Tag Archives: nes

Revenge Of PAVC

Remember my old PAVC idea? I have been thinking about it again. As a refresher, this idea concerns efficiently and losslessly compressing RGB video frames output from an emulator for early video game systems such as the Nintendo Entertainment System (NES) and the Super NES. This time, I have been considering backing off my original generalized approach and going with a PPU-specific approach. (PPU stands for picture processing unit, which is what they used to call the video hardware in these old video games systems.) Naturally, I would want to start this experiment (again) with my favorite — nay — the greatest video game console of all time, the NES. Time for more obligatory, if superfluous, NES screenshots.

Little Samson (NES) game map
Little Samson
, all-around awesome game

Here’s the pitch: Modify an emulator (I’m working with FCE-Ultra) to dump PPU data to a file. Step 2 is to take that data and run it through a compression tool. What kind of data would I care about for step 1? On the first frame, dump out all of the interesting areas of the PPU memory space. This may sound huge, but it is only about 9-12 kilobytes, depending on the cartridge hardware. Also, dump the initial states of a few key PPU registers that are mapped into the CPU’s memory space. As the game runs, watch all of these memory and register values and log changes. This really isn’t as difficult as it sounds since FCEU already cares deeply when one of these values changes. When something changes, mark it as “dirty” and dump that value during the next scanline update.

With that data captured, the next challenge is to compress it. I am open to suggestions on how best to encode this change data. I would hope that we could come up with something a little better than shoving a frame of change data through zlib.

Decompression and playback would entail unraveling whatever was performed in step 2 above. Then, the decoder simulates the NES PPU by drawing scanline by scanline, and applying state change data between scanlines.

What are the benefits to this approach? Ideally, I am aiming not only for lossless compression, but for better compression than what is ordinarily achieved with the large files distributed via BitTorrent and coordinated at tasvideos.org. When I first started investigating this idea over 2 years ago, MPEG-4 variants were still popular for compressing the videos. These days, H.264 seems to have taken over, which performs much better, even on this type of data (allegedly, H.264’s 4×4 transform allows for lower artifacts on sharp edge data such as material from old video game consoles).

Sword Master (NES)
Sword Master
, mediocre game with great graphics

There are also some benefits from the perspective of NES purists. The most flexible NES emulators allow the user to switch palettes in order to get one that is “just right”. A decoder for this type of data could offer the same benefits.

Of course, an encoder is not much use without an analogous decoder that end users can easily install and use. I think this is less of an issue due to the possibility of creating a decoder in Flash or Java.

Shortcut To The Treasure

Followup: Some Reddit readers tackled this challenge and conquered it. Read up on it here.

Treasure Master (NES) cartridge

Back in the glory days of the old 8-bit Nintendo Entertainment System, I used to read my Nintendo Power magazine issues religiously. One issue that stood out to me, and that I never forgot about, is one that briefly mentioned Treasure Master (volume 26, July 1991, Robin Hood: Prince of Thieves issue).

This will be the first NES game where you can actually win prizes by playing it to the finish! The Game Pak will be released in the fall, and everyone will have time to master it. When you finish the game, you’ll reach a point where you can enter a speical password. In February of 1992, American Softworks will reveal the password that will allow you to play a secret portion of the game. The first person to finish the secret level and call in will win a $25,000 bond. Many of those who finish later will still be eligible for prizes– the sooner you finish, the better the prize. As you can imagine, the code is top secret, and the password system has been proven uncrackable by MIT and the CIA. (emphasis added)

Nintendo Power -- Robin Hood cover       Treasure Master (NES) -- Nintendo Power
click for larger image

So the gimmick for this substandard, side-scrolling, run & jump game was that players would buy it, play it, and build up skill in a few months. Then, after everyone has had a chance to get really good at the game, the company would release a password that would unlock a secret stage. Play through this stage and you could win big prizes.

Treasure Master (NES) -- Title screen

Naturally, the part about the uncrackable code caught my attention. I didn’t even realize the CIA provided such a vetting service. Anyway, I didn’t hear anything else about the game again. Many years passed and I saw the game in a used video game shop. I figured it was time to revisit the uncrackable code issue since I know a little more about computers and codes now. And I also know better than to accept an uncrackable code claim at face value.

How uncrackable is the code? The introductory blurb from Nintendo Power raises some questions, many of which can be answered by the Treasure Master instruction manual. The full details of the contest are provided. Apparently, the password was to be announced on MTV on April 11, 1992, probably during a commercial. Players would enter the password, along with their game cartridge’s unique serial number, in order to unlock the special levels of the game. Upon completion of the levels, the game would return a special winning number that the player could give to the operator on the other end of a 1-900 phone number to try to win a prize.

To be fair, the official manual doesn’t mention the uncrackable code nonsense. The James Bond material highlighted in the Nintendo Power preview can probably be attributed to some Marketing/PR flunkie at American Softworks working more closely with the magazine than their own engineering department.

Also, Nintendo really wants you to know that they have nothing to do with the contest:

Treasure Master (NES) -- Disclaimers

Threat Model
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