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Speaker Optimization Circuit (SOC)

Speaker Optimization Circuit (SOC). ECE 445, Group 13 Joe Lee and Steve Meadows April 23, 2008. Introduction. The SOC can be used to provide a better Dolby Digital 5.1 Surround Sound experience

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Speaker Optimization Circuit (SOC)

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  1. Speaker Optimization Circuit (SOC) • ECE 445, Group 13 • Joe Lee and Steve Meadows • April 23, 2008

  2. Introduction • The SOC can be used to provide a better Dolby Digital 5.1 Surround Sound experience • Utilizes a TMS320VC5510/5510A Fixed-Point Digital Signal Processor along with a microphone, and a custom built remote control and analog multiplexer. • DSP coding done in C and Assembly.

  3. DD 5.1 Surround Sound Basics • A quick introduction for those who may be unfamiliar with the system. • 6 speakers total: 4 channel speakers (cs1-4), 1 center channel speaker (cc), and 1 sub woofer. • Normal setup:

  4. DD 5.1 Surround Sound set up • This is the “ideal” set up. Note the distance ratios. • Channel speakers aligned in a square with side length D. Center channel speaker placed exactly in between cs1 and cs2. Listening point in the center of the square. • Shown on next slide.

  5. Objective • The SOC “remixes” the amplifier output (by adding gains) to make it sound as if each speaker is ideally placed. • New set up shown on next slide.

  6. New set up

  7. Design Overview • The SOC is connected between the amplifier and the 4 channel speakers. • For each channel speaker, it determines the actual distance relative to the point of listening. Note: distance to the center channel speaker must be specified (hard coded). • The ratio of actual/ideal distances can be used to compute a gain for each channel.

  8. However... • The final implementation uses a ratio of intensity values instead of a ratio of radius values. Why is that?

  9. Acoustics theory (brief) • Intensity=(Sound Power)/(4*pi*r^2) • Goal: Ia=Ii => Define a gain K, such that Ia=K*Ii => Ia=Ii (Ia=actual intensity, Ii=ideal intensity). • Due to hardware limitations, this imposes a constraint that Ii >= Ia. • This constraint is explained in terms of actual radius limitations on the next slide.

  10. Speaker placement constraint

  11. System Block Diagram • Shown on next slide. • Following slide shows a picture of the SOC.

  12. The SOC

  13. Components • DSP • Microphone • Remote control • Analog multiplexer • DD 5.1 Surround Sound System

  14. Component details: DSP • TMS320VC5510/5510A Fixed-Point Digital Signal Processor(same board used with ECE 420). • Most programming done in C (main.c), but also some Assembly (filtercode.asm). • “Core” component. • Picture on next slide.

  15. DSP

  16. Component details: microphone • Fico CMP-808 Computer Microphone • Used to read intensity value of received signal during calibration. Sends this value to the DSP for computations. • Picture on next slide.

  17. Microphone

  18. Component details: remote control Sends control signals to the DSP. • Uses two buttons (serial signals) to encode 3 modes of operation. • These are: normal operation, calibration, and reset. • Picture on next slide. Block diagram on slide after.

  19. Remote control

  20. Remote control schematic

  21. Component details: analog mux Used to select between incoming signals from the surround sound amplifier and the microphone.

  22. Component details: DD 5.1 system • COBY DVD-755 Home Theatre System • Output power: 20W, max (sound power)

  23. Tests performed • Test 1: test ability to pass a signal through the DSP unmodified. • See oscilloscope output on the next slide. Channel 1 (above) is DSP output, channel 2 (below) is input signal.

  24. Test 1 results (1)

  25. Test 1 results (2)

  26. Tests performed (cont.) • Test 2: test ability to send a tone through each speaker (used during calibration). • See oscilloscope output on the next slide. • Vpp~2V, T~2ms • Picture of waveform on next slide.

  27. Test 2 results

  28. Tests performed (cont.) • Test 3: test ability to calculate amplification factors based on received intensity value and hard coded ideal intensity value. • Ideal intensity: 15854 (0.4838), Received intensity: 20853 (0.6364) => K=24912 (0.7603=0.4838/0.6364) • See debugging output on next slide.

  29. Test 3 results

  30. Tests performed (cont.) • Test 4: test ability to add a gain to input signal. • See oscilloscope output on the next few slides. Channel 1 (above) is DSP output, channel 2 (below) is input signal. • Results show are with gains of ~.7, ~.5, ~.2

  31. Test 4 results (gain ~.7)

  32. Test 4 results (gain ~.5)

  33. Test 4 results (gain ~.2)

  34. Successes • All 4 tests described were successful. • Most important components functioning properly.

  35. Challenges • Neither of us had previous experience programming a DSP. • No floating point processor. 16Bit gain values must be less than 1 (added constraint). • Custom built hardware compatibility issues. • Calibration happens to quickly for the microphone to get a good reading.

  36. Recommendations • Use a DSP with more (at least 6) inputs so as not to impose constraints. • Make calibration take longer.

  37. End • Thank you for viewing our presentation!

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