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[svn r75] presentation for wednesdaty
author rlm
date Wed, 12 May 2010 02:25:34 -0400
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73:0f86d486e38e 74:31fef269ae58
1 #LyX 1.6.4 created this file. For more info see http://www.lyx.org/
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38 \author ""
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40 \end_header
41
42 \begin_body
43
44 \begin_layout Title
45 Pygar: Parallel Audio Processing
46 \end_layout
47
48 \begin_layout Author
49 Laurel Pardue, Robert McIntyre
50 \end_layout
51
52 \begin_layout Subsection*
53 Problem
54 \end_layout
55
56 \begin_layout Standard
57 Music naturally comes in parallel sequences of samples called
58 \emph on
59 voices
60 \emph default
61 (ex.
62 from multiple instruments).
63 Pure-software mixers are forced to pass these voices through the Von Neuman
64 bottleneck of a single processor, operating on these streams in series
65 and switching between each one quickly.
66 They are therefore naturally limited in the number of voices they can handle.
67 Worse, since the processing of each voice has to share the same processor,
68 too many voices at once can fully max out the processor and crash the system.
69 On typical laptop hardware and a high end software tool like ProTools,
70 this number is around 5.
71 Embedded devices have an even tougher time at meeting any sort of reasonable
72 timing requirements.
73 \end_layout
74
75 \begin_layout Standard
76 [screenie Just 6 voices are enough to bring this session of ProTools to
77 it's knees.]
78 \end_layout
79
80 \begin_layout Standard
81 We want the power of writing transforms for voices in a high level language
82 combined with a framework that applies these transforms to the voices in
83 parallel.
84 \end_layout
85
86 \begin_layout Subsection*
87 Vision --- Pygar
88 \end_layout
89
90 \begin_layout Standard
91 Our system addresses the limitations of pure software mixers.
92 It is a grid of SMIPS processors capped by a mixer.
93 The voices flow through the processors in parallel and are combined at
94 the final mixer into a single stream.
95 Each processor can be loaded with any arbitrary C program.
96 \end_layout
97
98 \begin_layout Standard
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107 filename ../../../../Pygar/documents/000402.png
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110 \end_inset
111
112
113 \begin_inset Caption
114
115 \begin_layout Plain Layout
116 The audio data (“samples”) start in the memory, but are soon pulled into
117 action by the DMA (direct memory access).
118 The DMA sends the samples to a chain of 0 or more soft-cores, where they
119 are transformed according to the soft-cores’ algorithms.
120 After running the gauntlet of soft-cores, the samples flow first to a buffering
121 FIFO, and finally to a mixer, which sends the samples off to be played
122 by speakers or stored in a file.
123
124 \end_layout
125
126 \end_inset
127
128
129 \end_layout
130
131 \begin_layout Plain Layout
132
133 \end_layout
134
135 \end_inset
136
137
138 \end_layout
139
140 \begin_layout Subsection*
141 Steps
142 \end_layout
143
144 \begin_layout Standard
145 The difficult part of this project is managing code reuse.
146 We need three things for success.
147
148 \end_layout
149
150 \begin_layout Itemize
151 SMIPS processor -- Easy.
152 Just use the Lab 5 processors.
153 \end_layout
154
155 \begin_layout Itemize
156 Some way to program the processors
157 \end_layout
158
159 \begin_layout Itemize
160 DMA (Direct Memory Access) to load voices into the processors.
161 \end_layout
162
163 \begin_layout Standard
164 We use ScratchPad to load code into the processors.
165 ScratchPad is an Intel module which implements a cache hierarchy.
166 The hierarchy reaches all the way from RAM created on the FPGA to on-chip
167 DRAM to RAM on the host computer all the way to the Hard Disk of the host
168 computer.
169 The first time a processor tries to access one of its instructions, the
170 cache goes all the way to the hard disk of the host computer to retrieve
171 the data.
172 Subsequent attempts to access this data only go as far as the on-chip DRAM.
173 Each processor has its own ScratchPad and thus can be programmed independently.
174 The ScratchPad abstraction allows each processor to run a program of any
175 size.
176 \end_layout
177
178 \begin_layout Standard
179 Music access is achieved through RRR, another Intel abstraction which allows
180 us to treat the hard disk of the host computer as if it were a normal FIFO.
181 \end_layout
182
183 \begin_layout Subsection*
184 News
185 \end_layout
186
187 \begin_layout Standard
188 We have run our system with 12 sample voices and various combinations of
189 simple c voice processing programs and the results have been better than
190 software implementations.
191 Significantly, increasing the number of voices does not increase the processing
192 load since each voice is processed in parallel.
193 \end_layout
194
195 \begin_layout Subsection*
196 Contributions
197 \end_layout
198
199 \begin_layout Itemize
200 Implemented Pygar, a system for quick parallel processing of audio.
201
202 \end_layout
203
204 \begin_layout Itemize
205 Implemented 4 basic algorithms which serve as components for this system
206 (identity, bit-shift, volume-change, and delay)
207 \end_layout
208
209 \begin_layout Itemize
210 Demonstrated Pygar out-performs software-only systems.
211 Pure-software systems have a limit of around 6 voices, while our system
212 achieves 12 voices in parallel with no architecturally imposed limit on
213 the number of voices.
214 \end_layout
215
216 \end_body
217 \end_document