Manfred Kuechler

Streaming Video (Helix) Server Test Page


Last update: 11 July 2003

I make this document available in an effort to stimulate discussion and cooperation among professionals (faculty as well as IT folks) interested in instructional technology. I appreciate any comments you may have as well as reports if things do not work as described below.  When reporting errors/glitches, try to be very specific. In particular, provide exact versions for the software (browser, players) and the platform (Win ?, Mac ?) you are using as well as your connection mode (telephone modem, DSL, cable, T1, etc.) and speed.

Significant changes/additions
July 10/11:  Discussion of WME version 9 and Windows MBR files added.

Objective and Scope of Exploration

The Helix Server (version 9) does not  only serve RealMedia's own streaming video (.rm) files, but also  Windows Media files (.asf, .wmv, .wma) for display with the Windows Media Player and QuickTime (.mov) files for display with the QT player. Thus, one server can be used to stream all files -- accommodating all faculty among which  preferences with respect to software used for the production of instructional video material may differ. It would make sense to set up one powerful (hardware) server and use it exclusively for the Helix Server as a complement to the Bb server -- rather than running separate streaming servers (like Helix and QuickTime Streaming Server).

However, vendor descriptions often do not fully match the actual performance of their products. This page documents a practical exploration of the Helix server's ability to serve as a truly "universal" server. For now, it is limited to "on demand" video -- in contrast to (live) broadcasts -- which is the more important mode for asynchronous distance learning and web enhanced traditional and "hybrid" courses.

Though it is beyond the scope of this document to describe the production side of video material in detail, it is useful to discuss the production aspects briefly as well. Windows media files appropriate for streaming can be produced with the (free) Windows Media Encoder (version 9 for Win 2000/XP, version 7 for Win98/Me), QT files appropriate for streaming with the full version of the QT player. The player itself is free, but to unlock the production features a paid registration is necessary. The Helix Producer is used to generate .rm files; a free version with limited functionality is available. Both WME and Helix Producer offer the option to use input directly from a video device (VCR, camcorder, camera) using a suitable hardware connection (video capture card, firewire/1394 adapter, etc.). For this exploration, video material already captured and saved as .mpg file is used.  It is a brief excerpt of some 15 seconds taken from a bio clip. This clip was recorded with a digital camcorder (Canon Ultura 10 equipped with a directional microphone [DM 50]) on a miniDV cassette. The video was captured using a 1394 adapter and Sonic MyDVD software which stores the file in MPEG-2 format using Ligos/Indeo codecs which may require an additional mpeg-2 adapter to be played by WM, QT, and Real players (contingent upon platform and installation of additional software).  In addition, ArcSoft's ShowBiz video editing software was used to saved the original files in both .mov and MPEG-1 format to work around mpeg-2 access problems.

The original .mpg file was 640x480 (full frame) and some 13 MB in size. Resaving as mpeg1 and changing the video size to 340x240 reduced the file size to under 4MB. The original video clip is far from perfect, it was shot quickly to have some material for this exploration. In particular, the brightness should be adjusted (and this has been done for the QT files, but not for the others). Note that the shirt I am wearing in this clip provides a tough test for producing  streaming video file of decent quality. Especially in the modem version, it tends to  show some distortion of actual fabric patters (either "moire" or "wash out"). The audio quality, however, is quite good in all versions.  Some variations is due to varying audio settings (e.g., mono vs. stereo) as I have not been fully consistent in producing the different versions.

In producing the streaming versions, I assumed the latest version of each player (RealOne version 2, WMP version 9, QT 6.3) and have made no attempt of providing compatibility with older versions of the player. To play all the files linked below, it may be necessary to update your players and/or download additional codecs (like mpeg-4).  Most of the streaming video files were produced on a Win Me (my home) station, the initial capture and editing (with ShowBiz) was done on a Win XP (my office) station. Using WME version 9 (e.g., for MBR files -- see below) also required the use of an XP station.

The Helix server used here resides on a RH Linux 7.1 box ("maxweber.hunter.cuny.edu") which also serves as a regular web server with just 512 MB of memory, the very minimum required for the Helix server. The current license allows for 60 concurrent streams.

