Sound
Sampling an analogue wave: sample rate, bit depth, quality against file size.
Transcript
Sound is analogue: a smooth wave that changes continuously. A computer can only store digital values, so it has to measure the wave.
This is called sampling. The wave is measured at regular intervals, and each measurement, called a sample, is stored as a binary number.
The sample rate is the number of samples taken every second, measured in hertz. A CD takes forty four thousand one hundred samples every second.
The sample resolution, or bit depth, is the number of bits used for each sample. More bits means each sample is more accurate.
A higher sample rate and a higher bit depth sound closer to the original, but they make the file bigger.
Sound file size is the sample rate, times the bit depth, times the length in seconds. Eight thousand hertz, eight bits, for five seconds, is forty thousand bytes.
Measure the wave, store each sample in binary. More samples and more bits sound better, and cost more space.
More in this series
2:41Denary, binary and hexadecimal
Place values, converting denary to binary and back, and why hex is used for bytes.
2:30Binary addition, overflow and shifts
Adding binary numbers with carries, overflow when a ninth bit is needed, and logical shifts as multiply and divide.
2:12Two's complement
Negative numbers in binary: the -128 place value, invert and add one, and reading a signed byte.
1:45Text: ASCII and Unicode
Character sets give every character a code. ASCII's 128 codes, Unicode's millions, and the storage trade-off.
1:27Images
Pixels, resolution, colour depth, image file size and metadata.
1:50Storage units and file sizes
Bit to pebibyte in steps of 1024, and calculating image and sound file sizes.
1:58Compression
Why files are compressed, lossy against lossless, and run-length encoding step by step.
5:38Unit 1 quiz
Ten questions with a think-time countdown and explained answers.