Theo Verelst Local Diary Page 61

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  Fri Dec 12 17:06, 2008

Dennis chambers! into Cuda

Heavy processing in graphics cards. I was able to put in a GF9500 in a still reasonably fast machine, and compile the cuda examples (after installing the drivers and libraries) on Linux (Fedora 8/64), and view them on the big HD screen:


This is a picture from me from my homepage being abused to act as a proijected texture in a Cg shader example application, also running on the same system:

I didn´t make a movie of this, but the light and the projected picture move in the animation, an effect like a unusual disco ball.

A more serious looking application, GLC with a tie fighter model to view:

It seems I could plan Gelato renderings and paths for animations by adapting this application, but this one was the precompiled version, though I have the sources.

Another shading app:

And more heavy cuda:

Those are real-time smoke particels, translucent, moving and acting as smoke, with shadow and camera motion. In fact it is possible to run a cuda application and a shader application at the same time, that makes the graphics chip really work, I just didn´t try in on application.

Another Cuda example which I modified (I compiled all the above myself) to write frames from, it the partices example:

That accuray is actually in the VBR mpeg movie, it´s a random unprocessed frame. A much less quality (and much smaller) mp4 film of a minute is here. I´ve put some links up here on the NVidia Cuda for Linux forum. A maybe easier flash inpression is on vimeo where I´ve made the high quality (albeith 720p) movie available for download.

Maybe Cuda can run Connection Machine LISP:


Graphics card replacing

Ignoring a fan breaking down for a long year is not a good idea, and although I kept a constant watch on temperature and think it never went where I though it would be critical according to some number in a dialog box, I think a graphics card broke down.

Anyway to be sure I replaced it with another card, which I ripped from the server machine for testing, and that appeared to solve the problem.

So after some searching and discussion I got a new one, for way under E100, with Cuda!

The Audi questions

When I bought an Audi in ´91 it had to be a model 100, 5 cylinder, galvanized (to totally not corrode), at least 100HP (easily), and at the time it had to be in a bit of a condition, i.e. look ok, and be not in some way messed up. In fact it had some additional things like a nice interior and natural gas installation. I knew it had at the time the new model was introduced the worlds lowest drag factor (0.30), and I knew a simular model was succesfull in ralleys, which I found interesting, and proved likely when I took it to a slip-course once. I think the Audis interested me since I drove some distance in a 80 model on some job trip at the time: the combination of sportiveness and comfort are of course known.

I saw some audi flyers lately which contained a lot of that sort of information:

More Of the good stuff: blu-rays

The Nasa bluray is a weird case, it has 295 (!) minutes on one disc, which is encoded somewhere between 15 and 20 Megabit/Sec from the looks of it. It isn´t all great film quality, but as it works at least grainy film is film as opposed to pixels and bad motion algorithms, and the bluray´s 1080 doesn´t interfere much with the film character (as would be the case on dvd) so still even those fragments are quite nice, and the whole looks still very impressive on the beamer. It´s great to sit like 3 meters away from a 2 meter 30 cm wide screen showing the stuff in intense enough 1500 Lumens (max) and blazing fast DLP with all kinds of optimisations set right.

Illuminated remotes

So that is like being a cinema operator, but it took quite some work to get there, mind you. First of all the beamer needs to be good, although the HD1000 (Mitsubishi) is a year and a half old now (I seem to remember) it has been only replaced by a simular model, or maybe it´s still being made even. And there´s not much really like it, which has to do also with the required accuray (colours, the driver processing, in this  case the TI DLP chips).

These are my latest views at the moment:

A screen picture (unprocessed, this is what it looks like on the 106 inch pro grade screen), clearly from the NASA bluray:

 295 minutes of certainly not all very good HD quality but great material on one disc!

Reflecting surround

After of course listening to all the blurays I can acces/rented with interest, I tried out a indirect rear (side) sound because I wasn´t totally satisfied, even though a great sound is almost instantaneously there with every disc on my big audio system and very good back (side) powered biamped speakers.

