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Propunerea de subiect este al lui Tudor, eu doar il ajut sa treaca pragul analogic catre cel digital. Am sa incep cu un mic dictionar de termeni specifici domeniului. Asa ne va fi mai usor sa evitam viitoarele neintelegeri. ADC: Analogue-to-Digital Converter. This device converts analogue input signals (from, e.g., a microphone) to a digital signal that can be used in computations (for example in a PC program) (Anti-) aliasing filter: Filter designed to remove any signal larger than the Nyquist frequency. Authoring: Process in which the final disc image is created. This includes lossless compression, creation of the table of contents etc.. Clipping: The phenomenon that when a format is designed to handle signal levels no larger than a level C, every level larger than C is coded as C. For example, the digital format on a CD cannot handle more than 65536 sub-levels; any signal corresponding to a level larger than +32767 is represented as +32767 (and likewise for negative signals less than -32768). Clock jitter: Technically the unwanted phase shift of digital pulses over a transmission medium. A discrepancy between when a digital edge transition is supposed to occur and when it actually does occur. DAC: Digital-to-Analogue Converter: the reverse of a ADC. Distortion: Any deviation from a linear input/output relationship, where a linear relationship is defined such that the output equals (apart from a constant gain factor) the input. Dithering: The addition of a (quasi-)random number to the signal which is subsequently quantised. Due to the dither, the quantization appears as an (almost) linear process. DSD: The digital format stored in Super Audio CD. DSD is a format in which 2822400 times per second a 1-bit signal is stored. Lowpass-filtering this signal will restore the original waveform. DST encoding: Direct Stream Digital, a lossless compression algorithm specifically tailored to the lossless compression of DSD signals. Filter ringing: The effect that a filter with a steep transition band in the frequency domain produces artefacts in the time domain that extent over a significant period of time. Idle tone: Tone appearing at the output of a noise shaper that bears a simple relation to the input of the Sigma Delta Modulator. Limit cycle: Signal at the output of a Sigma Delta Modulator that requires a precisely defined input in order to occur, and disappears if the input deviates slightly from the mentioned precise value. Linearity: See distortion. Noise shaping: The shift of spectral content of the (quantization) noise. For example, in a Sigma Delta Modulator the energy of the quantization noise is shifted to high frequencies, leaving no or little noise at low frequency. Nyquist Frequency: The largest frequency that can be represented by a digital format; the Nyquist frequency is half the sample frequency. PCM: Pulse Code Modulation. A digital format, used for example in CD, whereby a digital signal is represented by an accurate representation (e.g., 16 bits, meaning that the range -1,+1 is subdivided in 65536 sub-intervals) of the wave form at equidistant points in time (for example, in CD 44100 times per second a 16-bit approximation of the wave form is stored). Pulse Density Modulation: A form of pulse modulation where a large positive signal is represented by a long series of positive pulses; a zero signal is represented by alernating positive and negative pulses. (Re-)Quantization: The mapping of a signal of infinite precision to a signal with limited precision. On a CD, e.g., a signal is quantized to 16 bits. Sigma Delta Modulator: Device which transforms an analogue or PCM signal in a DSD signal. Often abbreviated to SDM, and also often referred to as Delta Sigma Modulator. Super Audio CD: Super Audio Compact Disc. Format for music distribution proposed by Philips and Sony. Super Audio CD is based on a new digital format called DSD. Topology: Particular way of connecting building blocks to create a circuit. Up/Down sampling: A signal processing technique whereby the sample rate of a digital signal is enlarged or reduced. In the latter case, this also corresponds to a loss of information.