Theo Verelst Local Diary Page 35

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  Wed Aug 16  20:36,  2006

   Thats when I started the html of this page, I've made images, and like if my .org would be on the stock market I have to make clear to the stockholders that its intrinsic value is steadily on the increase (or staying at a high level...) so lets see if I can double the stakes (subjects) again this time...

Kidding of course, I don't even have a company (let alone money...) and I don't believe .org s  should be on the stock market. Another joke from a recent (for me) fortune:

All science is either physics or stamp collecting.
                -- Ernest Rutherford

That's the scientist who invented the early 20th century atom model, before quantum mechanics shattered it...

Well, I got some good stamps here, and I AM really a very good physicist, and have grades and work to prove it, so maybe I'll do something in that line here.

The finishing of this page is now done a lot later, so various texts are from later date, now it is Nov 25... Don't forget to check out the next diary page, too that's a pretty cool one.

   A Nasa top lunch joke

   Well, one can be without income, without public status maybe, and society can be so rotten a well educated engineer doesn´t even want to work in many jobs anymore, but they can't take a man's dreams away.

   So lets dream of having time and space to have lunch with important people of Nasa, maybe Neil would be around, so lets say today I´d have lunch with oKeefe or the current head-administrator  mc Griffin (both  Irish ancestors,  thinking about the "Bonfire Of Vanities" descriptions ?). So I´d play the ball of wanting to be on a Jupiter mission as astrounaut/scientiest or so, an dof course I´d have to tell a good story or a good joke. I read one in a dutch (Jewish) joke book:

   You know this one about the guy visiting the Kremlin?
This guy runs into a russion party head who talks to him and says "You know we have a big publicity problem here, I think we're being called anti-semitic". No no, the guy says, that´s not so, don't worry, that was in the time of Stalin, maybe during the cold war, but not now... Well, the party head counters, I think it is really opportune to send a good will signal so lets do something nice for the jews here, lets see, maybe you organize a jewish worship service here in Moscow, you know, give them a nice place. The guy leaves, and returns again later a bit upset, " Well, how did it go, you found some good rabbi to lead the service?". The guy shakes his head: "there are a lot of rabbis around". Surprised the party head asks what the problem was: "There're all jewish..."

   Quality pictures howto ?

The last say 3/4th of a decade I´ve on and off be dealing with relatively high quality photographs and artwork, Before that, I made some pictures as a kid an teenager, some black and white, some color holiday pictures, and more recently I did a (up to good standard' video course while I worked at university, and used the university music centre video recording and editing equipment to do nice super VHS video work, for instance I taped all kinds of works at the 1991 or '92 Dokumenta (World famous art exhibition in Kassel, Germany) recorded a (amature) stage play, things like that.

The quality of the picture below is fairly good, the original is 5 Mega Pixel (25xx X 18xx or so)

Of course how that comes across to you depends on the quality and picture reproduction characteristics of you monitor or your printout, likethe size, the darkness or lightness and natural color saturation and gamma curve of your viewer, and the influence of the browser on that.

I find the folowing pictures from a 70s book very pleasing even though there are clearly issues with the color, I guess its a matter of how the sun shone, too:




What a space and rest, and interest of colours and playfullness, so incomparable with the new age we're living in, so infinitely superior.

The next one is a bit dorky I agree but pretty too:

Oh I scanned these pictures from here, I hope that's ok:

I found it somewhere by chance.

Below I screendumped a frame from a HD movie experiment I filmed at dusk, so with just enough light to make a picture, and noise in it. I ffmpeg-ed the movie to 720p format, and looked at the noise and motion after transcoding it from mpeg2 transport format to Quicktime for Linux mp4, and then back to mp2 to view it with a purevideo hardware accelerated viewer to get no glitches, delays or any artifacts even at very high resolution (720p or 1080i).

The motion interpolation going on in mp4 makes the motion nicer, and even at low bandwidth (such as above) its still possible to get a high resolution feel, especially with moving picture, which looks better than stills.

In the next picture I've used Gimp image processing to give sky another look, for just one frame:

that would be better, but on the other hand its very unnatural, I really like the noisyness too, when it's real noise.

