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Wrote design/implementation section.

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DSP/Assignment_2_report/U1265119_Assignment2_report.tex
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\restylefloat{table}
\usepackage{perpage}
\MakePerPage{footnote}
\usepackage{abstract}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{blindtext}
\setkomafont{disposition}{\normalfont\bfseries}
\addbibresource{~/PerryPerrySource/LaTeX/DSP_Bibliography.bib}
\begin{document}
\DeclareCiteCommand{\citeyearpar}
{}
{\mkbibparens{\bibhyperref{\printdate}}}
{\multicitedelim}
{}
\begin{document}
\title{DSP Assignment 2\\Digital Audio Effects Implementation}
\subtitle{Technical Report}
\subtitle{\LARGE{Technical Report}}
\author{Sam Perry\\U1265119}
\date{}
\maketitle
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changes that could be made to improve performance.
\end{abstract}
\section{Background/Literature - Digital Signal Processor/Microcontroller
\section{Background/Literature:\\Digital Signal Processor/Microcontroller
Overview}
A digital signal processor (DSP) is form of specialized microprocessor
designed specifically for the processing of signals (such as audio signals
@@ -82,7 +94,7 @@
be used for programming.
\paragraph{Data Memory}~\\
RAM (Random-access memory) is volatile memory that is used for storing data
RAM (random-access memory) is volatile memory that is used for storing data
used when executing instructions. Unlike ROM memory, RAM can be both read
from and written to at runtime and is used for the storage of data that can
change as instructions are executed. This is used for the storage of data
@@ -105,7 +117,6 @@
the processing architechuture from the bit depth of the DSP components as
they affect different aspects of the system.
\subsubsection{CPU}\label{CPU}
The CPU (Central Processing Unit) is the component that executes
instructions and performs calculations on data. The speed at which the CPU
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architecture allows for simulataneous access of data and program memory,
making it the more efficient of the two designs.
\section{DSP Specific Factors}
DSP specific factors relate to components specically affecting the systems
ability to handle audio signals. These will determine the quality of audio
manipulation and affect the computational requirements for the system.
\subsection{A/D \& D/A Converters}
A/D and D/A converters are required for audio input and output.
A/D and D/A converters are required for audio input and output. Depending
on the microcontroller used, these may intergrated in the main circuit
board or available as peripherals that can be attached via ports (as is the
case for the PIC24 board used). The quality and accuracy of these
converters will clearly have an effect on the audio output and using
converters that can perform as transparently as possible is essential for a
high quality system.
\subsection{Samplerate}
The samplerate defines the frequency at which a measurement will be taken
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to be computed per second.
\subsection{Bit Depth}
This section should include:\\
The general requirements for digital audio processing systems, DSP
processors\\
dsPIC Development system\\
The audio bit depth determines the accuracy to which amplitudes can be
differentiated. Higher bit depths result in a higher dynamic range in the
signal. This has implications for the converters as higher bit rates
require higher accuracy in generating values for each sample.
\section{Design/Analysis}
This section should include:\\
Design of software, in Flowcode or C for artificial reverberation\\
User Interface - Input from the switches to select Echo, Reverb, or
Chorus effects\\
Effect implementation wase largely dicatated by the limitations of the
dsPIC. As the device had sever memory and processing limitations, it was
not possible to create effects to the standard of the first assignment. As
a result effects were created to emulate the perceptual effect of an echo,
reverb and chorus under these limitations.
\subsection{Echo}
The echo was implemented using a single tap FIR filter. This was intended
to maximise available memory for the delay time. Through stripping out all
unnessesary features, a maximum delay size of 700 samples was acheived with
the addition of two UI switches that could be used for increasing and
decreasing delay size at runtime.
At a samplerate of 8Khz, this allowed for a single delay of \textgreater50ms defined
as the minimum for the definition of an echo
by Z{\"o}lzer~\citeyearpar[p.]{zolzer2011dafx}
\subsection{Chorus}
To emulate the multiple instrument effect created by a chorus, three delays
of variable size were used. This created 3 phase shifted versions of the
original signal which creates the perception of multiple instruments. The
delay time modulation was not possible due to the computational power
required to implement this for modulating a delay time on a sample by
sample basis.
\subsection{Reverb}
The reverb implementation involved a combination of an FIR and IIR filter
as defined by Z{\"o}lzer~\citeyearpar[p.]{zolzer2011dafx}. This performed
poorly when compared to the moorer reverb structure used in assignment 1,
however the complexity of such a structure would require superior
performance in almost all aspects of the system.
The design used created a delayed echo that could act as a crude reverb.
\subsection{User Interface}
The UI was designed using eight switches and the LCD to create a
navigatable menu that can be used for the section of effect, effect
parameters and voculme control. The effect parameter menu is able to update
it's items dynamically based on the active effects. The desired effect can
then be selected by cycling through using repeated presses of the effects
menu button. Parameter varaibles can then be increased and decreased for
the selected effect using two switches.\\
It was not possible to use the UI in conjunction with any actual audio
effect as proper threading of the menu alongside the DSP process was not
possible. Having the menu run in the same thread as signal processing
forced menu logic to complete at signal rate. When this did not occur this
would create unexpected results and graphical error in the LCD as logic was
not completed fully. As a result, the project presented is a prototype to
demonstrate possibilities given a capable system.
Compare to assignment 1\\
\subsection{Echo}
Assignment 1: Variable tap FIR/IIR combination
\subsection{Chorus}
Assignment 1: Full chorus with single varying tap driven by sine wave
\subsection{Reverb}
Moorer reverb delay structure comprising multiple styles of filter
\section{Results}
The results of real-time system implementation section should include:\\
Implementation on dsPIC based system\\