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Streaming video

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Video on internet.

There are two different basic ways of presenting video on internet:

• The receiver downloads the entire video file and than plays it using some kind of media player

• The receiver starts the download and the video is played during the process. A specific plug in is required (streaming video)

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• The video sequence will start to play almost immediately.

• Data is then transmitted with necessary speed to keep the film rolling. No data is stored by the receiver.

• The transmission can be adapted to the bandwidth of the receiver. Lower bandwidth will result in lower video quality.

Streaming video, live or on demand (VOD)

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HTTP-streaming (progres-sive download.)

• Used when video is transmitted from a standard www-server ( HTTP-protocol ). Intheory the entire file should be transferred before video starts. In practice the film starts when enough data is received to be certain that the remaining time is enough for the rest of the download.

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The need for video on the internet

Various media are used in Internet for applications such as video conferencing, video archives and libraries, remote learning, multi-media presentations, and video on demand. Here is a list of the common applications:

•Internet Multimedia.

•Interactive Video Games.

•Personal Communications.

•Video Storage.

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•Multimedia Email.

•Database Services and Archives.

•Video Surveillance.

•Emergency Systems.

•Broadcasting

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How Does it Work ?

• A web designer can add links that reference a media hosting network, to a website.

• When a viewer clicks on one of the links, the media network streams the clip directly to the viewer's PC as though it was coming from the original website.

• Because the media files are hosted on a separate network, the streaming has no impact on any existing web servers.

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The fundamental problem.

• To play one second of uncompressed 8-bit color, 640 X 480 resolution, digital video requires approximately 9 MB of storage.

• One minute requires about 0.5 GB. A CD-ROM can only hold about 700MB

• Data storage and transfer problems increase proportionally with 16-bit and 24-bit color playback.

• Without compression digital video would not be possible with current technology.

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There are three different server techniques for streaming video:

• RTSP (Remote Transfer Streaming Protocol) This is a standard method used by QuickTime

• RealNetworks uses RTSP ( RealPlayer works only with RealServers

•Windows Media is a nonstandard method developed by Microsoft

Server techniques.

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Streaming media: download

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Streaming media: meta files

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Streaming media: RTSP

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• RTSP uses RTP (Real-Time Transport Protocol) to format packets of multimedia content. RTSP is designed to efficiently broadcasting audio-visual data to large groups.

•To handle the streaming a special server is required.

• With the advantages that live transmissions are possible with short delays.

• Since nothing is stored at the receiver copyrights can be maintained

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Publishing.

•The first step is to create the audio or video file which has an extension of .ra (RealAudio) or .rm (RealMedia).

•You create this file from your audio or video source using the RealEncoder or RealProducer.

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• The second step is creating the metafile with the extension .ram. The ram metafile is a text file contain-ing a special url telling the Real server to send your clip to the browser. The call is as follows:

rtsp://machinename.host4u.net/your-userid/name-of-clip.ra

your-userid = your-domain with no extension like .com

The clip will either be a .rm or .ra depending on the media type.

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• If you want to automatically play several videos or audios one after another, list each file on a separate line in the metafile:

rtsp://machinename.host4u.net/your-userid/name-of-clip1.rartsp://machinename.host4u.net/your-userid/name-of-clip2.rartsp://machinename.host4u.net/your-userid/name-of-clip3.ra

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• Upload your .ram and .ra or .rm files to the /realaudio subdirectory in your web directory. When you ftp these files, it is important that the .ram files be transferred in ASCII mode, and the .ra or .rm files sent in BINARY mode.

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1. Plan your video shots in advance.

A valuable technique for doing this is to use a storyboard. The storyboard is your road map, a device that shows you where you are going. Here, you plot out all the steps you will take in order to give your story flow and consistency. It has been said that when your storyboard is complete, so is the movie. All that remains is the execution.

Preparing for streaming video.

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2. Keep all camera movements down to a minimum.

Constant panning or zooming will not translate well to the web. It is better to tell your story using a series of set shots, instead of multiple zooming and panning. If you are panning, keep the motion slow.

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3. Video needs proper lighting.

Although many of the newer video cameras allow you to record low light images, these images will degrade considerably by the time your production has been assembled and broadcast. Visit web sites where lighting has been properly addressed for reference before shooting.

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4. Be careful with your background

Avoid areas of high contrast or intensely bright backgrounds. Extremely bright images can cause the digital image format to tear or smear.

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5. Keep the backgrounds simple.

