Suggestions needed, anyone up for decoding! :)

[dsfii]

Here's the scoop. I need to decode a wav file that I have. Let me tell you all that I know about it and see if anyone can lead me in the right direction.

The wav file contains (i believe) 100 bits of data that is transmitted over and over roughly 40 times a second. These values I am pretty sure of but the numbers are not definate. So these 100 data bits are encoded on this data stream somehow, that I don't know of.

I need a way to decode this wav file and extract these 100 channels so to speak. When I discover the method, I should be able to play the wav through my decoder and watch each channel 1-100 go high / low respectively ~ 40/sec.

I can see by looking at the wav file there is a start bit, so i think.. But what Im asking mainly is can anyone who's familiar look at this file and tell what method was used to encode.

Any help greatly appreciated!

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[dsfii]

Ok so I'm pretty sure this is a Manchester encoded wav form. Can anyone at least verify this by looking at the wav form I included above? ANyone know of any good manchester decoder software I can run it through to see if I get any results.

 

[Nigel Goodwin]

As far as I'm aware a WAV file is pretty well a plain audio file, with some header information - if you google you should be able to find all the information about it.

 

[Russlk]

When I play the .wav file on my computer, I just get the sound. You need to convert the sound to an oscilloscope display and post that.

 

[dsfii]

Im sorry!! I had assumed everyone could open it in an oscil. view themselves... here ya go...

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[Russlk]

It looks like a repeating pattern, not any kind of coding.

 

[dsfii]

Well i know for a fact there is hidden in there 100 bits 40 times a second.. Just hoping someone could lead me in the right direction for extraction

 

[Nigel Goodwin]

Assuming it is a digital data sequence?, then you need to know how it's coded - it's no good just guessing (unless you have a LOT of time to spare).

However, for a start it's useless as an audio file - presumably it's from a modem?, so you need to convert it to ones and zeros to have somewhere to begin.

But you've never even mentioned what it is?, which will probably make a BIG difference!.

 

[Someone Electro]

It looks somthing like FM modulation to me

 

[dsfii]

Well that was the point to see if someone can guide me in the decryption. And what is it,, ITS a SECRET haha it is a streaming data that runs an animatronic robot.

I've counted 71 peaks between the common start bit which means to me that I must have lied about there being 100 bits here... Unless I've missed some logic in my head, to run 100 bits of data here I'd need 100 or more peaks wouldnt I?

So,, this is fun!

 

[Nigel Goodwin]

Why is it a WAV file?.

 

[dsfii]

because its played on 1 track while audio is played on the other track to sync movements to the sound.

 

[Nigel Goodwin]

because its played on 1 track while audio is played on the other track to sync movements to the sound.

OK, so at that point it's an audio track, you first need to convert it to a digital data signal - presumably it uses some kind of modem internally? (or at least the 'dom' part!). A simple modem method uses one tone for ONE and a second for ZERO, and you can demodulate it with a simple tone decoder PLL (like an NE567).

 

[Russlk]

It does appear that there are two frequencies but sometimes the high frequency is only one cycle. I don't think a PLL will respond to that, but perhaps the one cycle in an anomaly and the system is not supposed to respond to that anyway.

 

[dsfii]

Anyone familiar with CMI? I think it sorta resembles this type of coding... Either way, I have strong belief that the six short burst together have something to do with the start bit... then the short burst in between are indicating the 1's being sent. Sorta like CMI or Manchester.

 

[Nigel Goodwin]

Anyone familiar with CMI? I think it sorta resembles this type of coding... Either way, I have strong belief that the six short burst together have something to do with the start bit... then the short burst in between are indicating the 1's being sent. Sorta like CMI or Manchester.

You appear to be ignoring my previous post?.

You need to first get the digital data from the audio file - it's not stored there as digital data, but as audio tones - for a start you need to convert that back to the data. Presumably using a modem of some type!.

Assuming you have access to the original machine?, you should be able to read the data after demodulation in that!.

 

[dsfii]

ignoring? Im trying to get help here and your not helping me.

I dont have the machine or else I wouldnt have posted silly.

Now... The data is NOT an audio, it is a square wave digital bit stream that has been recorded onto a tape. its wave form has been degraded over time as well as this was pulled off of a tape itself....

Now I ask this... If this were CMI incoded, and indeed there was 6 1's representing the start bit, how could you have 100 bits of valid data after the start bit without worrying about a consecutive 6 data bits triggering a false start bit? Any theories...

 

[Nigel Goodwin]

ignoring? Im trying to get help here and your not helping me.

I dont have the machine or else I wouldnt have posted silly.

Now... The data is NOT an audio, it is a square wave digital bit stream that has been recorded onto a tape. its wave form has been degraded over time as well as this was pulled off of a tape itself....

Now I ask this... If this were CMI incoded, and indeed there was 6 1's representing the start bit, how could you have 100 bits of valid data after the start bit without worrying about a consecutive 6 data bits triggering a false start bit? Any theories...

It would be VERY unusual to try and record a digital bit stream directly to an audio tape (which I presume is what is being used, as you have audio on one track?) - what would be usual is to convert it to audio tones and record those. You then convert it back to the original digital data when you play it back - you either use a modem (hardware) to do this, or you can do it in software - see all the early home computers (Commodore 64, Sinclair Spectrum etc.) which did this to audio cassettes.

As you don't have the machine, presumably you are trying to reverse engineer the data?.

 

[dsfii]

Ok, now we're gettin somewhere

Well.. Yes reverse engineering this,, decoding what ever you want to call it... I can see on a time line here that the 6 bit start section that is so prominent are 30mS apart... Thus means this common pulse is sent about 35 times a second which is about what the frame rate is of the amimatronic. And taking these FACTS -> 100 data bits sent every 35-40 times a second.. I don't see how it could send that much data that fast if this were sent as an audio file like you propose.

I mean,, if your telling me that it's impossible to record a digital bit stream onto a tape then please say so cause we can eliminate this idea, but I just really feel to get that much data out so fast here this must be the case??

btw,, I've noted that the 2 frequencies here are tone1=2khz and tone2=4.366khz

 

[Nigel Goodwin]

Ok, now we're gettin somewhere

Well.. Yes reverse engineering this,, decoding what ever you want to call it... I can see on a time line here that the 6 bit start section that is so prominent are 30mS apart... Thus means this common pulse is sent about 35 times a second which is about what the frame rate is of the amimatronic. And taking these FACTS -> 100 data bits sent every 35-40 times a second.. I don't see how it could send that much data that fast if this were sent as an audio file like you propose.

I mean,, if your telling me that it's impossible to record a digital bit stream onto a tape then please say so cause we can eliminate this idea, but I just really feel to get that much data out so fast here this must be the case??

It's not 'impossible', but it has reliability problems on an audio recorder, so it's not normally used.

btw,, I've noted that the 2 frequencies here are tone1=2khz and tone2=4.366khz

Perhaps you might try assuming one tone is a ONE and the other a ZERO, and see what you get?.

What degree of movement, and how many different items, are you talking about?.