From 16fedc94d2bc68668cafefc1c4afd0f5b2682bee Mon Sep 17 00:00:00 2001
From: Moritz Bunkus <moritz@bunkus.org>
Date: Fri, 13 Mar 2020 15:19:59 +0100
Subject: [PATCH] MP4 reader: use track duration for frame duration for
 single-frame video tracks

Fixes #2747.
---
 NEWS.md                                        |  8 ++++++++
 src/input/r_qtmp4.cpp                          | 18 +++++++++++++++---
 tests/results.txt                              |  1 +
 .../test-690mp4_single_video_frame_duration.rb |  5 +++++
 4 files changed, 29 insertions(+), 3 deletions(-)
 create mode 100755 tests/test-690mp4_single_video_frame_duration.rb

diff --git a/NEWS.md b/NEWS.md
index 4a84c7a8e..74d9ead45 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,3 +1,11 @@
+# Version ?
+
+## Bug fixes
+
+* mkvmerge: MP4 reader: fixed calculating the duration of video tracks that
+  only contain a single frame. Fixes #2747.
+
+
 # Version 44.0.0 "Domino" 2020-03-08
 
 ## New features and enhancements
diff --git a/src/input/r_qtmp4.cpp b/src/input/r_qtmp4.cpp
index c37a448db..4c3703f9f 100644
--- a/src/input/r_qtmp4.cpp
+++ b/src/input/r_qtmp4.cpp
@@ -2104,8 +2104,20 @@ qtmp4_demuxer_c::calculate_frame_rate() {
     return;
   }
 
+  if (('v' == type) && time_scale && global_duration && (sample_table.size() < 2)) {
+    frame_rate = mtx::frame_timing::determine_frame_rate(static_cast<uint64_t>(global_duration) * 1'000'000'000ull / static_cast<uint64_t>(time_scale));
+    if (frame_rate)
+      m_use_frame_rate_for_duration = boost::rational_cast<int64_t>(int64_rational_c{1'000'000'000ll} / frame_rate);
+
+    mxdebug_if(m_debug_frame_rate,
+               fmt::format("calculate_frame_rate: case 2: video track with time scale {0} & duration {1} result: {2}\n",
+                           time_scale, global_duration, frame_rate ? format_timestamp(*m_use_frame_rate_for_duration) : "<invalid>"s));
+
+    return;
+  }
+
   if (sample_table.size() < 2) {
-    mxdebug_if(m_debug_frame_rate, fmt::format("calculate_frame_rate: case 2: sample table too small\n"));
+    mxdebug_if(m_debug_frame_rate, fmt::format("calculate_frame_rate: case 3: sample table too small\n"));
     return;
   }
 
@@ -2126,7 +2138,7 @@ qtmp4_demuxer_c::calculate_frame_rate() {
       m_use_frame_rate_for_duration = boost::rational_cast<int64_t>(int64_rational_c{1'000'000'000ll} / frame_rate);
 
     mxdebug_if(m_debug_frame_rate,
-               fmt::format("calculate_frame_rate: case 3: duration {0} num_frames {1} frame_duration {2} frame_rate {3}/{4} use_frame_rate_for_duration {5}\n",
+               fmt::format("calculate_frame_rate: case 4: duration {0} num_frames {1} frame_duration {2} frame_rate {3}/{4} use_frame_rate_for_duration {5}\n",
                            duration, num_frames, duration / num_frames, frame_rate.numerator(), frame_rate.denominator(), m_use_frame_rate_for_duration ? *m_use_frame_rate_for_duration : -1));
 
     return;
@@ -2146,7 +2158,7 @@ qtmp4_demuxer_c::calculate_frame_rate() {
     frame_rate.assign(static_cast<int64_t>(1000000000ll), to_nsecs(most_common.first));
 
   mxdebug_if(m_debug_frame_rate,
-             fmt::format("calculate_frame_rate: case 4: duration {0} num_frames {1} frame_duration {2} most_common.num_occurances {3} most_common.duration {4} frame_rate {5}/{6}\n",
+             fmt::format("calculate_frame_rate: case 5: duration {0} num_frames {1} frame_duration {2} most_common.num_occurances {3} most_common.duration {4} frame_rate {5}/{6}\n",
                          duration, num_frames, duration / num_frames, most_common.second, to_nsecs(most_common.first), frame_rate.numerator(), frame_rate.denominator()));
 }
 
diff --git a/tests/results.txt b/tests/results.txt
index 11f2dd61a..e0695564c 100644
--- a/tests/results.txt
+++ b/tests/results.txt
@@ -535,3 +535,4 @@ T_686container_wrong_num_channels:true:passed:20200101-235713:0.009057097
 T_687h264_additional_sps_pps_in_middle:3c9e0781b9b5e75be5dc3da6d59b8795:passed:20200105-163253:0.029150634
 T_688opus_single_page:6ce93001a667609670ec7103450f622f:passed:20200113-193521:0.011219948
 T_689mpeg_ts_mpeg_2_two_frames_only:b187d13ae7af1f6a61e7369c549cf2c4:passed:20200126-124111:0.034034657
+T_690mp4_single_video_frame_duration:ff234c76e7626f78aded30b3c2ad6669:passed:20200313-151900:0.040140889
diff --git a/tests/test-690mp4_single_video_frame_duration.rb b/tests/test-690mp4_single_video_frame_duration.rb
new file mode 100755
index 000000000..5310dce5d
--- /dev/null
+++ b/tests/test-690mp4_single_video_frame_duration.rb
@@ -0,0 +1,5 @@
+#!/usr/bin/ruby -w
+
+# T_690mp4_single_video_frame_duration
+describe "mkvmerge / MP4/MOV with a single video frame, calculating the frame duration"
+test_merge "data/mp4/single_video_frame.mov", :args => "-A"