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EECS > W6( representing video) > Flashcards

W6( representing video) Flashcards

1
Q

-_- Name Analog TV (history) in order?

A

There are 5.
1) NTSC
2) CRT
3) Resolution
4) Frame/ Field Rate
5) Colour TV

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2
Q

What is NTSC?

A

National Television Standards Committee (1952)

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3
Q

What is CRT ( cathode Ray Tube)

A
  • Electron Gun sweeps the lines with phosphor dots
  • Visibly flickers when you refresh it too slowly
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4
Q

What is resolution in analog tv?

A
  • Resolution: 525 lines fully refreshed at 30 Hz (every 2 fields)
  • Over-scanning: 525 lines reduced to 484 visible lines
  • Aspect Ratio: 4:3 (screen width-to-height ratio)
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5
Q

What is the Frame/ field Rate in Analog TV?

A

30 [fully refreshed] frames per second (60
fields per second)
* Interlaced scan: scan 1 field at a time (for faster partial refresh)
* Fields: frames divided into 2 fields (e.g., odd # vs even #)

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6
Q

What is the color TV?

A

composite signal of luminance (the black-and-white
part) & chrominance (how different the colour is from gray)
(Critics: NTSC = “Never Twice the Same Colour”; PAL was an
improvement, so was SECAM)

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7
Q

What factors are no longer useful in analog television (history)?

A

1) CRTs
2) interlaced scan ( but remains in some surviving standards: 1080i vs 1080p)
3) progressive scan is the norm
4) no hidden line ( since there is no beam to move)

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8
Q

the difference between the old TVs and the new ones?

A

CRTs are not used anymore
* Interlaced scan is not needed (but remains in some surviving
standards: 1080i vs 1080p)
* Progressive scan is the norm
* No hidden lines are needed, since there is no beam to move
* Transmission and storage are digital
* So that compression can be used
* Resolution is much higher
* Colour was present in the new standards from the beginning
* New output devices have much higher accuracy
* High resolution requires more careful preparation
* More research on human perception exists
* High Dynamic Range techniques

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9
Q

what happened to the transmission and storage in todays TVs? And what will happen to compression?

A

Transmission and storage are digital, so
Compression can be used

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10
Q

What happen to the resolution in todays TVs?

A
  • Resolution is much higher
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11
Q

what is the place of the color in todays TVs?

A
  • Colour was present in the new standards from the beginning
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12
Q

what happened to the new output devices accuracy?

A
  • New output devices have much higher accuracy
  • High resolution requires more careful preparation
  • More research on human perception exists
  • High Dynamic Range techniques
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13
Q

virtual reality

A

“Immersive” technologies
* External: CAVE
* Head-mounted displays
* Images change with head
movements/rotations to always
show proper perspective

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14
Q

what are the challenges of the virtual reality ?

A
  • Processing power
  • More complex hardware
  • Images need to be generated
    much faster than for movies
  • Delays cause motion sickness
  • Cannot be used for too long
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15
Q

what the fuck is the video?

A

Comprised of frames of still images (combined with audio)
* When viewed in rapid succession, the images give the
appearance of motion
* Typical frame rates are 24–30 frames per second to 60 fp

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16
Q

what is the aspect ratio of the video?

A

16:9 typically

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17
Q

what are the resolution of video?

A

1) 4096* 2160 pixels, 4K
2) 1920* 1080 Full HD
3) 1280720, HD
4) 853480, SD

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18
Q

How much space uncompressed video occupied?

A

vast storage space. more than 100 MB per second for Full HD

Note: compression techniques are almost always used

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19
Q
A

p= progressive
i= interlaced

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20
Q

what are the techniques for video compression?

A

1) spatial (intra-frame)
2) temporal (inter-frame)

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21
Q

what is Spatial (Intra-frame) techniques ? And the example ?

A
  • Use information from within the ((((same)))) frame to reduce file size
    *e.g., M-JPEG
22
Q

what is theTemporal (Inter-frame) techniques? Example?

A
  • Use data from ((((nearby))))) frames (before or after) to reduce the file size
  • (e.g., MPEG)
23
Q

what is the key-frames (I-frame)

A
  • typically compressed using only spatial techniques (like JPEG)
  • can be reproduced independently
  • inserted automatically at scene changes and/or at regular intervals to
    preserve quality of streaming or playback
24
Q

what is the P-frames & B-frames?

