Topic: Reframe "Pangolin" WAVES !!!

[James]

New release!

http://akrobiz.com/laserboy/code/LaserBoy_2009_08_24.zip

This version brings a feature to the surface that has actually been there for a long time!

Since I have been working with waves for a while now, I thought I'd clean this up and make it more prominent.

I made a show back in 2003 for First Night Akron 2004. That show was recorded as a set of analog signals from a Pangolin QM-32, onto an ADAT machine. Since then, it has been transcribed to hard drive (wave) via the echo Layla 24/96.

One of the things that I immediately noticed about the QM output was the way it looks when you turn off all the blanking. There is always a hot spot that moves around the projected show. Normally this is blanked out.

Upon examination of the waves themselves I found that this is some sort of time soak, perhaps to allow the QM to do data acquisition and calculations.

At 48KHz, it is anywhere from about 150 to possibly over 800 consecutive, blank samples sitting at the same X, Y corridinate. I affectionately refer to this as "The Pangolin Beam Dump".

It is very obvious in the unblanked image. It's also easy to see in the waves. It happens between every frame coming from the QM.

So, I wrote some code that looks for it!

Now you can reframe wave files that were made on a QM-32.

I've never tried this with anything but the one tape that I made with the QM-32.

It might work on waves made from any of the Pangolin cards. 

It isn't perfect. There are some situations that cause ambiguity.

This version of LaserBoy is extra large because it contains an example wave in the folder LaserBoy/wav/unformatted/ called zippy.wav.

This wave was extracted from the entire 40 minute, 2004 show using only Audacity. LaserBoy had nothing to do with putting it together. It has no LaserBoy encoding in it.

But, we know it was projector ready, so we must assume that there is a delay between the scanner signals and the color signals.

This delay is about 7 samples at 48KHz.

To open this wave and properly reframe it, follow these steps:

From the main menu, go into menu 'b' wave utilities.
Choose option '5' to set your desired system sample offsets to:

X    0
Y    0
r    -7   (negative seven)
g    -7
b    -7
i    0
L    0
R    0

Since the wave has no LaserBoy information in its header, these offsets will be applied while reading it in.

Now escape back to the main menu.
Choose 'i' to input a file.
Choose '3' for wav.
Choose '6' for reframe based on blanking.

Take a look! 

Cool huh? 

James. 

[James]

UPDATE:

I just found a little bug related to this.

It's no big deal. It will be fixed in the next release.

The way it is now, it assumes that the whole wave is negative.

In the next version it will ask you for the global wave polarity.

James. 

[ImageLight]

What does negitive wave mean?  And is that why you need a correction amp for the dac.  I know...such a sound card noob question.

Mark

[James]

Perfectly good question.

With audio, you can't really tell if a wave is negative or positive. That is to say, as long as both channels (L + R) are the same phase, it doesn't matter if you invert the waves.

But with laser signals it does matter. If X and Y are inverted, then the image will be both upside down and backwards. If the colors are inverted, then what should be an all positive going voltage will be all negative and your color modulation won't work.

If you open a wave with laser signals in it in a program like Audacity, you will see the polarity in the color channels.

If the information is mostly above the zero volt line then it's positive. Otherwise, it's negative.

LaserBoy can invert the whole multi channel wave or individual tracks within the wave.

The reason is that some DACs invert and some do not. Also note that the LaserBoy Correction Amp is, itself, an analog (op-amp) inverter. Inverted signals in become noninverted signals out. So, you have to be ready to deal with whatever comes your way! 

The reason you need the correction amp is because most sound cards do all of their work entirely in the positive voltage domain. The digital information coming in gets translated to corresponding positive only voltages. The very last thing that the output of each DAC channel goes through before it comes out the jacks on the back of the card is a decoupling capacitor. This has the effect of knocking off the DC offset voltage, thus making the signal true AC and safe to send to an audio amplifier and speakers.

But, for laser, we must eliminate the output decoupling capacitors, so that we can play back signals that have sustained, steady, non-zero voltages. The correction amp does two things. 1. It adds a regulated negative voltage to the all positive signal coming from the output of each channel of the DAC, thus "correcting" or centering the signal over the zero volt line, while maintaining the DC coupling... And, 2. It gives each signal just enough gain to drive the galvos and the color channels to full swing.

James. 

[James]

There are two ways to dramatically improve your laser projector's total output power.

1. Clean your optics. 

2. Use LaserBoy! 

Option 2 can increase your "intelligent" radiated energy by double digit percentages (easily seen)! 

James. 

[James]

New new version !!!

http://akrobiz.com/laserboy/code/LaserBoy_2009_08_26.zip

Fixed more bugs and spiffied up the frame stats.

Now if you hit the '?' key you can see a lot more information about each frame.

You also see additional frame stats when in menu 'k' or 'l' (lower case L).

It is interesting to compare the stats that you get when you bring in an optimized LaserBoy wave vs. an imported wave from origins other than LaserBoy.

This version does not contain a copy of zippy.wav.

If you don't have that and you want it, download http://akrobiz.com/laserboy/code/LaserBoy_2009_08_24.zip

James. 

[Fanny Pack]

I think that being able to import the ADAT stuff and convert them to ILDA is pretty cool.  I would like to see some of those shows.  Do they have associated music?

[James]

There are tons of shows on ADAT and yes, most of them have music or a sound track.

One thing you need to be aware of is that someone owns most of that stuff. I don't think any of it is in the public domain.

I made a show and recorded it to ADAT. It's about 40 minutes long and it's silent. As a single 6 channel wave it is HUGE!

James. 

[James]

New new new version !!!

http://akrobiz.com/laserboy/code/LaserBoy_2009_08_27.zip

I fiddled with the frame stats display a bit more.

Now when you import wave data, it blanks the vertices that come in below the black level.

The code that looks for the hot-spot is a bit more precise.

Now frames imported from non-LaserBoy waves using option '6' or '7' reframe based on blanking, will contain the number of samples between the hot-spots or the setting specified for "f unframed wave samples per frame", whichever is less.

I also made sure that it all still compiles in Linux. I had to make a small adjustment to the Linux Makefile.

NOTE: This code compiles into a much smaller executable in Linux and it runs WAAAAAYYY faster!

If anyone out there is using Mac OSX, I'd like to know if it is still working OK for you.

Thanks!

James.