diff --git a/app/common/CMakeLists.txt b/app/common/CMakeLists.txt
index 6c5ca6ef6..cbe006e96 100644
--- a/app/common/CMakeLists.txt
+++ b/app/common/CMakeLists.txt
@@ -16,6 +16,7 @@
 
 set(OLIVE_SOURCES
   ${OLIVE_SOURCES}
+  common/channellayout.h
   common/clamp.h
   common/lerp.h
   common/rational.h
diff --git a/app/common/channellayout.h b/app/common/channellayout.h
new file mode 100644
index 000000000..7d62061eb
--- /dev/null
+++ b/app/common/channellayout.h
@@ -0,0 +1,8 @@
+#ifndef CHANNELLAYOUT_H
+#define CHANNELLAYOUT_H
+
+extern "C" {
+#include <libavcodec/avcodec.h>
+}
+
+#endif // CHANNELLAYOUT_H
diff --git a/app/common/decibel.cpp b/app/common/decibel.cpp
index 7393ba79c..c93efbc95 100644
--- a/app/common/decibel.cpp
+++ b/app/common/decibel.cpp
@@ -1,6 +1,11 @@
 #include "decibel.h"
 
-decibel::decibel()
-{
+#include <QtMath>
 
+double amplitude_to_db(double amplitude) {
+  return (20.0*(qLn(amplitude)/qLn(10.0)));
+}
+
+double db_to_amplitude(double db) {
+  return qPow(M_E, (db*qLn(10.0))/20.0);
 }
diff --git a/app/dialog/sequence/sequence.cpp b/app/dialog/sequence/sequence.cpp
index 9dee5c098..dc191e0e9 100644
--- a/app/dialog/sequence/sequence.cpp
+++ b/app/dialog/sequence/sequence.cpp
@@ -20,10 +20,6 @@
 
 #include "sequence.h"
 
-extern "C" {
-#include <libavformat/avformat.h>
-}
-
 #include <QDialogButtonBox>
 #include <QGroupBox>
 #include <QLabel>
@@ -31,6 +27,7 @@ extern "C" {
 #include <QMessageBox>
 #include <QVBoxLayout>
 
+#include "common/channellayout.h"
 #include "common/rational.h"
 #include "undo/undostack.h"
 
diff --git a/app/project/item/footage/audiostream.h b/app/project/item/footage/audiostream.h
index 92e826301..6a89b953a 100644
--- a/app/project/item/footage/audiostream.h
+++ b/app/project/item/footage/audiostream.h
@@ -21,10 +21,6 @@
 #ifndef AUDIOSTREAM_H
 #define AUDIOSTREAM_H
 
-extern "C" {
-#include <libavcodec/avcodec.h>
-}
-
 #include "common/rational.h"
 #include "stream.h"
 
diff --git a/app/project/item/sequence/sequence.cpp b/app/project/item/sequence/sequence.cpp
index a903f1c33..7b604da11 100644
--- a/app/project/item/sequence/sequence.cpp
+++ b/app/project/item/sequence/sequence.cpp
@@ -20,10 +20,7 @@
 
 #include "sequence.h"
 
-extern "C" {
-#include <libavcodec/avcodec.h>
-}
-
+#include "common/channellayout.h"
 #include "ui/icons/icons.h"
 
 Sequence::Sequence()