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Mobile Audio Synthesiser - Final Year Thesis

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A Mobile Audio Synthesiser
Sean William Rooney
Final Year Project – 4th
Year
B.Sc. Single Honours in
Computer Science
Depa...
Abstract
The objective of this project was to design and develop an android mobile application which
generates and control...
Introduction:
Topic:
The topic being addressed in this project is a mobile app whichcan synthesise sound, as well as
modul...
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Mobile Audio Synthesiser - Final Year Thesis

  1. 1. A Mobile Audio Synthesiser Sean William Rooney Final Year Project – 4th Year B.Sc. Single Honours in Computer Science Department of Computer Science Maynooth University Maynooth, Co. Kildare Ireland A thesis submitted in partial fulfilment of the requirements for the B.Sc. Single Honours in Computer Science. Supervisor: Thomas Lysaght
  2. 2. Abstract The objective of this project was to design and develop an android mobile application which generates and controls various audio synthesis techniques as per the project specification. This project will build an Android Mobile Application to generate and control various audio synthesis techniques such as delay, FM, AM, and ring modulation. Various filtering techniques associated with synthesisers should be implemented to shape the sound such as, low pass, band pass, as well as delay and reverb. The interface should be modelled using typical audio synthesis widgets and should scale to different mobile devices. I chose this particular project based on my interest in music production and mobile application development. My familiarity with the Java language also motivated me to choose this project. I primarily used Android Studio to create the app as opposed to Eclipse, due to the former now being the official IDE for Android. Using custom widgets, buttons, and rotary knobs resulted in an appealing UI, through which, values were read and used to manipulate the various audio synthesis techniques as required. Some problems were encountered during development, some were overcome. However, I could not overcome some problems prior to the project deadline. In conclusion, I created a mobile audio synthesiser featuring most of the required synthesis techniques and despite the deadline, I will continue to build upon the app until I am satisfied it is complete. Keywords: Android, modulation, audio synthesis, mobile application.
  3. 3. Introduction: Topic: The topic being addressed in this project is a mobile app whichcan synthesise sound, as well as modulate and shape this sound to the users liking. This mobile app willoperate on the android platform and willscale to other android mobile devices. It will perform the same functions as a physical synthesiser with the benefit of being much more compactand ‘mobile’. Motivation: My motivationwhen taking on this project revolvesmainly around my interest in sound production, music production and audio effects.I am familiar with various FM synthesisers such as FM8 and Massive, both made by Native Instruments. Using these synthesisers, I learned to create, shape and model various sounds using ADSR (Attack, Decay,Sustain and Release), filter envelopes, LFO’s and band pass filters. Other than already having an interest in audio synthesis, I believe that having experience in mobile development is becoming more relevant in present times. The variety of apps now available for mobile devices is beginning to affectthe relevance of desktop machines. I am personally observing a trend leaning towards mobile platforms as opposed to desktop in the context of device usage as a workstation. If the processing power within mobile devices continues to increase over the next few years at the rate it currently is, desktop platforms could become obsolete. If youtake into account,a person’s busy lifestyle in current times, along with the compact portability of a mobile phone or tablet, they make foran ideal combination resulting in efficiency and productivity. Re-enforcing my beliefs regarding the importance of knowledge in mobile app development is a report on the U.S. mobile app. The report, “TheU.S. Mobile App Report” researched by Adam Lella, and Andrew Lipsman of comScore.com,states “Thedays of desktop dominance are over”.[www.comscore.com/Insights/Presentations-and-Whitepapers/2014/The- US-Mobile-App-Report Accessedon:22/03/16,Publishedon:21/08/14,Author: AndrewLipsman] ProblemStatement: I need to synthesise audio. ThereforeI first need to be able to play audio through the android devices speakers. To do this, I willneed to create an Android Audio Track and send an array of type ‘short’ to this Audio Track.For the Audio Track I willneed to specify a sample rate and for the array, I willneed to find the minimum buffersize of the Audio Track, this will be the size of the array. Tohear any sound when the Audio Trackis playing, I will need to fillthe array with a sine or cosine wave at a certain phase, or some variation of these waves, depending on the desired sound, cast to a short. The effectsand wavetypes selected by the user will affecthow the array is filled; therefore I will need to create a function whichdeals with all these possible parameters. Keeping in mind that the project specifies that the app must scale to other mobile devices, I may not be able to fitthe entire app onto a single screen; therefore I will need to create one or more intents and activities whichdeal withmultiple screens. As well as including the effects and modulations as per the project specification,I need to provide controls to the user, so that they may manipulate these effectsand modulations as they wish and change the amount of an effect applied. Depending on the capabilities of the Android deviceand the limitations of the Java Development kit, I may need to deal withanti-aliasing and audio stutter, particularly when trying to implement the delay effect.
