Digital Video

The key to successful digital video is compression and deployment.  Here are Kevin’s tips for success.

MPEG-4 video Compression (H.264)

Since the iPod is an MPEG 4 device, I like to compress video that will work on it, even if my video will be online and never download to an iPod.

iPod Video capabilities

iPod Touch / iPhone/ iPod Classic / iPod Nano

• H.264 video up to 1.5 Mbps, 640 by 480 pixels 30 frames per second
• MPEG-4 video, up to 2.5 Mbps 640 * 480 pixels, 30 frames per second

As you can see the iPod can play video that is a greater resolution than it’s screen displays resolution.  This is cool because you can create video (640 * 480) that will look good on a computer at full screen or near full screen and will also play on an iPod.

Keep in mind the smaller the resolution the lower the date rate is needed. This means smaller files, less stress on a server to deliver the video, less bandwidth needed to deliver the video, less computing power to decompress the video.

The resolution, (size of the video) and the data rate you will need to compress it as, is a variable that will need to be chosen based on the content of the video.

Initial Settings

Video Resoultion 320 * 240

Average bit rate  500 kbit/s (Start here and adjust up or down depending on motion in the video)

Audio  Mono (use stereo only if really needed)

Audio try 32000 Hz (44100 Hz or 48000 Hz if you need full CD quality audio )

This quality video will even look good when blown up a bit.

NOTE: You will be able to reduce the data rate for camtasia or powerpoint/audio type presentations.

Playing video in your online course

Use the JW Media Player http://www.longtailvideo.com/players/jw-flv-player

This free player is flash based and can be embedded into an web page.  In fact your institution can have a webpage with the player embedded and you can launch it and feed a video clip to it through the URL.  This is really a cool player.  Once you use this, your tech support will really drop.  All students need is the Adobe Flash Player installed on their machine.  Nothing else.

Tip

If you increase the video resolution from 640 * 480 you will need to increase the data rate some.  If you are only showing in a player at 320 * 240, then probably not.  A good test is to encode the video at 320 * 240 and then open in quicktime player.  Go to Window - Show Movie Inspector.  This will show you what the video was encoded at.  It will also show you the current resolution, which if you now make the video window larger it will show you the size. Make the video window larger until it reaches 640 * 480 and look at the quality.  This will give you a good indication.

It is reccommended that you take a sample of several video clips and encode them at several data rates.  See what works best for your institution then set those as standards.  Come up with some instructions or tools with those presets for encoding.  Realize that every tool you use may use a different brand of encoder, so the same results may not happen across different tools.