EEVblog Electronics Community Forum
General => General Technical Chat => Topic started by: firewalker on May 29, 2012, 05:15:11 pm
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Have anyone received a Raspberry Pi yet?
I was wondering if it is possible to unlock all the extra features of the GPU like mpeg2 decoding. Is it "hackable"?
People over the Raspberry Pi believe such a thing is almost impossible.
Alexander.
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Hah ! if you'd find someone in the open-sauce community that is willing to shell out for the licence and you can convince broadcomm to release the core ... maybe ...
my guess is chances are slim.
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Considering the numbers that will be in the field i think it is inevitable that a lot of currently-hidden info will lbe reverse-enineered out eventually - the only unknown is when.
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One of the main reasons I have no interest in the Raspberry Pi is the fact that Broadcomm is the chipset maker. I have already fought enough battles over Broadcomm chips and Linux, thanks. No more for me.
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Yes, broadcomm won't so easily let info out, they take the money and keep quiet about the info
That's why i fought a battle with a broadcomm wifi chip from a laptop and gave up :)
It's still in my box
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If it is like other similar chips (Samsung etc.) then its main GPU has nothing to do with mpeg. There are independent accelerators for 2d, 3d, video decoding, windowing, rotation and jpeg, and they technically may be present in any combination. They are controlled with completely different register sets mapped to different i/o addresses. If one of them is not present, it is just not present.
The PowerVR 3d core is theoretically capable of doing 2d on its shaders in OpenGL too, like any GPGPU used for computations, but this is not the usual way. Probably nobody ever tried it.
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the problem sits in accessing the registers for the mpeg functionality. despite popular belief MPEG needs payment of royalties...
And you can bet the house that broadcomm will NOT release info on how to use these advanced features ( especially since they have HDMI which has crypto ... ) unless NDA's are signed and money is being forked over ... As the open-sauce community is penny-less and 'NDA' doesn't work very well with 'Open' .... fat chance of this ever happening.
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I can see one approach - This chip must be used in other products that use all the functionality.
Reverse-engineering the code that runs on those products would be a possible way in.
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I have to ask this!
What are you trying to achieve?
Leo
P.S. I already massively don't like Raspberry because everybody else falls head over heels to have one. Just another wannabeduino.
If someone wants to leave a dent in the Universe give African kids a 4-bit microcontroller demoboard with an LED and a pushbutton, not Wi-Fing and HDMIng *nix based MP3 player.
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P.S. I already massively don't like Raspberry because everybody else falls head over heels to have one. Just another wannabeduino.
If someone wants to leave a dent in the Universe give African kids a 4-bit microcontroller demoboard with an LED and a pushbutton, not Wi-Fing and HDMIng *nix based MP3 player.
I don't think it's intended for African schoolchildren - its original intention was to help UK Computing students. As one of them, let me tell you, the computer science lessons we have are dire, boring, uninspiring, and do not teach you how to actually program properly. I would like to see how they could be integrated into a coursework module; perhaps the low processing power would encourage optimised applications and limited resources would lead to unique solutions - and maybe if younger programmers learn this then the next Windows OS won't need 8 GB of RAM?
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perhaps the low processing power would encourage optimised applications and limited resources would lead to unique solutions - and maybe if younger programmers learn this then the next Windows OS won't need 8 GB of RAM?
32-bit RISC core running at 700MHz with hardware FP and 256MB RAM is a limited resource?! :-\
It's exactly the same spec as eMac http://en.wikipedia.org/wiki/EMac (http://en.wikipedia.org/wiki/EMac) that was purpose-built for education market. All the schools had them (i.e. cost to students was zero.) How many students went beyond using it as a fancy jukebox?
Leo
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The PowerVR 3d core is theoretically capable of doing 2d on its shaders in OpenGL too, like any GPGPU used for computations, but this is not the usual way. Probably nobody ever tried it.