  4. 4. Approach: I approached the initial problem of synthesising sound by first importing android media packages. I imported AudioTrack, AudioFormat and AudioManager. With these packages imported into the project,I was able to create an instance of an AudioTrack whichI named trackOne. I declared this trackOnewithin a thread named “t”.There are fourfunctions associated with AudioTrackwhichI used in concurrencewith trackOne, play(),write(),stop() and release(). Immediately after declaring and initialising trackOne,I called trackOne.play(). This will begin to play that which has been written to trackOne, though at this point in my thread, nothing has yet been written to trackOne. To hear a sound while trackOne.play() Iwould need to write something to the track. The write functionassociated with the track requires an array of short values I would callsamples and a specified buffer size. How the array of samples is filled woulddepend on the sound I wish to produce, whichis determined by the buttons and knobs on the screen. There are multiple possibilities regarding whichsound could be produced. I wouldtherefore create multiple functions to fillthe array of samples in different ways depending on the desired sound. For example, a functionto fill the array with a sine wave wouldconsist of the following;A ‘for’ loop whichwould run froman integer i = 0 up to i < the buffersize, whichis the size of the array. Within this loop, I wouldset the sample array at position I to be filled with the following function;“amplitude * cos(ph)” whereph represents the phase of the waveand at this point is 0. Amplitude is an integer which is set at 10000 and its value can be modified by a rotary knob on the screen. After this line is executed, the value of ph is incremented as such; ph = ph + 2 * pi * frequency/sample rate. This function will run within a while loop, and the array of samples willcontinue to be written to trackOne until the loopis broken. This wouldbe achieved by a boolean whichI would call isRunning. This boolean is set to true while a button is held down on screen, so during this time, the array of samples will be filled as per a specified function and written to trackOne. The boolean is set to false once the button is released which breaks the while loop. Upon the loop being exited, the followingtwofunctions to run are stop() and release(). trackOne.stop()will cease any sound from playing and trackOne.release() will empty the track. In order to determine whichfunction should run to fill the array of samples in the desired manner, corresponding boolean values wouldbe required. If a particular switch is turned on, its corresponding boolean value would be changed to true and thus, an if statement in the aforementioned while loop woulddetermine whichmethod would be run to fill the samples array. For example, if I were to turn a switchlabelled “Ring Mod” to the on position, a boolean value called ringMod wouldbe changed to true from false. Then when the sound is played and the while loop is entered, an ‘if’ statement is encountered which states if ringMod is true then run the function that fills the array with the ring modulator samples. My approach forthe UI,which allows the user to select and controla sound or effect,revolves around various widgets in the form of image buttons, as well as, a custom widget called a rotor knob. The aforementioned boolean values wouldbe controlledby various switches placed about the UI in an ergonomic fashion. These switches would be made from Android image buttons, buttons whichcarry out a functionupon being clicked.This button being an image button means that its appearance is determined by a .png image which is set as its background; this allows you to make the button look howeveryoulike. As well as executing a functionupon being clicked,I
  5. 5. would calla command which changes the background image of an off button to an on button, and viceversa when clicked again. In order to controlthe amount of an effectbeing used I would need to implement a custom widget called a rotary knob. This wouldbe a widget that can rotate when dragged to the left, right, up or down, similar to the functionality of a potentiometer. I would limit the knob to rotate between 0 and 290 degrees and map values between 0 and 100 to be outputted relative to the angle of rotation. I would use a variation of this knob to select which waveformis being used. As opposed to mapping values 0 to 100 onto the output angle, I wouldset the knob to output string values depending on which range of angles the knob is pointing. For example if the current angle is between 0 and 50, the string “Sine” would be outputted, and I wouldmap Square, Saw and Triangle to other angle ranges. Two‘if’ statements would ensure that the rotary or clickknob would not go beyond the range of 0 or 290 degrees. If the angle would ever go below 0 or above 290, a line of codewould execute to set the angle to 0 or 290 accordingly. In order to run