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 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 in-
teger 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 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).
SEE ALSO
CURLOPT_INTERLEAVEDATA(3), CURLOPT_RTSP_REQUEST(3)
libcurl 2026-07-12 CURLOPT_IN...VEFUNCTION(3)
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