(click image for original HD version, which is jpeg compress of course)

The above image is made from a moving camera (a pan from right to left) of course there is fuzzyness on mainly the side edges. Depending on light and diafragm setting and lens size and film sensitivity and of course the speed of the motion, that is normal and called motion blur. Only with enough light and small shutter (exposure)  times compared with the frame rate, stills would look like pictures without fuzziness. During playback, this is important also to make motion look natural, either for film (shutter time based) television (electron beam travel across the screen based) or mpeg or other LCD/TFT screen update regime based (per screen or row or column, with varying response time).

With practice or education (I suppose) one can see wether a still has natural or artificial noise and motion blur effects, and I happen most of the time to like it to transcode material over mp4 which improves the motion effects. I'm aware of the limitation that 3D motion can be messed up a bit when interpolation is done, so it' s just a general idea, not in every way correct. Just like a motion stabelizer in a camera r in software cannot predict the parts coming up in the next frame which were previously hidden.

This is from the HDnet 720 HD film which is downloadable from the internet about the return to flight space shuttle flight from 2005. A lot of different feels are present in the movie, the 70's like not unsubtly enhanced look is what I prefer by fat the most.

Below another scene from that movie, on an actual screen dump from a big screen, which is great to work with, together with a gelato 3D graphics rendering of the famous teapot with an environment picture mapped onto it from a picture I made and nice glossyness.

Gelato is a movie rendering quality set of programs/libraries for curved surface, complex lighting scenes which makes use of NVidia graphics cards with up to date engines (at least 6200, but that isn't perfect), preferably a Quadro card. In right bottom corner another gelato rendering (which is uncomparably faster than for instance POVray, and not similar) with smooth shadows in it.

On the the BBC widescreen I suppose 576p there was a program which I watch primarily because of the HD-ish pictures from good cameras with houses an interiors and countryscapes in it, which is nice to watch from  digital satelite.

A recent playlist, good for conservatory use...

Filters ?!?

Well, that's different from coffefilters for electronicists. This is a screendump from Qucs, which is a relatively new circuit simulator from europe (I'm sure the origins lie elsewhere) which allows one to relive some potent and good network theory basics (I'm a network theory (EE) master of science by eduction, but is is first year stuff) for instance this first order filter circuit, of course analog, not digital:

The calculator shows the cutoff frequency for the filter circuit according to the 1/(2 x pi x R x C) formula, the graph shows a simulation of the circuit which rendered a frequency vs amplitude plot, which indeed shows that cutoff frequency, and the expected low pass response.

This image shows the simulation of a second order filter I designed using an approach from the past (I did this already back in the end of the 70s), which actually in implementation lives in the powered bi-amped monitors I made last year. As can be seen from the vout and vout pins'  response, the cutoff frequency, which is in practice a takeover frequency because there is a complementary circuit for the tweeter amplifiers, is 5 kHz. Taking into acount the 0.5 damping through the filter and its resistive load of 22kOhm this is a cascade of two first order filter responses which is 0.25 at the -3dB point (-3dB + -3dB + -6dB = -12 dB --> 1/4).

This filter, in analog form as above has been appied to my powered monitor biamplifier chain which can be seen in the Freely reusable schematics below. Using a Very high quality opamp stage as preamplifier the overall quality and behaviour of the circuit is excellent and very natural, and also an extra AD/DA stage is prevented, including anti aliasing filter and reconstruction filter are alleviated which is very good for unsampled sources or very high quality DA converter outputs being fed into the monitors.

Those opamps are recent high quality audio opamps of BurrBrown / Texas Instruments, which are quite expensive in comparison with run of the mill audio amp chips, but very good numerically and in listening tests it also performs very neutral and beautifully, I had some samples form TI through which I knew this, and I was able to order directly from Newark InOne (New Jersey, USA).

Better Sound Through Research

Thats a Slogan from Bose (Research) and it applied to probably most or all of the good audio things from the organs in the middle ages and greek string theory to the latest synthesizers and theater sound systems.

