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Reverse Engineering an MPEG Driver
An anonymous reader writes "Following on from the recent spate of reverse engineering articles, there is an interesting summary of the reverse engineering of a binary only Linux driver.
The driver is for the integrated MPEG decoder on VIA's popular EPIA-M boards. At the moment VIA has not publicly released the source code for the MPEG chipset on these boards and will only make the code available under NDA saying that "Typically, only requests from companies developing product for sale will be approved."
As a result this is holding back development of open source tools (e.g. xine, mplayer, vdr) that would be able to make use of the interesting hardware on these boards."
IANAL, but I don't think the source code is legally safe if VIA wants to go after it.
-mse
Fiat Lux.
To me, it just seemed like a general description of the RE process that people able to RE already know. EPIA M boxes are already good for small PVR boxes using mythtv when a Hauppauge PVR card is added (and a larger power supply). If the MPEG decoder can be used, I'm sure that even the lesser models of EPIA will be able to be used.
bananas like monkeys.
Should developers/users be afraid of the iron fist of moronic law in this case?
Or is it perfectly legal and VIA can not do anything about it? They seem to have an interest in suppresing such efforts though, since they've stated they are interested in revealing the code only to entities that want to make a buck off of it.
So, even if DMCA dosn't apply here, are there any chances they could be nasty about it? U-Boot
Driver code is the biggest liability that a device maker has. It earns no money, it costs quite a bit to make, and it must be written multiple times for multiple platforms and operating systems.
Via's reluctance to free the driver software is pure evil. They sit like slavemasters on the code and hold it hostage as if it were a servant or slave.
Even if the reverse engineering works out and the code runs equally well as the enslaved code, what will become of the original unfree code? Will that unfortunate code be relegated to living out the rest of its days in slavery? Sadly, I think the answer is affirmative.
Who will fight for the rights of software? I only wish the FSF was more vocal about the Freedom of Software that they purportedly base their ideology upon.
But does it ru-- :)
Nevermind, no points to spare
I've setup a mirror for the source at http://43.244.87.231/cle266.tgz
Be nice to it, and check the original site after slashdot effect goes away.
My lil epia box does better than my parents faster Wintel box at playing dvd's and vob's. Sure a lot of that is because MPlayer and Linux are so much better but you're mistaken if you think the epia systems don't have the muscle for the job. If they could enable the hardware decoding it might even make the playback better. They also run much cooler, more energy effecient, and quieter.. something that IMO is a mark of quality.. not of being 'cheap'. Besides, price compare the CPU's.. you'll find they aren't that cheap. :)
At what price learning? At what cost wisdom? The price is a man's peace of mind, and the cost is his life.
The silly thing with all of this is that the drivers and support for this card that result from the reverse engineering will ultimately result in more sales. It seems so counter-intuitive for VIA to resist this.
Let's harass them for not releasing the code, reverse engineer it and post it everywhere, until they get mad and discontinue Linux driver development altogether! Then xine and mplayer will work GREAT!
Why not use a program that automaticlly takes the binary and builds a C program from it? You still have to pick through the logic to give things helpful function/variable names and refactor but it'd save the step discribed here. In the past when I've reverse engineered binaries that is the type of tool I used. Any good reason for doing this by hand?
This still begs the question.. why not just release the damn source? If we can reverse engineer the drivers what would keep the competition from doing so? Why harm your customers for a false sense of security?
At what price learning? At what cost wisdom? The price is a man's peace of mind, and the cost is his life.
From the article:
Oh yeah. Much more readable.
"A great democracy must be progressive or it will soon cease to be a great democracy." --Theodore Roosevelt
Hardware decoding allows for much higher resolution video. Furthermore, specialized hardware typically have more accuracy when decoding the stream. There's additional features too: you can allocate, say, more bits for dynamic color range, fractalize regions that have semi-random "noise" distribution (like tree leaves from a distance) and so on that can improve video quality (to help eliminate obvious artifacts). I am not saying all hardware decoders do this, but these are some advantages. It's very analogous to having specialized 3D hardware to handle graphics rather than "letting the CPU do it".
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It won't produce the same code. Different compilers do things different ways. In the end the binary produced will run the hardware the same way and that's the goal.
Very clever, but I thought reverse engineering worked on a functional level.
He did do functional analysis to make it work. He understood what the thing was doing. If he did not, his code would never have worked. He made little doodles and what have you to make it clear to himself. Now it's in C, the diagrams are much easier to make, though we can be sure he's going to share his diagrams as well. That way other people can make nice software too.