PowerVR chips are really not that brilliant at GPGPU. In shaders, 128-bit vector operations are executed as four independent 32-bit scalar ops, for instance. And memory bandwidth is really limited.
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its original intention was to help UK Computing students. As one of them, let me tell you, the computer science lessons we have are dire, boring, uninspiring, and do not teach you how to actually program properly.
And how should a board like the RPi fix this? It is a question of proper selection of tools, like programming languages, proper teaching and proper supervising. Nothing of this requires an RPi. The RPi won't make your teachers better.
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Not only that. the RPi will also promot bloatware and mindless library reuse.
Teach programming fits on a simple 8 bit machine with limited resources like 8 k rom en 128 bytes ram and give students something to chew on...
We already have truckload of 'library using' codemonkeys. what we don't have enough off are people that can actually code something without an operating system and massive prechewed libraries , or without wasting 5000 calls to a library to configure some i/o pins ...
programming is not about a language.. it is about mechanism and learning to use the cpu and its hardware effectively to perform work.
People wrote whole bookkeeping and payroll programs in a PET with 20k ram and a casette ... They landed on the moon with 14K of code ... and that thing was multitasking , flying the lander ,doing radar ranging and tons of other things. all at the same time... with a clock in the kilohertz range ... Now we have cellphones with quadcore 2 GHz and six core graphics accelerators .. to play 'angry birds'.... i foresee a VERY grim future ... Forget global warming ...the global dumbing down is coming... go wathc the movie 'idiocracy'.. we're not far off ...
Now even the bootloader won't fit in that anymore .. and turning on a LCD or plasma tv and staring at the manufacturer splashscreen for 10 seconds is perfectly acceptable ... because it has to 'boot'. And don't get me started on blu-ray and dvd players. The people who write that code these days should be publicly forced to eat that tv....
I have an old daewoo dvd player. Power-on to first image is under a second. pop in a dvd disc , it spins up and 2 seconds later i have the dvd menu. it has a braindead mips processor running at 27MHz for the video processing and decoding and a 8051 to do remote control ,display and operate the drive mechanism. Works beautifully.
Compare this to my latest blu ray player. Power on to first splash screen is also 2 seconds and then there is the scroll bar with 'initializing... that takes 30 seconds because it wants to go all wonky and see if it can get an update from the internet ( i have no cable plugged in... why do you keep waiting you piece of shit. can't you do a simple 'cable detect' that would take 1 microsecond. ) and it needs to boot some open-sores / broken-source operating system.
Then you put in a disc and you stare at a black screen for another 20 seconds while the drive is grinding away trying to load the java code to run on the virtual machine. What is wrong with the processor that is in the box ? why do you need to run a virtual machine on top of it ? you blithering codemonkeys! Just write code for the real processor you flaming-turd-code-shitters. Sony should rename themselves to ShitCo.
And then it goes through some handshaking on the crypto and if you are really lucky you may get the menu ( if it hasn't crashed by now ) , if you are a bit less lucky it comes with a message that it needs internet connection to check for an update. Here you have a carrier medium that can hold 50 gigabytes of data , and you tell me there is no room for a bit of code ?
and then you finally have gone through all the hoops , select 'main feature' and press play and it first goes off for another 10 second 'grinding session' ... aaaaargh !
If i want to enjoy a movie that i bought i have to sit there jumping through updates , endless waiting , and all sorts of misery before i can see something ( and then i haven't even started ranting an raving about all the 'coming soon drab' they inject on the disc... don't you understand that , if i watch this disc 1 year later that stuff is old and i don't want to see the 'coming ssoon crap anymore ? put it on the disc if you must but do not start playing that shit by default ! Friggin shit-for-brains movie studio's )
And this is acceptable practice these days ? Anyone that writes and release such code should be banished for eternity and locked in a room full of eproms, each loaded with a single byte of their code... Eproms that are in ceramic dil packages so they always land on the floor with their pins turned upward ... and they go in barefoot .. ;D if you know what i mean ... ( if you have ever stepped barefoot on an upturned dil package , you do know what i mean... multiply that one package by a few million , one chip per byte of crap code... my guess is about 16 megabytes of code in a blueray ... eternity isn't long enough for those nitwits.
