Subject : Networking Multimedia Second Exam Spring 2015/2016
Q2 ] A digitized video is to be compressed using the MPEG-1 standard .Assuming a frame sequence of: IBBPBPBBIBBPBPBBI and average compression ratios of : 12:1 (I) , 20:1 (P) ,40:1 (B) . A)What is the reordered sequence ? Answer: IPBBPBIBBPBBPBIBB B)Derive the average compression ratio .
C)Derive the average bit rate that is generated by the encoder for NTSC digitization format.
Q3) Recall the simple model for HTTP streaming s. B denotes the size of the client’s application buffer=5Mbps and Q denotes the number of bits that must be buffered before the client application begins play-out =3Mbits Also r denotes the video consumption rate=1Mbps . Assume that the server sends bits at a constant rate x whenever the client buffer is not full. a. Suppose that x=3Mbps. in this case playout will alternate between periods of continuous playout and period of freezing. Determine the length of each continuous playout and freezing period as a function of Q, r, and x.
b. Now suppose that x > r. At what time t = tf does the client application buffer become full?
Q4) Consider A sender begins sending packetized audio periodically at t = 0. The first packet arrives at the receiver at t = 3.ass following . pkt#
Sending time
Receiving time
1
0
3
2
1
4.5
3
2
6
4
3
6.7
5
4
6.8
6
5
8.9
7
6
9.4
8
7
9.6
9
8
11.8
10
9
14.2
A) If audio play-out begins as soon as the first packet arrives at the receiver , which of the packets sent will not arrive in time for play-out? Answer: If the scheduled play-out time is less than arrival time , the packet will be too late 2,3,4,6,7,9,10 pkt#
Sending time
Receiving time
Scheduled play-out time
1
0
3
3
2
1
4.5
4
3
2
6
5
4
3
6.7
6
5
4
6.8
7
6
5
8.9
8
7
6
9.4
9
8
7
9.6
10
9
8
11.8
11
10
9
14.2
12
B) If audio play-out begins at t = 4.5, which of the packets sent will not arrive in time for play-out? Answer: pkt 10 , since it's scheduled play-out time is less than it's arrival time pkt#
Sending time
Receiving time
Scheduled play-out time
1
0
3
4.5
2
1
4.5
5.5
3
2
6
6.5
4
3
6.7
7.5
5
4
6.8
8.5
6
5
8.9
9.5
7
6
9.4
10.5
8
7
9.6
11.5
9
8
11.8
12.5
10
9
14.2
13.5
C. What is the minimum play-out delay at the receiver that results in all of the packets arriving in time for their play-out? Answer :If play out begins at 5.2 , no packets will arrive after it's play-out time , since maximum Network delay is 5.2 (for pkt #10 )