diff --git a/src/decoders/rttrp.ts b/src/decoders/rttrp.ts
index 0a6f2b8..192acf7 100644
--- a/src/decoders/rttrp.ts
+++ b/src/decoders/rttrp.ts
@@ -12,37 +12,35 @@ export default (bytes: Uint8Array): RTTrPHeader => {
   let isLittleEndian = false;
   const intHeader = view.getUint16(dataOffset, isLittleEndian);
   dataOffset += 2;
-  const fltHeader = view.getUint16(dataOffset, isLittleEndian);
+  const floatHeader = view.getUint16(dataOffset, isLittleEndian);
   dataOffset += 2;
-  if (intHeader === 0x4154) {
-    isLittleEndian = false;
-  }
   const version = view.getUint16(dataOffset, isLittleEndian);
   dataOffset += 2;
   if (version !== 0x0002) {
     throw new Error('Only version 2 of the RTTrP header is currently supported');
   }
-  const pID = view.getUint32(dataOffset, isLittleEndian);
+  if (intHeader === 0x5441) {
+    isLittleEndian = true;
+  }
+  const packetID = view.getUint32(dataOffset, isLittleEndian);
   dataOffset += 4;
 
-  const pForm = view.getUint8(dataOffset);
+  const packetFormat = view.getUint8(dataOffset);
   dataOffset += 1;
-  const pktSize = view.getUint16(dataOffset, isLittleEndian);
+  const size = view.getUint16(dataOffset, isLittleEndian);
   dataOffset += 2;
   const context = view.getUint32(dataOffset, isLittleEndian);
   dataOffset += 4;
-  const numMods = view.getUint8(dataOffset);
+  const subModuleCount = view.getUint8(dataOffset);
   dataOffset += 1;
-  const data = bytes.slice(dataOffset);
   return {
     intHeader,
-    fltHeader,
+    floatHeader,
     version,
-    pID,
-    pForm,
-    pktSize,
+    packetID,
+    packetFormat,
+    size,
     context,
-    numMods,
-    data,
+    subModuleCount,
   };
 };
diff --git a/src/encoders/rttrp-header.ts b/src/encoders/rttrp-header.ts
new file mode 100644
index 0000000..77c1435
--- /dev/null
+++ b/src/encoders/rttrp-header.ts
@@ -0,0 +1,45 @@
+const HEADER_SIZE = 18;
+
+export default (
+  floatSignature: number,
+  version: number,
+  packetID: number,
+  packetFormat: number,
+  context: number,
+  subModules: Uint8Array[],
+  isLittleEndian: boolean = false
+): Uint8Array => {
+  if (version !== 2) {
+    throw new Error('Only version 2 of the RTTrP header is currently supported');
+  }
+  const bytes = new Uint8Array(HEADER_SIZE);
+
+  let totalPacketSize = bytes.byteLength;
+  subModules.forEach((subModule) => {
+    totalPacketSize += subModule.length;
+  });
+
+  const view = new DataView(bytes.buffer, bytes.byteOffset, bytes.byteLength);
+  let dataOffset = 0;
+
+  view.setUint16(dataOffset, 0x4154, isLittleEndian);
+  dataOffset += 2;
+  view.setUint16(dataOffset, floatSignature, isLittleEndian);
+  dataOffset += 2;
+  view.setUint16(dataOffset, version);
+  dataOffset += 2;
+
+  view.setUint32(dataOffset, packetID, isLittleEndian);
+  dataOffset += 4;
+
+  view.setUint8(dataOffset, packetFormat);
+  dataOffset += 1;
+  view.setUint16(dataOffset, totalPacketSize, isLittleEndian);
+  dataOffset += 2;
+  view.setUint32(dataOffset, context, isLittleEndian);
+  dataOffset += 4;
+  view.setUint8(dataOffset, subModules.length);
+  dataOffset += 1;
+
+  return bytes;
+};
diff --git a/src/encoders/rttrp.ts b/src/encoders/rttrp.ts
deleted file mode 100644
index 514ae07..0000000
--- a/src/encoders/rttrp.ts
+++ /dev/null
@@ -1,37 +0,0 @@
-import { RTTrPHeader } from '../models';
-
-export default (header: RTTrPHeader): Uint8Array => {
-  if (header.version !== 2) {
