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Implement a spectrogram application in the Native Android environment. Signal processing includes windowing, zero-padding, overlapping, FFT, and working with complex numbers.

Lab overview

In this lab, you will create an Android application that plots the spectrogram of streaming audio, and deploy it on the Google Nexus 7 tablet.

Similar to the previous labs, you will be provided with an existing project with all of the required peripherals already set up. Unlike the previous labs where data was processed sample-by-sample, this lab requires block-based processing.

What is the minimum latency for processing a block of length 256, with an audio sampling rate of 8 kHz?

[link] shows a block diagram of the system you will be implementing. The project is already configured to stream audio and display the processed output to the screen.

System-level block diagram

Audio capture -> Audio buffer -> Preprocessing -> FFT -> Energy calculation -> Display

You will be focusing on the signal processing tasks, which will be implemented in native C code. For those that are interested in the Android Java specifics, we will provide an optional tutorial that shows you how to build the project from scratch, explains the different Android classes that were used, and along the way, provides supplemental links to references and other useful Android tutorials available on the web.

Part 1: getting started with android and eclipse

In this section, you first setup your Android device in development mode, import a skeleton project into Eclipse, and familiarize yourself with the Android project structure and build process.

Setting up the google nexus for development

On the tablet, you must enable the Developer options under Settings :

  1. Go to Settings ,
  2. Click on About tablet ,
  3. Click Build number seven times (yes, 7).

Under Settings>Developer options , enable the Stay awake and USB debugging options.

Setting up eclipse

The development environment you will be using is the Nvidia Tegra Android Development Pack 2.0 . To get started:

  1. Start Cygwin by double-clicking on C:\NvPack\cygwin\cygwin.bat
  2. In the prompt, navigate to the Eclipse folder by typing cd /cygdrive/c/NvPack/eclipse
  3. Launch Eclipse with ./eclipse
Cygwin provides a Linux-like environment for Windows, and launching Eclipse from within Cygwin is required for native C debugging to work correctly.

Choose a new workspace on your U: drive, similar to what you did in Lab 0. This step feels familiar because CCS is actually based on the Eclipse framework.

Importing the project

Once Eclipse opens, select File>Import...

  1. General>Existing Projects into Workspace
  2. V:\ece420\nexus\Lab4\
  3. Check "Copy into Workspace"
Close out of the "Welcome" screen.

Once the project is imported, it will try to build automatically. If you see a build error, you will need to define the $NDKROOT variable in your workspace:

  1. Go to Project>Properties
  2. Expand C/C++ Build>Environment
  3. Add...
  4. Name: NDKROOT, Value: C:\NvPack\android-ndk-r8

Understanding the android project structure

An Android project with Native code support has 4 main components:

  • .\AndroidManifest.xml - contains app-related information, such as project name, activities, and required peripherals (e.g., microphone).
  • .\res\layout\main.xml - describes the layout of the user interface. In our project, we define an ImageView , which is used to display the spectrogram.
  • .\src\ - contains the Java source files.
  • .\jni\ - contains the native C source and Make files.

Questions & Answers

what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
How can I make nanorobot?
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
how can I make nanorobot?
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
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Source:  OpenStax, Ece 420 fall 2013. OpenStax CNX. Sep 26, 2013 Download for free at http://cnx.org/content/col11560/1.3
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