IANAL, but I don't think the source code is legally safe if VIA wants to go after it.
I don't know why you think that. He could have had his computer tell him what it was doing instead of using IDC, no? It's not like he dumpster dived code like old Bill Gates did BASIC. He understood what the code did and reimplemented it himself. Even if he did have dumpster dived code, he could use that to make a functional diagram and then use that to write new code and the results would be the same.
If there is a legal problem with this, there should not be. Why should people be afraid to understand what their machines do and then share that information? So someone else can make money of evryone else's ignorance? Shit, no one would be able to get anything done that way.
Friends don't help friends install M$ junk.
Well, he has done the first part of a reverse engineering process - he has worked out, by inspection of the target, what is being done.
However, he now needs to write the specifications for the hardware, and publish THAT, so that somebody else, somebody who has not seen the binary driver, can write a program based upon the specifications.
Should this not be done, then this code, while interesting to individuals, would be pure poison to anybody who has any intention of distributing this code in a commercial way (e.g. a distro).
And writing a specification for the chip, by inspecting the code, is far more difficult than simply reverse compiling the binary.
www.eFax.com are spammers
With the ever-increasing clock speed of our CPUs, what is the point of having a hardware MPEG decoder? I understand that p2-400 is sufficient to play DVD-quality movies. The amount you spend on the hardware decoder could have been better spent on memory or video card or CPU or whatever. Now, a hardware encoder would certainly be useful as encoding is still very CPU-intensive. I was contemplating a tivo-like box with a hardware encoder. Does anyone know if hardware MPEG encoders are supported on Linux?
___
If you think big enough, you'll never have to do it.
Just to prove it exists:
Reverse Engineering Compiler
They're not reverse-engineering the hardware, they're reverse-engineering the driver software that is used to talk to the hardware. In the absence of an authoritative interface document, the driver can serve as one. In the absence of source code for the driver, the reverse-engineered driver code can serve as one.
the decoded mpeg2 cannot be captured, it's decoded directly to the video memory.
Can you imagine what would happen to VIA's sales if they somehow offended M$ and M$ retaliated? They could keep VIA in the dark or give them bogus SDK info so that their hardware would not run well under Windblows. Even witholding a dinky little check here is damaging. Harware makers that defy Microsoft are doing something heroic and should be rewarded.
Once enough hardware makers tell Microsoft to shove off, it's all over. In fact, it's already all over. Windows already enjoys the bad reputation they deserve. When you buy something for Windows, the odds of it working are only marginally better with the goofey M$ binary driver than they are with a free driver. There are some exceptions to this rule, like winmodems and crappy little digicams, but the gap is closing quickly. Everyone will be better off when stuff can be chosen on grounds of technical merit rather than M$ favor.
Friends don't help friends install M$ junk.
Obviously you've never used VIA processors before. They are notorious for their slow FPU's. In fact, before their latest top-of-the line model - the Nehemiah, their FPU's of previous models always ran at HALF CLOCK. Ouchy.
:O
But, even at full speed a similarly clocked Celeron kicks it's ass in every which way. That said, high performance is not the stated purpose of the Centaur/Via CPU. Its low watts, coupled with the decoder make for an excellent all-around box. I've built around 7 or 8 of these myself and they are excellent for what they are designed for (think: mom and dad or net terminals, not Half Life 2).
I have a few of these floating around the school here now as basic net access / workstation terminals and they are hugely popular - especially in light of what they replaced (AMD 300's). There's nothing like tearing apart some ancient computer and putting one of these boards in it. 90% of the time, it's simply cavernous in there (so much space!)
Last week I put one in an Aptiva and realized that if I was an enterprising person (read: man with a Dremel) I could have fit TWO of them in there as a dual workstation!
So to sum up, they're small as hell (you have to see it to believe it), simple, fun, easy to configure, but don't plan of using them at the next Fragfest 2003 (c)
"...Well, there's egg and bacon; egg sausage and bacon; egg and spam; egg bacon and spam; egg bacon sausage and spam..."
This is not reverse engineering, he dissassembled the code and pretty much copied/ported the result to C. I don't think this meets any cleanroom standards and the code is dangerously contaminated. To use this work you would have to get someone else to reimplement the driver without looking at this contaminated code base. That means they need to be passed a description of the hardware interface inferred from observations of how this driver works, and the code produced by dissassebling the driver needs to be tossed in the garbage can.
Who taught anyone that dissassembling someone's proprietary code and doing a line for line port then publishing the result was in any way legitimate?
First of all, it's just a small wrapper library that is comparatively easy to reverse engineer.
