CURLOPT_INTERLEAVEFUNCTION(3) Library Functions Manual
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).
SEE ALSO
CURLOPT_INTERLEAVEDATA(3), CURLOPT_RTSP_REQUEST(3)
libcurl 2025-02-08 CURLOPT_INTERLEAVEFUNCTION(3)
curl 8.12.0 - Generated Sat Feb 15 10:47:57 CST 2025