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Sampling

Before digital recording took over the audio and video industries, everything was recorded in analog. Audio was recorded to devices like cassette tapes and records. Video was recorded to Beta and VHS tapes. The media was even edited in analog format, using multichannel audio tapes (such as 8-tracks) for music, and film reels for video recordings. This method involved a lot of rewinding and fast-forwarding, which resulted in a time-consuming process.

Fortunately, digital recording has now almost completely replaced analog recording. Digital editing can be done much more efficiently than analog editing and the media does not lose any quality in the process. However, since what humans see and hear is in analog format (linear waves of light and sound), saving audio and video in a digital format requires converting the signal from analog to digital. This process is called sampling.

Sampling involves taking snapshots of an audio or video signal at very fast intervals ? usually tens of thousands of times per second. The quality of the digital signal is determined largely by the sampling rate, or the bit rate the signal is sampled at. The higher the bit rate, the more samples are created per second, and the more realistic the resulting audio or video file will be. For example, CD-quality audio is sampled at 44.1 kHz, or 44,100 samples per second. The difference between a 44.1 kHz digital recording and the original audio signal is imperceptible to most people. However, if the audio was recorded at 22 kHz (half the CD-quality rate), most people would notice the drop in quality right away.

Samples can be created by sampling live audio and video or by sampling previously recorded analog media. Since samples estimate the analog signal, the digital representation is never as accurate as the analog data. However, if a high enough sampling rate is used, the difference is not noticeable to the human senses. Because digital information can be edited and saved using a computer and will not deteriorate like analog media, the quality/convenience tradeoff involved in sampling is well worthwhile.

Tech Factor:
Updated: November 6, 2006
Category: Technical Terms