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perhaps the low processing power would encourage optimised applications and limited resources would lead to unique solutions - and maybe if younger programmers learn this then the next Windows OS won't need 8 GB of RAM?
32-bit RISC core running at 700MHz with hardware FP and 256MB RAM is a limited resource?! :-\
It's exactly the same spec as eMac http://en.wikipedia.org/wiki/EMac (http://en.wikipedia.org/wiki/EMac) that was purpose-built for education market. All the schools had them (i.e. cost to students was zero.) How many students went beyond using it as a fancy jukebox?
Leo
The processor is a RISC architecture, so the performance is closer to a 300 MHz PIII/PII than anything else. 256 MB of RAM is shared between the CPU and GPU and try getting an OS written in the last 10 years to run within 128 MB.
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try getting an OS written in the last 10 years to run within 128 MB.
For what reason? If non fits, use one that was written in the last 20 years.
Uhmm, what is that sudden smell? Ah, kids all around shitting their pants on the suggestion of using something "old". What a horrible though for the generation that throws away their electronics every half year, because it got "old".
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We shouldn't say the same things again and again for "What Raspberry P" is or is not". It wasn't my intention.
Lets keep only the engineering aspect of it.
Alexander.
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People wrote whole bookkeeping and payroll programs in a PET with 20k ram and a casette ...
That was me. I did that when I was 17. I worked at BPI Microsystems and we wrote G/L, A/R, A/P, payroll, inventory and cost accounting for CBM/PET and Apple ][, later the VIC20 and C64, C128, Apple IIc, IIgs, Apple III ( or Apple ///) and the Olivetti M20 (they paid us to port our code). That was all done in BASIC. ugh! I did some 6502 coding on the 9090 hard drive firmware back then, too. I think I still have the hard drive schematics and firmware source code; it was a lot of the same code as was in the PET ROMs -- bit banging the IEEE-488 bus, similar internal layout as the PETs. That made it pretty easy to wrap your head around the drive firmware, it just looked like another PET inside.
...Eproms that are in ceramic dil packages so they always land on the floor with their pins turned upward ... and they go in barefoot .. ;D if you know what i mean ... ( if you have ever stepped barefoot on an upturned dil package , you do know what i mean..
you made me cringe, for a pain I once knew... now I can't even get a tickle from a SO-8 pins up on the floor. :(
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( if you have ever stepped barefoot on an upturned dil package , you do know what i mean...
It hurt and bled a lot :(
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Uhmm, what is that sudden smell? Ah, kids all around shitting their pants on the suggestion of using something "old". What a horrible though for the generation that throws away their electronics every half year, because it got "old".
If you look at any of my development Windows PC screens most of the time you will see Norton Commander v4.0 (released January 22 1993) in its full blue glory. By the time kids click through animated Windows start menu crap to locate File manager (or is it Program Manager (or is it Explorer?)) I can navigate down ten subfolders, open a file in hex editor, change the contents, save it and go back to where I was.
Leo
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I can see one approach - This chip must be used in other products that use all the functionality.
Reverse-engineering the code that runs on those products would be a possible way in.
Or decap and get die photos, then reverse-engineer the layout. SoCs are usually laid out in well-defined blocks with connections to a common bus, so there is only a need to focus on the desired sections. There are various companies in China that can do this for (relatively) cheaply if the process size isn't too small.
I've read that Broadcom uses hidden tricks like different register addresses and datasheets for each customer, so that leaked info could easily be traced back to its source. This is a strong deterrent against anyone doing so.
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We already have truckload of 'library using' codemonkeys. what we don't have enough off are people that can actually code something without an operating system and massive prechewed libraries...
