Computers π» | Text, sounds, images | 1.2 Flashcards
How do we hear sound?
When sound is created, a continuously changing wave of vibrations travels through the air towards our ears, where we are able to βhearβ it.
A sound wave is usually represented by _
A curving line.
What does the height of a sound wave represent?
The height of the curving line represents how loud the sound is and is called the amplitude. The
higher the amplitude (i.e. the taller the wave), the louder the sound is.
What is the number of waves that occur in a period of time called?
The number of waves that occur in a period of time is called the frequency. The higher the frequency (i.e. the closer together the waves are), the higher pitch the sound is
What is sampling?
Sampling is the process whereby an analogue wave is converted into a digital signal. At specific intervals of time, measurements of the amplitude of the wave are taken and stored as a binary value
The sound recorded at each sample point is converted to _
Its nearest binary equivalent.
What is the sample rate?
Sample rate is the number of samples recorded in any given period of time. The higher the sample
rate, the closer the recorded signal is to the original.
What is sample rate measured in?
Hertz (Hz)
The higher the sample rate, the larger the resulting _
However, the higher the sample rate, the larger the resulting file. As a result, sound files are often
a compromise between quality and size of file.
What is an audio file usually recorded at?
An audio file is usually recorded at 44.1 kilohertz. This is high enough for good sound quality while
keeping file size down to sensible levels.
What is the sample resolution?
Sample Resolution refers to the number of bits used to record each sample. In other words, this is
the number of bits used to store each measurement of amplitude.
What is the CD sample resolution?
16 bits
What is the reccomended high quality sample resolution?
The recommendation is to record it using 24 bits to gather over 16 million possible measurements of amplitude.
What is the bit rate?
A measure of how much data is processed for each second of sound.
How is the bit rate calculated?
Bit rate = sample rate x bit depth
What is the formula for the file size of audio?
File size (bits) = Sampling Rate X Resolution X Time in Seconds
Why is the formula for file size not always the full file size?
There is always metadata stored with the sound file, which allows the computer to know what the sample rate and resolution is to allow it to play the sound more accurately. This increases the file size in general
Images are also represented as _
Binary
Images are either _
Bitmap or vector
What are bitmap images made of?
Bitmap images are made of small parts called
pixels
What are vector graphics made of?
Vector images are made using coordinates and
geometry.
What is a pixel?
A pixel is the smallest unit (picture element) of a digital image or graphic that can be displayed and represented on a digital display device.
What is resolution?
Resolution is a measure of pixel density, usually measured in pixels per inch (ppi), which refers to how many pixels are displayed per inch of an image.
What is the ppi of most images on websites?
72ppi
Higher resolution images look _
Higher resolutions look better. There are more pixels per inch (PPI), resulting in more pixel information and creating a high-quality, crisp image.
Lower resolution images look _
Images with lower resolutions look worse because they have fewer pixels, and if those few pixels are too large
(usually when an image is stretched), they can become visible
What is color depth?
Many images need to use colours. To add colour, more bits are required for each pixel. The number of bits determines the range of colours. This is known as an imageβs colour depth.
The more colour an image requires, the _
The more colours an image requires, the more bits per pixel are needed. Therefore, the more the colour depth, the larger the image file will be.
How is image file size calculated?
Image file size = pixel count x bit depth
What is data storage capacity?
Data storage capacity is the measurement of how much data can be stored in a storage device.
What are data storage capacities measured in?
Data storage capacities are measured in bytes.
How many bytes is 1 petabyte?
10^15 bytes
How many bytes is 1 exabyte?
10^18 bytes.
What is the ISU?
International system of units. Each unit of measurement is 1000 times bigger than the unit before it.
What is the IEC?
International Electrotechnical Commission. Unlike the ISU, Each unit of measurement is 1024 times bigger than the unit before it
What is data compression?
Data compression is the process of encoding, restructuring or otherwise modifying data to reduce its size. Fundamentally, it involves re-encoding information using fewer bits than the original
representation.
Compression is done by _
Compression is done by a program that uses functions or an algorithm to effectively discover how
to reduce the size of the data.
How does file compression help storage space and processing power?
Processing power and storage space is very valuable on a computer we need to get the best out of both by reducing the file size of text, image, and audio data to transfer it more quickly and take up less storage.
How does file compression aid the internet?
Large files take a lot longer to download or upload, leading to web pages, song, and videos taking a lot longer to load and play when using the internet. Data compression can make it so that the files that are down/uploaded are a lot smaller.
What are the main advantages of data compression?
- Reductions in storage hardware
- Reduction in data transmission time
- Communication bandwidth.
Consuming less network bandwith and reductions in storage hardware means _
Significant costs savings
How do text files undergo file compression, simply?
Repeats words and sections of words are put into a data dictionary and replaced with βkeysβ for each of them.
What are the two kinds of data compression?
Lossy and lossless.
What is lossless compression?
Lossless compression reduces the size of a file without any damage to the file or reduction in quality.
The file can be decompressed to its original state, with all the data bits reconstructed.
What file types use lossless compression?
PNG, GIF, and ZIP files.
How does lossless compression work?
It makes use of repetition and patterns. A compression algorithm is used to find repreated words or patterns within the data, replaced with numeric values.
What is lossy compression?
Lossy compression permanently removes data from the file that the computer believes you can do without (redundant data). We can hardly notice the difference.
What is lossy compression best for?
Creating really small file sizes, ideally for downloads or streaming.
What file types use lossy compression?
MP3, MP4 and JPG.
What is lossless compression ideal for?
Text or numeric files where a loss of data is unacceptable (eg: spreadsheets)
