103 lines
3 KiB
Markdown
103 lines
3 KiB
Markdown
---
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c: Copyright (C) Daniel Stenberg, <daniel.se>, et al.
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SPDX-License-Identifier: curl
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Title: CURLOPT_INTERLEAVEFUNCTION
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Section: 3
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Source: libcurl
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See-also:
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- CURLOPT_INTERLEAVEDATA (3)
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- CURLOPT_RTSP_REQUEST (3)
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---
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# NAME
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CURLOPT_INTERLEAVEFUNCTION - callback for RTSP interleaved data
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# SYNOPSIS
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~~~c
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#include <curl/curl.h>
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size_t interleave_callback(void *ptr, size_t size, size_t nmemb,
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void *userdata);
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CURLcode curl_easy_setopt(CURL *handle, CURLOPT_INTERLEAVEFUNCTION,
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interleave_callback);
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~~~
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# DESCRIPTION
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Pass a pointer to your callback function, which should match the prototype
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shown above.
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This callback function gets called by libcurl as soon as it has received
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interleaved RTP data. This function gets called for each $ block and therefore
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contains exactly one upper-layer protocol unit (e.g. one RTP packet). Curl
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writes the interleaved header as well as the included data for each call. The
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first byte is always an ASCII dollar sign. The dollar sign is followed by a
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one byte channel identifier and then a 2 byte integer length in network byte
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order. See RFC 2326 Section 10.12 for more information on how RTP interleaving
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behaves. If unset or set to NULL, curl uses the default write function.
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Interleaved RTP poses some challenges for the client application. Since the
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stream data is sharing the RTSP control connection, it is critical to service
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the RTP in a timely fashion. If the RTP data is not handled quickly,
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subsequent response processing may become unreasonably delayed and the
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connection may close. The application may use *CURL_RTSPREQ_RECEIVE* to
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service RTP data when no requests are desired. If the application makes a
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request, (e.g. *CURL_RTSPREQ_PAUSE*) then the response handler processes
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any pending RTP data before marking the request as finished.
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The CURLOPT_INTERLEAVEDATA(3) is passed in the *userdata* argument in
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the callback.
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Your callback should return the number of bytes actually taken care of. If
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that amount differs from the amount passed to your callback function, it
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signals an error condition to the library. This causes the transfer to abort
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and the libcurl function used returns *CURLE_WRITE_ERROR*.
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You can also abort the transfer by returning CURL_WRITEFUNC_ERROR. (7.87.0)
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# DEFAULT
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NULL, the interleave data is then passed to the regular write function:
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CURLOPT_WRITEFUNCTION(3).
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# PROTOCOLS
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RTSP
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# EXAMPLE
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~~~c
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struct local {
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void *custom;
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};
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static size_t rtp_write(void *ptr, size_t size, size_t nmemb, void *userp)
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{
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struct local *l = userp;
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printf("our ptr: %p\n", l->custom);
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/* take care of the packet in 'ptr', then return... */
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return size * nmemb;
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}
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int main(void)
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{
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struct local rtp_data;
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CURL *curl = curl_easy_init();
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if(curl) {
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curl_easy_setopt(curl, CURLOPT_INTERLEAVEFUNCTION, rtp_write);
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curl_easy_setopt(curl, CURLOPT_INTERLEAVEDATA, &rtp_data);
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}
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}
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~~~
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# AVAILABILITY
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Added in 7.20.0
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# RETURN VALUE
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Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
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