Tribblix: manual page: CURLOPT_INTERLEAVEFUNCTION.3

CURLOPT_INTERLEAVEFUNCTION(3) Introduction to Library Functions

NAME

CURLOPT_INTERLEAVEFUNCTION - callback for RTSP interleaved data

SYNOPSIS

#include <curl/curl.h>

size_t interleave_callback(void *ptr, size_t size, size_t nmemb,
void *userdata);

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_INTERLEAVEFUNCTION,
interleave_callback);

DESCRIPTION

Pass a pointer to your callback function, which should match the
prototype shown above.

This callback function gets called by libcurl as soon as it has
received interleaved RTP data. This function gets called for each $
block and therefore contains exactly one upper-layer protocol unit
(e.g. one RTP packet). curl writes the interleaved header as well as
the included data for each call. The first byte is always an ASCII
dollar sign. The dollar sign is followed by a one byte channel
identifier and then a 2 byte integer length in network byte order.
See RFC 2326 Section 10.12 for more information on how RTP
interleaving behaves. If unset or set to NULL, curl uses the default
write function.

Interleaved RTP poses some challenges for the client application.
Since the stream data is sharing the RTSP control connection, it is
critical to service the RTP in a timely fashion. If the RTP data is
not handled quickly, subsequent response processing may become
unreasonably delayed and the connection may close. The application
may use CURL_RTSPREQ_RECEIVE to service RTP data when no requests are
desired. If the application makes a request, (e.g.
CURL_RTSPREQ_PAUSE) then the response handler processes any pending
RTP data before marking the request as finished.

The CURLOPT_INTERLEAVEDATA(3) is passed in the userdata argument in
the callback.

Your callback should return the number of bytes actually taken care
of. If that amount differs from the amount passed to your callback
function, it signals an error condition to the library. This causes
the transfer to abort and the libcurl function used returns
CURLE_WRITE_ERROR.

You can also abort the transfer by returning CURL_WRITEFUNC_ERROR.
(7.87.0)

DEFAULT

NULL, the interleave data is then passed to the regular write
function: CURLOPT_WRITEFUNCTION(3).

PROTOCOLS

This functionality affects rtsp only

EXAMPLE

struct local {
void *custom;
};

static size_t rtp_write(void *ptr, size_t size, size_t nmemb, void *userp)
{
struct local *l = userp;
printf("our ptr: %p\n", l->custom);
/* take care of the packet in 'ptr', then return... */
return size * nmemb;
}

int main(void)
{
struct local rtp_data;
CURL *curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_INTERLEAVEFUNCTION, rtp_write);
curl_easy_setopt(curl, CURLOPT_INTERLEAVEDATA, &rtp_data);
}
}

AVAILABILITY

Added in curl 7.20.0

RETURN VALUE

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error
occurred, see libcurl-errors(3).