# RtpSession API

## Name

RtpSession API -- The RtpSession object provides control on a RTP session as defined in RFC 1889.

## Synopsis

    #include <ortp.h>

                RtpSession;
    enum        RtpSessionMode;
    #define     RTP_CALLBACK_TABLE_MAX_ENTRIES
    RtpSession* rtp_session_new                 (int mode);
    void        rtp_session_set_scheduling_mode (RtpSession *session,
                                                 int yesno);
    void        rtp_session_set_blocking_mode   (RtpSession *session,
                                                 int yesno);
    void        rtp_session_set_profile         (RtpSession *session,
                                                 RtpProfile *profile);
    RtpProfile* rtp_session_get_profile         (RtpSession *session);
    int         rtp_session_set_local_addr      (RtpSession *session,
                                                 const char *addr,
                                                 int port);
    int         rtp_session_set_remote_addr     (RtpSession *session,
                                                 const char *addr,
                                                 int port);
    int         rtp_session_get_local_port      (const RtpSession *session);
    void        rtp_session_set_jitter_compensation
                                                (RtpSession *session,
                                                 int milisec);
    void        rtp_session_set_ssrc            (RtpSession *session,
                                                 uint32_t ssrc);
    void        rtp_session_set_seq_number      (RtpSession *session,
                                                 uint16_t seq);
    int         rtp_session_set_send_payload_type
                                                (RtpSession *session,
                                                 int paytype);
    int         rtp_session_set_recv_payload_type
                                                (RtpSession *session,
                                                 int pt);
    int         rtp_session_get_send_payload_type
                                                (const RtpSession *session);
    int         rtp_session_get_recv_payload_type
                                                (const RtpSession *session);
    int         rtp_session_set_payload_type    (RtpSession *session,
                                                 int pt);
    int         rtp_session_signal_connect      (RtpSession *session,
                                                 const char *signal,
                                                 RtpCallback cb,
                                                 unsigned long user_data);
    int         rtp_session_signal_disconnect_by_callback
                                                (RtpSession *session,
                                                 const char *signal,
                                                 RtpCallback cb);
    int         rtp_session_send_with_ts        (RtpSession *session,
                                                 const char *buffer,
                                                 int len,
                                                 uint32_t userts);
    int         rtp_session_recv_with_ts        (RtpSession *session,
                                                 char *buffer,
                                                 int len,
                                                 uint32_t time,
                                                 int *have_more);
    mblk_t*     rtp_session_recvm_with_ts       (RtpSession *session,
                                                 uint32_t user_ts);
    mblk_t*     rtp_session_create_packet       (RtpSession *session,
                                                 int header_size,
                                                 const char *payload,
                                                 int payload_size);
    mblk_t*     rtp_session_create_packet_with_data
                                                (RtpSession *session,
                                                 char *payload,
                                                 int payload_size,
                                                 void (*freefn) (void*));
    int         rtp_session_sendm_with_ts       (RtpSession *session,
                                                 mblk_t *mp,
                                                 uint32_t userts);
    uint32_t    rtp_session_get_current_send_ts (RtpSession *session);
    void        rtp_session_flush_sockets       (RtpSession *session);
    void        rtp_session_set_time_jump_limit (RtpSession *session,
                                                 int miliseconds);
    void        rtp_session_set_recv_buf_size   (RtpSession *session,
                                                 int bufsize);
    void        rtp_session_reset               (RtpSession *session);
    void        rtp_session_set_data            (RtpSession *session,
                                                 void *data);
    void*       rtp_session_get_data            (const RtpSession *session);

## Description

The following api provides the application a way to define a RTP session, send or receives data through it, and to keep informed of the evolution of the RTP session through a simple callback mecanism (see `rtp_session_signal_connect()` for details).

## Details

### RtpSession

    typedef struct {
    	RtpSession *next;	/* next RtpSession, when the session are enqueued by the scheduler */
    	int mask_pos;	/* the position in the scheduler mask of RtpSession : do not move this field: it is part of the ABI since the session_set macros use it*/
    	RtpProfile *profile;
    	WaitPoint recv_wp;
    	WaitPoint send_wp;
    	ortp_mutex_t lock;
    	uint32_t send_ssrc;
    	uint32_t recv_ssrc;
    	int send_pt;/* sent payload type */
    	int recv_pt;/* recv payload type */
    	int hw_recv_pt; /* recv payload type before jitter buffer */
    	int recv_buf_size;
    	RtpSignalTable on_ssrc_changed;
    	RtpSignalTable on_payload_type_changed;
    	RtpSignalTable on_telephone_event_packet;
    	RtpSignalTable on_telephone_event;
    	RtpSignalTable on_timestamp_jump;
    	RtpSignalTable on_network_error;
    	RtpSignalTable on_rtcp_bye;
    	struct _OList *signal_tables;
    	OrtpEvQueue eventq;
    	RtpStream rtp;
    	RtcpStream rtcp;
    	RtpSessionMode mode;
    	struct _RtpScheduler *sched;
    	uint32_t flags;
    	int multicast_ttl;
    	int multicast_loopback;
    	void * user_data;
    	/* FIXME: Should be a table for all session participants. */
    	struct timeval last_recv_time; /* Time of receiving the RTP/RTCP packet. */

