docs/libcurl/opts/CURLOPT_INTERLEAVEFUNCTION.3

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.TH CURLOPT_INTERLEAVEFUNCTION 3 "November 04, 2020" "libcurl 7.78.0" "curl_easy_setopt options"

.SH NAME
CURLOPT_INTERLEAVEFUNCTION \- callback function for RTSP interleaved data
.SH SYNOPSIS
.nf
#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);
.SH 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 \fIRFC2326 Section 10.12\fP for more information on how RTP
interleaving behaves. If unset or set to NULL, curl will use 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 \fICURL_RTSPREQ_RECEIVE\fP to
service RTP data when no requests are desired. If the application makes a
request, (e.g.  \fICURL_RTSPREQ_PAUSE\fP) then the response handler will
process any pending RTP data before marking the request as finished.

The \fICURLOPT_INTERLEAVEDATA(3)\fP is passed in the \fIuserdata\fP argument in
the callback.
.SH DEFAULT
NULL, the interleave data is then passed to the regular write function:
\fICURLOPT_WRITEFUNCTION(3)\fP.
.SH PROTOCOLS
RTSP
.SH EXAMPLE
.nf
static size_t rtp_write(void *ptr, size_t size, size_t nmemb, void *user)
{
  struct local *l = (struct local *)user;
  /* take care of the packet in 'ptr', then return... */
  return size * nmemb;
}
{
  struct local rtp_data;
  curl_easy_setopt(curl, CURLOPT_INTERLEAVEFUNCTION, rtp_write);
  curl_easy_setopt(curl, CURLOPT_INTERLEAVEDATA, &rtp_data);
}
.fi
.SH AVAILABILITY
Added in 7.20.0
.SH RETURN VALUE
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
.SH "SEE ALSO"
.BR CURLOPT_INTERLEAVEDATA "(3), " CURLOPT_RTSP_REQUEST "(3), "