If you use a solid, simple background, your subject will stand out, but if the background is too busy, the subject will tend to blend in. Worse, complex backgrounds increase the odds of artifacts (where portions of the image clump together) and jaggies (lack of a smooth edge) appearing on the edges of your subject.

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6. Avoid unsuitable effects

All dissolves, page curls, and motion effects may look slick on a television screen but will probably fall apart when streaming. That is because streaming codecs do not like a lot of full screen motion.

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7. Use suitable effects

Try using a still frame. Or slow motion. Both of these effects slow down or stop the change from frame to frame. Sometimes a still or slow motion can seem very unnatural with some subjects. But if your videographer has painted you into a corner, you might just have to reach for any trick you can get your hands on.

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8. Use Large Titles

There is nothing worse than text that is unreadable. People will tolerate smudgy video far more than they will tolerate text that cannot be understood.

Make all of your titles big and proud. Don't go for frilly and exotic typefaces. Choose fonts that can be clearly read and put them on backgrounds that are bland and non-descript.

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9. Garbage in means allways garbage out

Capture your source material at the highest quality video and audio settings. It is better to start with a high quality source and scale down the quality than start with a low quality source and try to get by.

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Video quality for different window sizes.

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• When the Wizard pops up, select

"Live Broadcast"and hit the next button.

How to set up a live stream with Real Producer.

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• Select audio and video.Check the box depending on what you plan on using, You will also have to select the audio source driver and video source you want to use

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•You are asked to fill in necessaryinformation .

This will appear on the listeners RealPlayer

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• You will have to decide here if you just want to send your Real stream to the RealServer in a single rate, or in a Multipule rate,SureStream ( if you intend on targeting different bit rates). The more you add to Multi-rate the higher the bandwidth to the RealServer.

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•This depends on what you plan on using, check just one, or as many as you intend on send-ing.But remem-ber if you select more than one rate, it then becomes a Multiratestream (SureStream) and be sure your RealServeraccount can cope with this!.

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• Chose your Audio format.Voice only, voice and background, Music and Stereo Music. Here you should select either Music or Stereo Music, for the best quality, the others are for lower bandwidth work and are not for broadcasting music.

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•This will vary, ifyou have chosen video then you will be asked to select the type from Normal motion video, Smoothest motion video, Sharpest image video or slide show, if this part applies to your broadcast select Normal Motion at 15 frames for dialup modems or 30 frames for broadband.

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•You will now be asked to enter the IP number of the RealServer, Server port, File name and your user and password which you signed up with. these details will be emailed to you by MediaCast1.

You will also notice an archive file box at the bottom, if selected you can make an archive of your broadcast, if you dont wish to leave it blank.

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You should now see all the information you have entered to the encoder. Prepare to record.

You are now ready to start encoding live to the MediaCast1 RealServer!!

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Your broadcast will normally be sent to the RealServer in UDP. If you get any problems using UDP from your firewall, then go to optionson the RealProducerand select "Preferences" then click on the Live broadcast tab.and change it to TCP. Click ok and close. Easy to set-up :-)

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Key words in streamingtechnology.

•BufferingReceiving and storing data before playing it back.

•CodecCoder/decoder. Codecs convert data between uncompressed and compressed formats, thereby reducing the bandwidth a clip consumes.

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•EncodingConverting a file into a compressed, streaming format. For example, you can encode WAV files as RealAudio.

•SMILSynchronized Multimedia Integration Language. A mark-up language for specifying how and when each clip plays. SMIL files use the .smil or .smi extension.

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•StreamA flow of a single type of data, measured in kilobits per second (Kbps).

•MulticastUsed for broadcasting large events over the Internet. Allows a single computer to create the content (film, etc.) and many computers to play the same single stream simultaneously.

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•StreamingWhen a large media file (audio, video, etc.) is broken into smaller pieces so it can viewed or heard immediately. This avoids the wait for the whole file to be downloaded first.

•On-DemandA type of streaming in which a clip plays from start to finish when a user clicks a link. Most clips are streamed this way.

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•Request headersRequest headers are used in client requests to communicate information about the client.

•Response HeadersResponse headers are used in server responses to communicate information about the server and how it may handle requests.

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•MPEGMPEG (pronounced M-peg) stands for Moving Picture Experts Group. MPEG is the name given to the family of standards used for coding audio-visual information (e.g., movies, video, music) in a digitally compressed format.

•ASFASF (Advanced Streaming Format) is a file format that stores audio and video information and is specially designed to run over networks like the Internet.