    	/* telephony events extension */
    	int telephone_events_pt;	/* the payload type used for telephony events */
    	mblk_t *current_tev;		/* the pending telephony events */
    	mblk_t *sd;
    	queue_t contributing_sources;
    	bool_t symmetric_rtp;
    	bool_t permissive; /*use the permissive algorithm*/
    } RtpSession;

Users should not manipulate this structure directly.

### enum RtpSessionMode

    typedef enum {
    	RTP_SESSION_RECVONLY,
    	RTP_SESSION_SENDONLY,
    	RTP_SESSION_SENDRECV
    } RtpSessionMode;

### RTP_CALLBACK_TABLE_MAX_ENTRIES

    #define RTP_CALLBACK_TABLE_MAX_ENTRIES	5

### rtp_session_new ()

    RtpSession* rtp_session_new                 (int mode);

Creates a new rtp session. If the session is able to send data (RTP_SESSION_SENDONLY or RTP_SESSION_SENDRECV), then a random SSRC number is choosed for the outgoing stream.

`mode` : | One of the RtpSessionMode flags.
Returns : | the newly created rtp session.

### rtp_session_set_scheduling_mode ()

    void        rtp_session_set_scheduling_mode (RtpSession *session,
                                                 int yesno);

Sets the scheduling mode of the rtp session. If `yesno` is TRUE, the rtp session is in the scheduled mode, that means that you can use `session_set_select()` to block until it's time to receive or send on this session according to the timestamp passed to the respective functions. You can also use blocking mode (see `rtp_session_set_blocking_mode()` ), to simply block within the receive and send functions. If `yesno` is FALSE, the ortp scheduler will not manage those sessions, meaning that blocking mode and the use of `session_set_select()` for this session are disabled.

`session` : | a rtp session.
`yesno` : | a boolean to indicate the scheduling mode.

### rtp_session_set_blocking_mode ()

    void        rtp_session_set_blocking_mode   (RtpSession *session,
                                                 int yesno);

Using this function implies that you previously enabled scheduled mode on the session (see `rtp_session_set_scheduling_mode()` ). `rtp_session_set_blocking_mode()` defines the behaviour of the `rtp_session_recv_with_ts()` and `rtp_session_send_with_ts()` functions. If `yesno` is TRUE, `rtp_session_recv_with_ts()` will block until it is time for the packet to be received, according to the timestamp passed to the function. After this time, the function returns. For `rtp_session_send_with_ts()`, it will block until it is time for the packet to be sent. If `yesno` is FALSE, then the two functions will return immediately.

`session` : | a rtp session
`yesno` : | a boolean

### rtp_session_set_profile ()

    void        rtp_session_set_profile         (RtpSession *session,
                                                 RtpProfile *profile);

Set the RTP profile to be used for the session. By default, all session are created by `rtp_session_new()` are initialized with the AV profile, as defined in RFC 3551. The application can set any other profile instead using that function.

`session` : | a rtp session
`profile` : | a rtp profile

### rtp_session_get_profile ()

    RtpProfile* rtp_session_get_profile         (RtpSession *session);

`session` : | a rtp session
Returns : | current profile.

### rtp_session_set_local_addr ()

    int         rtp_session_set_local_addr      (RtpSession *session,
                                                 const char *addr,
                                                 int port);

Specify the local addr to be use to listen for rtp packets or to send rtp packet from. In case where the rtp session is send-only, then it is not required to call this function: when calling `rtp_session_set_remote_addr()`, if no local address has been set, then the default INADRR_ANY (0.0.0.0) IP address with a random port will be used. Calling `rtp_sesession_set_local_addr()` is mandatory when the session is recv-only or duplex.

`session` : | a rtp session freshly created.
`addr` : | a local IP address in the xxx.xxx.xxx.xxx form.
`port` : | a local port or -1 to let oRTP choose the port randomly
Returns : | 0 on success.

