From eb8acb6942c4d15c06fd8db041401f6114fbf757 Mon Sep 17 00:00:00 2001
From: Moritz Bunkus <moritz@bunkus.org>
Date: Mon, 4 Jan 2016 20:58:10 +0100
Subject: [PATCH] TruehD parser: be more strict during resync

AC-3 frame recognition is much too unreliable as the AC-3 sync word is
only 12 bits long. Therefore the resync mechanism should only look for
the 32 bits long TrueHD/MLP sync words.
---
 ChangeLog                                            | 6 ++++++
 src/common/truehd.cpp                                | 4 ++--
 tests/results.txt                                    | 1 +
 tests/test-525truehd_doesnt_start_with_sync_frame.rb | 5 +++++
 4 files changed, 14 insertions(+), 2 deletions(-)
 create mode 100755 tests/test-525truehd_doesnt_start_with_sync_frame.rb

diff --git a/ChangeLog b/ChangeLog
index ea4f1a33f..1e4eca356 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2016-01-04  Moritz Bunkus  <moritz@bunkus.org>
+
+        * mkvmerge: bug fix: fixed TrueHD detection both as raw streams as
+        well as inside other contains if the stream does not start with a
+        TrueHD sync frame.
+
 2016-01-03  Moritz Bunkus  <moritz@bunkus.org>
 
         * MKVToolNix GUI: new merge tool feature: added a layout for the
diff --git a/src/common/truehd.cpp b/src/common/truehd.cpp
index de26199c2..52a378fe8 100644
--- a/src/common/truehd.cpp
+++ b/src/common/truehd.cpp
@@ -58,7 +58,7 @@ truehd_frame_t::parse_ac3_header(unsigned char const *data,
   m_type  = truehd_frame_t::sync;
   m_size  = m_ac3_header.m_bytes;
 
-  return size >= m_ac3_header.m_bytes;
+  return size >= m_ac3_header.m_bytes ? verify_ac3_checksum(data, size) : false;
 }
 
 bool
@@ -235,7 +235,7 @@ truehd_parser_c::resync(unsigned int offset) {
 
   for (offset = offset + 4; (offset + 4) < size; ++offset) {
     uint32_t sync_word = get_uint32_be(&data[offset]);
-    if ((TRUEHD_SYNC_WORD == sync_word) || (MLP_SYNC_WORD == sync_word) || (AC3_SYNC_WORD == get_uint16_be(&data[offset - 4]))) {
+    if (mtx::included_in(sync_word, TRUEHD_SYNC_WORD, MLP_SYNC_WORD)) {
       m_sync_state  = state_synced;
       return offset - 4;
     }
diff --git a/tests/results.txt b/tests/results.txt
index bbad16ca8..23b835429 100644
--- a/tests/results.txt
+++ b/tests/results.txt
@@ -370,3 +370,4 @@ T_521mp4_edit_list_constant_offset_with_segment_duration_not_0:07984c40325903cbc
 T_522mpeg_1_2_es_no_start_code_at_beginning:067554d94399178b6bb56b49746b04b6:passed:20151230-182435:0.299243222
 T_523mpeg_ts_pes_size_0:5351b2c74ad4327eeecee1ccf658ef5f-217f7e6e3e04a6afe253487af08c0598:passed:20151230-221825:1.635929691
 T_524mpeg2_misdetected_as_truehd:b023d230d68c2545c6cb6859786c692b:passed:20160102-222743:1.10526128
+T_525truehd_doesnt_start_with_sync_frame:a7f55b158ec9a3438eaee8b28b13a7cf:passed:20160104-205804:0.313378755
diff --git a/tests/test-525truehd_doesnt_start_with_sync_frame.rb b/tests/test-525truehd_doesnt_start_with_sync_frame.rb
new file mode 100755
index 000000000..1675e5fa2
--- /dev/null
+++ b/tests/test-525truehd_doesnt_start_with_sync_frame.rb
@@ -0,0 +1,5 @@
+#!/usr/bin/ruby -w
+
+# T_525truehd_doesnt_start_with_sync_frame
+describe "mkvmerge / TrueHD recognition if the stream doesn't start with a TrueHD sync frame"
+test_identify "data/truehd/truehd-not-starting-with-sync-frame.thd"