the codeon a device and test its functionality,I woulduse the Android Virtual Devicewhich is built into Android Studio, making code testing on a devicevery handy. The virtual device can emulate any android device with any size screen running any version of the android OS from Cupcake all the way up o Marshmallow and beyond. However, in order to take advantage of the “Intel x86 Emulator Accelerator”,a computer with an Intel processor is required. Unfortunately the computer I am using to create the application is running an AMD processing unit and I am unable to take advantage of the accelerator.As a result, using the Android Virtual Deviceis an unbearably slow process and therefore unfeasible considering how often I wouldneed to checkthe stability of my code. With this in mind, along withintentions to learn more about mobile development in the future, I decided to purchase an Android Phone, an LG G3 running Android Lollipop. The devicewould be perfect for testing the functionality of the code and I couldstill use the Virtual Device at a later stage in development to checkhow the application scales to other devices. To allow USB debugging on the deviceI would need to go into the settings menu and enable developer options (forthis option to become available, one needs to first enter the softwareinfo menu and tap the build number 7 times). After this I would enter the new “DeveloperOptions” menu and turn on USB debugging. My Android deviceis now recognised within Android Studio and can select it as a deviceto run the code on while in development. Metrics: Once the testing device is set up to be recognised by the computer, I would begin testing the code. Upon running the code, I am greeted with UIon the devicewhich I wouldfirst compare to the preview layout within Android Studio. This stage of evaluation is to ensure the layout of the app is both ergonomic and user friendly. When implementing value mapping into one of the various functions of the app, I wouldinclude a text box in the UI whichwould display the mapped values. I wouldobserve this text box when testing the app to ensure the values are mapping correctly and then remove the text box later or use it for other value mappings. Next we have evaluation of the sound. At this stage I would listen to the sound playback with each of the various modulations and wavetypes selected, and then compare these to the corresponding functions found on a well-made reputable audio synthesiser found on the Android Play Store. The app I mainly used for sound comparison was “Common FM synthesiser” by “oxide”.
  6. 6. Project: Before this project, i had never developed an application fora mobile device or studied sound synthesis nor any associated modulation techniques. Now that I am nearing the projectdeadline, I can create and run a stable, functional,user friendly mobile app that willscale to other mobile devices. I now have the tools and skills necessary to continue developing forthe mobile platform, as wellas the tools required to expand development beyond the mobile platform, to the wearable technology platform (Smartwatch, Google Glass etc.). I now have a much deeper knowledge into the math and programming behind sound synthesis. I now know how to create functionsto generate various sound waves,how to manipulate a sine wavein order to achieve various waveforms, for example, creating a square waveby means of a Fourier Transform. Priorto taking on this project,I was familiar with using a sound synthesiser and its associated effects,but I now know how to create these effectssuch as the ring modulator, frequency modulator or a band pass filter forexample. Taking on this project also gave me the opportunity to learn about creating a stable and user friendly UIon a mobile device. Android Studio creates its widgets and layout using XML whichI was somewhat familiar with prior to the projecthaving created style sheets for a HTML webpage in the past. I was able to create a custom widget from scratchwhich workedperfectly and I was able to manipulate it to behave in different waysas I needed it to. I was able to improve my Adobe Photoshop skills as I used this resource extensively through the course of creating my UI. I used it to create backgrounds and create second instances of buttons and switches to use to appropriately change the appearance of a switch when flickedor a button while pushed. Finally, I learned a great deal about the Android NDK (NativeDevelopment Kit) and the JNI(Java Native Interface).Using these tools I was able to code a C++ file and its associated header file, and then call it within a java class file. I used this method when trying to implement a Delay functioninto the application due to issues occurring when trying to program the same functionin java. As a result, I was able to make use of my knowledge of the C++ language as well as Javaand XML.Programming a Delay effectin C++ would avoid risk of audio stutter and anti- aliasing while streaming the audio.
