rohc_comp_set_rtp_detection_cb

NAME
SYNOPSIS
DESCRIPTION
PARAMETERS
STRUCTURES
RETURN VALUE
EXAMPLE
SEE ALSO

NAME

rohc_comp_set_rtp_detection_cb − Set the RTP detection callback function.

SYNOPSIS

#include <rohc/rohc_comp.h>

bool rohc_comp_set_rtp_detection_cb(
struct rohc_comp *const comp,
rohc_rtp_detection_callback_t callback,
void *const rtp_private
);

DESCRIPTION

Set or replace the callback function that the ROHC library will call to detect RTP streams among other UDP streams.

The function is called once per UDP packet to compress, with the IP and UDP headers and the UDP payload. If the callback function returns true, the RTP profile is used for compression, otherwise the IP/UDP profile is used instead.

Special value NULL may be used to disable the detection of RTP streams with the callback method. The detection will then be based on a list of UDP ports dedicated for RTP streams.

PARAMETERS

comp

The ROHC compressor

callback

The callback function used to detect RTP packets The callback is deactivated if NULL is given as parameter

rtp_private

A pointer to an external memory area provided and used by the callback user

STRUCTURES

RETURN VALUE

true on success, false otherwise

EXAMPLE

/**
* @brief The RTP detection callback which does detect RTP stream
*
* @param ip The innermost IP packet
* @param udp The UDP header of the packet
* @param payload The UDP payload of the packet
* @param payload_size The size of the UDP payload (in bytes)
* @return true if the packet is an RTP packet, false otherwise
*/
static bool rtp_detect(const unsigned char *const ip,
const unsigned char *const udp,
const unsigned char *const payload,
const unsigned int payload_size,
void *const rtp_private)
{
uint16_t udp_dport;
bool is_rtp;

/* check UDP destination port */
memcpy(&udp_dport, udp + 2, sizeof(uint16_t));
if(ntohs(udp_dport) == 10042)
{
/* we think that the UDP packet is a RTP packet */
fprintf(stderr, "RTP packet detected (expected UDP port)0);
is_rtp = true;
}
else
{
/* we think that the UDP packet is not a RTP packet */
fprintf(stderr, "RTP packet not detected (wrong UDP port)0);
is_rtp = false;
}

return is_rtp;
}

...

struct rohc_comp *compressor; /* the ROHC compressor */

...

compressor = rohc_comp_new2(ROHC_SMALL_CID, ROHC_SMALL_CID_MAX,
gen_random_num, NULL);
if(compressor == NULL)
{
fprintf(stderr, "failed create the ROHC compressor0);
goto error;
}

...

if(!rohc_comp_set_rtp_detection_cb(compressor, rtp_detect, NULL))
{
fprintf(stderr, "failed to set RTP detection callback0);
goto error;
}

...

rohc_comp_free(compressor);