diff --git a/types/fluent-ffmpeg/fluent-ffmpeg-tests.ts b/types/fluent-ffmpeg/fluent-ffmpeg-tests.ts
index 65124d9fc8..c4e50497d7 100644
--- a/types/fluent-ffmpeg/fluent-ffmpeg-tests.ts
+++ b/types/fluent-ffmpeg/fluent-ffmpeg-tests.ts
@@ -23,6 +23,25 @@ ffmpeg('/path/to/file.avi')
     .preset('divx')
     .size('640x480');
 
+// get arguments
+ffmpeg('/path/to/file.avi')
+
+    ._getArguments();
+
+// ComplexFilter
+ffmpeg('/path/to/file.avi')
+
+    .output('outputfile.mp4')
+    .complexFilter([
+      { inputs: '0:v', filter: 'scale', options: { w: 1920, h: 1080, interl: 1 }, outputs: [] },
+      { inputs: '0:a', filter: 'amerge', options: { inputs: 2 }, outputs: 'am'},
+      '[am]aresample=48000:async=1[are]',
+      { inputs: 'are', filter: 'channelsplit' , options: { channel_layout: 'stereo'}, outputs: [] }
+    ], [])
+    .audioCodec('libfaac')
+    .videoCodec('libx264')
+    .size('320x200');
+
 // Use the run() method to run commands with multiple outputs
 ffmpeg('/path/to/file.avi')
     .output('outputfile.mp4')
diff --git a/types/fluent-ffmpeg/index.d.ts b/types/fluent-ffmpeg/index.d.ts
index aa4c8cb02d..94debda123 100644
--- a/types/fluent-ffmpeg/index.d.ts
+++ b/types/fluent-ffmpeg/index.d.ts
@@ -3,6 +3,7 @@
 // Definitions by: KIM Jaesuck a.k.a. gim tcaesvk <https://github.com/tcaesvk>
 //                 DingWeizhe <https://github.com/DingWeizhe>
 //                 Mounir Abid <https://github.com/mabidina>
+//                 Doyoung Ha <https://github.com/hados99>
 // Definitions: https://github.com/DefinitelyType/DefinitelyTyped
 
 /// <reference types="node" />
@@ -31,8 +32,8 @@ declare namespace Ffmpeg {
 
     interface FilterSpecification {
         filter: string;
-        inputs: string | string[];
-        outputs: string | string[];
+        inputs?: string | string[];
+        outputs?: string | string[];
         options?: any | string | any[];
     }
 
@@ -271,8 +272,8 @@ declare namespace Ffmpeg {
         outputOption(...options: string[]): FfmpegCommand;
         outputOptions(options: string[]): FfmpegCommand;
         outputOptions(...options: string[]): FfmpegCommand;
-        filterGraph(spec: string | FilterSpecification[], map: string[]): FfmpegCommand;
-        complexFilter(spec: string | FilterSpecification[], map: string[]): FfmpegCommand;
+        filterGraph(spec: string | FilterSpecification | Array<string | FilterSpecification>, map: string[]): FfmpegCommand;
+        complexFilter(spec: string | FilterSpecification | Array<string | FilterSpecification>, map: string[]): FfmpegCommand;
 
         // options/misc
         usingPreset(proset: string | GetPreset): FfmpegCommand;
@@ -281,6 +282,7 @@ declare namespace Ffmpeg {
         // processor
         renice(niceness: number): FfmpegCommand;
         kill(signal: string): FfmpegCommand;
+        _getArguments(): string[];
 
         // capabilities
         setFfmpegPath(path: string): FfmpegCommand;