RhemaTech

Streaming Service upon Flex and Rails

RhemaTech

We work in Rhematech Inc.

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We provide live Streaming service over Internet on web

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100+ concurrent channels

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50000+ concurrent audience per channel

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Short demo(todo)

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System Structure

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Event Management

System

Channel Management

System

Media Server

Encoder/Audience UI Flex

Rails

Java/C++

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Main Challenges :Cost and Scalability

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We choose Flex and Railsbecause of

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COST

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We were used to be .NET users

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We suffered from high development and deployment cost

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It fails to respond dynamic requirements

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We did take Silverlight into consideration

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Not popular enough

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Poor designer support

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No alternatives for media server

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Flex and Rails save us

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Serve multimedia on web

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Rich user interaction

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Run over standard protocols

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Low development and deployment cost

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Good looking

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Service on mobile device(in the future)

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Lessons we learned

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#1. Be RESTful

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Consistent API design

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Consistent error handling

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Easier to extend and modify

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Always return errors in JSON/XML with 200 Ok

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flash.net.URLLoader does not handle HTTP error code well

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remove protect_from_forgeryfrom environment.rb

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#2. Use JSON instead of XML

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Less Traffic(quite important for large service)

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Easier to parse complex response

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Rails JSON Gotcha

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Rails does not unescapeunicode while decoding

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Fixed in Rails 2.3

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#3. Flash uses different session for file uploading on non-IE browsers

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Flash uses its http socket for file uploading on non-IE browsers

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Work Around -Session Migration

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#4. Handle Browser onbeforeunload event.

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Flash does not close NetConnection until you close all browser windows!

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#5. Create a controller to deliver debug .swf file in development mode.

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map.connect '/encoder.swf', :controller => “debug", :action => "encoder"if RAILS_ENV == ‘development'

route.rb

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def encodersend_file(path_to_debug_swf, options)

end

debug_controller.rb

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Makes debug and trace with rails much easier

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#6. Pick right video codec

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H263 vs. VP6 vs. H264

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H.263Pros: Flash Player build-inCons: Poor quality

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VP6Pros: Good video qualityCons: Expensive

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H264Pros: Good QualityCons: 2~6s more latency

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Questions?