diff --git a/ac/ax_boost_base.m4 b/ac/ax_boost_base.m4
index 4f74018d5..6f788b772 100644
--- a/ac/ax_boost_base.m4
+++ b/ac/ax_boost_base.m4
@@ -70,7 +70,7 @@ AC_DEFUN([AX_BOOST_BASE],
         AC_MSG_ERROR(The Boost library is required for building MKVToolNix)
     fi
 
-    boost_lib_version_req=ifelse([$1], ,1.29.0,$1)
+    boost_lib_version_req=ifelse([$1], ,1.32.0,$1)
     boost_lib_version_req_shorten=`expr $boost_lib_version_req : '\([[0-9]]*\.[[0-9]]*\)'`
     boost_lib_version_req_major=`expr $boost_lib_version_req : '\([[0-9]]*\)'`
     boost_lib_version_req_minor=`expr $boost_lib_version_req : '[[0-9]]*\.\([[0-9]]*\)'`
diff --git a/src/merge/pr_generic.cpp b/src/merge/pr_generic.cpp
index 3c576a2e2..9139bd0cd 100644
--- a/src/merge/pr_generic.cpp
+++ b/src/merge/pr_generic.cpp
@@ -110,13 +110,10 @@ generic_packetizer_c::generic_packetizer_c(generic_reader_c *p_reader,
     ti.cues = ti.cue_creations[-1];
 
   // Let's see if the user has given a default track flag for this track.
-  if (map_has_key(ti.default_track_flags, ti.id)) {
+  if (map_has_key(ti.default_track_flags, ti.id))
     ti.default_track = ti.default_track_flags[ti.id];
-    ti.default_track_flag_present = true;
-  } else if (map_has_key(ti.default_track_flags, -1)) {
+  else if (map_has_key(ti.default_track_flags, -1))
     ti.default_track = ti.default_track_flags[-1];
-    ti.default_track_flag_present = true;
-  }
 
   // Let's see if the user has specified a language for this track.
   if (map_has_key(ti.languages, ti.id))
@@ -219,12 +216,6 @@ generic_packetizer_c::generic_packetizer_c(generic_reader_c *p_reader,
   else if (map_has_key(ti.max_blockadd_ids, -1))
     htrack_max_add_block_ids = ti.max_blockadd_ids[-1];
 
-  // Let's see if the user has specified "AAC is SBR" for this track.
-  if (map_has_key(ti.all_aac_is_sbr, ti.id))
-    ti.aac_is_sbr = ti.all_aac_is_sbr[ti.id] ? 1 : 0;
-  else if (map_has_key(ti.all_aac_is_sbr, -1))
-    ti.aac_is_sbr = ti.all_aac_is_sbr[-1] ? 1 : 0;
-
   // Let's see if the user has specified a NALU size length for this track.
   if (map_has_key(ti.nalu_size_lengths, ti.id))
     ti.nalu_size_length = ti.nalu_size_lengths[ti.id];
@@ -560,7 +551,7 @@ generic_packetizer_c::set_headers() {
 
   idx = TRACK_TYPE_TO_DEFTRACK_TYPE(htrack_type);
 
-  if (!ti.default_track_flag_present)
+  if (boost::logic::indeterminate(ti.default_track))
     set_as_default_track(idx, DEFAULT_TRACK_PRIORITY_FROM_TYPE);
   else if (ti.default_track)
     set_as_default_track(idx, DEFAULT_TRACK_PRIORITY_CMDLINE);
@@ -1376,10 +1367,8 @@ track_info_c::track_info_c()
   , aspect_ratio_is_factor(false)
   , display_dimensions_given(false)
   , cues(CUE_STRATEGY_UNSPECIFIED)
-  , default_track(false)
-  , default_track_flag_present(false)
+  , default_track(boost::logic::indeterminate)
   , tags(NULL)
-  , aac_is_sbr(-1)
   , compression(COMPRESSION_UNSPECIFIED)
   , pixel_cropping_specified(false)
   , stereo_mode(STEREO_MODE_UNSPECIFIED)
@@ -1442,7 +1431,6 @@ track_info_c::operator =(const track_info_c &src) {
 
   default_track_flags        = src.default_track_flags;
   default_track              = src.default_track;
-  default_track_flag_present = src.default_track_flag_present;
 
   languages                  = src.languages;
   language                   = src.language;
@@ -1455,7 +1443,6 @@ track_info_c::operator =(const track_info_c &src) {
   tags                       = NULL != src.tags ? static_cast<KaxTags *>(src.tags->Clone()) : NULL;
 
   all_aac_is_sbr             = src.all_aac_is_sbr;
-  aac_is_sbr                 = src.aac_is_sbr;
 
   compression_list           = src.compression_list;
   compression                = src.compression;
diff --git a/src/merge/pr_generic.h b/src/merge/pr_generic.h
index 850593a1a..db82e1dc9 100644
--- a/src/merge/pr_generic.h
+++ b/src/merge/pr_generic.h
@@ -17,6 +17,7 @@
 
 #include "os.h"
 
+#include <boost/logic/tribool.hpp>
 #include <deque>
 #include <map>
 #include <vector>
@@ -202,8 +203,7 @@ public:
   cue_strategy_e cues;          // For this very track
 
   map<int64_t, bool> default_track_flags; // As given on the command line
-  bool default_track;           // For this very track
-  bool default_track_flag_present;
+  boost::logic::tribool default_track;    // For this very track
 
   map<int64_t, string> languages; // As given on the command line
   string language;              // For this very track
@@ -215,8 +215,7 @@ public:
   string tags_file_name;        // For this very track
   KaxTags *tags;                // For this very track
 
-  map<int64_t, bool> all_aac_is_sbr;  // For AAC+/HE-AAC/SBR
-  int aac_is_sbr;                     // For this track. -1 = unspecified
+  map<int64_t, bool> all_aac_is_sbr; // For AAC+/HE-AAC/SBR
 
   map<int64_t, compression_method_e> compression_list; // As given on the cmd line
   compression_method_e compression; // For this very track