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Comment: JBIG2 (Score 1) 290

by GoRK (#44491051) Attached to: Xerox Photocopiers Randomly Alter Numbers, Says German Researcher

I haven't even read this article and I know the culprit exactly: JBIG2.

The compression algorithm operates on binary (2 color) images and has two modes, a lossless mode which is sort of like the love child of RLE and JPEG and a higher compression mode which operates by running the lossless blocks through a comparison routine and discarding and replacing any blocks that are sufficiently similar with references to the first copy. It's actually a good algorithm, but you have to understand how it works to implement it properly. When you have a perfect storm of certain fonts (especially small ones where a glyph can fit perfectly inside a block), have some noise in the bitonal images and have the compression threshold too high you can get some real zingers.. 9, 6, 0, 3, and 8 can all easily get muddled up, not to mention what happens to letters like e o c etc. The key to the whole thing is having good algorithms that can produce quality bitonal images from poor originals and scanning at sufficient resolution (or lowering the compression threshold enough) that blocks cannot hold an entire glyph.

As to why the copier is using the lossy mode of JBIG2 internally is mystery, especially in the "copy" pipeline. I can think of no good reason that it should use anything other than the lossless mode or uncompressed data.

Comment: Re:Interesting (Score 2) 239

by GoRK (#43668945) Attached to: Interview: John McAfee Answers Your Questions

I'm curious why you like that interview so much; reading that is when I realized that that dude is nothing more than a talking head. Why do you think he needed the Internet to do commentary for Iron Chef America? IIRC he not only got a question about cooking with lava completely wrong, but he insulted the person asking as a way to avoid answering it. When Google failed him, he just bailed.

Comment: Re:IPV6 on AT&T Residential DSL (Score 1) 155

by GoRK (#40964335) Attached to: US IPv6 Usage Grows To 3 Million Users

AT&T is not issuing you an IPv6 on your residential DSL. I know this because they don't do it. Your computer is generating an IPv6 link local address. Depending on your router and a couple of other factors, you may (probably can) access IPv6 sites using a public 6to4 gateway.

The only advantage to you is that you at least have the ability to access Internet resources that are only available via ipv6, but currently I would imagine that there are probably not any that are particularly relevant to you.

Comment: Overblown (Score 1) 205

by GoRK (#38251228) Attached to: Apple, Android Devices Swamp NYC Schools' ActiveSync Server

$1MM of iPads represents about 2500-3000 users depending on the discount they received. First, I'm presuming that these users already had mailboxes and it's just the additional load of ActiveSync that is causing the trouble. If that's the case, with the types of discounts that government and education receive from microsoft and hardware vendors this is like a $15,000 problem at best. In the scope of a million-dollar project a 1.5% budget problem represents poor planning, but I've seen much much worse.

Comment: Passive cooled GPU (Score 1) 205

by GoRK (#38251180) Attached to: Ask Slashdot: Parallel Cluster In a Box?

Don't use high end GTX cards; twice as many lower end passively-cooled GPU cards will provide more than the equivalent performance with far less cost and failure rate. If your application really benefits more from additional threads vs single thread execution speed, this is the way to go. Most GPGPU clusters that aren't built using Tegra use this approach.

Comment: Re:But weren't they on anyway? (Score 1) 621

by GoRK (#30303402) Attached to: SETI@Home Install Leads To School Tech Supervisor's Resignation

Wait, you really don't believe this? I have a kill-a-watt and can assure you he speaks the truth. I don't have a ridiculously high end computer, but I can get its power consumption to vary by more than 300W between it being idle + LCD's in DPMS power save and me actively pushing the cpu and gpu with something. Putting it into S3 suspend will break off another 50W or so.

Now 10 year old hardware pushing 40W delta between unloaded and loaded not including a CRT going to sleep or something? Doubtful. Maybe 15-20W tops. But then again some of that school district's hardware was much newer and $0.06/kWh is a pretty decent utility rate too. I'd say $1 million is a pretty good round number here even though it probably represents a modest 10-20% increase over the bill were 5000 machines simply left on and idle. But consider if this guy who had enough control to install software on 5000 machines had simply set them to go to S3 after a couple hours of not being used? He could have saved the school district millions on power just as easily as he wasted it.

Comment: Re:Standard Calculus (Score 2, Informative) 369

by GoRK (#30014478) Attached to: Radar Beats GPS In Court — Or Does It?

The real answer here is it depends a great deal on the GPS itself, then it depends on how whatever software is reporting and logging this information post processes it.