Then you put in a disc and you stare at a black screen for another 20 seconds while the drive is grinding away trying to load the java code to run on the virtual machine...
And this is acceptable practice these days ? Anyone that writes and release such code should be banished for eternity and locked in a room full of eproms
i think this is my thought as well these days. and there's another buzz... an application built on top of another application or "platform". i dont know why my recently installed app that can only do a simple thing load much slower than my older professional grade app. i think ramping up cpu clock is just another waste of effort. people should build "AI" applications by now, not making it dumber.
Now we have cellphones with quadcore 2 GHz and six core graphics accelerators .. to play 'angry birds'.... i foresee a VERY grim...
the swmbo just unplugged the atom cpu upstairs, the kiddos always sit infront and forgetting whats inside their schoolbag. sigh! i should build a simple arithmetic program with angry bird as background.
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You thought you've seen the worst.
how about the people who buy iPhones or Galaxy S III's just 'cause it's the most expensive
and those idiots who claim their iPhone 4S's has a much better then my Sensation
HOW about those 'fanboys' we know as abominations
All of them are blind to what their phone is actually made to do
but in my opinion you know what's the worst abomination of a "invention" ?
Smart TV's. Yeah. Pay a big premium and still you don't even get to be able to play flash apps and videos
Those media boxes have android and costs like 200$ onwards and you only get a meagre 800MHz Dual Core ARM chip!
This would be okay if this was 2005!
Heck, for the price premiums one pays for smart TVs i can easily build a entire PC with a full featured HD5450 and an Intel chip!
My parents were on the hunt for a new LED-backlit TV, (I'm not gonna talk about the cheap ones, POS)
saw a few but only one 46" caught my eye but again, the 'abomination' is in it
and phillips ain't making a non-smart tv version.
Why i say it caught my eye? A standard 46" cheapie (the good ones? None. no one has a 46" non smart TV)
would already cost 999$
The phillips has a 400Hz panel and it has those "Smart/Stupid TV things" and a 14bit video DAC
for only 1399$ but i must say ... who the heck needs a 14bit DAC on a TV?
A samsung ( no one else sold a 400Hz that day ... ) 400Hz goes for 1799$ without ANYTHING
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I don't think it's intended for African schoolchildren - its original intention was to help UK Computing students. As one of them, let me tell you, the computer science lessons we have are dire, boring, uninspiring, and do not teach you how to actually program properly. I would like to see how they could be integrated into a coursework module; perhaps the low processing power would encourage optimised applications and limited resources would lead to unique solutions - and maybe if younger programmers learn this then the next Windows OS won't need 8 GB of RAM?
I'm not quite sure how the hardware can influence this? Surely the problem with the lesson content is the lesson content? As I understand it, almost every schoolchild/student needs to have access to a PC today to write their essays and assignments? I have the impression that hand written essays are no more. If that is the case, then there are many inspiring programming environments available on PCs, not least of which is Visual Studio Express.
Just for fun, here are the machines I first learned programming on when I was at school:
http://en.wikipedia.org/wiki/Research_Machines_380Z (http://en.wikipedia.org/wiki/Research_Machines_380Z) (Ooh! Shiny!)
http://en.wikipedia.org/wiki/PDP-11 (http://en.wikipedia.org/wiki/PDP-11)
http://en.wikipedia.org/wiki/PDP-10 (http://en.wikipedia.org/wiki/PDP-10)
And note that the PDP-11 and PDP-10 ran proper multi-user, multitasking, time sharing operating systems in a memory space generally measured in kilobytes. (Megabytes were for millionaires.)
On the downside, software engineering concepts like structured programming and modularity were not part of the lesson plans. Would they even be today, I wonder?
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The phillips has a 400Hz panel and it has those "Smart/Stupid TV things" and a 14bit video DAC
can anyone explain me what the purpose of a DAC is in a flatpanel TV ? especially since the pixels are digitally controlled... why do you need a dac ? marketing bullshittery ?
