Computer Audio Video for david nicholson's WWW

The Redirector
Much like RealNetworks and its RAM file, Windows Media Technologies uses a "redirector" file for the Advanced Streaming Format. This ASF Streaming Redirector file (ASX) is an XML format file that basically creates a shortcut to the actual ASF file on the server. So when your browser links to the ASX file, the ASX file in turn links to the ASF file. That may sound kind of complicated but it really does little more than create a hand off from your Web browser to your Windows Media Player.

Creating the ASX
Creating your ASX file is as easy as opening your text editor. An ASX is a lot like writing HTML except the file ends with a ".asx" extension. So in your blank text file, type the following markup to stream a file from your HTTP Web server:

<asx version = "3.0">
<title>Your Show Title</title>
<entry>
<ref href= "http://www.yourisp.com/yourfolder/yourasf.asf" />
</entry>
</asx>

Then save your file with the ".asx" extension and you are ready to go. It's that easy. In the above code, the "asx version" identifies the current version of the ASX format. Even though the Windows Media Player is version 4, ASX version 3 is the current requirement. The "title" field information will appear in the "Show" box of the player. "entry" creates the block that contains the clip itself. You can add additional attributes here for clip name, author, and copyright. Consult the Microsoft documentation for further information on adding these attributes. For our reference to the ASF clip itself, a "ref href=" command makes the link to the media. In this case, I'm linking to a file sitting on a standard HTTP Web server. If you are coming from a Microsoft Media Services Server, an "mms:" in the place of "http:" will do the trick.

Linking to the ASX
From here, putting the first clip online only gets easier. It is time to link our HTML to the ASX file. If you are using a relative link to an ASX file in the same folder as your HTML, use the following approach in your HTML:

<a href="myasxfile.asx">Click for Video</a>

That is all there is to it. Upload your ASF, ASX and HTML files to your Web server and you are ready to try it out. You can try my WMT/ASF sample as well.

Shooting Video for Streaming (2)

What The Web Needs Now
So you need a streaming system. You need a streaming architecture that can figure out what to do with all that data.

Enter the Codec
Streaming architectures are made up of codecs. Codecs, short for compressor-decompressor, are basically mathematical formulas for handing your video information. As stated in their name, they do two things. They mathematically compress video data into something smaller. On the receiving end, they decompress that data into some form of displaying the video.

So the goal for a mathematically based codec is to do all this work as efficiently as possible. On the compression side, this usually means playing garbage man. The golden question becomes "how much can the codec throw away before the video is basically unusable?" After all, if you throw away data, you don’t have to pack it and ship it.

Obviously, quality is the first cost of this kind of process. You have to make things smaller in memory size so you shrink display size. Or you might cut down on the number of frames per second that are shown. You might throw out the fine details. Or make the audio sound less clear. Or, as is most common, do all of these steps and then some.

At this point most traditional video people get very righteous. "Look at that junk," they proclaim. "How can people use this stuff?"

It’s the Access, Stupid!
What critics of streaming video miss is the most obvious part. The game is about access to content. Streaming video is incredibly hot not because of the quality, but because that video can be effectively transmitted, on-demand, to any Internet connected device in the world. As bandwidth gradually improves, the long awaited age of interactive television is finally coming to pass.

What person with a good story to tell wouldn't accept some loss in quality in exchange for worldwide access to their content?

Understanding the Codec
So how does a compression formula (algorithm) really work. It gets pretty complicated. But there are some basics that apply to most compression technologies. Take advantage of those basics and you are well on your way.

Video

Shooting Video for Streaming (3)

Why is Change so Critical?

Two frames compared.
Codecs focus on change. Here, the change in the lion's head is where the codec can focus its attention.

A compression algorithm typically works best when there is no change in what it is trying to compress. Look at the graphic to the right. I have represented two frames of a video source. This is like one of those visual puzzles you find in kids magazines. What is different between frame one and frame two? A compression algorithm looks for change.