### rtp_session_set_remote_addr ()

    int         rtp_session_set_remote_addr     (RtpSession *session,
                                                 const char *addr,
                                                 int port);

Sets the remote address of the rtp session, ie the destination address where rtp packet are sent. If the session is recv-only or duplex, it also sets the origin of incoming RTP packets. Rtp packets that don't come from addr:port are discarded.

`session` : | a rtp session freshly created.
`addr` : | a local IP address in the xxx.xxx.xxx.xxx form.
`port` : | a local port.
Returns : | 0 on success.

### rtp_session_get_local_port ()

    int         rtp_session_get_local_port      (const RtpSession *session);

This function can be useful to retrieve the local port that was randomly choosen by `rtp_session_set_remote_addr()` when `rtp_session_set_local_addr()` was not called.

`session` : | a rtp session for which `rtp_session_set_local_addr()` or `rtp_session_set_remote_addr()` has been called
Returns : | the local port used to listen for rtp packets, -1 if not set.

### rtp_session_set_jitter_compensation ()

    void        rtp_session_set_jitter_compensation
                                                (RtpSession *session,
                                                 int milisec);

Sets the time interval for which packet are buffered instead of being delivered to the application.

`session` : | a RtpSession
`milisec` : | the time interval in milisec to be jitter compensed.

### rtp_session_set_ssrc ()

    void        rtp_session_set_ssrc            (RtpSession *session,
                                                 uint32_t ssrc);

Sets the SSRC for the outgoing stream. If not done, a random ssrc is used.

`session` : | a rtp session.
`ssrc` : | an unsigned 32bit integer representing the synchronisation source identifier (SSRC).

### rtp_session_set_seq_number ()

    void        rtp_session_set_seq_number      (RtpSession *session,
                                                 uint16_t seq);

sets the initial sequence number of a sending session.

`session` : | a rtp session freshly created.
`seq` : |

### rtp_session_set_send_payload_type ()

    int         rtp_session_set_send_payload_type
                                                (RtpSession *session,
                                                 int paytype);

Sets the payload type of the rtp session. It decides of the payload types written in the of the rtp header for the outgoing stream, if the session is SENDRECV or SENDONLY. For payload type in incoming packets, the application can be informed by registering for the "payload_type_changed" signal, so that it can make the necessary changes on the downstream decoder that deals with the payload of the packets.

`session` : | a rtp session
`paytype` : | the payload type
Returns : | 0 on success, -1 if the payload is not defined.

### rtp_session_set_recv_payload_type ()

    int         rtp_session_set_recv_payload_type
                                                (RtpSession *session,
                                                 int pt);

Sets the expected payload type for incoming packets. If the actual payload type in incoming packets is different that this expected payload type, thus the "payload_type_changed" signal is emitted.

`session` : | a rtp session
`pt` : |
Returns : | 0 on success, -1 if the payload is not defined.

### rtp_session_get_send_payload_type ()

    int         rtp_session_get_send_payload_type
                                                (const RtpSession *session);

`session` : | a rtp session
Returns : | the payload type currently used in outgoing rtp packets

### rtp_session_get_recv_payload_type ()

    int         rtp_session_get_recv_payload_type
                                                (const RtpSession *session);

`session` : | a rtp session
Returns : | the payload type currently used in incoming rtp packets

### rtp_session_set_payload_type ()

    int         rtp_session_set_payload_type    (RtpSession *session,
                                                 int pt);

Sets the expected payload type for incoming packets and payload type to be used for outgoing packets. If the actual payload type in incoming packets is different that this expected payload type, thus the "payload_type_changed" signal is emitted.

`session` : | a rtp session
`pt` : |
Returns : | 0 on success, -1 if the payload is not defined.

### rtp_session_signal_connect ()

    int         rtp_session_signal_connect      (RtpSession *session,
                                                 const char *signal,
                                                 RtpCallback cb,
                                                 unsigned long user_data);

This function provides the way for an application to be informed of various events that may occur during a rtp session. `signal` is a string identifying the event, and `cb` is a user supplied function in charge of processing it. The application can register several callbacks for the same signal, in the limit of RTP_CALLBACK_TABLE_MAX_ENTRIES. Here are name and meaning of supported signals types:

"ssrc_changed" : the SSRC of the incoming stream has changed.

"payload_type_changed" : the payload type of the incoming stream has changed.

"telephone-event_packet" : a telephone-event rtp packet (RFC2833) is received.

"telephone-event" : a telephone event has occured. This is a high-level shortcut for "telephone-event_packet".

"network_error" : a network error happened on a socket. Arguments of the callback functions are a const char * explaining the error, an int errno error code and the user_data as usual.

