Group PJMED_STRM

group PJMED_STRM

Communicating with remote peer via the network.

A media stream is a bidirectional multimedia communication between two endpoints. It corresponds to a media description (m= line) in SDP session descriptor.

A media stream consists of two unidirectional channels:

• encoding channel, which transmits unidirectional media to remote, and

• decoding channel, which receives unidirectional media from remote.

A media stream exports media port interface (see Media Ports Framework) and application normally uses this interface to interconnect the stream to other PJMEDIA components.

A media stream internally manages the following objects:

• an instance of media codec (see Codec Framework),

• an Adaptive jitter buffer,

• two instances of RTP sessions (pjmedia_rtp_session, one for each direction),

• one instance of RTCP session (pjmedia_rtcp_session),

• and a reference to media transport to send and receive packets to/from the network (see Media Transport).

Streams are created by calling pjmedia_stream_create(), specifying pjmedia_stream_info structure in the parameter. Application can construct the pjmedia_stream_info structure manually, or use pjmedia_stream_info_from_sdp() or pjmedia_session_info_from_sdp() functions to construct the pjmedia_stream_info from local and remote SDP session descriptors.

Application can also use Media Sessions to indirectly create the streams.

Typedefs

typedef struct pjmedia_channel pjmedia_channel

Opaque declaration for media channel. Media channel is unidirectional flow of media from sender to receiver.

Functions

pj_status_t pjmedia_stream_create(pjmedia_endpt *endpt, pj_pool_t *pool, const pjmedia_stream_info *info, pjmedia_transport *tp, void *user_data, pjmedia_stream **p_stream)

Create a media stream based on the specified parameter. After the stream has been created, application normally would want to get the media port interface of the streams, by calling pjmedia_stream_get_port(). The media port interface exports put_frame() and get_frame() function, used to transmit and receive media frames from the stream.

Without application calling put_frame() and get_frame(), there will be no media frames transmitted or received by the stream.

Parameters

• endpt – Media endpoint.

• pool – Pool to allocate memory for the stream. A large number of memory may be needed because jitter buffer needs to preallocate some storage.

• info – Stream information.

• tp – Stream transport instance used to transmit and receive RTP/RTCP packets to/from the underlying transport.

• user_data – Arbitrary user data (for future callback feature).

• p_stream – Pointer to receive the media stream.

Returns

PJ_SUCCESS on success.

pj_status_t pjmedia_stream_destroy(pjmedia_stream *stream)

Destroy the media stream.

Parameters

stream – The media stream.

Returns

PJ_SUCCESS on success.

char pjmedia_stream_get_last_jb_frame_type(pjmedia_stream *stream)

Get the last frame type retreived from the jitter buffer.

Parameters

stream – The media stream.

Returns

Jitter buffer frame type.

pj_status_t pjmedia_stream_get_port(pjmedia_stream *stream, pjmedia_port **p_port)

Get the media port interface of the stream. The media port interface declares put_frame() and get_frame() function, which is the only way for application to transmit and receive media frames from the stream.

Parameters

• stream – The media stream.

• p_port – Pointer to receive the port interface.

Returns

PJ_SUCCESS on success.

pjmedia_transport *pjmedia_stream_get_transport(pjmedia_stream *st)

Get the media transport object associated with this stream.

Parameters

st – The media stream.

Returns

The transport object being used by the stream.

pj_status_t pjmedia_stream_start(pjmedia_stream *stream)

Start the media stream. This will start the appropriate channels in the media stream, depending on the media direction that was set when the stream was created.

Parameters

stream – The media stream.

Returns

PJ_SUCCESS on success.

pj_status_t pjmedia_stream_get_stat(const pjmedia_stream *stream, pjmedia_rtcp_stat *stat)

Get the stream statistics. See also pjmedia_stream_get_stat_jbuf()

Parameters

• stream – The media stream.

• stat – Media stream statistics.

Returns

PJ_SUCCESS on success.

pj_status_t pjmedia_stream_reset_stat(pjmedia_stream *stream)

Reset the stream statistics.

Parameters

stream – The media stream.

Returns

PJ_SUCCESS on success.

pj_status_t pjmedia_stream_get_stat_jbuf(const pjmedia_stream *stream, pjmedia_jb_state *state)

Get current jitter buffer state. See also pjmedia_stream_get_stat()

Parameters

• stream – The media stream.

• state – Jitter buffer state.

Returns

PJ_SUCCESS on success.

pj_status_t pjmedia_stream_pause(pjmedia_stream *stream, pjmedia_dir dir)

Pause the individual channel in the stream.

Parameters

• stream – The media channel.

• dir – Which direction to pause.

Returns

PJ_SUCCESS on success.

pj_status_t pjmedia_stream_resume(pjmedia_stream *stream, pjmedia_dir dir)

Resume the individual channel in the stream.

Parameters

• stream – The media channel.

• dir – Which direction to resume.

Returns

PJ_SUCCESS on success;

pj_status_t pjmedia_stream_dial_dtmf(pjmedia_stream *stream, const pj_str_t *ascii_digit)

Transmit DTMF to this stream. The DTMF will be transmitted uisng RTP telephone-events as described in RFC 2833. This operation is only valid for audio stream.

Parameters

• stream – The media stream.

• ascii_digit – String containing digits to be sent to remote. Currently the maximum number of digits are 32.

Returns

PJ_SUCCESS on success.

pj_bool_t pjmedia_stream_check_dtmf(pjmedia_stream *stream)

Check if the stream has incoming DTMF digits in the incoming DTMF queue. Incoming DTMF digits received via RFC 2833 mechanism are saved in the incoming digits queue.

Parameters

stream – The media stream.

Returns

Non-zero (PJ_TRUE) if the stream has received DTMF digits in the .

pj_status_t pjmedia_stream_get_dtmf(pjmedia_stream *stream, char *ascii_digits, unsigned *size)

Retrieve the incoming DTMF digits from the stream, and remove the digits from stream’s DTMF buffer. Note that the digits buffer will not be NULL terminated.

Parameters

• stream – The media stream.

• ascii_digits – Buffer to receive the digits. The length of this buffer is indicated in the “size” argument.

• size – On input, contains the maximum digits to be copied to the buffer. On output, it contains the actual digits that has been copied to the buffer.

Returns

Non-zero (PJ_TRUE) if the stream has received DTMF digits in the .

pj_status_t pjmedia_stream_set_dtmf_callback(pjmedia_stream *stream, void (*cb)(pjmedia_stream*, void *user_data, int digit), void *user_data, )

Set callback to be called upon receiving DTMF digits. If callback is registered, the stream will not buffer incoming DTMF but rather call the callback as soon as DTMF digit is received completely.

Parameters

• stream – The media stream.

• cb – Callback to be called upon receiving DTMF digits. The DTMF digits will be given to the callback as ASCII digits.

• user_data – User data to be returned back when the callback is called.

Returns

PJ_SUCCESS on success.

pj_status_t pjmedia_stream_send_rtcp_sdes(pjmedia_stream *stream)

Send RTCP SDES for the media stream.

Parameters

stream – The media stream.

Returns

PJ_SUCCESS on success.

pj_status_t pjmedia_stream_send_rtcp_bye(pjmedia_stream *stream)

Send RTCP BYE for the media stream.

Parameters

stream – The media stream.

Returns

PJ_SUCCESS on success.

struct pjmedia_stream_info

#include <stream.h>

This structure describes media stream information. Each media stream corresponds to one “m=” line in SDP session descriptor, and it has its own RTP/RTCP socket pair.

See

pjmedia_stream_info.