IFD:EAI SoS21/course material/Session 6: Getting Started with Teensyduino: Difference between revisions
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We want to code a so called envelope follower, it tracks the peaks of our audio signal and gets the rough volume shape. With the help of the volume (~loudness) of our signal we can detect wether there is vibration on our piezo or not. In rough terms we get the volume envelope in two steps: | We want to code a so called envelope follower, it tracks the peaks of our audio signal and gets the rough volume shape. With the help of the volume (~loudness) of our signal we can detect wether there is vibration on our piezo or not. In rough terms we get the volume envelope in two steps: | ||
# get the maximum of the signal samples seen so far | # get the maximum (peak) of the signal samples seen so far (this is also called a peak hold circuit) | ||
# multiply this maximum with a decay factor (<1) for every new sample | # multiply this maximum with a decay factor (<1) for every new sample, or sample block (envelope follower) | ||
To get a bit more accuracy you might want to get the absolute value of our signal before tracking the maximum. | |||
With the help of the [https://www.pjrc.com/teensy/td_libs_AudioNewObjects.html teensy documentation] and [[:File:envelope_follower_template.zip|my empty template file]] you should be able to grasp how this works. Basically you write your own teensy audio object by including a C++ class that is structured as documented in the link above. This class will receive a pointer to the audio input stream coming from the piezo and can do some work on it. If you have questions about the template code please ask on our [https://signal.group/#CjQKIGr9R1a7Znwe1Ca0pmbx3rvHHzDaS1c_LnmgwwVk1KoSEhB6aHUiokel3vtGVoTErtfB signal group]! | With the help of the [https://www.pjrc.com/teensy/td_libs_AudioNewObjects.html teensy documentation] and [[:File:envelope_follower_template.zip|my empty template file]] you should be able to grasp how this works. Basically you write your own teensy audio object by including a C++ class that is structured as documented in the link above. This class will receive a pointer to the audio input stream coming from the piezo and can do some work on it. If you have questions about the template code please ask on our [https://signal.group/#CjQKIGr9R1a7Znwe1Ca0pmbx3rvHHzDaS1c_LnmgwwVk1KoSEhB6aHUiokel3vtGVoTErtfB signal group]! | ||