A

Other frames encoded by saving differences
between it and previous key-frame (P=Predictive, B=Bidirectional)
* If a key-frame is lost (e.g., during streaming) or skipped (e.g., when
skipping forwards or backwards) the displayed video can be
distorted
* Suitable for video distribution, but not video editing

25
Q

what would happen if the bitrate is too low?

A

the video becomes pixelated

26
Q

what is the difference between bitrate and size

A

Bitrate is the number of bits per second. The symbol is bit/s. It generally determines the size and quality of video and audio files: the higher the bitrate, the better the quality, and the larger the file size because of File size = bitrate (kilobits per second) x duration.

27
Q

what is Constant bitrate (CBR)?

A

same bit rate throughout the video

28
Q

what is Variable bitrate (VBR)?

A

can vary (up to a maximum)
* Allows higher bitrates during fast motion scenes, and lower
bitrates when there is little motion

29
Q

what are the example of constant bitrate and variable bitrate?

A
  • EECS 1520 Zoom Lecture recordings: HD (1920 × 968 × 25 fps)
    approx. 0.2 Mbps VBR, static slides are very easy to compress!
  • Netflix: 5 Mbps at 1080p, up to 16 Mbps for 4K
  • Blu-ray: about 40 Mbits/s for 1080p (older, less efficient scheme)
  • “Do you need a Gigabit fiber?
30
Q

how many example codecs we have name them?

A

1) HuffYUV ( Huffman, YUV colour space)
2) MPEG-2
3) H.264
4) H.265 (HEVC)

31
Q

name all example codecs which is lossy?

A

MPEG-2/ H.264

32
Q

what is HuffYUV (Huffman, YUV colour space?

A
  • Lossless, Huffman encoding, compression ratios around 47%
33
Q

what is the compression ratio of HuffYUV?

A

around 47%

34
Q

what is MPEG-2?

A
  • Lossy, temporal and spatial compression, Huffman encoding
  • Compression ratios around 3.3%
  • Highly dependent on bitrate and other encoding options
35
Q

what is the compression ratio of MPEG-2?

A

3.3%

36
Q

What is the H.264?

A

Lossy, temporal and spatial compression, frame prediction
* Predicts the next frame using spatial and temporal information, compares with
the actual frame, saves only the difference
* Compression ratios around 1.6%
* Highly dependent on bitrate and other encoding options
* Perceived quality higher than MPEG-2 at same bitrate

37
Q

what is the H.265 (HEVC)?

A

successor of H.264: further 50 % reduction of size, much more complex!
* Often drains battery faster

38
Q

what is the compression ratio of the H.264?

A

1.6%

39
Q

What is the compression ratio of the H.265 (HEVC)?

A
40
Q

which one of the example codecs often drains battery faster?

A

H.265 (HEVC)

41
Q

Does file necessarily indicate the codecs use?

A

Nooooooooooooo :D

42
Q

What is the file containers?

A
  • Combine a video stream and an audio stream into one file
43
Q

what is file extension?

A

Extensions tell your computer which application created or can open the file and which icon to use for the file. For example, the docx extension tells your computer that Microsoft Word can open the file and to display a Word icon when you view it in File Explorer.

44
Q
A

Some allow for additional data:
* Additional video stream representing different viewing angles
* Multiple language audio tracks
* Optional subtitles

45
Q

what is the difference between the container and file extention?

A

A container is the file that contains your video, audio streams, and any closed caption files as well. It’s common for a container to be called a file extension since they are often seen at the end of file names (e.g. filename. mp4).

46
Q

name all container we have?

A

1) .avi (Audio Video Interleave)
2) .mp4 (MPEG-4)
3) .mkv (Matroska)

47
Q

what is avi?

A

(Audio Video Interleave): very old; not good for streaming

48
Q

how containers are indicated?

A

by the file extension

49
Q

what is mp4?

A

(MPEG-4): supports multiple audio/video streams and
subtitles, but limited codecs, very popular on mobile devices

50
Q

what is mkv?

A

(Matroska): like mp4, but supports unlimited streams and
unlimited codecs, support on mobile devices varies

51
Q

name all the film 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)

52
Q

Aya gharare berini?

A

Naaaa kheir -

EECS (6 decks)

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