  7. 7. Technical Background: TopicMaterial: [“The Audio Programming Blog”, Author: “VictorLazzarini”, https://audioprograming.wordpress.com/catagory/android/ Accessed on: 24/03/2016] This blog by Victor provided me witha lot of insight into the Android NDK and how it could be used with audio synthesis, as well as providing examples of how a synthesiser couldbe programmed using Javaand the Android SDK. In some of his blogs, Victor explores the problem of latency with audio development on Android. He details how he overcame the latency issue by taking advantage of the NDK and wrapping C++ codein Javathen published his results and findings onto the blog. Overthe course of the projectI attempted to implement Victor’s solutions into my application in an effortto constructa workingdelay function. Android Studio, The IDE itself contains a help section and prompts you witha tip of the day each time youopen it. These small pieces of information helped me to familiarise myself with the navigation of Android Studio, customise the look and layout,as well as understand how Android Studio differsfrom MicrosoftVisual Studio. Technical Material: [“Android Studio Development Essentials – Second Edition”,Author: “Neil Smyth”] As this is my first endeavour into the world of development on the mobile platform, this book served as a very helpful starting point. The goal of the book is to teach the skills necessary to develop Android based applications using the Android Studio IDE and the Android SDK. Combining this with my prior knowledge and experience in java programming, I foundit very easy to begin creating and testing my first applications. [“The Android Developers Cookbook - Building Applications withthe Android SDK”, Authors: “James Steele and Nelson To”] This is a 355 page book whichdiscusses the main conceptof Android OS and creating applications forit using the Android SDK. The bookgoes into great detail on these topics. I downloaded this bookas a PDF and referenced it many times throughout the course of creating the application. This material makes a great addition to the aforementioned “Android Studio Development Essentials” as required in area that needed to be discussed in more depth. From this bookI also learned a great deal about the Android OS as it is and how it came to be, i.e. its evolution, its structure, how a deviceruns the OS etc. Maynooth University Moodle Resources: Uponchoosing this project, my supervisor Thomas Lysaght granted me access to the “CS322 – Music Programming” and “CS385 – Mobile Application Development” modules on Moodle. The notes provided here from both Thomas Lysaght and Joseph Timoney provided me witha much better understanding of how music and audio is programmed, and gave me a great foundation to begin my approach. The lecture note PDFsalong with the Java codesamples helped me to build an initial application whichI could build upon.
  8. 8. The Problem The user should be able to create and play a sound withease, such that a minimal amount of steps between starting the app and hearing the sound is preferred. A simply Activity Diagram can be seen in [appendix A] in the attachments folder. Here you can see the user has a choice between creating and playing a sound on the first tab of the application, or clickingto the next tab to build more upon the sound, and then play it. Generating the sound is a problem that wouldrequire a main run function in the code. This function could take in various boolean and float or double values whichwould determine how the note sounds. The user requires a button to play the note, a means of controlling the frequency and amplitude and switches to toggle various effectssuch as ring modulation and frequency modulation. After setting up the desired sound, applying effects,specifying a wave shape, the user would need a screen where they could easily sample the sound at different frequencies/pitches. This screen should allow at least a fulloctaveof notes so the user may hear an entire range of the sound. The four basic waveshapes that can be generated by a synthesiser willneed to be recreated in this application. Studying the resources available to me in the CS322 – Music Programming module on Moodle, I was able tocome up with Pseudo codefor the Sine, Saw and Triangle and Square waveforms.I took record of these forlater use and can be seen in [appendix B] in the attachments folder. These are the equations I would need to fill an array with and load into the Audio track to play through the speakers. The size of the device’s screen could be seen as somewhat of a limitation when thinking about fitting the required toggles, buttons and switches onto it. Multiple Activities/Classes would be required for both unction and aesthetic purposes. The problem of maintaining a variables value when moving from one Activity to another will need to be handled so as not to lose the sound the user has created when clicking onto the next screen. For example, if I start up the application and I choosethe wavetype on the first page to be a Saw wave,I need the Boolean value saw to remain “true” when I start the next activity as I move to the next page. The problem of latency with audio development on android willneed to be addressed as to maintain a quality performance throughout the app. Research into this has led me to believe the best course of action is to use the Android NDK and JNIwhen programming some of the more processor demanding sound functions. For this I would need to download the NDK. Although it is still an experimental feature, this method of programming for Android should result in the best performance. Anti-aliasing is another issue with audio development that could present over the course of this project. To solvethis I may need to experiment with the sampling rate and the buffersize I use with the Audio Track. The sound may crackand stutter if the sample rate is too high and thus must be examined carefully as I test the audio output.