GPS itself is capable of reporting an instantaneous velocity vector calculated by measuring the doppler shift from each satellite. (Comes in as a GPVTG sentence in the NMEA data) So if the receiver is tracking a lot of satellites with a good distribution and there isnt a lot of multipath problems, the accuracy of this vector is ridiculously good. Also, a receiver may not support GPVTG.

Now you can also get velocity data from a GPRMC (ie normal position data) sentence too. According to the specification, the bearing here is supposed to be calculated based on position track angle (presumably so that you dont have to be moving to have a GPS bearing).. The spec seems silent to the origin of the speed reported in this sentence -- seems like it could be calculated as track speed (average speed over the interval) but could easily be reported as instantaneous speed as well.

Of course I haven't tested any, but I imagine in practice, GPS receivers would normally report track/position averaged data in GPRMC and instantaneous data in GPVTG. Any software that is supposed to present this data to a user would have to determine how to aggregate and filter it to provide for its intended purpose. If you really intend to beat a speeding ticket with GPS I would suggest that you need data points of either type (instantaneous or averaged) with at least 1Hz if not 5Hz granularity along with knowledge of what the data represents and how the raw data is filtered and processed. This 30s interval business in this case is just dumb, and nobody ever bothered to determine anything about the nature of the data it seems.

Hardware Hacking

How To Play Poker With Your Rock Band Guitar 121

Posted by timothy
from the jumprope-can-be-hifi-if-it's-got-usb dept.
An anonymous reader writes 'Sean Lind over at PokerListings has written a really interesting piece on how to configure Rock Band (or Guitar Hero) instruments to use them as controllers for playing online poker. The instructions given in his how-to could really be used to configure the instruments for any game.' Or how about a genuine chording keyboard?

Comment: Re:Iridium? (Score 1) 438

by GoRK (#29458863) Attached to: (Near) Constant Internet While RV'ing?

Thank you; very good information here; I didnt realize a station had to reply inside of the same frame. There IS therefore a timing issue but the BSS could counteract it obviously as you said by maintaining an additional frame offset internally. So this explains a 35km limit on GSM itself but do the 3g GSM technologies attempt to pack additional data in by shortening the guard period? If so that would explain a smaller distance limit, but I don't think data would be rejected; seems you'd just fall back to EDGE or GPRS?

Comment: Re:Iridium? (Score 1) 438

by GoRK (#29447151) Attached to: (Near) Constant Internet While RV'ing?

You are sure of this? Can you give some reference material? I would really like to know how or why this is true. I have hit EDGE data over some pretty impressive distances (10 miles) with the proper equipment. I really can't see how the BSS would reject a distant signal if it were good enough. The distances aren't great enough to cause any timing issues.

Comment: Re:Who Cares (Score 1) 364

by GoRK (#29303341) Attached to: Game Over For Sony and Open Source?

Since the Linux kernel only interfaces with the virtualized devices presented by the PS3 hypervisor, and since this hypervisor presents exactly the same interfaces to GameOS as it does to OtherOS (where it simply blocks many hypervisor calls) this is exactly what I'm suggesting. No shit!

If Sony is actually realizing cost savings by dropping this feature, it's certainly not happening in development, but in QA, Support, and Legal. It's still sad to see it go, and I hope they bring it back.

Comment: Re:Who Cares (Score 1) 364

by GoRK (#29291159) Attached to: Game Over For Sony and Open Source?

They still have to support the feature on "Fat" ps3's so the software engineering and support cost is there regardless of the new model. The Hypervisor itself is at the absolute core of the PS3 regardless of whether or not it's hosting the XMB, GameOS, or OtherOS, so the software is basically running on the PS3 Slim already. I believe very strongly that there has not been a hardware change that would have affected supporting the OtherOS install and that this is a deliberate move by Sony to remove a popular feature. With the PS2 slim at least they were able to pass off dropping Linux support as a semi-legitimate hardware problem.

As to why they did it, I can only speculate. First, I think that Sony may believe that an exploit may be discovered in the Hypervisor that could open the door to piracy (a la the PSP). Secondly, the rumor is they are still losing money on the hardware. If this is true, given the price reduction, smaller size, and lower power requirements of the PS3 slim, it actually becomes more attractive to build into HPC clusters. Sony may not in this economy wish to hemorrhage millions of dollars building these inexpensive supercomputing clusters all over the place.

An engineer is someone who does list processing in FORTRAN.