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The processor is a RISC architecture, so the performance is closer to a 300 MHz PIII/PII than anything else. 256 MB of RAM is shared between the CPU and GPU and try getting an OS written in the last 10 years to run within 128 MB.
How about Tiny Core Linux: http://en.wikipedia.org/wiki/Tiny_Core_Linux (http://en.wikipedia.org/wiki/Tiny_Core_Linux)
It won't run on the RPi but it only requires 48Mb of RAM and was written within the last 10 years. Latest release was 8 days ago!
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I personally see the RPi as a toy - nothing more. I have one and will only be using it as a cheap and compact media player for my bedroom TV using OpenElec/XBMC.
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I personally see the RPi as a toy - nothing more. I have one and will only be using it as a cheap and compact media player for my bedroom TV using OpenElec/XBMC.
look at the bright side! its 700MHz and 256MB RAM. not like my 8MHz only few KB RAM ARM-M3 dev kit here. it should be able to do 100X more (guesstimate) than what mine can. but if you find it slower, then something wrong, probably a "monkey" programmed that thing :D
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The phillips has a 400Hz panel and it has those "Smart/Stupid TV things" and a 14bit video DAC
can anyone explain me what the purpose of a DAC is in a flatpanel TV ? especially since the pixels are digitally controlled... why do you need a dac ? marketing bullshittery ?
Yeah... marketing
I personally see the RPi as a toy - nothing more. I have one and will only be using it as a cheap and compact media player for my bedroom TV using OpenElec/XBMC.
look at the bright side! its 700MHz and 256MB RAM. not like my 8MHz only few KB RAM ARM-M3 dev kit here. it should be able to do 100X more (guesstimate) than what mine can. but if you find it slower, then something wrong, probably a "monkey" programmed that thing :D
O_o PIC that is, not ARM-M3, the lowest i've seen them go is 24MHz
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O_o PIC that is, not ARM-M3, the lowest i've seen them go is 24MHz
its HY-Mini STM32V 1hunglo dev kit i got from ebay. it has 8MHz crystal connected to STM32F103VCT6. i dont know, havent looked at ARM architecture/datasheet in detail, maybe it has clock multiplier inside. anyway, if rasberry is a toy, then this 1hunglo is "toy of the toy".
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On the downside, software engineering concepts like structured programming and modularity were not part of the lesson plans. Would they even be today, I wonder?
software engineering should be taught from ground up. first with conventional "old style" procedural programming. and then structured and modularity, and then OOP and then that "foundation class" or that c# things. its like mathematics you cant teach kids algebra where they cannot count 5+5 by fingers. otherwise in effect, the new breed of "java-code-shitter" (as free_electron termed it) will grow. i dont know i havent met one, but my senses tell me, they are growing out there... they dont have much sense what assembly codes look like (maybe only a few who can find their true self). my 2cnts.
ps: during my early kid... i just play with woods and sticks. :P until i'm old enough to remember then i met computer. todays kids... they play with touchscreen.
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I personally see the RPi as a toy - nothing more. I have one and will only be using it as a cheap and compact media player for my bedroom TV using OpenElec/XBMC.
look at the bright side! its 700MHz and 256MB RAM. not like my 8MHz only few KB RAM ARM-M3 dev kit here. it should be able to do 100X more (guesstimate) than what mine can. but if you find it slower, then something wrong, probably a "monkey" programmed that thing :D
Not sure I get the jist of your reply. My point was that if you want to really learn how to program a processor then get yourself a proper development kit.
I think students would learn alot more with something like a PIC Starter Kit/Board than the RPi.
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Or even just writing Pascal code on a PC.
99% of programming is just mathematics. Nothing else.
-- Professional software engineer, "Yandex"
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O_o PIC that is, not ARM-M3, the lowest i've seen them go is 24MHz
its HY-Mini STM32V 1hunglo dev kit i got from ebay. it has 8MHz crystal connected to STM32F103VCT6. i dont know, havent looked at ARM architecture/datasheet in detail, maybe it has clock multiplier inside. anyway, if rasberry is a toy, then this 1hunglo is "toy of the toy".
