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