Representing Video

Question 1

What are videos made of?

Answer 1

still frame images, combined with audio

Question 2

What is the typical frame rate?

Answer 2

24-60 frames per second

Question 3

What is the aspect ratio?

Answer 3

16:9 typically

Question 4

What is the resolution for 4K

Answer 4

4096 x 2160 pixels

Question 5

What is the resolution for Full HD?

Answer 5

1920 x 1080

Question 6

What is the resolution for HD?

Answer 6

1280 x 720

Question 7

What is the resolution for SD?

Answer 7

853 x 480

Question 8

What are the 2 main ways for video compression?

Answer 8

1. Spatial (Intra-frame)
2. Temporal (Inter-frame)

Question 9

Spatial refers to which format when saving?

Answer 9

M-JPEG

Question 10

Temporal refers to which format when saving?

Answer 10

MPEG

Question 11

What do spatial techniques do?

Answer 11

uses information from within the same frame to reduce file size

Question 12

What do temporal techniques do?

Answer 12

uses data from nearby frames to reduce file size

Question 13

What are keyframes/I-frames?

Answer 13

• typically compressed only using spatial techniques
• can be reproduced independently

Question 14

True or False
I-frames can be inserted automatically at scene changes and /or at regular intervals to preserve quality or streaming, or playback

Answer 14

True

Question 15

What are P and B frames?

Answer 15

P = Predictive
B = Bidirectional

Question 16

True or False
P and B frames are encoded by saving the difference between them and the previous key frames

Answer 16

True

Question 17

True or False
If a key frame is lost during streaming or skipped when skipping forwards or backwards, the display video can be distorted.

Answer 17

True

Question 18

What are the 4 codecs used in video compression?

Answer 18

1. HuffYUV
2. MPEG-2
3. H.264
4. H265 (HEVC)

Question 19

Which of the 4 codecs uses lossy compression techniques?

Answer 19

MPEG-2 and H.264

Question 20

Which of the 4 codecs uses lossless compression techniques?

Answer 20

HuffYUV

Question 21

What is the compression ratio for the Huffman compression technique?

Answer 21

74%

Question 22

What is the compression ratio for the MPEG-2 compression technique?

Answer 22

3.3%

Question 23

What is the compression ratio for the H.264 compression technique?

Answer 23

1.6%

Question 24

What is the compression ratio for the H.265 compression technique?

Answer 24

50%

Question 25

How does MPEG-2 use lossy techniques?

Answer 25

- Temporal and spatial compression - Huffman encoding - Highly dependent on bitrate and other encoding options

Question 26

How does MPEG-2 use lossy techniques?

Answer 26

- Temporal and spatial compression - Frame prediction - Predicts the next frame using the spatial and temporal information and compares it with the actual frames, and then saves only the difference

Question 27

Which has a better perceived quality, MPEG-2 or H.264 at the same bitrate?

Answer 27

H.264

Question 28

True or False H.265 often drains the battery faster

Answer 28

True

Question 29

File containers combine what?

Answer 29

A video stream and an audio stream into one file

Question 30

Can file containers always use codecs?

Answer 30

Not always

Question 31

What are 3 file extensions that can indicate file containers?

Answer 31

1. avi (audio video interleave) 2. mp4 (MPEG-4) 3. mkv (Matroska)

Question 32

What are the attributes for avi?

Answer 32

very old and not good for streaming

Question 33

What are the attributes of MP4?

Answer 33

- supports multiple audio/video streams and subtitles - limited codecs - very popular on mobile devices

Question 34

What are the attributes of MKV?

Answer 34

- supports unlimited streams - supports unlimited codecs - Support on mobile devices varies