Some i know bought this HY-Mini thing for 41$ and while using i find it pretty fast, the 8MHz is just RTC or the Watchdog i believe, as the STM32VLDisco has the 8MHz crystal too
the STM32F103VCT6 it has is no low performance bugger though, it's 72MHz
That explains why it can run the touchscreen and the built in OS
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I personally see the RPi as a toy - nothing more. I have one and will only be using it as a cheap and compact media player for my bedroom TV using OpenElec/XBMC.
look at the bright side! its 700MHz and 256MB RAM. not like my 8MHz only few KB RAM ARM-M3 dev kit here. it should be able to do 100X more (guesstimate) than what mine can. but if you find it slower, then something wrong, probably a "monkey" programmed that thing :D
Not sure I get the jist of your reply. My point was that if you want to really learn how to program a processor then get yourself a proper development kit.
I think students would learn alot more with something like a PIC Starter Kit/Board than the RPi.
Such a board probably isn't meant for PIC starter kit or something along the lines
But anyway the PIC boards are too expensive, we need something even cheaper then the arduino
I wouldn't recommend the STM32F4Disco for a first time developer either, it's got too much performance to cheat in the coding resulting in horrible code (And that is my people, why apps these days are awful)
But at the same time i might be 18, i have written assembler for windows ... AKA Hacking a app with assembler
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But anyway the PIC boards are too expensive, we need something even cheaper then the arduino
Your right about PIC development boards being expensive, but on the other hand if your serious about microcontroller development, 50 to 100 GBP for a development board is a worthwhile investment.
Thinking about it a bit more, I think the RPi probably isn't targeted at hardware development. It's focus will be application level software development.
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A cheap one i can think of is PIC DM164120-2 and DM164120-1
The expensive one is this one, it's so expensive but yet it can't do much and it needs another 100$ to break out the I/O
http://i492.photobucket.com/albums/rr283/DarkShadower/_DSC0323.jpg (http://i492.photobucket.com/albums/rr283/DarkShadower/_DSC0323.jpg)
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IMO if one is serious about getting into a MCU it's better to get a programmer and some DIP versions of it (or QFP100 on a breakout) and bread board it from the get go. It gets you into the habit of choosing for yourself how you'll connect the buttons and shit earlier and let you try out functions that aren't made unavailable because the guy to designed the dev board decided not to route it out or it got taken up by other buttons.
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+1 for DIP.
THE easiest way to learn is to use something like ATmega8515 in DIP-40 on a solderless breadboard. One can easily probe each pin individually and change the circuit very quickly.
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The phillips has a 400Hz panel and it has those "Smart/Stupid TV things" and a 14bit video DAC
can anyone explain me what the purpose of a DAC is in a flatpanel TV ? especially since the pixels are digitally controlled... why do you need a dac ? marketing bullshittery ?
What am I missing here? What exactly does "digitally controlled" mean in this context? In the end, each pixel has an analog value, and this is what the digital signal will control. CGA was also digitally controlled, in the truest sense of the word. I.e. 1 bit per primary color, plus an intensity bit, 16 colors in total. I suspect modern flatpanel TVs have a slightly higher color depth than that, so they need a DAC of some kind.
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This DAC is always integrated into TFT panel. The panel itself always has digital interface.
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like HDMI, which is commonly used now
Is there really a qualititive advantage of a 14bit over a 8bit?
By the way, there's no definitive method this 14bit DAC accesses a something that has a larger bit resolution for the phillips screen i'm talking about here has a something that is next inline that has 30bit because of their claimed 14million something display colours
47PFL6007H/12 is the model i'm talking about, the 3D version with ambilight
But i believe it's not neccesary at all!
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DaveXRQ: Please use punctuation! I can't figure out where one sentence ends and the next one starts.
