COM 597Streaming Media

Class 7July 13, 2006

General Notes and Comments

• Travis Petershagen, Seattle Podcasting Network

• Pete Grondal, Mobile Devices, TBA

Profiles

• Windows Media Encoder uses Profiles• What is a profile and how would I use one?• A profile determines how files or source groups are

encoded• Each profile may include one or many target

audiences, along with video and audio codec information

• You can save the profile and use it repeatedly

Target Audiences

• What is the concept of target audiences?

• This is the naming convention for their multiple bitrate technology

• With it you can select multiple target audiences (bit rates) and weave your different versions into one file

Moving Targets• An anomaly with the WindowsMedia version of MBR is

the video is encoded with multiple qualities of compression.

• But all the video files share only one Audio file• There are not multiple audio files only one so choose

wisely• The lowest audience profile will determine your audio

settings• All the video target audiences will share a video screen

size

Which encoding mode to choose?

• CBR? VBR?

• My recommendation:

• Start with VBR

• Then two pass CBR

• Then one pass CBR

Why VBR?• VBR when used on proper content• Long and varied in complexity• Will give you an appreciably better encoded clip given the same file

size. • CBR is often using the bits in the wrong places and not having

enough available in the difficult spots• The difference can be as high as 2-to-1• Another way to look at it. If two files have the same quality, the

VBR file will often be half the size of a CBR file• If your source is a file and you want to encode with CBR, then two

pass is better than one pass

Using the frame buffer with CBR

• Why use the default of 5 seconds?

• If you are streaming a longer file (over say 10 minutes) increasing the buffer to 30 seconds will accomplish many of the same increase in quality that VBR does.

Windows .NET

• If you are streaming over a server with Windows Media Services in Windows .NET Standard or Enterprise editions you can enable Fast Start

• This allows the server to burst data to the players and filling the buffer in a shorter time than indicated, thus starting the file quicker

Microsoft Buzzword Translator

• Fast Start: Instant on playback

• Fast Cache: Download and cache the streaming content

• Fast reconnect: Automatically reconnect to a stream if interrupted

• Fast Recovery: Use forward error correction

Other Buzzwords

Real’s version of the same stuff

• TurboPlay It is their rapid playback and seeking technology

Instant On is QuickTime’s version

More Buzzwords

• URLs on Media Servers

• Mount point – Real and QuickTIme

• Publishing Point – Microsoft Windows Media V9

• Station – Windows Media prior to V9

A brief introduction to Mobile Media

• 3G (3rd Generation) Mobile Networks• Capable of delivering vast quantities of data &

multimedia• Target is handheld devices• Mobile networks are evolving from

narrowband, circuit-switched networks• These were used primarily for voice and text

Brief cont.

• New networks are broadband and utilize packet switching

• Deliver broad range of internet-like media services

• 3G is a real paradigm shift for the telecommunications industry

• Once place to look is with the sales of camera phones v. digital still cameras

More mobile

• Several 3G networks are up and running in Europe and Asia

• Phones there can include:– Multiple cameras supporting real-time, person-to-

person video calling– Video messaging– Playback of media content (news, sports, music

videos, etc.)

A few technological challenges• No agreed to standards. Every company has a better

mousetrap• It is the Wild West when it comes to competing technologies• As opposed to computing where you can assume either MS or

Mac, with 3G it is a crap shoot what technology you will need to support, let alone screen size, color depth frame rate and screen direction (vertical or horizontal)

• MPEG4 is the only video format supported by all phones

You can visit www.3Gpp.org to review what standards have been defined for Mobile

Hardware problems

• Hardware variability also represents a significant challenge between mobile devices

• Every few months a new crop of phones with new features

• Not just screen display size and color quality changes

More Hardware problems

• Operating systems

• Processing power

• Memory

• Media format compatibility

Other technical challenges include:– Physical movement of a user from one network cell

to another– Signal strength problems on the edge of a network– User’s proximity to a tower – will effect data flow– Number of devices operating simultaneously on the

same cell– Physical speed that a device is traveling through the

cell (e.g. car)

Blog Assignment for class 8

– Where and how is digital rights management failing. If you can, give a first person account where managing the portability, the delivery or re-use of digital media didn’t go the way you think it should.

Workshop

• Creating and implementing profiles in Windows Media