Video distribution

Question 1

What is spacial encoding?

Answer 1

reuse of colours within an image(one shade of purple instead of all shades)

Question 2

what is temporal encoding examples?

Answer 2

reuse of colours between images(if purple appears i previous image use same purple in next image)

Question 3

What is VBR?

Answer 3

video encoding rate changes as amount of spatial, temporal coding changes

Question 4

What does DASH stand for?

Answer 4

Dynamic Adaptive Streaming over HTTP

Question 5

How does a server work under dash?

Answer 5

server:
• divides video file into multiple chunks
• each chunk stored, encoded at different rates
• manifest file: provides URLs for different chunks

Question 6

how does a client work under dash?

Answer 6

periodically measures server-to-client bandwidth
• consulting manifest, requests one chunk at a time
• chooses maximum coding rate sustainable given current bandwidth
• can choose different coding rates at different points in time (depending on available bandwidth at time)

“intelligence” at client: client determines
• when to request chunk (so that buffer starvation, or overflow does not occur)
• what encoding rate to request (higher quality when more bandwidth available)
• where to request chunk (can request from URL server that is “close” to client or has high available bandwidth)

Question 7

What are the 2 philosophies of content distribution networks?

Answer 7

• enter deep: push CDN servers deep into many access networks
• close to users
• used by Akamai, 1700 locations
• bring home: smaller number (10’s) of larger clusters in POPs near (but not within) access networks
• used by Limelight

Question 8

What are some flaws with a single server for content distribution?

Answer 8

• single point of failure
• point of network congestion
• long path to distant clients
• multiple copies of video sent over outgoing link