My original comment was for free_electron, who seemed to imply that there are no DACs to be found anywhere in an LCD panel.
Now, as to whether a 14 bit DAC makes any difference... It may not do for a TV, but I think it absolutely does for a high contrast monitor to be used in graphical design, for example. The consideration to make there is that you may want to calibrate the colors in the display. Even if not every one of 16384 values are actually being used, the values that come out after the gamma curve is applied, will be closer to the target value. And even if 14 bit may be overkill, it may be that it's so cheap to make a 14-bit video DAC there's no point in using 8 bit DACs anymore.
As for the panel in question, I can't seem to find any online source that actually says that it has 14 bit DACs, or anything at all about the video DACs. :-\
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My original comment was for free_electron, who seemed to imply that there are no DACs to be found anywhere in an LCD panel.
And that is correct. The LCD is driven using a stepped control voltage. A master step generator feeds the step voltages to the column drivers. The column driver selects a range in the step and potentially subdivides it. The steps are not linearly spaced but follow an S-curve tuned to the lcd material used. the light intensity follows a sinusoid behavior as it is a 90 degree rotation angle of the crystal that blocks the light. As temperature changes the step generator adapts the step voltages as well.
Once the base step voltage is switched in ( note that all these steps are a big bus with over a thousand independent , static , voltage levels. There is no DAC involved. ) using a multiplexer under control of the pixel data word the selected step voltage is loaded on a capacitor .
Depending on the phase of the backplane the cap is connected forward or reverse to the pixel. So when the backplane changes phase we reverse the polarity of the capacitor (lcd pixels need to toggle, they cant remain static....) there is a simple buffer opamp between cap and pixel line.
There are two capacitors. One holds the current 'value' of the pixel being applied while another is being loaded with the charge for the next line ( this example assumes the active drivers are column based ) . When the next line begins all caps have been charged and we do it all over again ..
No dacs have been harmed in driving the LCD panel. It's all pure digital.
Every column driver chip controls maybe 256 columns. For advanced panels that have matrixed backlighting that is controllable per tile ( whether white backlight or full spectrum RGB backlight ) they can actually reprogram the Step-curve to be in sync with the background RGB setting. This way they can 'boost' pixels and create larger dynamic range. The DCD technology from Faroudja is the absolute king in this. They now have full RGB backlight controllable per tile.
You could consider the step-generator and multiplexer a form of switched-cap DAC , but it really isn't .. the base principle is totally different. using a true dac per column driver would require a massive amount of silicon area , be a nightmare to trim them all identically, keep them tracking under temperature , and they would need fast settling times. the required logic would be immense... it's not feasible.
But, for the laymen the marketing bullshitters use the terminology 'DAC' because this is the highest level the 'layman' understands (they have been pavlovianly conditioned to drool when they hear technobabble) and 12 is higher than 10 so it must be good ... no ?
In reality it is nonsense.
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I have no idea because i haven't torn a LCD down before, but when i get to i will most certainly reverse engineer it.
just for fun ;D
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free_electron: Ok. Thank you for the detailed description. I learned something new. Since you seem to know a thing or two about LCD technology, and while we're at it, maybe you have the answer to a thing I've observed. There seems to be a change in green bias every frame in small groups of pixels.
.X.X.X.X
.X.X.X.X
X.X.X.X.
X.X.X.X.
.X.X.X.X
.X.X.X.X
X.X.X.X.
X.X.X.X.X = white and . = black. The pattern needs to be aligned.
If you draw this pattern and invert the color of the pattern every frame, you get a very slight either green bias or magenta (anti-green) tint. Me and a friend of mine have observed this on two completely different panels. I'm thinking this may be some trick where the panel electronics are changing the green value by one or two, every frame, to increase green resolution by one bit. Does this phenomenon ring a bell with you?
