Date post: | 19-Dec-2015 |
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What is the iAMP?
It’s interactive: the iAMP is an FPGA-based processor that lets YOU perform real-time manipulation of an input audio source.
More specifically, using a joystick, the user can graphically position the location of a sound source (such as a CD player) in real-time.
Overview
Physical Setup User Interface
video output joystick input
Audio Path audio cues how iAMP localizes sound
A-D and D-A
iAMP Setup
iAMP(Altera UP1)
D/A 1
D/A 2
A/DAudioSource
VGA Monitor joystick
AudioAmp
Left
Right
Left
Right
Rear
Front
Design Overview
Audio_Manipulator.vhdAdc_port.vhd
Ram_interface.vhd
Ram_port.vhd
Dac_port.vhd
Dac_port.vhd
Joystick.vhd Video.vhdUI.vhd
Dac_interface.vhd
Dac_interface.vhd
Main.vhd
Top-Level UI Interface
videoui
vga_red
vga_green
vga_blue
vga_h_sync
vga_v_sync
cursorY
cursorX
clock
vga_red
vga_green
vga_blue
vga_h_sync
vga_v_sync
mainclock
Video Interfaceclock
video
vga_red
vga_green
vga_blue
vga_h_sync
vga_v_sync
cursorX
cursorY
ColourChooser
countXcountY
count_xysyncgen HSync
VSync
Joystick
1
6789
5 4 3 2
Female DB-9
pin # function
1 up2 down3 left4 right5 unused6 button7 unused8 ground
9 unused
Audio Cues
What techniques exist to ‘fool’ the ear?
Auditory mechanism isn’t capable of understanding the environment as a domain.
Headphones -- externalization of sound.
We can take advantage of these weaknesses!
Audio Cues
Ears use many cues to comprehend its surrounding.
Binaural Intensity Difference Binaural Phase Difference Cone of Confusion Outer Ear Frequency Response Reverberation
Audio Cues
Binaural Intensity Difference BID aids the individual to localize sound by the
difference in signal intensity between the two ears.
Sound appears to originate from direction of higher intensity.
10 dB (10:1) difference required to place sound 45o to one side.
Binaural Phase Difference Not often used - only effective for pure sinusoidal
waves <1500 Hz.
Audio Cues
Cone of Confusion The ear cannot directly perceive whether a
sound is coming from ahead or behind, when source is to one side of the median plane. Any sound source along the edge of the “cone of confusion” is indistinguishable from any other sound source along the edge.
Audio Cues
Outer Ear Frequency Response Reverberation
Sounds closer to the ear have lower intensity echo signals vs. incident intensity.
Echoes and reverberation fool the brain into thinking a sound is farther away than it really is.
More echo means more diffused sound path to ear = farther away.
Sound Model
How does iAMP create the sound “location”?
Gain differences between speaker outputs. Echo created by delayed samples kept in RAM.
Our Simplified Model Multiplying 24-bit samples takes up too much
space! Simplified linear models applied. Not as
accurate, but saves lots of space on Flex 10K20!
Audio Path
RAM
D/A 1
A/D
D/A 1
Audio_Manipulator.vhdAdc_port.vhd
Ram_interface.vhd
Ram_port.vhd
Dac_port.vhd
Dac_port.vhd
Audio Manipulation
Sequentially capture 8 samples per sample period from RAM Sample Stack
4 ‘incident’ delayed samples (initial wavefronts) 4 ‘echo’ delayed samples (reflected wavefronts)
Multiply each sample by gain (1/16 to 15/16) Provides 11.8 dB Binaural Intensity Difference (> 10 dB)
“Mix” the echo and incident samples, output to DACs for conversion out to speakers.
(Really summing…)
Audio Manipulation
Audio Controller
Register Bank Register BankRegister Bank
sample_req
data_ready
delay
sample_in
X_loc Y_loc System_clock Sample_clock
sample_clock
gain
FL Speaker
FR Speaker
RL Speaker
RR Speaker
Speaker Gain vs. Cursor Location (/16)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 151 15 14 13 12 11 10 9 8 7 6 5 4 3 2 12 14 14 13 12 11 10 9 8 7 6 5 4 3 2 13 13 13 13 12 11 10 9 8 7 6 5 4 3 2 14 12 12 12 12 11 10 9 8 7 6 5 4 3 2 15 11 11 11 11 11 10 9 8 7 6 5 4 3 2 16 10 10 10 10 10 10 9 8 7 6 5 4 3 2 17 9 9 9 9 9 9 9 8 7 6 5 4 3 2 18 8 8 8 8 8 8 8 8 7 6 5 4 3 2 19 7 7 7 7 7 7 7 7 7 6 5 4 3 2 110 6 6 6 6 6 6 6 6 6 6 5 4 3 2 111 5 5 5 5 5 5 5 5 5 5 5 4 3 2 112 4 4 4 4 4 4 4 4 4 4 4 4 3 2 113 3 3 3 3 3 3 3 3 3 3 3 3 3 2 114 2 2 2 2 2 2 2 2 2 2 2 2 2 2 115 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
Similar for all four speakers.
Time Delay vs. Cursor Location ()
1 2 3 4 5 6 7 8 9 10 11 12 13 14 151 0 1 2 3 4 5 6 7 8 9 10 11 12 13 142 1 2 3 4 5 6 7 8 9 10 11 12 13 14 153 2 3 4 5 6 7 8 9 10 11 12 13 14 15 164 3 4 5 6 7 8 9 10 11 12 13 14 15 16 175 4 5 6 7 8 9 10 11 12 13 14 15 16 17 186 5 6 7 8 9 10 11 12 13 14 15 16 17 18 197 6 7 8 9 10 11 12 13 14 15 16 17 18 19 208 7 8 9 10 11 12 13 14 15 16 17 18 19 20 219 8 9 10 11 12 13 14 15 16 17 18 19 20 21 2210 9 10 11 12 13 14 15 16 17 18 19 20 21 22 2311 10 11 12 13 14 15 16 17 18 19 20 21 22 23 2412 11 12 13 14 15 16 17 18 19 20 21 22 23 24 2513 12 13 14 15 16 17 18 19 20 21 22 23 24 25 2614 13 14 15 16 17 18 19 20 21 22 23 24 25 26 2715 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
is a time constant based on the speed of sound and the distance between speakers.
Total Loudness
1 3 5 7 9
11 13 151
6
11
-2.5
-2
-1.5
-1
-0.5
0
0.5
Total Normalized Volume (dB)
X location
Y location
A/D Converter
CRYSTAL CS5360 24-Bit Stereo A/D Converter for Digital Audio
24-bit samples -- for 16 or 8 bit sampling, we take the most significant bits (Big-Endian -- the first 16 or 8 bits.)
D/A Converter
CRYSTAL CS4390 24-Bit Stereo D/A Converter for Digital Audio
24-bit samples -- for 16 or 8 bit sampling, we take the most significant bits (Big-Endian -- the first 16 or 8 bits.)