1. P2P Digital TV Recorder Supervisor: Professor Michael R. Lyu
Prepared by: Ho Tsz Wing, Andy
Lau Wai Shun, Jack

2. Content Project background and objectives
Summary of Work in Semester 1
Improvements in Semester 2
Decentralized searching algorithm and buddy list
Decentralized recording algorithm and bonus system
Streaming and video format conversion
Difficulties and Solution
Further Improvements
Conclusion

3. Project background Watching TV is a major entertainment
People often miss their favorite programs
People need to schedule the recording of the programs

4. Project objectives
Allow people to view back a previous TV program without doing scheduling themselves
Let the users view the program on demand
Increase the availability of the TV programs
Achieve load balancing among the participating peers

5. Summary of Work in Sem1 P2P Digital TV Recorder Program Core
Download the video file from other peers
No Buddy List
All peers’ information is stored in a centralized server
A centralized scheduling algorithm
Peers unable to reject the recording task
Using a complex algorithm to achieve high availability
Performance enhancement
Whole file replication
Erasure code replication
Research Results
In most cases, erasure code replication performs better than whole file replication
When the peer availability attains a certain level, the performance of the whole file replication close to erasure code replication

6. Improvement Work in Sem2
Problem
Cause
Solution
Queries needed to handle increase dramatically with the increase of the number of peers
Use buddy list system
Try to keep as less as information in the sever
Performance of the server become the bottleneck of the system

7. Improvement Work in Sem2
Problem
Cause
Solution
Peers cannot reject the recording tasks => Inflexible
A centralized server will assign the recording task to the online peer without considering their contribution to the system
A distributed scheduling algorithm
Implement a bonus system
The user is able to accept or reject the task

8. Improvement Work in Sem2
Problem
Cause
Solution
Replication methods take too much time and CPU resource
As the original video in dvr-ms format is too large, no matter which replication we use, much time is consumed.
Implement a streaming server
Real time encoding is fast enough

9. Improvement Work - 1 Decentralized searching algorithm and buddy list
Decentralized recording algorithm and bonus system

10. Component of Server Xml.asp Database Login/Logout Application
User Search Application

11. Login / Logout / User Search
Offline B
Login message A
Directory
Server C
Online
Offline
Online
Buddy Information E D
Online
Online

12. Task of Client Side Client Application Download Streaming Recording
Download (Implemented)
Basic function
Send the video file to the
requested peer
Download
Client Application
Streaming
Encoding to wmv
Preview function
Recording
Scheduling among peers
Bonus system
Streaming
Recording

13. Download Topology – Napster (Sem1)
Client N4
Server
Lookup(“TVB News”)
Key=“TVB News” N8 N9 N7 N6
Simple, but O(N) states and a single point of failure

14. Download Topology – Gnutella (Sem 2)
Lookup(“TVB News”) N3
Client N4
Key=“TVB News” N6 N8 N7 N9
Robust, but in the worst case O(N) messages per lookup

15. P2P Digital TV Recorder Protocol
Type ID
Port / Channel
Download & Streaming / Recording Message IP
Program Title
TTL / Hop

16. Performance Enhancement
Forward the message to other peers
All pass
Check IP
Field
Check Message ID
Check File Exist
Check
TTL

17. Scheduling of Recording Task
Centralized
Decentralized
Server will schedule the recording of all program in the morning
Send out the recording request to 2 peers randomly before the program starts
Peers who received the recording request cannot reject it.
Peers initialize the recording task when the program starts
Peers are able to determine recording or not if the bonus points of the peers attain a particular level
Peers forward the recording message to one of its buddies

18. Scheduling Policies

19. Scheduling Policies

20. unable to decide record or not
Bonus System 10
10+
Free Rider
Normal User
unable to decide record or not
able to decide record or not

21. Video-On-Demand (VoD) streaming
Improvement Work - 2
Video-On-Demand (VoD) streaming

22. Why use VoD streaming? Download VoD streaming
the user needs to wait for a long time
errors may occur in the downloading process
VoD streaming
save the user a lot of time and storage space
can be used as a preview function

23. Tools used in developing the streaming application
DirectShow Library
GraphEdit
Windows Media Encoder SDK

24. a media-streaming architecture for the Microsoft Windows® platform
DirectShow Library
a media-streaming architecture for the Microsoft Windows® platform
provides for high-quality capture and playback of multimedia streams
Example uses:
file players
video editing applications
file format converters etc.