Forget how you see video and think like a computer. If change happens between two frames of video, that change has to be represented on the screen. You have to show the change between frames to get movement. If no change happens, the first frame can stand in for the second. That is because the first frame has the same information as the second. So while you are seeing two frames, you only need the data for one.

During encoding, a video codec basically does just that kind of work. Areas of change need more information. Areas that don’t change offer savings. In our example to the right, the lion's head will need the data between frames. The still and nondescript background will not.

While I am at it, there is one more thought about change. Most codecs lose data by losing detail. That means that sharp things get blurry the more you compress. Hard edges are harder to mathematically compress and maintain quality than imprecise soft edges. Since our example background has no edges, that will be easier for the codec to hide the blurring caused by compression.

Shooting Tips for Better Streaming Video
Now that we have these ideas down, you will see that it is from these concepts that I will offer most of my basic tips for improving your streaming video.

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Tip #1: Use a Tripod

In this handheld shot, the significant change is the shakiness of the camcorder, forcing the algorithm to hunt for anything to lock on to. A fuzzy zebra and background is the result.

Remember how I said that a codec looks for change? And how I said that if you have no change, you save data between frames? Well then your first goal should be to cut down on the amount of unnecessary change between frames.

If you shoot video with the camera in your hands, every slight move you make is translated into change between frames. And not only is your subject moving but now every pixel in the frame is sliding around like it is in a washing machine. The compressor will do its best but these are rotten working conditions.

Buy a tripod. Then use it. Can’t use a tripod where you are going? Get a small monopod (a tripod that is missing two legs). Can’t carry a monopod? Find something to steady the camera. Lean up against a wall. Use a bench or a chair. Set the camera down on something and use a piece of clothing to position and cushion the camera. Do anything you can to lock that camera down. Camera stores even sell tiny table-top tripods.

Remember that the motion of your subject is what you are trying to capture. Why waste resources on other pixels that are not important?

Shooting Video for Streaming (5)

Tip #2: Avoid "Spray Painting" and the "Yo-Yo"
I have taught video production for a few years. There are three truths to the work of beginning students. One, they usually fail to use a tripod. Two, if there are homeless people or protests, that is what they’ll shoot. Three, when given a zoom lens and the ability to pan the camera, they will do so constantly.

Fuzzy tiger image
How about a game of find the tiger? In this panning shot of a pacing tiger, the video degrades to a blocky blur.
"Spray Painting" is a term sometimes used for bad panning of the camera. You see something on the right so you pan over to it. Then, you decide to go back where you were and pan back. You have just spray painted the scene.

A "Yo-Yo" is similar but with a zoom. You have a wide shot, but something happens and you want to feature that up close and personal. So you zoom in tight. Then, because you want to make sure the viewer understands the larger context, you zoom back out. That motion you are feeling when you watch the video is your eyeball yo-yo-ing in and out of their socket.

What did we learn already?
Movement is bad. Panning in any form is probably a no-no. If you are working on a presentation that will also go to tape, you might shoot a well-composed pan and a series of still shots. Use the pan in your taped presentation. Use the stills in your streaming presentation.

Zoom lenses create a feeling of power for anyone that holds a camera. But just because you can do something doesn’t mean you should. Use the zoom to compose your shot. Then start the tape. Then keep your fingers off the zoom. If you want to change the view, pick up the camera and move it (on the tripod, of course). Find your shot, then lock it down and record.

Shooting Video for Streaming (6)

Tip #3: Simplify the Background
Simplifying the background of your subject can greatly improve your streaming video. Why? If the compressor can ignore your background and concentrate resources on your subject, you end up with better streaming of your subject.

