Helix Server generally can stream MPEG-4 (.mp4) clips encoded with any codec, as long as the clips include a hint track. In addition, Helix Server can stream clips encoded with certain codecs whether or not the clips contain hint tracks. The following are the MPEG-4 audio and video codecs that do not need to include hint tracks. For these codecs, Helix Server refers to the hint track if it is present, but still streams the media packets if the track is absent:
- H.263 profile 0 and profile 3
- MPEG-4 Part 2 simple video
- AAC (all supported versions) [.aac is not supported]
- AMR-NB (narrowband) and AMR-WB (wideband) [.amr is not supported]
Storing Media Files on the Helix Server the First Time
To store media files on the Helix Server for the first time, you will need to fill out the application form found on the Streaming Media File Storage Application page. After submitting the form, you will receive an email confirming the application and further instructions on using the appropriate server.
A unique file directory will be set up on the Helix Server for your media files; you may create subdirectories within this directory. An FTP account is also created on the server for you. You will use FTP access to upload your media files to the server, enabling you to store files anytime and have them immediately available for streaming. After uploading a file you will need to advertise its URL, e.g., through your personal web page or web-based instruction page (such as Bb Learn). See the Helix Server Technical Information section below for more details on how to have your clients access your media files.
Why Use Helix Server for Media Files?
Why would you use the ITS Helix Server for your media files? Two key reasons are server features and 24-hour-a-day, all-year server support. Though some audio/video files may be hosted on an ordinary web server, there are limitations to their use. Web server playback uses the HTTP protocol and provides a reasonable method for sending simple presentations to a small number of users. However, it is not recommended for lengthy or complicated presentations, or for clips viewed simultaneously by large groups.
Some features that HTTP protocol cannot provide are the ability of RealPlayer to adjust the download speeds to adapt for network congestion. Also, HTTP cannot synchronize simultaneous clips such as animation and audio in RealFlash. Web servers cannot serve SureStream clips or present live broadcasts. Also, moving the Clip Position slider on RealPlayer will cause the file to stream data from its beginning to the player. As the video reaches the desired clip position, the user will see the buffering notice displayed, but no video or audio is displayed. HTTP cannot pick its starting position partway through a file.
Helix Server uses the RTSP protocol, which is designed specifically to stream clips that have timelines. RTSP lets RealPlayer and Helix Server exchange information about a presentation in progress and dynamically adjust the streaming data from pre-roll through the end to keep the clips playing smoothly throughout. Properly encoded media files on the Helix Server can begin playing at any start point after a short buffering time. The clip position slider can be moved on the RealPlayer, Windows Media Player, and QuickTime Player to any position. After the buffering time, the clip will start playing from that position. The clip does not have to start from its beginning and send all the video/audio up to the new starting position.
The RealNetworks SureStream technology, which is available exclusively in RealSystem and operational with a Helix Server, lets you encode a single RealAudio or RealVideo clip for up to six separate bandwidths, and even select a backwards compatibility option to include an encoding for earlier versions of RealPlayer.
RealPlayer will then automatically select and play the correct version for the bandwidth of each individual viewer, and can even shift dynamically to a lower or higher version as network conditions change. The Helix Server also can set up live broadcasts and employ password authentication.
Helix Server Technical Information
For FTP access to the ITS Helix Server video server, use this address: helixserver.its.iastate.edu
realserver.ait.iastate.edu will remain usable, but you are encouraged to use the new helixserver.its.iastate.edu name.
Login with your assigned username and password. You will be placed directly into your default directory. The directory name may not show on some FTP programs so you'll have to trust that you are in the correct location.
Referencing a Media File from a Web Page
The URLs below can be put in a web page. When they are clicked, the appropriate player will start in a new window.
- To reference Real media files on the server: http://helixserver.its.iastate.edu:8080/ramgen/directory/filename where directory and filename are replaced with the directory name listed above and the filename of any file uploaded to the server.
- To reference Microsoft Windows Media files on the server: http://helixserver.its.iastate.edu:8080/asxgen/directory/filename where directory and filename are to be replaced with the directory name listed above and the filename of any file uploaded to the server.
There is not an easy way to play QuickTime movies from a web page. A special MakeRefMovie file must be created that references the QuickTime movie, or a Poster movie file must be created. Keep in mind that all QuickTime movies created for streaming must be "hinted" for efficient and effective transfer. The frames that make up a video clip can become quite large for transmission, affecting efficiency. And, if any of these frames are lost in a streaming transmission, it can have a very negative effect on quality. When video data is hinted, frames are divided into smaller chunks of data called packets to increase speed of transfer and reduce the impact of lost data.
More about QuickTime movies can be found at: http://www.apple.com/quicktime/.
The MakeRefMovie tool is at: http://developer.apple.com/library/ios/#technotes/tn2266/_index.html.
To view media files from an embedded player in a web page, check out the web page: http://www.public.iastate.edu/~rdalhoff/embedvideo.html.
The page listed above contains samples of various ways to embed the different types of movies. Select View > Page Source in your browser to see the source of the web page and copy the code that you want to use for your particular media type.