25. DirectShow Filters and Filter Graphs
receive multimedia streams as input and produce output
A source filter introduces data into the graph.
A transform filter takes an input stream, processes the data, and creates an output stream.
Renderer filters receive data and present it to the user
Filter Graphs
A set of connected filters
controlled by a high-level component called the Filter Graph Manager

26. DirectShow Architecture

27. Writing a DirectShow Application
The application
creates an instance of the Filter Graph Manager.
uses the Filter Graph Manager to build a filter graph.
uses the Filter Graph Manager to control the filter graph and stream data through the filters.

28. Approaches in Graph Building
Method Used
The Filter Graph Manager builds the entire graph
RenderFile
The Filter Graph Manager builds part of the graph
Render
The application builds the entire graph
AddFilter, Connect or ConnectDirect

29. Reasons for using DirectShow Library
Windows MCE records TV programs in dvr-ms format
Dvr-ms files are not efficient for storage (1hr TV program recorded in good quality requires about 1668MB)
Dvr-ms files cannot be streamed over the internet
DirectShow is used to convert dvr-ms file to wmv file that can be used for streaming
The file size of 1 hr wmv file is only 101MB if the bit rate is 225kbps

30. Number of days of TV programmes that can be recorded with a given hard disk size
22.09
20.63
1.31
1.25

31. GraphEdit
The filter graph built by our application

32. Uses of DirectShow Library
Steps to convert dvr-ms file to wmv file using DirectShow Library:
start once Windows MCE has finished recording a particular TV program
create the filter graph and render the dvr-ms file
original dvr-ms file will be deleted in the case that the storage space is not sufficient for new recording

33. Experiment Result Bit Rate (Kbps) Video Size File Size (KB)
Conversion Time (s)
218
320 x 240
1,711 58
441
3,317 60
666
4,928 62
480 x 360
1,731
115
3,413
116
5,069
125
The dvr-ms file used in this experiment has a length of 60s, a file size of 27,399KB and is recorded in good quality

34. Experiment Result Bit Rate (Kbps) Video Size File Size (KB)
Conversion Time (s)
666
320 x 240
4,928 62
480 x 360
5,069
125
640 x 480
5,170
209
800 x 600
5,194
327
The dvr-ms file used in this experiment has a length of 60s, a file size of 27,399KB and is recorded in good quality

35. Windows Media Encoder SDK
used to compress live or stored audio and video content into Windows Media files or streams
create multimedia productions from devices attached to their computers

36. Steps to create an encoding application

37. Encoding with CBR and VBR
Constant Bit Rate (CBR) Encoding
bit rate and size of the content are known before encoding
for content that varies in complexity, the encoding quality is not constant
Variable Bit Rate (VBR) Encoding
it compensates for changes in the complexity of the content
bit rate and size of the content are not known before the encoding

38. Uses of Windows Media Encoder SDK
When the client receives a streaming request, it will create an encoder object, encode the appropriate file using CBR encoding and broadcast it at the address
It then connects to the requesting peer and the peer will view the file at the specified address

39. Streaming Architecture
Directory
Server B E C D A
Streaming Host
Streaming request
Connection established
Streaming request

40. Difficulties and Solutions
Difficulty
Dvr-ms file (the default file format for the recorded TV in Windows MCE) cannot be streamed over the Internet
Cause
Windows Media Encoder 9 Series SDK does not support the encoding and broadcasting of dvr-ms file
Solution
We have to use DirectShow Library to convert the dvr-ms file to a format that is compatible with Windows Media Encoder 9 Series SDK (i.e. wmv file).

41. Difficulties and Solutions
Difficulty
The wmv file resulted from the conversion of dvr-ms file by DirectShow Library has sound only but no video.
Cause
The default transform filter chosen by the RenderFile method (InterVideo Video Decoder) cannot decode MPEG-2 stream to MPEG-1 stream
Solution
So we have chosen to use the GPL MPEG-1/2 Decoder in our filter graph to solve this problem

42. It is possible to have real time streaming in the following ways:
Further improvement
It is possible to have real time streaming in the following ways:
First, we can start the file conversion as soon as Windows MCE starts to record the TV program
Next, we can use Windows Media Encoder SDK to encode the wmv file and broadcast it at
Finally, the client can connect to the above address to get the video content instantly
However, there is one drawback as doing recording and converting at the same time takes up a lot of CPU time

43. Further improvement
It is also possible to use p2p technique to stream the file
It can reduce the network bottleneck at the video server
It can provide a fault tolerant Video-on-Demand streaming
it raises technical, performance, quality, business, and legal issues

44. Conclusion
We have implemented our application in a decentralized ways using a buddy list system to enhance the performance.
We have introduced a distributed scheduling algorithm and a bonus system to enhance the availability of the TV programmes.
We have also developed a streaming server to reduce the storage requirement and enabled the user to preview the TV programmes.

45. Thank You !