  9. 9. The Solution (Design and Implementation) Analytical Work Various mathematical equations are used to make different wave types, and modulation effects. The pseudo code of the equations forthe fourwave types can be seen in [appendix B] in the attachments folder and the pseudo code forfrequency,amplitude and ring modulation can be found in [appendix D] in the same folder. Creating a ‘for’ loop whichiterates from 0 to the previously declared buffer size, will be used alongside these equations to fill the array fora desired sound. Architectural Level: The solution to having a streamlined, user friendly experience when using the application is a well laid out and ergonomic design. Initial sketches forthe layoutof the applications 3 Activities can be seen in [appendix C] in the attachments folder. In these sketches it can be seen how the streamlined 3 step process is achieved. Youare greeted with the main activity where youchoose your waveform, set the frequency and amplitude, and chooseif you wish to apply any modulation types and a button to sample the sound. The user can then clickthe tab arrow to be brought to the next activity wherethey can specify the ADSR values and clicka toggle button if they wish to apply an additional effectwiththe sample button at the bottom. The user can then use the toggle arrows to either go to the previous activity or go to the third and final activity.This activity is designed so that the user may extensively sample and test the sound through a full octaveof frequencies. In the centre of the Activity the user can see whichnote they are playing accordingto the frequency of the note. The layout of each page will be designed to be familiar as wellas ergonomic. The button for sampling will be thoughtfully placed at the bottom centre of the page so that when holding the mobile device, the users thumb willbe able to easily reach, it will feel natural. The buttons to switch whichActivity youare currently in willbe placed at the top of the screen in a similar fashion to that of tabs on an internet browser or the forwardand back buttons in a windows explorer window. Low-level Design Determining which equation to fill the array withwill be determined by boolean values, these boolean values willbe global and named according to the wave typeor modulation function they represent. All of these values willbe initialised and all but the sine boolean value will be false. Multiple functionswill be written in the first Activities’ class, they will also be named according to the wave types and modulations and contain the corresponding equations. The input parameters to these functionswill be the sample array and the global frequency of the application. The “playNote” functionwill be called upon a press of the button, and the sample array will be passed to one of the aforementioned functionsto be filled with relevant equation. Whichfunction the array is passed to willbe determined by if statements and the boolean values, as twowave formboolean values will never be set to true at the same time and the modulation functionswill override the waveform functions. To solve the problem of audio latency on Android, I will attempt to implement the NDK into my project when designing the delay effect.I will create a C class containing the functions to produce the delay, I willthen call the native Java functionin my main Activity and apply the result to the current Audio Trackand sample array.
  10. 10. Implementation: In order to create the custom widgets I willuse throughout the application, I willuse Adobe Photoshop extensively throughout the course of development, creating .png images with transparent backgrounds to replicate the lookof the sketches in [appendix C]. If I take an image of a round red button, and darken the red area, the button in the image will lookas if it has been pressed. Uponstarting an Activity,the first red button can be seen. While the button is being touched on screen I willchange its background image to the edited darker version and backto the original when the button is released. It is impossible foran android application to replicate the responsive, tactile feel of an actual synthesiser. However,I believe this extra level of detail, despite its subtlety, adds a level of immersion that will make the user feel less detached from the creative process of sound generation. Perhaps in the future I will add more detail, such as a clickingsound when switching on one of the modulation function switches. Evaluation SolutionVerification The result of the equations detailed in [appendix B] and [appendix D] willbe cast to a short and will be therefore eligible to be saved in the array of type short called samples. The iterations of the ‘for’ loop in whichthe array is filled, are constrained by the buffersize and thus impervious to overflow. SoftwareDesignVerification I have created a UMLdiagram coveringthe general layout and navigation of the application, taking into accounteach option fornavigation fromeach Activity.Each course of action is covered;this diagram can be found in [appendix F] in the attachments folder. During testing I shaped a sound by assigning values to variables before navigating to the next Activity and then checkedto see if the variables were still stored. The values stored were maintained as the application was navigated extensively, back and forththrough the Activities with no loss of data. From the screenshots provided in [appendix E] in the attachments folder it can be seen the final layoutand design of the application is fairly accurately replicated from the initial sketches. Both the Javacode and XMLlayout code I wroteseems to be working properly in accordancewith my proposed solutions. SoftwareVerification Testing was carried out by loading a debug version of the application onto my testing device,the LG G3 5.5 inch phone running Android Lollipop and assessing the stability of the applications functions from there. I can easily and quickly make small changes to the code and reload the debug onto the device and checkthe changes. Testing the accuracy of the sound being generated from the waveforms involved first running the debug version of the application on the test device, selecting the waveform I’d like to test, and then comparing the sound to the same waveformgenerated by a popular, renowned synthesiser application. The application I used as a control formy sound accuracy testing was “Massive” by “Native Instruments” or “N.I.”.From the screenshot in [appendix G] in the attachments folder, it can be seen that there is a vast amount of options within “Massive”, which
