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Computer Science > Digital Media > Flashcards

Digital Media Flashcards

1
Q

What is a transducer?

A
  • Electronic device that converts energy from one form to another
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2
Q

What are examples of transducers?

A

-Microphones, loudspeakers, thermometers, position and pressure sensors and antenna

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3
Q

What does a transducer do?

A
  • Converts audio (sound waves-analog) to electrical signals (digital) that can be stored in a computer
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4
Q

What are two ways of creating audio?

A
  1. Sampling

2. Synthesis

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5
Q

What is sampling?

A
  • A step used in converting an analog signal to a digital signal
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6
Q

What is synthesis?

A
  • Artificial sound produced from mathematical equations
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7
Q

What are the two steps of sampling?

A
  1. Take snapshots are regular intervals
  2. Truncation or Quantization: Lossy compression technique achieved by compressing a range of values to a single quantum value.
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8
Q

What is a period?

A
  • The time interval between two waves
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9
Q

How to find the amplitude and what it does relate to?

A
  • The distance between the center line of the function and the top or bottom of the function,
  • Relates to intensity of sound (loud or soft)
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10
Q

What is frequency?

A
  • Describes the number of waves that pass a fixed place in a given amount of time.
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11
Q

How to find the frequency?

A

1/ period

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12
Q

What is frequency related to?

A
  • Perceived pitch
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13
Q

What does phase relate to?

A
  • Can depend on the relative location of the sound
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14
Q

What is dB-SPL(sound pressure level) equal to?

A

20 log10 (sound/threshold)

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15
Q

What is the frequency limit that humans can hear?

A

16-20 Hz and as people get older, the range becomes lower

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16
Q

What does digitizing sound involve?

A

-Involves taking samples (measurements) at a fixed rate (sampling rate) and recording them

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17
Q

What does the Nyquist Shannon Therom state?

A
  • The sampling rate must be equal to or greater than twice the highest frequency in the signal.
  • The period or interval of your sample should be less than half of the original signal
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18
Q

What are three examples of CODECS

A
  1. FLAC (Free Loseless Audio Codecs)
  2. MP3 (Moving Pictures Experts Group)
  3. AAC (Advanced Audio Coding)
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19
Q

What is FLAC? (only lossless)

A
  • Most common lossless algorithm but it not as effective

- Used for archiving high quality audio

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20
Q

What is MP3?

A
  • Lossy compression
  • Uses psychoacoustics, Huffman encoding, and lower bit rates
  • Popular on most mobile devices
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21
Q

What is AAC?

A
  • Lossy compression
  • Uses psychoacoustics, Huffman encoding, and lower bit rates
  • Better perceived quality than MP3
  • Popular on Apple devices and most smartphones
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22
Q

What are three types of audio compression techniques?

A
  1. Lossy
  2. Lossless
  3. Codecs
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23
Q

What is lossless audio compression?

A
  • Compression technique that does not lose any data in the compression process.
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24
Q

What is lossy audio compression? (2 points)

A
  • Delete data that your ears can’t perceive in order to make files easier to transfer over the internet.
  • Reduce bit rate (less accurate reproduction of the original)
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25
Q

Codecs (2 points)

A
  • Device or software that is used to compress or decompress algorithms for audio and video
  • It’s job is to organize data in the media file
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26
Q

What was the only practice way to store massive amounts of data?

A
  • Videotape
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27
Q

Bit Rate (2 points)

A
  • Number of bits that are translated or processed per unit of time ( every second)
  • Bit rate: sampling rate x bit depth
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28
Q

What does a higher bit rate mean?

A
  • Higher bit rate = better quality = larger file size
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29
Q

Bit depth

A

-how many bits are used for each sample

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30
Q

What is uncompressed audio stored in?

A
  • Saved in a .wav format
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31
Q

What does a higher bit depth mean?

A
  • More accurate sample
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32
Q

What is quantization noise?

A
  • Difference between what the signal was vs. what the signal was recorded as
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33
Q

Bits <8

A

-Not used for sound
- Can be used to record physical processes like
blood pressure, heartbeat, motion due to walking or running

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34
Q

8 bits

A
  • Common in telephony

- Quantization noise can be perceptible sometimes

35
Q

16 bits

A
  • Most high-quality sound (CDs, DAT, MP3, movie audio tracks)
36
Q

24+ bits

A
  • Even higher quality/dynamic range (DVD-Audio, DTS)

- Often used before or during sound processing/editing (mastering)

37
Q

Name 4 colour models

A
  1. RGB
  2. Cyan, Magenta, Yellow, and blacK (CMYK)
  3. Hue, Saturation, Luminance (HSL)
  4. Luminance, Blue, Red (YUV)
38
Q

How many hexadecimal are in 1 byte for RBG Model?

A
  • Two hexadecimals
39
Q

How many bits are in each channel for RBG Model?

A

-There are 3 -8 bit channels, 24 bit colour

40
Q

How many bytes are in each of the RBG components?

A
  • 1 byte which is 3 bytes per pixel
41
Q

What is a pixel?

A
  • Dots of colour in an image (or on a display)
42
Q

What is resolution?

A
  • Number of pixels in an image (or on a display)
  • Size of an image, measured in pixels
    Sometimes refers to the pixel density, the number of pixels per unit of distance (e.g., pixels per inch or ppi)
43
Q

What are Vector Graphics?

