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/* GStreamer RIST plugin
* Copyright (C) 2019 Net Insight AB
* Author: Nicolas Dufresne <nicolas.dufresne@collabora.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301, USA.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "gstrist.h"
#include "gstroundrobin.h"
/*
* rtp_ext_seq:
* @extseq: (inout): a previous extended seqs
* @seq: a new seq
*
* Update the @extseq field with the extended seq of @seq
* For the first call of the method, @extseq should point to a location
* with a value of -1.
*
* This function is able to handle both forward and backward seqs taking
* into account:
* - seq wraparound making sure that the returned value is properly increased.
* - seq unwraparound making sure that the returned value is properly decreased.
*
* Returns: The extended seq of @seq or 0 if the result can't go anywhere backwards.
*
* NOTE: This is a calque of gst_rtp_buffer_ext_timestamp() but with
* s/32/16/ and s/64/32/ and s/0xffffffff/0xffff/ and s/timestamp/seqnum/.
*/
guint32
gst_rist_rtp_ext_seq (guint32 * extseqnum, guint16 seqnum)
{
guint32 result, ext;
g_return_val_if_fail (extseqnum != NULL, -1);
ext = *extseqnum;
if (ext == -1) {
result = seqnum;
} else {
/* pick wraparound counter from previous seqnum and add to new seqnum */
result = seqnum + (ext & ~(0xffff));
/* check for seqnum wraparound */
if (result < ext) {
guint32 diff = ext - result;
if (diff > G_MAXINT16) {
/* seqnum went backwards more than allowed, we wrap around and get
* updated extended seqnum. */
result += (1 << 16);
}
} else {
guint32 diff = result - ext;
if (diff > G_MAXINT16) {
if (result < (1 << 16)) {
GST_WARNING
("Cannot unwrap, any wrapping took place yet. Returning 0 without updating extended seqnum.");
return 0;
} else {
/* seqnum went forwards more than allowed, we unwrap around and get
* updated extended seqnum. */
result -= (1 << 16);
/* We don't want the extended seqnum storage to go back, ever */
return result;
}
}
}
}
*extseqnum = result;
return result;
}
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