  11. 11. allowed me to have many variations on my test. Using Oscillator 1, I picked a waveformand played it, then compared it to the same waveformon my testing device. For testing the overallstability of the application, I put the app under various “stress tests”. These tests involvedmy trying to crash the app, and checking the error log when I am successful and making necessary changes to the code in order to prevent this cash in the future. For example, quickly mashing the playNote button would result in the sound anti-aliasing and would output a very unpleasant tone. Quickly rotating the deviceand rotating backwould crash the app, only if device rotation is enabled. After attempting to implement a native java function fromthe NDK whichwould generate an audio delay effect,my tests were unsuccessful and the presence of this codewithin the project began to affectits stability and as a result, was removed. Testing revealed that values assigned to variables were not being maintained throughout the activities as I switchedbetween them. Upon closer investigation, I found that I was missing a line of code. Where I was loading the variables I wished to carry into a bundle, I did not put the bundle into the intent. It was also revealed that the tremolo functionwas increasing the frequency by the desired pitch on each loop but not decreasing it backto the original value. This resulted in the frequency of the note increasing infinitely as I held downthe play button. Though the application seemed mostly stable, there was still workneeded to be done on some of the functions. Validation/Measurements After extensive testing, the resulting application whichwas designed from my solution was fully functioning with most of the required sound synthesis functions. The comparison of sounds between my application and the controlapplication “Massive” was surprising as the sounds were similar to an acceptable degree withoutany alteration. As a result, it can be determined, that the equations forthe waveform functions and modulations presented in my solution, were successful in their attempt to create their corresponding sounds to an acceptable accuracy. After making necessary changes to how the variables were dealt with upon switching activities, the application successfully retained all its variable information regardless of how many times the Activitieswere switched. Despite having difficulties implementing the native Java functionwith the NDK to handle the delay effect,I was still able to set up and implement a simple JNIfunction. I created a text widget on the third activity page, whichhas its text set within the onCreate function of the Activity.The text which it is set to originates froma C file whichhas a functioncalled stringFromJNI and upon running the app it can be clearly seen in the third Activity,that the line of text written in the C file, has been written to the text widget at the bottom of the screen. The results have been incredible informativeand have allowed me to correcterrors were there once was, and improve aspects of the app in areas that were lacking. Various instances of a possible crash or loss of data when navigating the application have been eliminated, resulting in a much more stable app.
  12. 12. Conclusions The resulting application is, forme, a stepping stone towards further work in the area of mobile application development. Taking on this project has increased my already peaked interest in development forthis platform. My results fromthis project have confirmed that there is indeed a latency issue withaudio programming on the Android platform. A combination of anti-aliasing, a delayed response from the play button and the apps behaviour when you try generating a note quickly after a sound has ended are all evidence of the presence of this issue. While viewing C code within the Android Studio and that code is connected to a native Java functionin the project, you are constantly prompted with the notice that Android NDK is still an experimental feature. Despite some difficulties, I was able to utilise the NDK and call a native Javafunction and as a result, I can confirmthat this experimental feature is functional.The NDK can be very useful and broaden the spectrum of tools available to youwithin Android Studio, and though my current example of NDK utilisation may be quite basic, I will be studying and experimenting with the NDK in much more depth in the future. In the future I willcontinue tobuild upon this application until I am satisfied at its stability and functionality.I would like to add more audio synthesis functions to give the user as much freedom and as many options as possible. I will continue to workwith Android Studio and attempt to develop useful apps, learn more about the IDE and see how far I can push a mobile device in the context of how much a mobile application can achieve when looked at against a desktop machine. I have learned much about the Android OS, the Java Language and the Android SDK throughout the course of this project and am eager to learn more, and to create more.
  13. 13. References The U.S. Mobile App Report [www.comscore.com/Insights/Presentations-and-Whitepapers/2014/The-US-Mobile-App-Report Accessed on: 22/03/16, Published on: 21/08/14, Author: Andrew Lipsman] The Audio Programming Blog [https://audioprograming.wordpress.com/catagory/android/ “The Audio Programming Blog”, Author: “Victor Lazzarini”, Accessed on: 24/03/2016] The Android Studio IDE [http://developer.android.com/sdk/index.html Accessed on: 30/03/2016] Android Studio Development Essentials [“Android Studio Development Essentials – Second Edition”, Author: “Neil Smyth”] The Android Developers Cookbook [“The Android Developers Cookbook - Building Applications with the Android SDK”, Authors: “James Steele and Nelson To”]
  14. 14. Appendices Appendices are provided in the attachments folder of the supporting documents. If I were to repeat my attempt at this project, I wouldput more focus on the NDK and wrapping C code in a native java function, due to the factthe audio is handled more efficiently in C.

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