Parse and apply audio encoder delay information in MP4 files

Fix for bug 715.

ChangeLog

@@ -1,3 +1,9 @@
+2012-02-06  Moritz Bunkus  <moritz@bunkus.org>
+
+	* mkvmerge: new feature: mkvmerge will parse and apply the audio
+	encoder delay in MP4 files that contain said information in the
+	format that iTunes writes it. Fix for bug 715.
+
 2012-02-02  Moritz Bunkus  <moritz@bunkus.org>
 
 	* mkvmerge: new feature: Implemented support for treating several

src/input/r_qtmp4.cpp

@@ -32,6 +32,7 @@
 #include "common/iso639.h"
 #include "common/matroska.h"
 #include "common/strings/formatting.h"
+#include "common/strings/parsing.h"
 #include "input/r_qtmp4.h"
 #include "merge/output_control.h"
 #include "output/p_aac.h"
@@ -110,6 +111,7 @@ qtmp4_reader_c::qtmp4_reader_c(const track_info_c &ti,
   , m_time_scale(1)
   , m_compression_algorithm(0)
   , m_main_dmx(-1)
+  , m_audio_encoder_delay_samples(0)
   , m_debug_chapters(    debugging_requested("qtmp4") || debugging_requested("qtmp4_full") || debugging_requested("qtmp4_chapters"))
   , m_debug_headers(     debugging_requested("qtmp4") || debugging_requested("qtmp4_full") || debugging_requested("qtmp4_headers"))
   , m_debug_tables(                                      debugging_requested("qtmp4_full") || debugging_requested("qtmp4_tables"))
@@ -344,6 +346,15 @@ qtmp4_reader_c::calculate_timecodes() {
     dmx->build_index();
 }
 
+void
+qtmp4_reader_c::handle_audio_encoder_delay(qtmp4_demuxer_cptr &dmx) {
+  if ((0 == m_audio_encoder_delay_samples) || (0 == dmx->a_samplerate) || (-1 == dmx->ptzr))
+    return;
+
+  PTZR(dmx->ptzr)->m_ti.m_tcsync.displacement -= (m_audio_encoder_delay_samples * 1000000000ll) / dmx->a_samplerate;
+  m_audio_encoder_delay_samples                = 0;
+}
+
 void
 qtmp4_reader_c::parse_video_header_priv_atoms(qtmp4_demuxer_cptr &dmx,
                                               unsigned char *mem,
@@ -735,6 +746,9 @@ qtmp4_reader_c::handle_udta_atom(qt_atom_t parent,
     if (FOURCC('c', 'h', 'p', 'l') == atom.fourcc)
       handle_chpl_atom(atom.to_parent(), level + 1);
 
+    else if (FOURCC('m', 'e', 't', 'a') == atom.fourcc)
+      handle_meta_atom(atom.to_parent(), level + 1);
+
     skip_atom();
     parent.size -= atom.size;
   }
@@ -772,6 +786,94 @@ qtmp4_reader_c::handle_chpl_atom(qt_atom_t,
   process_chapter_entries(level, entries);
 }
 
+void
+qtmp4_reader_c::handle_meta_atom(qt_atom_t parent,
+                                 int level) {
+  m_in->skip(1 + 3);        // version & flags
+
+  while (8 <= parent.size) {
+    qt_atom_t atom = read_atom();
+    print_basic_atom_info();
+
+    if (FOURCC('i', 'l', 's', 't') == atom.fourcc)
+      handle_ilst_atom(atom.to_parent(), level + 1);
+
+    skip_atom();
+    parent.size -= atom.size;
+  }
+}
+
+void
+qtmp4_reader_c::handle_ilst_atom(qt_atom_t parent,
+                                 int level) {
+  while (8 <= parent.size) {
+    qt_atom_t atom = read_atom();
+    print_basic_atom_info();
+
+    if (FOURCC('-', '-', '-', '-') == atom.fourcc)
+      handle_4dashes_atom(atom.to_parent(), level + 1);
+
+    skip_atom();
+    parent.size -= atom.size;
+  }
+}
+
+std::string
+qtmp4_reader_c::read_string_atom(qt_atom_t atom,
+                                 size_t num_skipped) {
+  if ((num_skipped + atom.hsize) > atom.size)
+    return "";
+
+  std::string string;
+  size_t length = atom.size - atom.hsize - num_skipped;
+
+  m_in->skip(num_skipped);
+  m_in->read(string, length);
+
+  return string;
+}
+
+void
+qtmp4_reader_c::handle_4dashes_atom(qt_atom_t parent,
+                                    int level) {
+  std::string name, mean, data;
+
+  while (8 <= parent.size) {
+    qt_atom_t atom = read_atom();
+    print_basic_atom_info();
+
+    if (FOURCC('n', 'a', 'm', 'e') == atom.fourcc)
+      name = read_string_atom(atom, 4);
+
+    else if (FOURCC('m', 'e', 'a', 'n') == atom.fourcc)
+      mean = read_string_atom(atom, 4);
+
+    else if (FOURCC('d', 'a', 't', 'a') == atom.fourcc)
+      data = read_string_atom(atom, 8);
+
+    skip_atom();
+    parent.size -= atom.size;
+  }
+
+  mxdebug_if(m_debug_headers, boost::format("'----' content: name=%1% mean=%2% data=%3%\n") % name % mean % data);
+
+  if (name == "iTunSMPB")
+    parse_itunsmpb(data);
+}
+
+void
+qtmp4_reader_c::parse_itunsmpb(std::string data) {
+  data = boost::regex_replace(data, boost::regex("[^\\da-fA-F]+", boost::regex::perl), "");
+
+  if (16 > data.length())
+    return;
+
+  try {
+    m_audio_encoder_delay_samples = from_hex(data.substr(8, 8));
+  } catch (std::bad_cast &) {
+  }
+}
+
 void
 qtmp4_reader_c::read_chapter_track() {
   if (m_ti.m_no_chapters || (NULL != m_chapters) || !m_chapter_dmx.is_set())
@@ -1593,6 +1695,8 @@ qtmp4_reader_c::create_packetizer(int64_t tid) {
 
