P2P Digital TV Recorder

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P2P Digital TV Recorder

• Supervisor Professor Michael R. Lyu
• Prepared by Ho Tsz Wing, Andy
• Lau Wai Shun, Jack

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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

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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

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Summary of Work in Sem1
P2P Digital TV Recorder

• 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

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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
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Improvement Work in Sem2
Problem
Cause
Solution
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

• Peers cannot reject the recording tasks gt
  Inflexible

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Improvement Work in Sem2
Problem
Cause
Solution
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
Replication methods take too much time and CPU
resource
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Improvement Work - 1

• Decentralized searching algorithm and buddy list
• Decentralized recording algorithm and bonus system

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Component of Server
Xml.asp
Database
Login/Logout Application
User Search Application
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Login / Logout / User Search
Offline
Login message
Online
Offline
Online
Buddy Information
Online
Online
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Task of Client Side

• 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
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Download Topology Napster (Sem1)
N2
N1
N3
Client
N4
Server
Owner_at_
Lookup(TVB News)
KeyTVB News
N8
N9
N7
N6
Simple, but O(N) states and a single point of
failure
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Download Topology Gnutella (Sem 2)
N2
N1
Lookup(TVB News)
N3
Client
N4
Owner_at_
KeyTVB News
N6
N8
N7
N9
Robust, but in the worst case O(N) messages per
lookup
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P2P Digital TV Recorder Protocol
Type
ID
Port / Channel
Download Streaming / Recording Message
IP
Program Title
TTL / Hop
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Performance Enhancement
Forward the message to other peers
All pass
Check IP Field
Check Message ID
Check File Exist
Check TTL
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Scheduling of Recording Task
Centralized
Decentralized

• 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

• 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.

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Scheduling Policies
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Scheduling Policies
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Bonus System
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10
Free Rider
Normal User
unable to decide record or not
able to decide record or not
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Improvement Work - 2

• Video-On-Demand (VoD) streaming

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Why use VoD streaming?

• Download
• 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

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

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DirectShow Filters and Filter Graphs

• DirectShow Filters
• 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

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DirectShow Architecture
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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.

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Approaches in Graph Building
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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

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

• The filter graph built by our application

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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

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Experiment Result
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
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Experiment Result
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
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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

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Steps to create an encoding application
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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

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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 http//localhost8080
• It then connects to the requesting peer and the
  peer will view the file at the specified address

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Streaming Architecture
Streaming request
Connection established
Streaming request
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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).

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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

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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
  http//localhost8080
• 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

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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

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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.

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Thank You !