WebTV custom dialing progress text demo

I think I've accomplished at least what only one person has ever done before: hacking the "TellyScripts" used for dialing access numbers from WebTV (later MSN TV) boxes and loading it onto a box of my own to change the normal dialing progress text to my own. This was recorded from a Sony INT-W100 unit through composite video on September 9th, 2021. Needless to say, I'm impressed I was able to get it to work on my first try, even if my edits were just changing the dialing text. And I'll just quickly preface this by saying no, I'm not a WebTV hacker from the scene, although a few people from it have been helpful with covering various aspects of WebTV/MSN TV to me, mainly for the WebTV/MSN TV Wiki I run.

This wasn't a trivial task, either. TellyScripts are a completely proprietary dialing script format developed by WebTV in-house, and while the script format itself is almost completely documented now, the compression algorithm it used wasn't very documented. At the time I took on this task, there was only working code that could decompress TellyScripts, not compress them. The compression used is a variation of the LZSS algorithm, and while WebTV hacker Eric MacDonald had already written code in Python that could compress data with this algorithm, the code he had sent that I received appeared to not work very well. Since this individual isn't very active online, I figured I'd challenge myself by figuring out the algorithm myself. So I found a version of the algorithm in C that was identical to Eric's and tried to cross-reference it with the homegrown code to see what was different. After a day of tinkering and frustration with understanding C, I was surprisingly able to figure out the algorithm WebTV used, which changed very little from the original algorithm, and I was able to create 1:1 matches using it on an existing TellyScript that I had already decompressed. With that, I was able to compress a TellyScript I edited (the one you see being demonstrated in the video) and convert it into a format WebTV would download from the phone line. Thankfully, the task of setting up a local server was trivial for the most part. I already had a DreamPi I could hook up, and with the few open source servers targeting WebTV that are now available, I went with using zefie's "mini server" on the Pi with a few tweaks to make it serve the custom TellyScript I made and to show the original splash screen after connecting. Imagine my shock when I found out that after my box downloaded the custom script, it started showing all those stupid messages I added to it. In total this took around two days to create and put together. I'll consider at least publishing the modified LZSS compression code soon if it isn't too much of a hassle to clean up.

Hopefully this might convince others to pursue other hacking endeavors with WebTV/MSN TV and announce them to the world. Much has been done with WebTV/MSN TV and hacking already, but mostly in private. Think it's time we change that.

By the way, I'd like to thank the following for making any of this possible:
Ex-WebTV Networks employee Andy McFadden for completely documenting the TellyScript format: https://gist.github.com/fadden/09b581...
Eric MacDonald, for taking the time to reverse engineer the WebTV LZSS compression and assisting with other technical aspects of WebTV/MSN TV that I can't even imagine trying to figure out right now.
zefie, for creating the mini server and saving me hours of writing another program just for this project: https://github.com/zefie/zefie_wtvp_m...
My incredibly hacky DreamPi setup, for making it possible to get the WebTV online in any capacity.
The quality Hauppauge USB capture device used to record this video. Seriously worth the $50. :)
The eBay seller who was kind enough to send me a free INT-W100 during an auction mishap.
Perseverance

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This channel is part of a bigger project to document any and all information on WebTV/MSN TV. Check it out: https://wiki.webtv.zone