Lecture 10 - Intro to Video Part 2

Question 1

What is a Codec?

Answer 1

A piece of code or program that compresses video or audio as it is created (exported from the editing software) and then when displaying it to the user decompresses the video or audio

There are a lot of Codecs

Question 2

What are two compression strategies?

Answer 2

1. Pick a codec that does higher compression

2. Lower the picture quality of the video

Question 3

What are two compression techniques?

Answer 3

Spatial Compression

Temporal Compression

Question 4

Spatial Compression

Answer 4

Looks for similarities within a frame

Best for high action videos (fast movement changes between frames)

Compresses each frame individually

Animation and PlanarRGB

Question 5

Temporal Compression

Answer 5

Identifies differences between frames and stores them relative to a keyframe

Good when the difference between current frame and keyframe are small

Sorenson Video and H.264

Question 6

Is Spatial Compression lossless or lossy?

Answer 6

Lossless

Question 7

Is Temporal Compression lossless or lossy?

Answer 7

Lossy (discards data)

Question 8

What three video formats does HTML5 support?

Answer 8

mp4

webM

Ogg

Question 9

Does HTML5 support .flv?

Answer 9

NO

Question 10

What does #t=10,22 mean?

Answer 10

Start at second 10 and ending at 22 seconds

Question 11

What is a container file format?

Answer 11

.avi

Stores both the data (the frames) and how to play the data (which codec to use)

Question 12

Bandwidth

Answer 12

How much data can be pushed across a connection (the capacity) in a given amount of time

Question 13

Bit Rate

Answer 13

Amount of data required to encode (compress) a single second of video or audio

Higher the bit rate the better quality of video

Question 14

Four main ways to get video/audio from a website onto your computer so you can view it

Answer 14

1. Download
2. Progressive Download
3. Streaming
4. Adaptive Streaming

Question 15

Unicast

Answer 15

Each user gets his/her own stream of video, the server has to send out a lot of data if several users are watching at once

Question 16

Multicast

Answer 16

Send the same stream to a bunch of users but then they lose the ability to pause, rewind etc

Question 17

Adaptive Streaming

Answer 17

Does not need a streaming server, can use http

Question 18

Name three ways of reducing the file size of a piece of video before moving it onto your website

Answer 18

1. Lower frame size
2. Choose codec
3. Lower frame rate