John Wells, M5AML.  QTH: Derby,  IO92GW.

PICTOAUD


Pictoaud is an SSTV (Slow Scan TeleVision) system devised by Samuel Hunt  some years ago.  At the time it generated quite a bit of interest but development in the mode seemed to end and the web site disappeared.  I recently decided to try and find the Pictoaud software and after a few months of searching I found it!

Below are the most interesting parts of the original web page reproduced without permission.


"First of all, the brief history:-

Pictoaud 1 was invented in 1998 by Samuel Hunt. It featured no start codes, no syncs and no noise reduction. It, however, caught on because of where it was marketed. It was marketed at small, isolated, communities who had a local radio station which shut down during the night, and no local newspaper. During the night, they would transmit the news of the day in picture form, with captions across the airwaves.

The system had its limitations, such as horrendous amounts of noise. So:-

Pictoaud 2 was created in May 2000. By the same creator, this had little benefit, except a complete, more efficient, code rewrite. Also, it had a form of noise and time reduction. It did, however, suffer in much the same way as Pictoaud 1.

Pictoaud 3 is the brand new top of the range system. It has a much more efficient noise reduction system, so noise is almost non-existent, and it offers full syncs and line identifiers.

So, how (Basically) does it work?

Let us presume it is recorded on tape (For ease of explaining it. However it is stored or transmitted, it is always the same form of signal).

Two "Demi Pixels" make up a proper visible pixel. The first "Demi Pixel" is fixed at peak white. The second is at the colour value.

This means that if the signal drops in strength, then instead of going dark, both the pixels go dark, so the lighter of the two is used to normalise the other, so the effect is counteracted, and so you do not notice the effect.

On the last 5 pixels of every line, these are below black. These are used to set the "pixel tracer" back to the beginning of the line. This means that if a few pixels go missing, then the whole picture does not shift to the left, like Pictoaud 1 and 2 did.

On the first 11, there is a digital line code. This is so that if more than 1 line is lost, then colour missync does not occur. The last full line is repeated, so the effect is not very obvious.

All of these methods are mainly unnecessary over normal working conditions. This is why Pictoaud 1 and 2 worked. However, in weak signal areas, where a large area is being covered by a small transmitter, then the system comes into its own, since it can keep the picture in a viewable state long after Pictoaud 1 and 2 would have given up.

This system is not perfect in weak signals. In very weak signals, it just won't work. Since all of the syncs are digital, then, like digital, they work perfectly up until 75% noise (At which point they, very suddenly, cease functioning!) Over longer distances, some other mode may be better. However, try this mode. The important thing is that this mode can RECOVER from major disturbances, which no other mode can.


(screen shot by John R Wells, M5AML 2009)



So, how do I use the program?

To encode, simply type in the name of the file, then click on "Load from File", or you can paste from the clipboard. The image will appear in the window..

Make sure the resolution is correctly selected. It is better to crop than to cut areas off. It saves transmission time substantially! One note:- Bear in mind the recommended resolutions times, since these are generally more than adequate.

Click on "Encode" to encode the file, which will encode it to the specified audio file. When encoding is complete, a dialog box will pop up alerting you of this fact.

You can then play it through the soundcard via sound recorder by clicking on "Play".

If you have done all this correctly, you should hear the tones. Send these through the transmitter, tape recorder, etc. Try not to lose any of the audio or clip it.

For decoding:-

First, you want to click on "Record", BEFORE the transmission begins. This will bring up sound recoder, ready to record. WHEN you hear the pilot tone, press the SPACEBAR. Recording will now commence. Click on the Stop (Square) to stop recording when transmission has ended, then close sound recorder and save the file.

So far, so good. Now, do a setup run if you have never received from this person/played from this tape before.

Turn OFF auto lining. This is the line adding, but it improves the picture quality if you try and get the picture in a good state before the auto lining does its work.

You want to try and have the Resolution Manual Override ON for best detection (this doesn't take the resolution from the resolution codes, but takes the resolution which you force upon it), but you have to be certain what resolution the picture is being transmitted at.

Everything should now be set up for the trial run. Click on Decode, to run the trial decode. You should see a small version of the picture decoding in a little box in the top left of the program after a pause of a few seconds. If you see NO PICTURE after at least 30 seconds (Just in case something is being very slow), then click on STOP, and then turn off the Leader.

If you still REALLY can't get a picture, then try turning off Horizonal Syncs, and trying again. You should get a picture which is off-sync. If you haven't, then my honest advice is - GIVE UP! Your source is probably corrupt!
Anyway, if it is too black (All the blacks are washed out), then try changing the active normalisation level, and turning back on the Horizontal Syncs.

Optimize the sync level. Set it to minumum (-16), then start the decoding by clicking on Decode. Click it up higher and higher (-24, then -32, then -48), until the picture quality starts to degrade again. Find the optimum level, where the vertical lines are straight, and don't jump from side to side.

Now, stop the decoding and turn back on auto lining. Nothing appears during auto lining, until the VERY END of the process, wherupon you see the picture quickly scan onto the screen. If you got a good picture before, and you get no picture now, then the LIC inset could be bad. Try experimenting with this (Run with 7, then with 9, then with 6, then with 10, etc. until you get a good picture)

Anyway, lets presume you get a picture. You now, naturally, want to save it. The best way to save it is to a file. Type the filename to save to, then click on Save to file. Alternatively, you can save to the clipboard, so you can paste the image into a better image editor (Like Paint Shop Pro 6, my favourite!). To do this, click on Save to Clipboard.

You see, it wasn't really that difficult! In fact, it was very easy!

Now, about the software:-

You need 2 programs. The first, obviously is Pictoaud. The second is RAW2WAV. This converts the RAW audio file (Internal) to a WAV file (Usable by Sound Recorder).

The Raw2Wav should be copied to the WINDOWS directory (C:\WINDOWS normally). This will never need to be updated. This is a freeware program, not written by Samuel Hunt.

You may also want the test images. Put them in whatever directory you want, and when the program first starts, type in the directory.

Pictoaud can be copied to whatever directory you like.

You MAY need the VB5 runtime files. "


So that's about it!  Click HERE to download both Pictoaud and Raw2Wav in one .zip file.  VB5 runtime files should be available elsewhere on the internet.

Happy Pictoauding!

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