From 18aeb5bac1862e9f3da45ca2587ad2fe2b9c5fe4 Mon Sep 17 00:00:00 2001
From: Thibault Saunier <tsaunier@igalia.com>
Date: Wed, 22 Jul 2020 14:31:13 -0400
Subject: [PATCH] matroskamux: Do caps renegotiation when it only adds fields

Matroskamux can accept caps renegotiation if the new caps is a
superset of the old one, meaning upstream added new info to
the caps.

Same logic as a5f22f03aa25b04726f78ae619f40b3b648f7d48 in qtmux.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/merge_requests/678>
---
 gst/matroska/matroska-mux.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/gst/matroska/matroska-mux.c b/gst/matroska/matroska-mux.c
index b99dd71c1e..3d3a233fbe 100644
--- a/gst/matroska/matroska-mux.c
+++ b/gst/matroska/matroska-mux.c
@@ -970,9 +970,10 @@ gst_matroska_mux_video_pad_setcaps (GstPad * pad, GstCaps * caps)
 
   if ((old_caps = gst_pad_get_current_caps (pad))) {
     if (mux->state >= GST_MATROSKA_MUX_STATE_HEADER
-        && !gst_caps_is_equal (caps, old_caps)) {
+        && !gst_caps_is_subset (caps, old_caps)) {
       GST_ELEMENT_ERROR (mux, STREAM, MUX, (NULL),
-          ("Caps changes are not supported by Matroska"));
+          ("Caps changes are not supported by Matroska\nCurrent: `%"
+              GST_PTR_FORMAT "`\nNew: `%" GST_PTR_FORMAT "`", old_caps, caps));
       gst_caps_unref (old_caps);
       goto refuse_caps;
     }