From 0596871b98aed296b6fd89f001557f3c53f4b6aa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20Dr=C3=B6ge?= <sebastian@centricular.com>
Date: Thu, 4 Apr 2024 13:21:44 +0300
Subject: [PATCH] rtpbin: Don't re-use a variable for a completely different
 purpose temporarily

During RTP-Info synchronization, clock_base was temporarily switched
from the actual clock-base to the base RTP time and then back some lines
later.

Instead directly work with the base RTP time. The comment about using a
signed variable for convenience doesn't make any sense because all
calculations done with the value are unsigned.

Similarly, rtp_clock_base was overridden with the rtp_delta when
calculating it, which was fine because it is not used anymore
afterwards. Instead, introduce a new variable `rtp_delta` to make this
calculation clearer.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/6536>
---
 .../gst/rtpmanager/gstrtpbin.c                | 23 +++++++++----------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/subprojects/gst-plugins-good/gst/rtpmanager/gstrtpbin.c b/subprojects/gst-plugins-good/gst/rtpmanager/gstrtpbin.c
index 92d72f2bb8..4389df56f4 100644
--- a/subprojects/gst-plugins-good/gst/rtpmanager/gstrtpbin.c
+++ b/subprojects/gst-plugins-good/gst/rtpmanager/gstrtpbin.c
@@ -1567,7 +1567,7 @@ gst_rtp_bin_associate (GstRtpBin * bin, GstRtpBinStream * stream, guint8 len,
     stream_set_ts_offset (bin, stream, stream->rt_delta, bin->max_ts_offset,
         bin->min_ts_offset, FALSE);
   } else {
-    gint64 min, rtp_min, clock_base = stream->clock_base;
+    gint64 min, rtp_min, clock_base;
     gboolean all_sync, use_rtp;
     gboolean rtcp_sync = g_atomic_int_get (&bin->rtcp_sync);
 
@@ -1594,25 +1594,24 @@ gst_rtp_bin_associate (GstRtpBin * bin, GstRtpBinStream * stream, guint8 len,
     use_rtp = FALSE;
     if (rtcp_sync == GST_RTP_BIN_RTCP_SYNC_RTP) {
       guint64 ext_base = -1;
+      gint64 rtp_delta = 0;
 
       use_rtp = TRUE;
-      /* signed version for convenience */
-      clock_base = base_rtptime;
       /* convert to extended RTP time */
       rtp_clock_base = gst_rtp_buffer_ext_timestamp (&ext_base, rtp_clock_base);
       /* sanity check; base rtp and provided clock_base should be close */
-      if (rtp_clock_base >= clock_base) {
-        if (rtp_clock_base - clock_base < 10 * clock_rate) {
-          rtp_clock_base = base_time +
-              gst_util_uint64_scale_int (rtp_clock_base - clock_base,
+      if (rtp_clock_base >= base_rtptime) {
+        if (rtp_clock_base - base_rtptime < 10 * clock_rate) {
+          rtp_delta = base_time +
+              gst_util_uint64_scale_int (rtp_clock_base - base_rtptime,
               GST_SECOND, clock_rate);
         } else {
           use_rtp = FALSE;
         }
       } else {
-        if (clock_base - rtp_clock_base < 10 * clock_rate) {
-          rtp_clock_base = base_time -
-              gst_util_uint64_scale_int (clock_base - rtp_clock_base,
+        if (base_rtptime - rtp_clock_base < 10 * clock_rate) {
+          rtp_delta = base_time -
+              gst_util_uint64_scale_int (base_rtptime - rtp_clock_base,
               GST_SECOND, clock_rate);
         } else {
           use_rtp = FALSE;
@@ -1624,11 +1623,11 @@ gst_rtp_bin_associate (GstRtpBin * bin, GstRtpBinStream * stream, guint8 len,
         return;
       }
       /* store to track changes */
-      clock_base = rtp_clock_base;
+      clock_base = rtp_delta;
       /* generate a fake as before,
        * now equating rtptime obtained from RTP-Info,
        * where the large time represent the otherwise irrelevant npt/ntp time */
-      stream->rtp_delta = (GST_SECOND << 28) - rtp_clock_base;
+      stream->rtp_delta = (GST_SECOND << 28) - rtp_delta;
     } else {
       clock_base = rtp_clock_base;
     }