RealPix: The SMIL Graphics Format

In my first article, Introduction to SMIL, I gave a broad overview of RealNetworks' implementation of Synchronized Multimedia Integration Language. If you haven't read that article, it might be a good idea to do so now, before continuing with this more advanced "Part II." In this piece, we'll focus in on one of the most important parts of RealNetworks' strategy for using SMIL, the newly introduced RealPix picture format. Much like RealAudio and RealVideo, which define audio and video respectively, RealPix defines (as you might expect) graphics.

RealPix is not a new graphics format. They are special JPEG files or GIF files that can be streamed over the net from a Real G2 server. GIF files can be used unmodified. JPEG files are transformed using a horrible little program called JPEGTRAN that unbelievably still needs to be run from the DOS command line. There is no Macintosh version available at this time. JPEGTRAN modifies JPEG files so that if any of the information is lost during streaming the lost data is randomly dispersed instead of appearing as continuous blank lines across the image. The JPEGTRAN program should be placed in the same directory as the JPEG images that you wish to convert. Start up a DOS window and move to the directory containing the JPEG files. Once in the directory the JPEG files can only be converted one at a time using the syntax listed below. Output.jpg is the new name of the RealPix file and input.jpg is the current name of the JPEG file. You can not overwrite the old file.

jpegtran -restart 1B 
-outfile output.jpg input.jpg

Yes, it is horrifying that such an important step in SMIL production must be done one at a time in a DOS window. Fortunately there are some workarounds. Real does provide a batch conversion capability.

You can run jpegtran.exe in batch mode from the RealPix Bandwidth Calculator. For exact instructions on how to run JPEGTRAN from the Calculator click here. Some of the third party WYSIWYG tools also contain batch conversion utilities. T.A.G. Editor 2.0 - for RealSystem G2 is a good example of such an editor available for both Mac and PC. Another good WYSIWYG editor is Veon's V-Active for RealSystem G2.

T.A.G WYSIWYG SMIL Editor

There are some additional tips and tricks I've picked up doing everyday SMIL production at Discovery Channel. You can use JPEG files that have not been run through JPEGTRAN. In reality you will have data loss during streaming that results in a "black bar" on JPEG maybe once every 1000 downloads. If this is acceptable you can forgo converting with JPEGTRAN. The Real G2 Player does not do caching of data. Thus every time you play the SMIL presentation it must be streamed. Also Real Pix does not support progressive JPEGs or grayscale JPEG. Grayscale will display, but the horizontal resolution is cut in half to produce a very strange image.

• The RP File
• The <fill/> Tag
• Examples
• Conclusion

RealPix: The RP File