Eagle image with simplified background.
Here is a high-action frame of an eagle compressed at the same settings as the tiger on the previous page. A tripod and a simplified background raise the quality significantly.
Obviously, if you can put your talent in front of a very blank wall you will be ahead of the game. But that is not always possible. Look for other options. Perhaps you should look down on the subject and get more uniform grass than chaotic trees in the background. Or maybe you should go the opposite direction and lose ground objects by shooting up toward the sky. Anything do to cut down on the background clutter will make the codec happier.

Portrait of Success
Consumer camcorders often come with a portrait mode. This feature takes advantage of a physical reality of lenses called depth-of-field. Depth-of-field is the range in the scene before you at which the lens is in focus. Things that are outside of the depth-of-field are out of focus. All lenses let light into the camera through a hole. The wider the hole, the shorter range or depth-of-field that the camera can show in the scene. The smaller the hole, the greater the depth-of-field the camera can show.

Since the goal of a portrait is to focus on the subject at the expense of the background, a portrait mode on a camcorder is to make the subject sharp while the background is out of focus. It does this by raising the camera shutter speed. That in turn balances the exposure by widening the hole (aperture) and letting more light in. Professional camcorders don’t always have a convenient portrait mode to choose from. In that case, just raise the shutter and open the aperture manually.

If you have had trouble following the two previous paragraphs, let’s stop and catch up. You know you want to simplify the background for the compressor. So, by using a portrait mode, we blur the background. Not only will that make your subject more pleasing to look at, but that smudgy soft background is now easier for the codec to mathematically crunch aggressively.

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Tip #4: Get Up Close and Personal
Of course, one way to lose the background is to fill the screen with your subject. This is something you really need to work on when shooting your video. But it has more advantages than just the mechanics of compression.

small ape
By its nature, streaming video is often a smaller image to begin with. That can make an acceptable video image unusable on the computer screen.Unlike our eagle on the previous page, this wider shot of a gorilla loses him in the grass. If possible, get in much closer by moving the camera or zooming the lens.
Using a video camera changes your perception. You are trying to catch everything going on. So you naturally choose a relatively wide shot of the scene. In your eyepiece, it seems fine. On your monitor or television, it seems fine. Online, you can’t see what is going on.

When shooting video for online use, step in and get close to your subject. At about the point it feels psychologically too close, step in further. There are a lot of reasons for doing this. Remember that your online video is probably going to be displayed much smaller than full screen. That drop in scale helps the compressor save data. Also, close-up video will seem sharper, even if it really is not. That is because the viewer can back up to see the details instead of leaning in. It is the same approach that billboards use. And finally, getting in close means your portrait mode will be more effective at blurring the background. That is because the lens depth-of-field is shorter the closer you get.

With all of these characteristics working for you, getting up close and personal will make your video more effective online.

Tip #5: Use an External Microphone
Getting in close works for more than just the camcorder. It is also a principle to use when capturing audio. You want the closest and cleanest audio you can gather. You need to use an external microphone.

The built-in microphone on your camera is designed for convenience first, quality second. It is a non-discriminating device that usually picks up everything around it. That means your tape captures great sound of the camcorder itself, the ringing phones in the outer office, the centralized air system, and the honking taxi outside.

All that background noise creates the same problems for an audio codec that background detail creates for a video codec. If the audio is clear, it is easier for the codec to pull constructive patterns from the mix and throw away the rest.

But there is another side to this issue that you might not consider. Since audio and video are handled separately, getting good clean audio has another big advantage. The better the audio, the more you can compress. Good clean audio that is compressed at the most aggressive settings is often still acceptable. That means you can balance more resources to getting the most out of the video.

So plug-in a microphone and go right to the source of your audio. Not only will you get cleaner results, but your video may gain the room it needs to look better.

Choices not Restrictions
It is important to view these tips as choices, not restrictions. Armed with the knowledge you have gained, you can choose to implement these solutions in your video shooting. If you choose not to, expect that you are going to have to compromise in your streaming video somewhere else.

So where do we go from here? In my next article in this series, I will take a look at tips you can use in the editing process to get the most of your streaming video.

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