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• Learn Multimedia Programming By Writing A JPEG Decoder

  6 janvier 2011, par Multimedia Mike — Programming

  For those of you who hack on multimedia tech, how did you get started ? Did you begin by studying the mathematical underpinnings of multimedia codec algorithms ? Or did you find a practical problem and jump right in by writing code ? (Personally, I was always more of a nuts & bolts hacker than a math guy.) I ask because I occasionally get emails from aspiring multimedia hackers who want to know where to begin. Invariably, they want to go the math-first route. I heavily discourage this approach.

  I have a crazy idea for anyone who wants a crash course on multimedia hacking : write a JPEG decoder. In doing so, you will be exposed to a lot of key domain concepts such as bitstream parsing, Huffman decoding, dequantization, zigzagging, the dreaded (inverse) discrete cosine transform, YUV vs. RGB colorspaces, macroblock organization, delta coding, and run length coding.

  Sure, JPEG decoding is a solved problem. But that’s hardly the point. Why would you enter an unfamiliar field and hope to come up to speed on the basics by leaping straight into the domain’s unsolved problems ? If you are successful in this exercise, no one will ever use the fruits of your labor, but that doesn’t really matter.

  So, do you want to learn multimedia hacking quickly ? Then grab a JPEG file (maybe create a few contrived ones that are small, have friendly dimensions, and feature predictable patterns), grab a good JPEG reference, and implement the decoding algorithm in the language and platform of your choice.

  On the matter of the reference, my personal favorite reference has always been A note about the JPEG decoding algorithm by Cristi Cuturicu. The English grammar is a bit dodgy but overall, it might be the best reference you’ll find on the matter— as simple as it needs to be, but no simpler.

  Good luck !

• Tele-Arena Lives On

  25 février 2011, par Multimedia Mike — Game Hacking

  Readers know I have a peculiar interest in taking apart video games and that I would rather study a game’s inner workings than actually play it. I take an interest on others’ efforts in this same area. It’s still in my backlog to take a closer look at Clone2727’s body of work. But I wanted to highlight my friend’s work on re-implementing a game called Tele-Arena.

  
  
  

  Back In The Day
  As some of you are likely aware, there was a dark age of online communication that predated the era of widespread internet access. This was known as "The BBS Age". People dialed into these BBSes using modems that operated at abysmal transfer speeds and would communicate with other users, upload and download files, and play an occasional game.

  BBS software evolved and perhaps the ultimate (and final) evolution was Galacticomm’s MajorBBS (MBBS). There were assorted games that plugged into the MBBS, all rendered in glorious color ANSI graphics. One of the most famous of these games was Tele-Arena (TA). TA was a multiplayer fantasy-themed text adventure game. Perhaps you could think of it as World of Warcraft, only rendered as interactive fiction instead of a rich 3D landscape. (Disclaimer : I might not be qualified to make that comparison since I have never experienced WoW firsthand, though I did play TA on and off about 17 years ago).

  TA was often compared to multi-user dungeons — or MUDs — that were played by telneting into internet servers hosting games. Such comparisons were usually unfavorable as people who had experience with both TA and MUDs were sniffy elitists with internet access who thought they were sooooo much better than those filthy, BBS-dialing serfs.

  Sorry, didn’t mean to open old wounds.

  Modern Retelling of A Classic Tale
  Anyway, my friend Ron Kinney is perhaps the world’s biggest fan of TA. So much so that he has re-implemented the engine in Java under the project name Ether. He’s in a similar situation as the ScummVM project in that, while the independent, open source engine is fair game for redistribution, it would be questionable to redistribute the original data files. That’s why he created an AreaBuilder application that generates independent game data files.

  Ironically, you can also telnet into a server on which Ron hosts an instance of Tele-Arena (ironic in the sense that the internet/BBS conflict gets a little blurry).

  I hope that one day Ron will regale us with the strangest tales from the classic TA days. My personal favorite was "Wrath of a Sysop."

• Dreamcast Development Desktop

  28 mars 2011, par Multimedia Mike — Sega Dreamcast

  Some people are curious about what kind of equipment is required to program a Sega Dreamcast. This is my setup :

  
  
  

  It’s a bit overcomplicated. The only piece in that picture which doesn’t play a role in the Dreamcast development process is the scanner. The Eee PC does the heavy lifting of development (i.e., text editing and cross compilation) and uploads to the Dreamcast via a special serial cable. Those are the most essential parts and are really the only pieces necessary for a lot of algorithmic stuff (things that can be validated via a serial console). But then I have to go up a level where I output video. That’s where things get messy.

  
  
  

  The Mac Mini and giant monitor really just act as a glorified TV in this case. Ideally, it will be more than that. The DC outputs audio and video via composite cables to a Canopus DV capture bridge. That’s connected via FireWire to the external hard drive underneath the Mac Mini, which is connected to the Mac. Adobe Premiere Pro handles the DV capture / display.

  One day I hope to have something worthwhile to capture.