Second of all, there is a library we can reverse engineer.
Third of all, the guy is using the VIA forums to spread the word, so VIA obviously knows about this, and they haven't sued.
To me this rather looks like they were waiting for someone to reverse engineer this, because they couldn't release the sources themselves for contractual reasons. Don't just assume people are evil, maybe they didn't have a choice and did what was in their power to give you the means to help yourself.
"..Typically, only requests from companies developing product for sale will be approved.."
/. ?
Has the article submitter actually asked them instead of going by a press release and venting on
Gotta start somewhere though - an opensource driver is a good place to start building your superior functionality on.
Code porting MPEG driver from assembly to C.
"Too slow chicken marengo" - The Cat
Ironically, the sources to that "Reverse Engineering Compiler" are not available in the public domain...
I.O.U One Sig.
Lets not forget the hardware mpeg2 decoder - dxr3. A lot of people have worked on this and it has resulted in a very decent driver. It has had absolutely zero help from sigma. There is even hacks to make it display rgb directly to your tv, bypassing the crappy composite and svideo.
reverse "engineering"?
is that what it's called now?
back in the day, i used to just double click on the mpeg clip on my computer, and all you could see were "reverse cowgirls". whatever these "engineers" (or pr0nstars as we used to call them) are doing is just great. My "intellectual property" is now as WIDE-OPEN as open source for you!
ackk kids.... when do they ever use the proper symmentics.. (old man like me cant spell...)
my blog
Although it did only start about a fortnight ago.
It's not like you'd need a Linux driver for it to be relatively straightforward to reverse engineer - most hardware drivers are relatively simple, they act as relatively thin layers to abstract out low level hardware access - and reverse engineering them isn't a big deal.
The most notable exceptions are winmodem drivers, where the drivers provide more or less a full modem protocol stack, and 3d graphics cards drivers that tend to provide quite high level interfaces to relatively low level hardware primitives.
If any hardware vendor for more simple hardware devices believe that anyone will have a problem reverse engineering their drivers, they are clueless idiots and will only benefit from learning a lesson.
A Mini-ITX Linux system that used the functionality provided by this driver, had a 3-second BIOS bootup time using Linuxbios, plus a PCI TV tuner card with hardware MPEG-2 encoding, would be a pretty impressive media center.
He owns the hardware; therefore, he has a right to make use of it. The details required to write a driver form a part of the operating instructions for the hardware, and anyone claiming them to be "proprietary secrets" should be laughed out of court with a dusty bootprint on their arse.
Is it a proprietary secret that "Esc", "K", followed by a two-byte binary number presented units-first between 1 and 480, followed by that many bytes, is the code used to select bit-image mode on an Epson-compatible Dot Matrix Printer? Of course not! why, Back In The Days, when if you wanted software you pretty much had to write your own, the printer would have been useless without such information. So the manufacturers used to provide it in the handbooks. Kit that didn't come with adequate documentation, didn't get bought.
Today, with pre-written software in abundance, manufacturers are becoming sloppy and not documenting fully how to interact with their products. For the casual user, this isn't a big problem, because they were never going to do anything with this information anyway, so why waste paper or plastic telling them it? But if there is even one user who wishes to do more than what it says on the box, then it suddenly becomes a very big deal indeed.
My analogy is that he used "reasonable force" to obtain information to which he was entitled, after polite request had failed. The law is quite clear that in certain situations, reasonable force may be used. This situation is more "gentle" and relies less on quick decisions than, say, physically moving a person who is trying to resist. {He could have obtained said information by holding a knife to someone's throat at the manufacturer; this would likely be seen as more than reasonable force.}
We should be writing to our elected representatives now to make sure it becomes mandatory for manufacturers to supply full hardware specifications, gratis or at cost, to anybody who wants them. Concealing details is a dirty, lowdown, scumbag, coward's trick that will cost companies sales. Please don't betray your cowardice by bleating about "competitors gaining an advantage" - you will have access to your competitors' documents, too, and if your competitors manage to do a better job than you, then you failed it! I have no sympathy, either, for those who whine that people might find it easier to break the law if they were given certain information. It is already more than easy enough to break the law. A few extra ways aren't going to make any difference here or there. You shouldn't rely on doing crap design and keeping things secret; it's another form of corner-cutting. Do it properly or not at all.
If the guy is ever taken to court, his best chance is to push for a trial by jury an hope that, out of twelve people, he can convince two of them that, although he does not deny what he did, it is the law that is wrong this time and they can acquit him. If this happens often enough the law will be changed.
Je fume. Tu fumes. Nous fûmes!