Research in that sense doesn't mean checking out associations, wether mother or mr so and so is felt in the system or work, but of course there is more to music and musical processing than dry scientific analysis and probably certain issues are subjective and relative to cultural assumptions, though most of the good work I'd say is hardly cultural except for its history. Meaning that there are various clear sources who worked on music, like the old classical composers and performers, the various people working on the new musical styles and the number of pioneers who made modern music possible.

I of course don't mean the up the attic boys with samples and a great idea about scratch patterns, that's ridiculous, but people like Chuck Berry, Robert Johnson, Irving Berlin, mainly american dance orchestras from the 20s through the 60s, Bill Haley, Bob Moog, Laurens Hammond, Goodman, J. Hendrix, the Commodores, and many many others. I'm talking about the top, the pioneers who were really inventors and musicians of high standing, not wannabees or  takers of other peoples samples or so!

Of course, music making requires instruments, and making music sound may require recording or tranmission machinery, which has mainly been invented in the 20th century.

As another electronics created possibility not just recording and broadcasting became available but also amplification and electronic musical instruments of various kinds. On of the most influencial and far stretching electronical musical instruments apart from organs us the synthesizer. Below an add from the 60s with a picture of the 'back room' from the moog synthesizer company.

They recorded. apart from numerous hits with the moogs on them, a demo record which is also available on the internet.

I did a little research or checking if theory known to me works in practice and wether my self built and used equipment lives up to the theoretical quality levels. See here a recording from notes from my synthesizer with the filter all open, and one oscillator working, digitized with a Lexicon Omega USB AD/DA converter (24bits), which is of very high fidelity:

The saftooth waves are all the same, and their highest harmonics, which are limited to no more than half the sampling rate (the Niquist rate) become visible as part of the perfect additive synthesis of a frequency limited sawtooth wave, and are shown to be sampled with sampling points which are not linked with the clock of the DA converter of the origina wave.  So when the waves are shown with a simple reconstruction filter o the screen, ik this case a zeroth or first order approximation (straight lines) there is visible unevenness of the samples, which is completely correct, according to theory, and can be perfectly reconstructed!!! Indeed, the outcoming sound is hardly uneven or distorted, which is not true for just about every software synthesizer I've heard (and that's a lot of them). A little ' running' effect in thehigh is there which is logical because of the non-perfect reconstruction filter, and in the hioghest 1/2 octave there is noticable foldback (aliasing). Also, it is possible to hear a bit grain or harmonic distortion in the very high (note that I have some very serious amplification to hear that) both in the original synthesiuzer DA conversion and there is a bit muffled of that effect audible also at the lexicon output, a bit brick wall (good) filtered, and a bit less brigth (not perfect). Both effects are about sawtooth waves with harmonic components fully present to the last octave where those are just under the Niquist frequency...

Half a Bose sticker makes this Ikea stool look more scientific:

In my highschool time, around '80, I had acces to Hameg Oscilloscopes to play (seriously and under strict rules..) and work with, and at the time probably tectronics was a slightly sexier (if possible) brand of measurement equipment. I saw them at the Ibc in Amsterdam, and had a quick cam sweep over the stand, showing a mpeg audio stream analyser, which is sort of like a digital stream and protocol analyzer:

Interesting in the context of measurement, I saw this article in the conditions of use or license for some microsoft product, I think it was media encoder or the studio version, which requires the installation of .net, increasing security riscs, disc use and startup time, and the product was worthless thus far, can´t even read standard mpeg-2 transport stream, though maybe I´ll be able with it to write microsoft windows media format HD video files This is the quote (in dutch):.

3.     Aanvullende rechten en beperkingen.

        3.1    De Client OS-componenten kunnen de Microsoft .NET structuur bevatten. U mag de resultaten van enige vergelijkende test van het .NET Framework niet aan derden bekendmaken zonder voorafgaande schriftelijke toestemming van Microsoft.

One may not publish comparison tests about the .net framework without prior permission of microsoft.
Dolby is actually closed and licensed...

Audio waves

That´s a bit harder than a digital single signal, because audio waves pass through a 3 dimensional space, speaking as a physicist.