"timestamp_jump" : we have received a packet with timestamp in far future compared to last timestamp received. The farness of far future is set by `rtp_sesssion_set_time_jump_limit()` "rtcp_bye": we have received a RTCP bye packet. Arguments of the callback functions are a const char * containing the leaving reason and the user_data.

`session` : | a rtp session
`signal` : | the name of a signal
`cb` : | a RtpCallback
`Param4` : |
Returns : | 0 on success, -EOPNOTSUPP if the signal does not exists, -1 if no more callbacks can be assigned to the signal type.

### rtp_session_signal_disconnect_by_callback ()

    int         rtp_session_signal_disconnect_by_callback
                                                (RtpSession *session,
                                                 const char *signal,
                                                 RtpCallback cb);

Removes callback function `cb` to the list of callbacks for signal `signal`.

`session` : | a rtp session
`signal` : | a signal name
`cb` : | a callback function.
Returns : | 0 on success, -ENOENT if the callbacks was not found.

### rtp_session_send_with_ts ()

    int         rtp_session_send_with_ts        (RtpSession *session,
                                                 const char *buffer,
                                                 int len,
                                                 uint32_t userts);

Send a rtp datagram to the destination set by `rtp_session_set_remote_addr()` containing the data from `buffer` with timestamp `userts`. This is a high level function that uses `rtp_session_create_packet()` and `rtp_session_sendm_with_ts()` to send the data.

`session` : | a rtp session.
`buffer` : | a buffer containing the data to be sent in a rtp packet.
`len` : | the length of the data buffer, in bytes.
`userts` : | the timestamp of the data to be sent. Refer to the rfc to know what it is.
Returns : | the number of bytes sent over the network.

### rtp_session_recv_with_ts ()

    int         rtp_session_recv_with_ts        (RtpSession *session,
                                                 char *buffer,
                                                 int len,
                                                 uint32_t time,
                                                 int *have_more);

Tries to read the bytes of the incoming rtp stream related to timestamp `time`. In case where the user supplied buffer `buffer` is not large enough to get all the data related to timestamp `time`, then *( `have_more`) is set to 1 to indicate that the application should recall the function with the same timestamp to get more data.

When the rtp session is scheduled (see `rtp_session_set_scheduling_mode()` ), and the blocking mode is on (see `rtp_session_set_blocking_mode()` ), then the calling thread is suspended until the timestamp given as argument expires, whatever a received packet fits the query or not.

Important note: it is clear that the application cannot know the timestamp of the first packet of the incoming stream, because it can be random. The `time` timestamp given to the function is used relatively to first timestamp of the stream. In simple words, 0 is a good value to start calling this function.

This function internally calls `rtp_session_recvm_with_ts()` to get a rtp packet. The content of this packet is then copied into the user supplied buffer in an intelligent manner: the function takes care of the size of the supplied buffer and the timestamp given in argument. Using this function it is possible to read continous audio data (e.g. pcma,pcmu...) with for example a standart buffer of size of 160 with timestamp incrementing by 160 while the incoming stream has a different packet size.

`session` : | a rtp session.
`buffer` : | a user supplied buffer to write the data.
`len` : | the length in bytes of the user supplied buffer.
`time` : | the timestamp wanted.
`have_more` : | the address of an integer to indicate if more data is availlable for the given timestamp.
Returns : | if a packet was availlable with the corresponding timestamp supplied in argument then the number of bytes written in the user supplied buffer is returned. If no packets are availlable, either because the sender has not started to send the stream, or either because silence packet are not transmitted, or either because the packet was lost during network transport, then the function returns zero.

### rtp_session_recvm_with_ts ()

    mblk_t*     rtp_session_recvm_with_ts       (RtpSession *session,
                                                 uint32_t user_ts);

Try to get a rtp packet presented as a mblk_t structure from the rtp session. The `user_ts` parameter is relative to the first timestamp of the incoming stream. In other words, the application does not have to know the first timestamp of the stream, it can simply call for the first time this function with `user_ts`=0, and then incrementing it as it want. The RtpSession takes care of synchronisation between the stream timestamp and the user timestamp given here.

`session` : | a rtp session.
`user_ts` : | a timestamp.
Returns : | a rtp packet presented as a mblk_t.

### rtp_session_create_packet ()

    mblk_t*     rtp_session_create_packet       (RtpSession *session,
                                                 int header_size,
                                                 const char *payload,
                                                 int payload_size);

Allocates a new rtp packet. In the header, ssrc and payload_type according to the session's context. Timestamp and seq number are not set, there will be set when the packet is going to be sent with `rtp_session_sendm_with_ts()`. If payload_size is zero, thus an empty packet (just a RTP header) is returned.

