From ab3b1744b9a6c7cc33e16538e175af2b00d3c2e3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kacper=20Michaj=C5=82ow?= <kasper93@gmail.com>
Date: Tue, 16 Apr 2024 05:27:46 +0200
Subject: [PATCH] demux_mkv: add BCP 47 language tags support

Section 12 of Matroska Media Container Format Specifications says:

If a BCP 47 Language Element and an ISO 639-2 Language Element are used
within the same Parent Element, then the ISO 639-2 Language Element MUST
be ignored and precedence given to the BCP 47 Language Element.

Fixes: #8144
---
 TOOLS/matroska.py | 3 +++
 demux/demux_mkv.c | 5 ++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/TOOLS/matroska.py b/TOOLS/matroska.py
index 52bac48c92..61a33ffb84 100755
--- a/TOOLS/matroska.py
+++ b/TOOLS/matroska.py
@@ -92,6 +92,7 @@ elements_matroska = (
                 'MaxBlockAdditionID, 55ee, uint',
                 'Name, 536e, str',
                 'Language, 22b59c, str',
+                'LanguageBCP47, 22b59d, str',
                 'CodecID, 86, str',
                 'CodecPrivate, 63a2, binary',
                 'CodecName, 258688, str',
@@ -206,6 +207,7 @@ elements_matroska = (
                     'ChapterDisplay*, 80, sub', (
                         'ChapString, 85, str',
                         'ChapLanguage*, 437c, str',
+                        'ChapLanguageBCP47*, 437d, str',
                         'ChapCountry*, 437e, str',
                     ),
                 ),
@@ -224,6 +226,7 @@ elements_matroska = (
                 'SimpleTag*, 67c8, sub', (
                     'TagName, 45a3, str',
                     'TagLanguage, 447a, str',
+                    'TagLanguageBCP47, 447b, str',
                     'TagString, 4487, str',
                     'TagDefault, 4484, uint',
                 ),
diff --git a/demux/demux_mkv.c b/demux/demux_mkv.c
index be606975bb..004efebfc0 100644
--- a/demux/demux_mkv.c
+++ b/demux/demux_mkv.c
@@ -820,7 +820,10 @@ static void parse_trackentry(struct demuxer *demuxer,
         MP_DBG(demuxer, "|  + CodecPrivate, length %u\n", track->private_size);
     }
 
-    if (entry->language) {
+    if (entry->language_bcp47) {
+        track->language = talloc_strdup(track, entry->language_bcp47);
+        MP_DBG(demuxer, "|  + LanguageBCP47: %s\n", track->language);
+    } else if (entry->language) {
         track->language = talloc_strdup(track, entry->language);
         MP_DBG(demuxer, "|  + Language: %s\n", track->language);
     } else {