Streaming Media

James Madison University

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Information

• Home Page
• Overview
• JMU Specs

Create

• Digitizing
• Ripping
• Encoding

Implement

• Logging In
• Uploading
• Linking

Encoding

Encoding is where we convert the video we captured in the digitizing or ripping stage and convert it to a format appropriate for streaming on the web. This is the stage where many decisions need to be made. It's worth noting that we will mostly be speaking in terms of video, though the same concepts apply to audio files as well.

Who is my audience and how are they connected to the web?

Streaming media is usually measured in terms of it's bitrate. That is, how much data is required per second (or kbits per second) to display the video. A high bitrate means better looking files, but excludes those with lesser internet connections. A lower bitrate means that your users will get sub-par video and may not bother. As with most things, the best choice is found somewhere in the middle and may be different for different applications. A video viewed almost entirely by JMU undergrad students can likely be encoded at a higher bitrate since most have access to a high speed connection.

Once you have determined a reasonable bitrate for your files you'll need to adjust the physical dimensions, frame rate and the codec you use in order to get the best looking video for the smallest file size.

Physical Dimensions

The native size of standard definition video (most currently available video) is roughly 640x480. Cutting this size of your frame down to even 512x384 can reduce your bitrate needs by up to 50%. 320 x 240 is usually as small as most video can get and still be instructionally useful.

Frame Rate

Video is made up of rapidly moving still images. There are as many as 30 of the images (or frames) each second. Bringing this frame rate down is another way to drastically reduce the amount of data necessary to display your video. The low frame rates can cause your video to flicker however, so it is usally advised not to go much lower than 15 frames per second unless absolutely necessary.

Codec

This is where things get a bit tricky. Choosing a codec is like choosing the language the server will use to communicate the video to the viewer. In order for the viewer to watch your video, he/she will have to "teach" his/her computer how to understand and display that video. You teach you computer to understand a codec by installing that codec on the computer. This brings us to two generally conflicted aspects of codec choice.

• We want to choose a codec that is widely deployed so that as few people as possible will have to download extra software in order to view our video.
• These widely deployed codecs are generally of a much poorer quality than more modern codecs.

A much more technical explanation of codecs can be found in this Wikipedia article.

In the classroom setting, it's ususally best to pick codec and stick with it. This way, you can simply warn your students at the beginning of the semester that they'll need to download the software ahead of time in order to view the content. If you're making use of many online technologies, it's generally a good idea to have a place set aside (say in Blackboard) where students can go to download any necessary software for the course. You can find similar links on the Resources page.

At CIT, we mostly use Sorenson Squeeze to encode files captured and editing using iMovie. There are many solutions for encoding video, though not all can create streaming compatible files. Many streaming formats provide inexpensive or free tools for encoding their particular formats. Just be sure that the format you choose is supported by the streaming server you intend to use (check the Specs page for our supported formats). Other resources for encoding, including free ones, can also be found on the Resources page.

Commonly Used Codecs and Formats for Streaming

Download players for any of these formats from our Resources page.

• MP3
  • This older but still widely popular format is the source of the majority of digital audio files. Our server will treat .mp3 files as QT files. Nothing special needs to be done to the .mp3 file in order to spend it.
• Quicktime/MPEG-4/AVC/H.264
  • MPEG-4 has essentially become the native streaming file format for Quicktime. All of Apple's own streams are MPEG-4. AVC and H.264 are essentially just improvements to the MPEG-4 format. QT files have to be "hinted" before they can be streamed. QT streaming file can end in .mp4 or .mov. This is the format favored in CIT for it's excellent quality and solid cross platform support (.mp4 files can be played even on alternative platforms such as Linux).
• Windows Media
  • Microsofts own streaming media format has much to recommend it in high quality and the fact that it's player is already installed on most student's machines. It's failing is it's shoddy support on the Mac and Linux.
• Real Media
  • Judged on technical merit alone, Real is a fine format. Real is not supported on our streaming server due to the intrustive nature of it's player and the expensive of offering the service.
• Flash Video
  • Flash video differs from all the other formats we've mentioned in that it can not be played by a standalone player. With the introduction of Flash 8, Flash video has comparable quality to that of other modern video formats. In order to deploy Flash video, instructors must build their own player using Flash, which can be a daunting task. It's worth noting that Dreamweaver 8 includes some tools to make this feat much simpler. CIT is also developing a system that will allow users to build their own player directly from My Account.