`session` : | a rtp session.
`header_size` : | the rtp header size. For standart size (without extensions), it is RTP_FIXED_HEADER_SIZE
`payload` : | data to be copied into the rtp packet.
`payload_size` : | size of data carried by the rtp packet.
Returns : | a rtp packet in a mblk_t (message block) structure.

### rtp_session_create_packet_with_data ()

    mblk_t*     rtp_session_create_packet_with_data
                                                (RtpSession *session,
                                                 char *payload,
                                                 int payload_size,
                                                 void (*freefn) (void*));

Creates a new rtp packet using the given payload buffer (no copy). The header will be allocated separetely. In the header, ssrc and payload_type according to the session's context. Timestamp and seq number are not set, there will be set when the packet is going to be sent with `rtp_session_sendm_with_ts()`. oRTP will send this packet using libc's `sendmsg()` (if this function is availlable!) so that there will be no packet concatenation involving copies to be done in user-space. `freefn` can be NULL, in that case payload will be kept untouched.

`session` : | a rtp session.
`payload` : | the data to be sent with this packet
`payload_size` : | size of data
`freefn` : | a function that will be called when the payload buffer is no more needed.
Returns : | a rtp packet in a mblk_t (message block) structure.

### rtp_session_sendm_with_ts ()

    int         rtp_session_sendm_with_ts       (RtpSession *session,
                                                 mblk_t *mp,
                                                 uint32_t userts);

Send the rtp datagram `mp` to the destination set by `rtp_session_set_remote_addr()` with timestamp `timestamp`. For audio data, the timestamp is the number of the first sample resulting of the data transmitted. See rfc1889 for details. The packet (`mp`) is freed once it is sended.

`session` : | a rtp session.
`mp` : | a rtp packet presented as a mblk_t.
`userts` : |
Returns : | the number of bytes sent over the network.

### rtp_session_get_current_send_ts ()

    uint32_t    rtp_session_get_current_send_ts (RtpSession *session);

When the rtp session is scheduled and has started to send packets, this function computes the timestamp that matches to the present time. Using this function can be usefull when sending discontinuous streams. Some time can be elapsed between the end of a stream burst and the begin of a new stream burst, and the application may be not not aware of this elapsed time. In order to get a valid (current) timestamp to pass to #`rtp_session_send_with_ts()` or #`rtp_session_sendm_with_ts()`, the application may use `rtp_session_get_current_send_ts()`.

`session` : | a rtp session.
Returns : | the current send timestamp for the rtp session.

### rtp_session_flush_sockets ()

    void        rtp_session_flush_sockets       (RtpSession *session);

Flushes the sockets for all pending incoming packets. This can be usefull if you did not listen to the stream for a while and wishes to start to receive again. During the time no receive is made packets get bufferised into the internal kernel socket structure.

`session` : | a rtp session

### rtp_session_set_time_jump_limit ()

    void        rtp_session_set_time_jump_limit (RtpSession *session,
                                                 int miliseconds);

oRTP has the possibility to inform the application through a callback registered with rtp_session_signal_connect about crazy incoming RTP stream that jumps from a timestamp N to N+<some crazy value>. This lets the opportunity for the application to reset the session in order to resynchronize, or any other action like stopping the call and reporting an error.

`session` : | the rtp session
`miliseconds` : |

### rtp_session_set_recv_buf_size ()

    void        rtp_session_set_recv_buf_size   (RtpSession *session,
                                                 int bufsize);

The default value is 65535 bytes, a big value which is working for everyone. However if your application can make assumption on the MTU, it can be interesting to set it to a lower value in order to save memory.

`session` : | a rtp session
`bufsize` : | buffer size in bytes for receiving packets

### rtp_session_reset ()

    void        rtp_session_reset               (RtpSession *session);

Reset the session: local and remote addresses are kept unchanged but the internal queue for ordering and buffering packets is flushed, the session is ready to be re-synchronised to another incoming stream.

`session` : | a rtp session.

### rtp_session_set_data ()

    void        rtp_session_set_data            (RtpSession *session,
                                                 void *data);

Stores some application specific data into the session, so that it is easy to retrieve it from the signal callbacks using `rtp_session_get_data()`.

`session` : | a rtp session
`data` : | an opaque pointer to be stored in the session

### rtp_session_get_data ()

    void*       rtp_session_get_data            (const RtpSession *session);

`session` : | a rtp session
Returns : | the void pointer previously set using `rtp_session_set_data()`