The above is a screen picture program (free from the internet) does the well known (highschool physics) experiment of a virtual waves in a virtual tub, the screen clearly shows the Huygens behaviour for waves emanating from holes which are small in comparison with the wavelength.

The waves from this electrical circuit were a bit in trouble, I open the machine,m anmd repqired the wiring from the graphics card connector, and now its running good again:

some work, though, and the machine is a bit noisy, but it has run for years and still runs XP and Linux pretty fast (2.6 GHz pentium), and the SMART readout doesn't compain that the disc has worn out, even though I'd have a installed and running replacement. The switched supply (150Watts...) has had its fan replaced, after it had autoshutdown when I was working with it in france on my Open Source Additive Synthesis software. But the machine would run like easily 8 hours a day already for more than a few years!

Very pleasing (righteous ?) soundwaves came from the Dr. John performance at the recent North Sea Jazz festival, from the piano, the bass (and the amp) the drums and the organ and guitar, except the PA system (those hangning arrays) soudns really harsh, cornerish, hyped bassy and generally distorted and limited, though luckily all those things within sime control and the volume not ot of bounds and not too soft.

But the heavenly sounds from the instruments (the bass sounded interesting for instance and very drive-full) were not very done well be the amping unfortunately, maybe something to change for such a top event.

Mr John had a skull on a scarf or cloth on the piano which reminds of the table in the from of the church I was taken to as a kid, and was very clearly not Dutch.

Thank God.

Open Source Very High Quality Biamped Monitors

I´ve shown them on musical instrument fairs a conference, several audio related places, taken them to france, used them for all kinds of things from HD video sound monitoring to playing CD´s on the waterside, from studio monitoring to guitar and keyboard amplification, and they perform really good for all the time and sound very natural, neutral, and strong.

The speaker units are Pioneer and Jvc, the former being a specific (fairly recent) type of car speaker, which I modified by clipping of the extra high frequency cone in the middle, and the dome tweeter was from a series I found in an electronics parts store, a quite powerfull one, like the woofer has a rated peak power of 175 Watts,which however probably cannot be produced by the built in amplifiers, but I didn´t measure this.

They are more made to drive about 40 Watts continuous, the continuous power rating of the woofers, and that real good, with very low distortion compared with anything except high rated studio monitors like Quested or so, and those 4 end amplifiers, which are integrated in the right speaker are driven by 2d order butterworth type electronic (cascaded 1st order sections without resonance or active parts, made with very good capacitors and metalfilm resistors) seperation filters which are driven by a very high quality pre amplifier.

The aluminium connector panel is on the right side, with a volume control, a 1/4" stereo jack audio input, an on/off switch and a stereo jack plug for connecting up the high and low signal for the passive left side speakerbox. also on the right on the lower back side there is a flexible and easy to use, slim plug, ungrounded mains cable, which is loaded by a good quality toroid transformer of 120Watts continuous on the bottom plate of the powered speaker, weight balanced.

The crossover frequency has been measured and tested (also with a digital filter) to be best at 5 kHz, see here. The aluminium (flat) back plate is the cooling plate for the 4 end amplifiers.

This is the filter prototype circuit board:

All these circuits are designed and built by me, this is the overall circuit:

Free to use for non-commercial purposes, email me. Notice that there is provision for preventing grounding loops, hum and crosstalk by using the grounding wire network as in the diagram. This is essential, just like using thick enough supply wires, the circuit is certain to underperform or even oscillate or not function at all when these overall network theoretical issues are not dealt with properly in the implementation.

This is the back of the synthesizer unit in use as main system pre amplifier, with the neutrix jack as input plug, with on top of it a Xilinx spartan 3 FPGA with bus connection to a dual core Blackfin DSP board which in this case runs a reverb with VU meters and surround (4 fold) audio output which I gave a decent toroid tranformer based supply unit to put aside the supplied switched unit to prevent noise in the pretty good 20/24 bit AD/DA converters of the reverb when connecting up with computer and synthesizer audio signals.

