Methods For Digitising Analog Data

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Methods For Digitising Analog Data

Post  admin on Tue 27 Jul 2010, 8:25 am

Sampling is where analogue data are converted into digital data.
Sampling size sets the range to which the data can be recorded, e.g. bit depth.
Sampling rate measures how many measurements are performed every second.

To digitize video data, a video digitizer measures and records signals that represent colours and light intensities.
A video capture card can also be used. It captures each frame as a bit-mapped image and then compresses the video clip using an algorithm that analyses the changes from one frame to the next.

In an optical scanner, an intense beam of light is shined at a document, and the detectors inside the scanner measure the intensities and colours of the reflected light. Analogue to digital converters turn these measurements into digital bit patterns that can be stored.
Digital cameras use a viewfinder, a lens and a storage medium to capture images. A video digitizer can be used to make measurements of a signal, converting them into bit patterns.

Sound is digitised by taking regular measurements of the amplitude (volume) and wavelength (pitch) of the sound. Normally, this sound is collected from a microphone, which can be connected to a sound card in a computer.
The number of measurements taken per second is the sampling rate. The higher the sampling rate, the better the quality of the sound recorded. Commonly used sampling rates for sound are 22.05 kHz, suitable for human speech, and 44.1 kHz, suitable for music and audio CD’s.
A rule for audio digitising is that the samling rate should be at least twice the frequency of the highest pitch sound to be recorded.


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