In total there are 5 high quality, high power stereo amplifiers working when the whole system is on, ranging from 2x40 Watt (appoximate short term continuous sine RMS power) to 2x120 (maybe 150 I didn´t measure) Watts, and one bridged amplifier up to at least a few hundreds (maybe 400...) sine RMS watts. In total well over half a kilowatt, sine RMS cont. power.

The total supply power is over a continuous kilowatt rated by the toroid transformers manufacturers, which of course is a lot of power, not to mention the possible peak music power. Lets not try that out, shall we. Good.

To put all this power into airwaves there are 13 speakers doing the job they do in the right frequency band, in the whole system active takeover filters are at work based on the worlds best quality audio opamps and high quality (neutral) filter parts, which are analog 2d order filter mostly (not all) not digital so they impart no unwanted delay or re-sampling noise and aliasing problems. The speakers are woofer and tweeter in the powered rear (side) speakers, and a 4 way system + a 15 inch subwoofer (on the left bottom in the below picture) as main (front L/R) system. The four way system has a 12 inch woofer of about a hundred watts, two mid frequency speakers of varying size, of which the highest frequency reproducing unit is made to act phaselinear with the fairly powerfull dome tweeter. All speakers are airtight, non-bass reflex, to create no ever-present backward reflected waves or other unwanted oscillations.

As can be seen from the pictures, the walls and the floor (2 layers) are acoustically damped for a large percentage with slidable panels. In essence a studio type setup, with limited room reflections (not acaustically dead).

As described on one of the previous reporting pages, the system as quadro system (I can make a good quality rear and side, and I´ve even made a well funtioning mid front channel, but I have no 7.1 blurays, and the mid front has to compete with an extremely well sounding 4 ways main system mix, and is therefore except for a better directionality outside the sweetline not so desirable) functions great, especially after setting up all parameters and volumes correctly.

However since I am a quality freak maybe, or at least I like to test how good things can get, I connected the Lexicon (a famous studio equipment brand already inventing practically and well working DSP in the 70s) 24 bit converter I have to the TOS output of the bluyray player to try out wether that would be better still, and indeed: the Lexicon in general does it again: betting definition, straighter low (it seemed) and it sounded more neutral and less sampling issued, somehow. That´s a bit of a trick, because the best audio tracks normally would be the DTS (master) tracks, and to work with the lexicon they have to be converted in the player to a 24 bit 96kHz digital audio signal, which isn´t without losses and possible issues. But it appears to work great in practice, and then I get to keep the rear and/or side signals from the excellent enough player outputs, after the DTS conversion. There are delay issues, of course, the distances in the player of the front with respect to the rear probably must be more offset than normal placement of the speakers would make practical. I tried putting the speakers close to the side of the listening position, which is different than the quadro setup, and closer to the side setup, for which the side signal is actually intended, and which indeed sounds probably as such.

That made the distance as short as possible, and so with the front needed timing compensation also unpractical. So I though about Bose(TM) in the 70s: reflecting sound! And so I turned the side speakers and made them blast against a hard, plastered wall and prepared a first reflected path by sliding the damping aside, so that the primary path to the listening would be longer, and that works great!

back to the listener:


The tos connected 24 bit Lexicon converter

Keeping the neigbours from experiencing excessive bass, and of course stopping annoying and unprofessional standing waves to an extend: double layers of damping material behind the 15 inch sub unit (> 100 Liters enclosure).

Without exageration I could now with the indirect sound create concert and cinema illusion at sufficient volume. To prevent direct frequencies coming from the side speakers anyhow I set them to ´small´ in the player menu, so low frequencies (which travel around the corner and ignore the different direction of the speakers and would be in counterphase, too) are filtered out, and the result is really pretty good.

I tried listening to the Black Crowes in the Fillmore in SF at some volume, and later to the Nasa missions disc and I could actually sit anywhere in the room and follow the films with great sound impression all over the room, of course the most realistic at the sweet spot, but the diffused back makes that a sweet line, and really, the sound is better than in certain cinemas I think!