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CURLOPT_IN...VEFUNCTION(3) Library Functions Manual CURLOPT_IN...VEFUNCTION(3)

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	proto-
       type shown above.

       This  callback  function	 gets  called by libcurl as soon as it has re-
       ceived 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_RE-
       CEIVE to	service	RTP data when no requests are desired. If the applica-
       tion makes a request, (e.g. CURL_RTSPREQ_PAUSE) then the	response  han-
       dler  processes any pending RTP data before marking the request as fin-
       ished.

       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	 func-
       tion,  it  signals  an  error condition to the library. This causes the
       transfer	to abort and the libcurl function used returns CURLE_WRITE_ER-
       ROR.

       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).

SEE ALSO
       CURLOPT_INTERLEAVEDATA(3), CURLOPT_RTSP_REQUEST(3)

libcurl				  2025-06-03	    CURLOPT_IN...VEFUNCTION(3)

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