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© 2003 Wayne Wolf Compact disc players zDevice characteristics. zHardware architectures. zSoftware.

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Presentation on theme: "© 2003 Wayne Wolf Compact disc players zDevice characteristics. zHardware architectures. zSoftware."— Presentation transcript:

1 © 2003 Wayne Wolf Compact disc players zDevice characteristics. zHardware architectures. zSoftware.

2 © 2003 Wayne Wolf CD audio z44.1 kHz sample rate. z16 bit samples. zStereo. zAdditional data tracks.

3 © 2003 Wayne Wolf Compact disc zData stored on bottom of disc: substrate aluminum coating plastic coating

4 © 2003 Wayne Wolf CD medium zRotational speed: m/s (CLV). zTrack pitch: 1.6 microns. zDiameter: 120 mm. zPit length: microns. zPit depth:.11 microns. zPit width: 0.5 microns. zLaser wavelength: 780 nm.

5 © 2003 Wayne Wolf CD layout zData stored in spiral, not concentric circle:

6 © 2003 Wayne Wolf CD mechanism zLaser, lens, sled: laser CD detectors diffraction grating sled track focus

7 © 2003 Wayne Wolf Laser focus zFocus controlled by vertical position of lens. zUnfocused beam causes irregular spot: In focusOut of focus

8 © 2003 Wayne Wolf Laser pickup A B C D F E Side spot detectors Level: A+B+C+D Focus error: (A+C)-(B+D) Tracking error: E-F

9 © 2003 Wayne Wolf Servo control zFour main signals: yfocus 245 kHz; ytracking 245 kHz; ysled 800 Hz; yDisc motor. Optical pickup

10 © 2003 Wayne Wolf EFM zEight-to-fourteen modulation: yFourteen-bit code guarantees a maximum distance between transitions

11 © 2003 Wayne Wolf Error correction zCD capacity: 6.99 GB raw, 700 MB formatted. zReed-Solomon code:  g(x) = (x-  ) (x-  2 ) … (x-  n-k-1 ) (x-  n-k ) zProduces data, erasure bits. zTime to solve varies greatly depending on noise. zCD interleaves Reed-Solomon blocks to reduce effects of large data gaps.

12 © 2003 Wayne Wolf CIRC encoding zCross-interleaved Reed-Solomon coding. yInterleaves to reduce burst errors. zEach 16-bit sample split into two 8-bit symbols. zSpecs: yMax correctable burst: 4000 bits = 2.5 mm yMax interpolatable burst: 12,300 bits = 7.7 mm

13 © 2003 Wayne Wolf CIRC algorithm zSample split into two symbols. zSix samples from each channel (=24 symbols) are chosen. zSamples are delayed and scrambled. zParity symbols (Q symbols) are generated. zValues are delayed by various amounts. zP parity symbols are generated. zEven words delayed by one symbol, P and Q words are inverted. zFrame = 32 8-bit symbols.

14 © 2003 Wayne Wolf Control word z8-bit control word for every 32-symbol block: yP: 1 during music/lead-in, 0 at start of selection. yQ: track number, time, etc (spread over 98 bits). yR, S, T, U, V, W: reserved.

15 © 2003 Wayne Wolf Control and error correction zSkips caused by physical disturbance. yWait for disturbance to subside. yRetry. zRead errors caused by disc/servo problems. yDetect error. yChoose location for retry. yRetry. yFail and interpolate.

16 © 2003 Wayne Wolf Retry problems zData is stored in a spiral. yCan’t seek track as on magnetic disc. ySled servo is very coarse. zData is only weakly addressed. yMust read data to know where to go.

17 © 2003 Wayne Wolf Audio playback zAudio CD needs no audio processing. zTasks: yconvert to analog; yamplify.

18 © 2003 Wayne Wolf Digital/analog conversion z1-bit MASH conversion: interpolation noise shaping PWMintegrator

19 © 2003 Wayne Wolf MP3 zDecoding is easier than encoding, but requires: ydecompression; yfiltering. zBasic CD standard for data discs. zNo standards for MP3 disc file structure: player must understand Windows, Mac, Unix discs.

20 © 2003 Wayne Wolf Jog/skip memory zRead samples into RAM, play back from RAM. zModern RAMs are larger than needed for reasonable jog/skip. zJog memory saves some power.

21 © 2003 Wayne Wolf CD/MP3 player Audio CPU amp Jog memory Error corrector Servo CPU Analog in Analog out FE, TE, amp focus, tracking, sled, motor head drive memory display DAC I2SI2S

22 © 2003 Wayne Wolf DVD format zSimilar to CD, but: yshorter wavelength laser; ytighter pits; ytwo layers of data.

23 © 2003 Wayne Wolf Audio on DVD zAlternatives: yMP3 on data DVD (stereo). yAudio track of video DVD (5.1). yDVD audio (5.1). ySACD (5.1).

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