ECE497 Project: PS EYE QT

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Team members: Mona Yan, Greg Harrison

Executive Summary

For our Final Project we wanted to be able to capture audio from the PlayStation Eye microphone array and then be able to display the audio waveforms all on the beagle. Initially we set out to display the waveforms in Qt using Qwt, which was later proved to be more difficult than initiall anticipated due to limitations on the Beagle and neither of us having prior C++ programming experience. The next thought was to try to use GnuPlot to try to plot the audio data. GnuPlot was really designed to produce static plots of information, not plots that were in realtime. We were able however to find different ways to "force" GnuPlot to plot the live data with the help of a clever script written by Thanassis Tsiodras, and then also edited by Andreas Bernauer which can be found here. When we implemented this script with our audio data on the beagle it still wasn't as realtime as we would have liked it to be due to the capabilities of the beagle, so we then had the idea to send the data back to a host computer which would then have the processing capability to produce the results we were after.

We currently have working plots of audio waveforms for channel1 and channel2 of the PS Eye microphone array. These plots are displayed on a host computer with the data being sent from the beagle via netcat.

In addition, lowpass and bandpass filters have been successfully implemented with Gstreamer. We are working on adding sound effects like flanging, reverberation and the "Wah-Wah", a classic guitar effect. We will also continue to explore Gstreamer to fit our needs. If time permits, it would be interesting to see if what we could also get netcat to do such as transferring video and/or audio from the beagle to the host.

This project turned out to be a lot more difficult then initially anticipated. Although it would be nice for this project to run solely on the beagle it is very interesting to discover all of the possibilities of utilizing netcat between the beagle and host.

Installation Instructions

Every package needed on the beagle should already be there with the current image we are working with. Start by cloning the git directory on the host computer:

user@host:~$ git clone

Then go into this directory and view all the files

user@host:~$cd ECE497-DisplayAudioWaveforms
user@host:~/ECE497-DisplayAudioWaveforms$ ls
Beagle  README

The folder Beagle now needs to be copied to the beagle. In this example is the IP address of the beagle replace with your beagles IP address:

user@host:~/ECE497-DisplayAudioWaveforms$ scp -r Beagle/ root@
root@'s password: 
audio_input_output.h                            100%  521     0.5KB/s   00:00    
Makefile                                        100% 6923     6.8KB/s   00:00                                       100%   56     0.1KB/s   00:00    
audio_input_output.c                            100%   12KB  11.7KB/s   00:00    
debug.h                                         100%  741     0.7KB/s   00:00    
audio_thread.h                                  100%  447     0.4KB/s   00:00    
audio_process.c                                 100%  879     0.9KB/s   00:00    
audio_process.h                                 100%   98     0.1KB/s   00:00    
app_DEBUG.Beagle                                100%   23KB  23.4KB/s   00:00    
main.c                                          100% 1806     1.8KB/s   00:00    
audio_thread.c                                  100% 9553     9.3KB/s   00:00 

The Beagle folder should now be on your beagleboard. Check and then enter that folder:

root@beagleboard:~# ls
Beagle	 a.out	   busybox	exercises
Desktop  autogain  byobu-4.25	esc-gst			network
Old	 bin	   c6run_build	esc-media		qt
root@beagleboard:~# cd Beagle
root@beagleboard:~/Beagle# ls	  audio_input_output.c	audio_process.h  debug.h
Makefile	  audio_input_output.h	audio_thread.c	 main.c
app_DEBUG.Beagle  audio_process.c	audio_thread.h

Now that that is all set up we need to get the gnuplot package on the host. This should be all you need to do:

user@host:~/ECE497-DisplayAudioWaveforms$ sudo apt-get install gnuplot

Now everything should be ready

  • Note: The PS Eye should be attached to the Beagle board and both the host computer and beagle should be on the same Internet network

User Instructions

After setting up everything on the host and Beagle, its time to see if everything works. First run the script on the Beagle board:

root@beagleboard:~/Beagle# ./

Then on the host run the script, which will ask a series of questions:

user@host:~/ECE497-DisplayAudioWaveforms$ ./ 
How many streams (enter:1 or 2)?
Would you like those streams in 1 window or 2 windows? (enter:1 or 2)
How many samples per window?
Enter Minimum Y axis:
Enter Maximum Y axis:
Enter window width:
Enter window height:
Enter IP address of Beagle:

If everything worked you should now see 2 plots of audio that are from the Beagle board being displayed on the host computer. To quit the plots just push ctrl-c in the terminal window of either the beagle or the host.


Currently our project can take audio data from a Playstation Eye microphone array running on the Beagle Board and then plot it on a host computer. We found this method to be the fastest and smoothest way to implement the plotting of the audio signals with the limited C++ programming experience and time we had. The script running on the host can take information about the plots including the range, number of channels, number of windows, and the number of samples displayed. A demo of what our project can do can be found here.

Theory of Operation

Our program works by running the AudioThru program we made work in Lab08 to generate the audio data. This audio data is then sent through a netcat connection with the host computer. This audio data is then plotted using GnuPlot with the given preferences for the plots supplied by the user. Scripts were created to simplify this entire process. The plots can be generated by only running one script on the beagle and one script on the host computer making the plotting easier for the user. The simple overview of our program can be summed up in the following diagram Diagram.JPG

Work Breakdown

Initial work with Qt-Greg

Plotting with gnuplot-Greg

Sending data back to host for faster plotting with netcat- Greg

Making scripts to somewhat automate the plotting- Greg

Audio effect using Gstreamer- Mona


Give some concluding thoughts about the project. Suggest some future additions that could make it even more interesting.