStream does not support telephony events or if no telephony event is being sent

Property Details

The "direction" property

  "direction"            guint                 : Read / Write / Construct Only

The direction of this stream. This should only be set at stream creation time.

Allowed values: <= 4

Default value: 3


The "media-type" property

  "media-type"           guint                 : Read / Write / Construct Only

The media type to be used by this stream specifed by FarsightMediaType.

Allowed values: <= 1

Default value: 0

Signal Details

The "codec-changed" signal

void        user_function                  (FarsightStream *self,
                                            gint            codec_id,
                                            gpointer        user_data)      : Run last

emitted if we automatically choose a new codec for some reason (e.g. high packet loss)

self : FarsightStream that emitted the signal
codec_id : id of codec to be used
user_data : user data set when the signal handler was connected.

The "error" signal

void        user_function                  (FarsightStream *self,
                                            gint            type,
                                            gchar          *message,
                                            gpointer        user_data)      : Run last

This signal is emitted in any error condition

self : FarsightStream that emmitted the signal
type : FarsightStreamError type of error
message : Error message
user_data : user data set when the signal handler was connected.

The "native-candidates-prepared" signal

void        user_function                  (FarsightStream *self,
                                            gpointer        user_data)      : Run last

This signal is emitted when the native candidates have been prepared. This usually means all of the local ports have been opened, local interfaces have been found, and/or external ports have been found, and/or relay server has been setup, or anything else the protocol needs. After emission of this signal, farsight_stream_get_native_candidate_list should return meaningful data

self : FarsightStream that emmitted the signal
user_data : user data set when the signal handler was connected.

The "new-active-candidate-pair" signal

void        user_function                  (FarsightStream *self,
                                            gchar          *native_candidate_id,
                                            gchar          *remote_candidate_id,
                                            gpointer        user_data)                : Run last

Emitted when this FarsightStream has chosen a new active candidate pair to use to connect to the remote client.

self : FarsightStream that emmitted the signal
native_candidate_id : string identifier for native side of the candidate pair
remote_candidate_id : string identifier for remote side of the candidate pair
user_data : user data set when the signal handler was connected.

The "new-native-candidate" signal

void        user_function                  (FarsightStream *self,
                                            gchar          *candidate_id,
                                            gpointer        user_data)         : Run last

This signal is emitted when the a new native candidate is found. After emission of this signal, farsight_stream_get_native_candidates should return meaningful data. This does not mean that the candidate has been prepared.

self : FarsightStream that emmitted the signal
candidate_id : id of the found candidate
user_data : user data set when the signal handler was connected.

The "sink-pad-ready" signal

void        user_function                  (FarsightStream *self,
                                            gpointer        pad,
                                            gpointer        user_data)      : Run last

This signal is emitted when a sink pad has been created on the Farsight stream bin.

Note : This signal is only valid when a user-defined pipeline has been provided by the user to farsight using farsight_stream_set_pipeline.

self : FarsightStream that emmitted the signal
pad : A GstPad that represents the sink
user_data : user data set when the signal handler was connected.

The "state-changed" signal

void        user_function                  (FarsightStream *self,
                                            gint            state,
                                            gint            direction,
                                            gpointer        user_data)      : Run last

This signal is emitted when we change FarsightStreamState.

self : FarsightStream that emmitted the signal
state : FarsightStreamState of new state
direction : FarsightStreamDirection for directions in which the stream is streaming
user_data : user data set when the signal handler was connected.