     else
       create_audio_packetizer_passthrough(dmx);
+
+    handle_audio_encoder_delay(dmx);
   }
 
   if (packetizer_ok && (-1 == m_main_dmx))

src/input/r_qtmp4.h

@@ -280,6 +280,8 @@ private:
   uint32_t m_time_scale, m_compression_algorithm;
   int m_main_dmx;
 
+  unsigned int m_audio_encoder_delay_samples;
+
   bool m_debug_chapters, m_debug_headers, m_debug_tables, m_debug_interleaving;
 
 public:
@@ -308,6 +310,7 @@ protected:
   virtual void parse_audio_header_priv_atoms(qtmp4_demuxer_cptr &dmx, unsigned char *mem, size_t size, int level);
   virtual bool parse_esds_atom(mm_mem_io_c &memio, qtmp4_demuxer_cptr &dmx, int level);
   virtual uint32_t read_esds_descr_len(mm_mem_io_c &memio);
+  virtual void parse_itunsmpb(std::string data);
 
   virtual void handle_cmov_atom(qt_atom_t parent, int level);
   virtual void handle_cmvd_atom(qt_atom_t parent, int level);
@@ -321,6 +324,9 @@ protected:
   virtual void handle_mvhd_atom(qt_atom_t parent, int level);
   virtual void handle_udta_atom(qt_atom_t parent, int level);
   virtual void handle_chpl_atom(qt_atom_t parent, int level);
+  virtual void handle_meta_atom(qt_atom_t parent, int level);
+  virtual void handle_ilst_atom(qt_atom_t parent, int level);
+  virtual void handle_4dashes_atom(qt_atom_t parent, int level);
   virtual void handle_stbl_atom(qtmp4_demuxer_cptr &new_dmx, qt_atom_t parent, int level);
   virtual void handle_stco_atom(qtmp4_demuxer_cptr &new_dmx, qt_atom_t parent, int level);
   virtual void handle_co64_atom(qtmp4_demuxer_cptr &new_dmx, qt_atom_t parent, int level);
@@ -349,12 +355,16 @@ protected:
   virtual void create_video_packetizer_standard(qtmp4_demuxer_cptr &dmx);
   virtual void create_video_packetizer_svq1(qtmp4_demuxer_cptr &dmx);
 
+  virtual void handle_audio_encoder_delay(qtmp4_demuxer_cptr &dmx);
+
   virtual std::string decode_and_verify_language(uint16_t coded_language);
   virtual void read_chapter_track();
   virtual void recode_chapter_entries(std::vector<qtmp4_chapter_entry_t> &entries);
   virtual void process_chapter_entries(int level, std::vector<qtmp4_chapter_entry_t> &entries);
 
   virtual void detect_interleaving();
+
+  virtual std::string read_string_atom(qt_atom_t atom, size_t num_skipped);
 };
 
 #endif  // __R_QTMP4_H

tests/results.txt

@@ -179,3 +179,4 @@ T_330dts_detection:38c941b579418e6c874950f4c55f84ce:passed:20120107-210130:1.227
 T_331read_buffer_underflow:3bdec07b9e45cafe2c35561e7f8ad2db:passed:20120125-232902:0.407400904
 T_332eac3_misdetected_as_avc:b4e0ac5954dbf57e4ad941f01c7de462:passed:20120131-145550:0.452730804
 T_333wavpack_with_correction:c561a04a67042b048f7059a80d1c366d-e33897409384ca5fd8ed5e497f8c3883+37f802510b43b2ab4bd7d8356a7ac606-ok:passed:20120131-164845:0.299865433
+T_334mp4_audio_encoder_delay:2afe7b533c9f1ed35168e60aaca20dff:passed:20120206-100443:0.195628019

tests/test-334mp4_audio_encoder_delay.rb

@@ -0,0 +1,6 @@
+#!/usr/bin/ruby -w
+
+# T_334mp4_audio_encoder_delay
+describe "mkvmerge / MP4 files & audio encoder delay information"
+
+test_merge "data/mp4/aac_encoder_delay_sample.m4a"