Thus far I like the neutrix jack connector plugs as the only ones to work real good, both to solder (I have used the new leadless solder already, but for this job I used the well working standard leaded roll) and to use, but of course they are a bit expensive.

On the bottom left of the circuit board I soldered a TI microphone preampifier with very high quality digital gain control which I will like to prototype with. The lead is being soldered to have two seperately shielded channels, connected together at one point, and a one side connected overall shield, so that the ground runs trough seperate inside wires per channel.

I´ve also made a cable to connect a switched supply synthesizer to a balanced input where the outputs of the synt are not balances but have the negative line connected to ground of the plug at the connected machine.

I´m lucky to use (not own) this setup to make recordings of high quality with, both audio and High Definition video, which is 1080(i). I´m using the most sold american microphones of the moment for audio recordings with the USB 4 input / 2 output 24 bit Lexicon box, which has very good microphone pre-amplifiers (with phantom voltage) built in, and a Sony very small HD camera which gives very pretty imagery when used right.

To make this work at all, the audio just requires a computer of any kind, but to use the Cubase LE program which comes with the lexicon, and th effects on a complex set of audio tracks requires computer power, and a lot worse with the HD video: at the moment there is probably no computer system apart possibly from high end unix systems or clusters, which can play that content with the standard players.

Well, a fast computer, like a pentium dual core with good motherboard I tried it on can probably play a 25 MegaBit/S HD stream to some extend even looking OK, but when deinterlacing or scaling is in order faults can be seen, and it is very likely that fast scene changes will cause trouble and at least artifacts can be seen like fast transient line patterns at block boundaries.

There is a solution though which I use to perfectly view the 1080 x1920 moving images at full 50 frames per second (interlaced) material with position estimated deinterlacing, and even noise filtereing and very good scaling operations, and that is based on acceleration by a potent video card, I used NVidia Purevideo for the purpose.

I´m not talking about setting a player to ´overlay mode´ as of course also causes some things to be processed in the graphics card hardware, thus loading the cpu less, but I´m talking about a specialized fast processor built in certain graphics cards which are able to decode mpeg2 (and other) video streams in real time and in high quality because they are sufficiently powerfull for that. NVidia offers access to their hardware mpeg decoder by use of the windows media player when it is unlocked by buying a driver from them, which cost only $20 and can be ordered over the internet from the US. Brilliant investment when you have a potent enough nvidia card and a big enough monitor or screen and interest in HD video.

It is thus far the only way I know, except for a direct connection over DVI with the camera to get high quality always stable and up to standard  HD content viewing on a computer, and I´ve tried a Athlon 3.3GHz/64, a Dual core centrino (T2400, 1.83GHz), with a NVidia 6200 card or (much) better, with media player or quicktime player, or powercinema or Nero player. In fact, if you compile a recent mplayer (on windows I´ve done that with cygwin), but on linux even better, you can play these streams pretty well, though by far not as crispy neat and well-deinterlaced .and motion-straight as with PureVideo. On Linux, I´ve tried recent Knoppix, ´Live´ and Redhat Fedora Core 4/64 and Core 5 (dual core), where various players are available, some work a bit for HD, In fact I´ve gotten Cinerella to Display 24 (full) frames per second on the fastest machines, which is really cool. Probably a well compiled (use a ramdisk for temp!)  mplayer on Fedora also works ok enough to use, but still not in the same league as purevideo.

The pinnacle box above is connected to the Linux server where it can be used with dune to get live and recorded tv of pretty good quality, with hardware mpeg encoding. The slim unit on the computer is a 60 GB usb disc which works good on linux or windows.

To get good audio listening experience, standard sound cards are out.

Audio Compressor use, analysis and repair

This is a picture of a pretty desirable analog (!) machine: a Valley People gainbrain II compressor:

This one was broken, and I fixed itto be used in a studio again.

I was able to find the schematic diagram of this 80s machine on the internet, which is quite complicated, but I tried to follow it. After a number of days of finding out various parts of the circuit seemed to measure to work good I did some opamp measuring and finally had to conclude on of the TL072 opamps was broken, and indeed it worked good again after replacing it.