Explanation:-- CLV: The CD player is also known as CLV or constant linear velocity system . In a CLV device such as the CD player the rotational speed of disc player is adjusted with movement of reading mechanism on the disc surface . This speed is changed to maintain constant linear velocity i.e. the signal on the disc surface always moves at constant speed of 1.3 m per second under the pick-up head.
Half-Full Memory: This half –full memory circuit makes the disc to maintain a constant linear velocity when the reading mechanism moves from outer tracks of disc to inner tracks or from inner tracks to outer tracks on disc surface.
Decoding CD: During the decoding , the digital data on the disc surface is read by the decoding circuit and is converted into the analog and that signals are required to drive the speakers and regenerate the stored music. Optical pick-up: The signal stored on the CD surface as pits and flat areas are first picked up by the optical pickup made of lens assembly, prism , photo detectors and laser diodes assembly in the optical pickup unit. High frequency amplifier: The signal is very weak so it is amplified by a high frequency RF amplifier circuit to bring signal to a proper level. This amplified and filtered high-frequency signal contains audio signal as well as synchronization signal in 14-bit EFM (eight to fourteen modulation)format , this signal is sent to an EFM demodulator circuit. EFM Demodulator: The EFM modulator separates the modulated data and the timing signal from the signal received at its input. It also removes the additional coupling bits and converts the 14-bit EFM symbol to actual 8-bit data. The amplified and filtered EFM signal from high frequency amplifier is also given to clock generation circuit to synchronize detecting and timing circuit. These circuits are used to recover the bit clock and sync pattern data .The timing separated by this system is used to provide timing signal to the system. ERCO Circuit: Demodulated data from EFM demodulator is send to error correction (ERCO)circuit. The demodulated data signals also send to control and display decoding circuit, which recovers the control and display signals which are further multiplexed into signals received from CD. The ERCO circuit mainly used for the error correction & detection. The ERCO circuit will communicate with servo microprocessor to reduce the error generated during CD scanning. Interpolation and muting: The ERCO circuit is used for error detection and correction purpose. Any error found in the incoming data signal is send to interpolation and muting section by the ERCO circuit . The interpolation and muting section uses the following methods to correct error found in data stream read from the disc. CLV using the Clock Signal: The ERCO also responsible for maintaining constant linear velocity of CD rotation motor , For this , The ERCO circuit compare the clock signal derived from the incoming data with reference clock frequency. De- interleaving : Signals from the ERCO contains audio signal in the interleaved format . Before doing any further operation on this signal, it must be interleaved. The signal is then de-interleaved in the interpolation and muting section to restore the original sequence of information. Digital Filter and De-multiplexer: The de-interleaved and regenerated is then send to digital filter and de-multiplexer , where it is filtered and separated in to left and right channel data. This circuit removes any effect of sampling frequency from the data signal , which would appear as interference in the form of aliasing noise in analog signal. Oversampling: During digital filtering oversampling method is used to remove both problems of aliasing noise and quantization error . D/A convertor: The output from digital filter and de-multiplexer circuit is send to D/A convertors. The right and left channels are processed by different D/A convertors. These convertors convert the 16-bit digital signal into the original analog audio signal. Because of the over sampling , done in the digital filter and de-multiplexer circuit simple low-pass filter is used following the D/A process. Stereo Amplifier: The analog output from converter is passed through a sample & hold circuit & a LPF circuit to obtain a smooth noise free output at the speakers. These signals are next fed to a stereo audio amplifier to raise left & right audio channel signal.