Some stuff » phone

the propellers go around (part 2)

admin — Wed, 06 Jul 2011 15:39:26 +0000

… but not on camera.

This is part of the Toronto visit series.

So I inadvertently took a picture of the running propeller on my side of the plane, and it came out weird. And I mean, really weird (1):

The propeller does not look like this. It has like six blades spaced out evenly and all of them straight. So of course this is due to aliasing of the damned camera. But wait now, I just said not too long ago that this is photography, so indeed, I only took this and

this (2)

and this (3)

along with this (4)

because I was strangely mesmerized. Not only is this pseudo-reality only observable through a cheap phone camera like this, but I’m measuring the camera as much as I’m measuring the propeller.

See, the effect is only possible because the phone camera has no shutter (so DSLR’s shouldn’t exhibit this). The image is literally read out line by line, top to bottom. By the looks of it, all pixels on one horizontal scanline are read out or replicated to memory in parallel, but different scanlines belong to different times, with a sampling time gap between lines. Meanwhile, the propeller moved on. Since the angle between attachment points of the blades is reduced in (1) and expanded in (4), the propeller is spinning clockwise.

However, what appears to be the blades in these photos, are not the blades! Otherwise how could some of them hang around in mid-air and also have two ends. Well, first note that the entire region where there are fin-like objects is circumscribed by the elliptical region that the real propeller traces out (from this viewpoint). This clue suggests that each discrete piece is a portion of an image of a single blade sweeping through a certain angular range. It’s only a portion, because the blade in question is captured only when it is within the current scanning region. Once it’s out, the camera doesn’t “see” it. There are gaps between these discrete pieces because there is an angular gap between two adjacent blades on the propeller.

If the rotational speed of the propeller is known then we can even figure out the rate at which image lines are scanned. As is, there are about a dozen or so discrete pieces in a single image, so given that there are only six blades, the propeller makes nearly two turns during the shot.

OEM laptop has max CPU frequency capped when on battery

admin — Sun, 30 Nov 2008 03:03:08 +0000

I was playing with a laptop from HP the last couple of days and noticed that when off AC power (on battery), the maximum CPU frequency is only half of the specification. The machine runs Windows Vista. The CPU is an AMD ZM-80, duo core 2.1GHz. On AC power, the processor can reach 2.1GHz on heavy load, but on battery power, the maximum it will go to is 1.05GHz on each core. This is really a problem because performance (especially for single-threaded applications) is pitiful at those levels. In fact, 1080p HD WMV demo videos could not play smoothly just like on a four-year-old Pentium M 1.6GHz.

This is apparently a common problem on a variety of laptops, especially as of late, see discussions at:

As usual, there is a bunch of crap on the internet about Vista or AMD being the culprit. No, this has nothing to do with Vista Power profiles, which are all set to 100% maximum processor state. After reading the above threads and thinking about this, I’m convinced that it is a system-level issue. When on battery power, something set in the BIOS must be throttling the CPU to half-speed, so any software controls will have no effect beyond that.

One of the threads did mention that turning off or altering a Power Management setting in the BIOS allowed the battery mode maximum CPU frequency to go higher. Unfortunately, I got a stupid InsydeH2O BIOS with nothing to set. The next step is perhaps to hack the BIOS.

Now for some entertainment:

Customer : CPU cannot go above 50% frequency when on battery power, no matter which Vista Power Plan is chosen.
[An agent will be with you shortly.][You are now chatting with Jarred .]
Jarred : Hello Customer
Jarred : Welcome to HP Total Care for HP notebooks. My name is Jarred. Please give me a few moments while I review your issue description details.
Customer : hello
Jarred : I understand that, your Notebook CPU does not go above 50% frequency on battery power. Am I right?
Customer : that is right
Jarred : I will certainly do my best to help you out with this information.
Customer : you can try it yourself
Jarred : Well Customer, let me inform you that this is normal for any Notebook that runs on battery power.
Customer : That is not normal, because I have another notebook (different manufacturer) that does not exhibit this behavior
Jarred : In these Notebook the settings are different, the Notebook does not run as it runs with AC power. Let me also inform you that if it Execeeds beyond 50% to 70% the Notebook will get freezed.
Customer : Frankly, that does not make any sense. Is this limitation documented anywhere?
Customer :And is there any way to get around it…
Jarred : May I know the processor if it is AMD or Intel?
Customer : It is an AMD ZM-80 processor
Customer : Turion X2 Ultra, for a TX2500Z build
Jarred : Well Customer in AMD process, there is a option set as ‘power no’, which will limit when running on battery.
Jarred : However you can try to check in BIOS if there is any option to change.
Customer : Do you mean PowerNow? I think that is certainly something that should be in the BIOS.
Customer : However, I checked the BIOS settings on this notebook, and there are very few options to change.
Customer : Do you offer a more sophisticated BIOS or an update that specifically lets me make this change?
Jarred : I am sorry it is powernow.
Jarred : Customer, i do understand your concern, I would have provided you right away, if there was any solution for this issue.
Customer : There are no power management options in the BIOS, unfortunately.
Customer : I believe this should be reported as a bug, because a 50% limit on the CPU on this notebook makes many online videos unplayable.
Customer : That makes this "Entertainment Notebook" very crippled on battery.
Customer : Can you open a support ticket with HP engineers to resolve this issue?
Jarred : Sure Customer, I will excalate a technical-exclation on this issue.
Jarred : If there is any advancement options provided you will be informed.
Customer : Will I get an email on the progress of this ticket?
Jarred : I need few details to do this.
Customer : Sure.
Jarred : Once if I create the case you will be intimated by email contacted by Phone once after this excalation is sent to the case managers.
Jarred : Untill then, you can have this chat session ID – XXXXX
Customer : Ok, I appreciate that.
Jarred : Please provide me Product Number p/n (eg:DS542U): Serial Number s/n (eg: CNS34915MC):
Customer : p/n: XXXXX
Customer : s/n: XXXXX
Jarred : Please provide me your shipping address and
phone number.
Customer : XXXXX
Customer : phone: XXXXX
Jarred : Thank you for the information you have
provided.
Customer : Sure.
Jarred : Okay Customer, I will create the case and you will be intimated by Email or by phone, by our case managers as soon as possible.
Customer : Thank you for your help. I appreciate it.
Jarred : Please let me know if there’s anything else I can assist you with, today?
Customer : That will be all.
Jarred : Thank you for contacting HP Total Care Support, please do not hesitate to contact us if you have any questions or clarifications. We assure you of our dedicated support, 24 hours, 365 days a year.
Bye Customer. Good Night.

cell phone # porting

admin — Sun, 19 Aug 2007 01:07:24 +0000

I have a good guess now of how cell phone number porting is implemented. Had a number transferred from AT&T to Sprint. The phone actually came with a randomly assigned number and a matching MSID (mobile station id), but Sprint told me to re-program the phone with the desired number and a new non-matching MSID in the area code of the desired number.

The porting process was as follows:

Immediately, random number stops working, new Sprint-assigned MSID works as phone number!
Within minutes, AT&T cuts off connection and accounts access to old number, which ceases to work.
Hours later, MSID stops working as phone number, old number now rings new phone.

The fact that the MSID works as a phone number during porting and remains in the phone’s settings, must mean that it is in fact the true “phone number” identifier for the phone. The phone just gives out its stored “phone number” for the purpose of outgoing calls. I’m guessing every carrier has a pool of phone numbers in each area code to give out, and there is a static allocation database somewhere. During porting, Sprint assigns a new number from its own pool, which becomes the MSID. Then AT&T (who owns the old number) changes its databse to forward calls to the old number on to Sprint, instead of processing them internally. Finally, Sprint changes its database to take those incoming calls and forwards them to the assigned MSID.

When you get a new line, a number from the carrier’s pool is assigned so no forwarding is needed, and that must be why the MSID matches the phone number in that case.

Now, if I were to port again to a third carrier, what would they do? Maybe they’ll look up the number and discover they should talk to AT&T?

Here’s some real information which I haven’t read but maybe corroborates or discounts what I wrote. http://www.syniverse.com/pdfs/GuidetoWNP6thedition.pdf

cell phone hacking

admin — Thu, 04 Jan 2007 03:38:33 +0000

Why are cell phone unlock keys and keygen algorithms still being sold?
I understand there is a great profit motive to guard the secret, since with this ruling, unlocking has become a legal profession (for at least the next three years), unlike warez cracking.
But come on, somebody must have an itch to set the information free, no?