RealMedia files

There are two versions differing by video size: half frame (320x240) and quarter frame (160x120). Both versions include subfiles for different target groups (56K modem connections and 256K  DSL/cable connections). Using "sure stream" technology, the server determines the approriate subfile automatically and may switch to a better suited subfile (during longer clips) if the connection quality changes. This, of course is not likely to happen with the short clip here and with only two options which are fairly wide apart. The quality of the "half frame" version under modem connections is pretty bad. For modem connections, the "quarter frame" version should be used.
Here are the links shown openly:
Note that the Helix Server produces a meta file (.ram) file automatically -- as indicated by the "/ramgen" part of the URL.  The .rm files are of size 568 and 508 KB, a great reduction from the original video file. Also note, that with sure stream technology only a subfile is actually delivered to the end user's computer.

Windows Media files

There used to be no equivalent to Real's surestream technology. Each streaming video could only serve one audience (connection speed). Using the default settings, WME (version 7) selects "half frame" for  256K DSL/cable connections and "quarter frame" for 56K connections. Here are the links shown openly:
Note that, again, the Helix server generates metafiles (indicated by the "/asxgen" part). Windows uses its own "mms" protocol (rather than "rtsp" as Real and QT do) and the metafile is used to tell the browser to start the Windows Media Player which in turn  generates the actual URLs for the media file it requests from the server using a specific port (default is 1755). The ".asx" at the end of the URL is not necessary if a user has a recent version of the Windows Media Player installed; it is not part of the actual file name (as stored on the server). Its sole purpose is to achieve compatibility with older versions of the Windows Media Player. Apart from the ".asx" affix, the handling of Real and of Windows streaming video files is quite similar. File sizes are 542 and 69 KB, not much different from the .rm files.

The latest version of WME (version 9), however, allows to produce MBR (multiple bit rate) files, quite similar to what you can do with the Helix Producer (and the RealProducer earlier). Here is the link to this MBR file created for 56K modem and 256 DSL/cable connections:
Clicking this link on a DSL connected computer starts the larger frame and clicking the link on a modem connected computer starts the smaller frame (as it should). However, while the small frame (modem connection) plays continuously, the larger frame does not. Rather the displays stops at a specific (always the same) point and WMP is rebuffering. Since the breakdown occurs at exactly the same spot (just before the "Hi, I am ..." part), general Internet congestion is not the cause. Unfortunately, I don't have access to a Windows Media Server so that I could check whether this MBR file would serve fine from there. For now, my working hypothesis is that the Helix server  does not  fully support .wmv MBR files.


Quicktime files

There is no equivalent meta file generation for QT files. Rather, a "reference movie" must be produced which serves as the meta file. Details about creating multi-audience (connection) streaming video files with QT can be found on the Apple web site. Again, as with Windows, a separate file must be produced for each audience first. However, using the reference movie is then possible to offer only one link on a web page, and the QT player will determine which video file to request from the server automatically. This decision, however, is based on how the end user configures the QT player (via properties/connections) not on the actual connection speed (as with Real). If the QT player is misconfigured, a telephone modem user may get the larger file -- which the connection cannot handle resulting in distorted video and/or lack of audio. On the other hand, a DSL/cable user may get the small frame meant for telephone user.  To eliminate the possibility of  a QT player misconfiguration, it may be prefereable to present the user with explicit choices -- omitting the creation of a reference movie.  However, steps 1-5 (as specified below) must still be followed and the movie(s) created in step 5 must be used in place of the reference movie.

While the instructions about creating reference movies on the Apple site are accurate and will work when followed in each detail, it be may be helpful to point out  a few possible glitches:
The instruction sheet from Apple recommends to embed the reference movie  (rather than just linking to it).  However, the <embed> tag does not work for  newer versions of MS IE (5.5 and up), so  it is necessary to  use an <object> specification as well. The details are described in another document on the Apple QT site.

Space for embedded QT Player


Rather than embedding the "reference movie" one could simply link to it.  Then, the browser will open the QT player in a separate window -- which may be preferable anyway. Note that users with a telephone modem connection should see a small (quarter) frame whereas other should see a larger (half) frame.

The actual media files (on the Helix server) are 1119 and 519 KB in size, considerably larger than the corresponding Real and Win files. These are the "hinted" versions, the initial versions (no hinting) are comparable in size to Real and Win with 581 and 84 KB.

Summary of Reader comments

9 July 2003:
Erik Kunnen (Grand Rapids Community College) alerted me to a software tool for batch processing of the encoding task, Cleaner  5, which they have used at his institution. A newer version Cleaner XL  (for Windows) and Cleaner 6 (for Macs) is now available. However, at over $500 , the expense is considerable and probably justified only if there is a high volume of video materials and all encoding is done centrally.