diff --git a/CMakeLists.txt b/CMakeLists.txt
index a3d9945..0f43042 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -9,8 +9,8 @@ set(META_APP_AUTHOR "Martchus")
 set(META_APP_URL "https://github.com/${META_APP_AUTHOR}/${META_PROJECT_NAME}")
 set(META_APP_DESCRIPTION "C++ library for reading and writing MP4 (iTunes), ID3, Vorbis, Opus, FLAC and Matroska tags")
 set(META_VERSION_MAJOR 9)
-set(META_VERSION_MINOR 0)
-set(META_VERSION_PATCH 1)
+set(META_VERSION_MINOR 1)
+set(META_VERSION_PATCH 0)
 set(META_REQUIRED_CPP_UNIT_VERSION 1.14.0)
 set(META_ADD_DEFAULT_CPP_UNIT_TEST_APPLICATION ON)
 
diff --git a/mp4/mp4ids.cpp b/mp4/mp4ids.cpp
index 94bf685..d359b6e 100644
--- a/mp4/mp4ids.cpp
+++ b/mp4/mp4ids.cpp
@@ -183,6 +183,10 @@ MediaFormat fourccToMediaFormat(std::uint32_t fourccId)
     case WindowsMediaVideoV2:
     case WindowsMediaVideoV8:
         return MediaFormat(GeneralMediaFormat::WindowsMediaVideo, 2);
+    case Flac:
+        return GeneralMediaFormat::Flac;
+    case Opus:
+        return GeneralMediaFormat::Opus;
     // TODO: map more FOURCCs
     default:
         return GeneralMediaFormat::Unknown;
diff --git a/mp4/mp4ids.h b/mp4/mp4ids.h
index 174f2a6..fec4fac 100644
--- a/mp4/mp4ids.h
+++ b/mp4/mp4ids.h
@@ -269,6 +269,7 @@ enum KnownValue : std::uint32_t {
     Explode = 0x78706C6F,
     FilmNoise = 0x666D6E73,
     Fire = 0x66697265,
+    Flac = 0x664C6143,
     FlashPixImage = 0x66706978,
     FlashScreenVideoDecoder = 0x46535631,
     FloatingPoint32Bit = 0x666C3332,
@@ -342,6 +343,7 @@ enum KnownValue : std::uint32_t {
     MsMpeg4V3Decoder2 = 0x6D703433,
     NtscDv25Video = 0x64766320, /**< NTSC DV-25 video */
     Oggs = 0x4F676753,
+    Opus = 0x4F707573,
     PalDv25Video = 0x64766370, /**< PAL DV-25 video */
     PdfImage = 0x70646620,
     Png = 0x706E6720, /**< Portable Network Graphics */
diff --git a/mp4/mp4track.cpp b/mp4/mp4track.cpp
index 74238dd..fd383db 100644
--- a/mp4/mp4track.cpp
+++ b/mp4/mp4track.cpp
@@ -1642,9 +1642,11 @@ void Mp4Track::internalParseHeader(Diagnostics &diag)
             for (Mp4Atom *codecConfigContainerAtom = m_stsdAtom->firstChild(); codecConfigContainerAtom;
                  codecConfigContainerAtom = codecConfigContainerAtom->nextSibling()) {
                 codecConfigContainerAtom->parse(diag);
+
                 // parse FOURCC
                 m_formatId = interpretIntegerAsString<std::uint32_t>(codecConfigContainerAtom->id());
                 m_format = FourccIds::fourccToMediaFormat(codecConfigContainerAtom->id());
+
                 // parse codecConfigContainerAtom
                 m_istream->seekg(static_cast<streamoff>(codecConfigContainerAtom->dataOffset()));
                 switch (codecConfigContainerAtom->id()) {
@@ -1660,6 +1662,8 @@ void Mp4Track::internalParseHeader(Diagnostics &diag)
                 case FourccIds::Dts:
                 case FourccIds::DtsH:
                 case FourccIds::DtsE:
+                case FourccIds::Flac:
+                case FourccIds::Opus:
                     m_istream->seekg(6 + 2, ios_base::cur); // skip reserved bytes, data reference index
                     tmp = reader.readUInt16BE(); // read sound version
                     m_istream->seekg(6, ios_base::cur);
diff --git a/scripts/download_testfiles.sh b/scripts/download_testfiles.sh
index 645b059..408cf59 100755
--- a/scripts/download_testfiles.sh
+++ b/scripts/download_testfiles.sh
@@ -117,6 +117,9 @@ convert flac/test.flac ffmpeg -i mtx-test-data/alac/othertest-itunes.m4a -c:a fl
 convert flac/test.ogg ffmpeg -i flac/test.flac -vn -c:a copy flac/test.ogg
 convert mkv/av1_test.mkv ffmpeg -i matroska_wave1/test1.mkv -t 1 -c:v libaom-av1 -crf 30 -cpu-used 5 -an -strict experimental mkv/av1_test.mkv
 convert mp4/av1_test.mp4 ffmpeg -i mkv/av1_test.mkv -c copy mp4/av1_test.mp4
+convert mp4/test1-flac.m4a ffmpeg -i mp4/test1.m4a -c:a flac -f mp4  -strict -2 mp4/test1-flac.m4a
+convert mp4/test1-opus.m4a ffmpeg -i mp4/test1.m4a -c:a libopus -f mp4  -strict -2 mp4/test1-opus.m4a
+convert mp4/test1-vorbis.m4a ffmpeg -i mp4/test1.m4a -c:a libvorbis -f mp4  -strict -2 mp4/test1-vorbis.m4a
 convert misc/av1.ivf ffmpeg -i mkv/av1_test.mkv -c copy misc/av1.ivf
 convert mkv/nested-tags.mkv \
         mkvmerge --ui-language en_US \