From f2a9111fb64379c8340c0fcee622512cc057af48 Mon Sep 17 00:00:00 2001
From: Richard Fuchs <rfuchs@sipwise.com>
Date: Tue, 12 Aug 2025 09:50:08 -0400
Subject: [PATCH] MT#55283 distinguish transcoding PTs

PTs that were remembered from a previous handshake to save codec options
must be flagged as such so that they're not considered as having been
present in the current offer, so that they can be flagged as transcoding
PTs.

closes #1989

Change-Id: I19c2aff7e83ed338a81be99544645821165304cd
---
 daemon/codec.c | 28 ++++++++++++++++++++--------
 lib/rtplib.h   |  1 +
 2 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/daemon/codec.c b/daemon/codec.c
index 20487ed00..9b9b0c920 100644
--- a/daemon/codec.c
+++ b/daemon/codec.c
@@ -5669,14 +5669,16 @@ void __codec_store_populate_reuse(struct codec_store *dst, struct codec_store *s
 		rtp_payload_type *pt = l->data;
 		rtp_payload_type *orig_pt = t_hash_table_lookup(src->codecs,
 				GINT_TO_POINTER(pt->payload_type));
-		if(!orig_pt){
-			if (a.merge_cs)
+		if (!orig_pt){
+			if (a.merge_cs) {
+				pt->removed = 1;
 				codec_store_add_raw_link(src, rtp_payload_type_dup(pt),
 						src->codec_prefs.head);
+			}
 			l = __codec_store_delete_link(l, dst);
-		}else{
-			l = l->next;
 		}
+		else
+			l = l->next;
 	}
 }
 
@@ -5705,6 +5707,7 @@ static void codec_store_merge(struct codec_store *dst, struct codec_store *src)
 		if (old_pt)
 			__codec_store_delete_link(old_pt->prefs_link, dst);
 
+		pt->removed = 1;
 		codec_store_add_raw_link(dst, pt, dst->codec_prefs.head);
 	}
 
@@ -6116,10 +6119,19 @@ void codec_store_transcode(struct codec_store *cs, str_q *offer, struct codec_st
 						STR_FMT(codec));
 				continue;
 			}
-			ilogs(codec, LOG_DEBUG, "Re-adding stripped codec " STR_FORMAT "/" STR_FORMAT " (%i)",
-					STR_FMT(&orig_pt->encoding_with_params),
-					STR_FMT0(&orig_pt->format_parameters),
-					orig_pt->payload_type);
+			if (orig_pt->removed) {
+				ilogs(codec, LOG_DEBUG, "Adding previously present codec "
+							STR_FORMAT "/" STR_FORMAT " (%i) for transcoding",
+						STR_FMT(&orig_pt->encoding_with_params),
+						STR_FMT0(&orig_pt->format_parameters),
+						orig_pt->payload_type);
+				orig_pt->for_transcoding = 1;
+			}
+			else
+				ilogs(codec, LOG_DEBUG, "Re-adding stripped codec " STR_FORMAT "/" STR_FORMAT " (%i)",
+						STR_FMT(&orig_pt->encoding_with_params),
+						STR_FMT0(&orig_pt->format_parameters),
+						orig_pt->payload_type);
 			codec_touched(cs, orig_pt);
 			codec_store_add_order(cs, orig_pt);
 		}
diff --git a/lib/rtplib.h b/lib/rtplib.h
index aa00e12e1..cc2e59450 100644
--- a/lib/rtplib.h
+++ b/lib/rtplib.h
@@ -118,6 +118,7 @@ struct rtp_payload_type {
 
 	unsigned int for_transcoding:1;
 	unsigned int accepted:1;
+	unsigned int removed:1;
 };