A
  • An image that is defined using mathematical equations representing lines, curves, and polygons
44
Q

What does each pixel represent?

A
  • Single colour and represents RBG
45
Q

The benefit of vector graphics?

A
  • Can be enlarged without loss of detail or change in file size
46
Q

How are vector graphics created?

A
  • Created through drawing applications or text editors
47
Q

What is SVG (Scalable Vector Graphics)?

A
  • Popular vector graphics format and are text-based
48
Q

What are Raster Graphics?

A
  • An image that is comprised of a matrix of pixels
49
Q

What are examples other than SVG that are examples of vector graphics?

A
  1. Computer fonts

2. Geometric shapes in various shapes

50
Q

How are raster graphics?

A
  • Images created/edited using painting applications
51
Q

Disadvantage of Raster Graphics

A
  • Good for photographs but suffers from pixelation
52
Q

What is a popular technique for compressing images?

A

-Indexed colour- Instead of representing all colours, save only those used (or those that are most useful to keep

53
Q

What type of encoding is similar to Indexed colour?

A
  • Keyword encoding but with colours instead and with some colours possibly removed
54
Q

What are some examples of image formats?

A
  1. GIF
  2. PNG
  3. JPEG
55
Q

What is a GIF and type of compression? (3 points)

A
  • Graphics Interchange Format
  • Lossless, indexed colours (maximum of 256), coding related to Huffman’s
  • Allows transparency and animation
  • low quality
56
Q

PNG + Type of Compression

A
  • Portable Network Graphics
  • Lossless compression using indexed colours, run-length encoding
  • Allows transparency and more modern
57
Q

What are PNG and GIF best used for?

A
  • line drawings, logos, or diagrams
58
Q

JPEG + Type of Compression

A
  • Joint Photographic Experts Group)

- Lossy compression technique (only one)

59
Q

What is JPEG good for?

A
  • Great for photos, bad for images with text or sharp lines
  • Reduce colour resolution (sharp colour transitions less
    noticeable than to sharp brightness transitions)
60
Q

What is a compression artifact?

A
  • Noticeable distortion of media caused by the application of lossy compression.
61
Q

Challenges with using Virtual Reality (four)

A
  1. Processing power
  2. More complex hardware
  3. Images need to be generated much faster than movies
  4. Cannot be used for too long
62
Q

What is a video comprised of?

A
  • Comprised of frames of still images (combined with audio)
63
Q

What are two video compression techniques?

A
  1. Spatial (Intra-frame) (e.g., M-JPEG)

2. Temporal (Inter-frame) techniques

64
Q

What is Spatial Compression? (2 points)

A
  • Intra frame technique (compression is done within that single frame)
  • Use information from within the same frame to reduce file size
65
Q

What is temporal compression?

A
  • ## Use data from nearby frames (before or after) to reduce the file size
66
Q

How are key frames compressed?

A
  • typically compressed using only spatial technique
67
Q

What are key frames and how are they reproduced?

A
  • defines the starting and ending points of any smooth transition
  • can be reproduced independently
68
Q

Where are keyframes inserted?

A
  • inserted automatically at scene changes and/or at regular intervals to preserve quality of streaming or playback
69
Q

What are P frames? (predictive)

A
  • Frames can use data from previous frames to decompress and are more compressible than I‑frames
70
Q

What are B frames? (Bidirectional)

A
  • Frames can use both previous and forward frames for data reference to get the highest amount of data compress
71
Q

What happens if bitrate becomes too low?

A
  • The video becomes pixelated
72
Q

What is variable bit rate?

A
  • Allows higher bitrates during fast motion scenes, and lower bitrates when there is little motion
  • A control technique which allows the bit rate to vary, but maintains the quality
73
Q

What is control bit rate?

A
  • A control technique which keeps the bitrate constant, but allows video quality to vary.
74
Q

Examples of 4 Codecs

A
  1. HuffYUV
  2. MPEG-2
  3. H.264
  4. H.265 (HEVC)
75
Q

What is HuffYUV?

A
  • a codec that uses lossless compression (Huffman encoding)
76
Q

MPEG2?

A
  • a codec that uses lossy temporal and spatial compression and Huffman encoding
77
Q

What is H.264?

A
  • a codec that uses lossy, temporal and spatial compression for frame prediction
  • Perceived quality higher than MPEG-2 at same bitrate
78
Q

What is H.265 (HEVC)

A
  • a codec that is lossy, 50% reduction is size from H.264

- more complex and drains battery faster

79
Q

What is a file container?

A

-Combine a video stream and an audio stream into one file

80
Q

What type of additional data does file container allow for ?

A
  • optional subtitles
  • Multiple language audio tracks
  • Additional video stream representing different viewing angles
81
Q

What is.avi? (Audio Video interleave)

A
  • a container that is very old not good for streaming
82
Q

What is .mp4? (MPEG4

A
  • a container that supports multiple audio/video streams and subtitles, but limited codecs
  • very popular on mobile devices
83
Q

What is mkv (Matroska)?

A
  • a container that is like like mp4, but supports unlimited streams and unlimited codecs
  • support on mobile devices varies
84
Q

Name 4 video editors

A
  1. iMovie ((macOS, iOS)
  2. OpenShot (Linux, macOS, Windows)
  3. VSDC Free Video Editor (Windows)
  4. Adobe Premiere Pro (macOS, Windows; professional app)

Computer Science (8 decks)

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