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most lcd's use the bayer filter.
there is 2 green pixels in an RGB set. contrary to a classic picture tube where they work with triplets
B/G\R B/G\R B/
/R B\G/R B\G/
an lcd uses a quadruplet
RG|RG|RG|RG|
GB|GB|GB|GB|
RG|RG|RG|RG|
GB|GB|GB|GB|
so yes, the panel needs to compensate if you switch from whit to black... as there are two greens switching they may be overdoing the compensation ...
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Neither of my panels (laptop, Sony LCD display) have the quadruplet subpixel layout. This is an image taken while drawing the pattern in question. You can't see the effect in question on a static image taken with a 1/500 s exposure time, but you can see that the pixels are laid out simply as RGB.
(http://i.imgur.com/Gu41L.jpg)
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BTW, sharp claims a RGB+Y colour setup
Real or not?
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most lcd's use the bayer filter.
Most?
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BTW, sharp claims a RGB+Y colour setup
Real or not?
yes ,if its a quattron display.
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BTW, sharp claims a RGB+Y colour setup
Real or not?
yes ,if its a quattron display.
but anyway i don't see a point in RGB+Y, doesn't make it better by a order of magnitude anyway
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most lcd's use the bayer filter.
Aren't you thinking of CCDs?
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oops brainfart.. forget the bayer pattern.. i was thingking bout picture captured by a camera sensor. these are trapped in a bayer pattern
when displayed they need de-mosaicing becasue of thre RGB order in an lcd monitor..
here is some info : http://www.cs.ubc.ca/~atcheson/f/atcheson%20-%20subpixel%20rendering%20of%20bayer-patterned%20images.pdf (http://www.cs.ubc.ca/~atcheson/f/atcheson%20-%20subpixel%20rendering%20of%20bayer-patterned%20images.pdf)
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MPEG-2 and VC-1 decode support.
http://www.raspberrypi.org/archives/1839 (http://www.raspberrypi.org/archives/1839)
http://www.raspberrypi.com/mpeg-2-license-key/ (http://www.raspberrypi.com/mpeg-2-license-key/)
I believe that someone will find a way through...
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Has anyone done anything with these besides just use them as tiny htpcs? I ordered one when I was finally able - it should be here in like sept/oct, but I still have no idea what I might do with it. It looked like a fun toy so I decided to order one, but I really have no interest in dedicating it as a htpc.
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PowerVR chips are really not that brilliant at GPGPU. In shaders, 128-bit vector operations are executed as four independent 32-bit scalar ops, for instance. And memory bandwidth is really limited.
PowerVR is infamous for being "the worst graphics core ever". That's true regardless of what silicon it's on - Broadcom, TI, or even Intel. Look up "Poulsbo" and see the flood of complaints for terrible drivers.
My Cedarview Atom was affected by that issue, so initially, I stuck in an old FX5200 card to get an acceptable level of performance. Now I installed some better drivers so I no longer need that FX5200, and I get great 2D performance and good video performance (it offloads but nowhere as well as Nvidia's VDPAU), but try to start any 3D program and it won't work. (Fortunately, the Atom system is not for gaming.)
As for Broadcom wireless chipsets, they just can't compare to the good brands like Atheros/Qualcomm, Intel, or Ralink. But if you have one that is supported by the open source driver, unlocking it to use extended channels is supposed to be easier than for the others.
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Has anyone done anything with these besides just use them as tiny htpcs? ...
I have a weather station and (soon) an outdoor webcam that will need some form of local processing and a Pi looked like a cheap way to get this done. I'm finding the delay in getting one to be frustrating so that's been put on hold.
I also have a GPS tracker application that would work well on the Pi but have decided to go with another device for that (Mele A1000 (http://rhombus-tech.net/allwinner_a10/hacking_the_mele_a1000)). I'll probably end up getting a Pi, as you say it looks like a fun toy.
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PowerVRs are terrible but at least they are ultra low power.
The savior for mobile graphical computing goes to previously-AMD Qualcomm Adreno And Nvidia Geforce ULP
Shall i throw Mali-400MP out of the equation?