-    throw new Error('Only version 2 of the RTTrP header is currently supported');
-  }
-  const bytes = new Uint8Array(18 + header.data.length);
-  bytes.set(header.data, 18);
-
-  const view = new DataView(bytes.buffer, bytes.byteOffset, bytes.byteLength);
-  let dataOffset = 0;
-
-  let isLittleEndian = false;
-  view.setUint16(dataOffset, header.intHeader, isLittleEndian);
-  dataOffset += 2;
-  view.setUint16(dataOffset, header.fltHeader, isLittleEndian);
-  dataOffset += 2;
-  if (header.intHeader === 0x4154) {
-    isLittleEndian = false;
-  }
-  view.setUint16(dataOffset, header.version, isLittleEndian);
-  dataOffset += 2;
-
-  view.setUint32(dataOffset, header.pID, isLittleEndian);
-  dataOffset += 4;
-
-  view.setUint8(dataOffset, header.pForm);
-  dataOffset += 1;
-  view.setUint16(dataOffset, header.pktSize, isLittleEndian);
-  dataOffset += 2;
-  view.setUint32(dataOffset, header.context, isLittleEndian);
-  dataOffset += 4;
-  view.setUint8(dataOffset, header.numMods);
-  dataOffset += 1;
-
-  return bytes;
-};
diff --git a/src/models.ts b/src/models.ts
index 805c4e9..67745f7 100644
--- a/src/models.ts
+++ b/src/models.ts
@@ -1,11 +1,11 @@
 export type RTTrPHeader = {
-  intHeader: number;
-  fltHeader: number;
+  intHeader?: number;
+  floatHeader: number;
   version: number;
-  pID: number;
-  pForm: number;
-  pktSize: number;
+  packetID: number;
+  packetFormat: number;
+  size: number;
   context: number;
-  numMods: number;
-  data: Uint8Array;
+  subModuleCount: number;
+};
 };
diff --git a/tests/decode.test.js b/tests/decode.test.js
index 41314a1..fb57a0e 100644
--- a/tests/decode.test.js
+++ b/tests/decode.test.js
@@ -9,14 +9,13 @@ const goodTests = [
     ]),
     expected: {
       intHeader: 0x4154,
-      fltHeader: 0x4334,
+      floatHeader: 0x4334,
       version: 2,
-      pID: 305419896,
-      pForm: 0,
-      pktSize: 18,
+      packetID: 305419896,
+      packetFormat: 0,
+      size: 18,
       context: 305419896,
-      numMods: 0,
-      data: new Uint8Array(),
+      subModuleCount: 0,
     },
     decoder: Decoders.RTTrPHeader,
   },
diff --git a/tests/encode.test.js b/tests/encode.test.js
index c1a3922..519c523 100644
--- a/tests/encode.test.js
+++ b/tests/encode.test.js
@@ -8,25 +8,17 @@ const goodTests = [
     expected: new Uint8Array([
       0x41, 0x54, 0x43, 0x34, 0x00, 0x02, 0x12, 0x34, 0x56, 0x78, 0x00, 0x00, 0x12, 0x12, 0x34, 0x56, 0x78, 0x00,
     ]),
-    message: {
-      intHeader: 0x4154,
-      fltHeader: 0x4334,
-      version: 2,
-      pID: 305419896,
-      pForm: 0,
-      pktSize: 18,
-      context: 305419896,
-      numMods: 0,
-      data: new Uint8Array(),
+    bytes: () => {
+      return Encoders.RTTrPHeader(0x4334, 2, 0x12345678, 0, 0x12345678, [], false);
     },
-    encoder: Encoders.RTTrPHeader,
+  },
   },
 ];
 
 describe('RTTrP Message Encoding', () => {
   goodTests.forEach((messageTest) => {
     it(messageTest.description, () => {
-      const actual = messageTest.encoder(messageTest.message);
+      const actual = messageTest.bytes();
       deepEqual(actual, messageTest.expected);
     });
   });
@@ -38,7 +30,7 @@ const badTests = [];
 describe('RTTrP Message Encoding Throws', () => {
   badTests.forEach((messageTest) => {
     it(messageTest.description, () => {
-      messageTest.encoder(messageTest.packet);
+      messageTest.bytes();
       throws(() => {}, messageTest.throwsMessage);
     });
   });