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converting patch files in audio format to sysex
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cappy2112



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PostPosted: Fri May 18, 2018 7:47 pm    Post subject: converting patch files in audio format to sysex Reply with quote  Mark this post and the followings unread

I want to write a program to convert patches from cassette into sysex, and eventually back again.

This is more for a programming exercise, I doubt that I would use it regularly.

I'm stuck trying to figure out how to detect the 1s and 0s in the audio format. Once that is done, it should be easy to save the patches to disk.

Do any of you have any ideas on how to do this?

Thanks


Tony

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Blue Hell
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PostPosted: Sat May 19, 2018 3:29 am    Post subject: Reply with quote  Mark this post and the followings unread

That would depend me thinks .. for cassette in the oolde days it would be FM usually ... some frequency a zero another a one ... could be done then with two filters and two AM detectors.

But in general .. its the same thing as was being used to send digital info over phone lines .. with modems.

It would be best to have the specs for the signals you want to decode. When you do not have those .. you could analyze the signals .. like could a spectrum view of it to see what frequencies are in it.

Then when you have the zeros and the ones .. there will likely be a next layer of encoding .. if only it were for error detection and / or correction. After that it might have to be turned into sysex info, or it might already be in that format .. who knows ... :-)

Anyways .. my thoughts about the subject.

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cappy2112



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PostPosted: Sat May 19, 2018 7:16 am    Post subject: Reply with quote  Mark this post and the followings unread

Blue Hell wrote:
O
But in general .. its the same thing as was being used to send digital info over phone lines .. with modems.

It would be best to have the specs for the signals you want to decode. When you do not have those .. you could analyze the signals .. like could a spectrum view of it to see what frequencies are in it


Ok, but I haven’t done this code for a modem.

Let’s say that I do know the frequencies for the 1s and 0s. How do you go about detecting a 1 and 0 in software? Reading the contents of the wave file is easy, there are libraries to do that.

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Blue Hell
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PostPosted: Sat May 19, 2018 9:16 am    Post subject: Reply with quote  Mark this post and the followings unread

Well you would first want to know if it in fact is Frequency Shift Keying by looking at the signal in the time (as a wave) and in the frequency domain (as a spectrum plot, or FFT plot) ... audacity could help you with that.

Then when it is FSK .. what you could do is make a couple of filters to filter out the frequencies you are interested in, then do amplitude tracking on the outputs of the filters and when they go over a certain threshold value you could assume that frequency to be present.

This simple approach may not be sufficient though, depending on how fast the signal changes frequency. There are better ways to do it, but more complicated of course.

You should do a google for FSK decoding in software .. but first study the signal to see what it actually is. That, or get a specification.

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MusicMan11712



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PostPosted: Fri May 25, 2018 9:39 am    Post subject: Reply with quote  Mark this post and the followings unread

I helped out someone a couple of years ago, by reading some Casio CZ-5000 cassette data and trying to reconstruct them. I know there are some tools out there for deciphering FSK data cassettes. I might have explored a software solution (converting the decoded tones) into hex data [e.g., sysex] and might have found some resources. Ultimately, I used some audio tools to play the data into my CZ-5000 and re-saved the data as an audio file direct to sound card (eliminates tape noise).

If you want, I can try to find the resources I used and post them in this thread. Maybe they will be helpful. I do recall there was more done with FSK-type stuff in recent years, but the stuff from the 80s which was more basic met my needs.

Steve
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cappy2112



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PostPosted: Fri May 25, 2018 9:53 am    Post subject: Reply with quote  Mark this post and the followings unread

MusicMan11712 wrote:
I helped out someone a couple of years ago, by reading some Casio CZ-5000 cassette data and trying to reconstruct them. I know there are some tools out there for deciphering FSK data cassettes. I might have explored a software solution (converting the decoded tones) into hex data [e.g., sysex] and might have found some resources. Ultimately, I used some audio tools to play the data into my CZ-5000 and re-saved the data as an audio file direct to sound card (eliminates tape noise).

If you want, I can try to find the resources I used and post them in this thread. Maybe they will be helpful. I do recall there was more done with FSK-type stuff in recent years, but the stuff from the 80s which was more basic met my needs.

Steve


Hello- thanks for the offer. The tools may be heflpful, once I get my head around the project better. Blue Hell gave me some information too, but FSK is something I"m not familair with, so I need to go read up on that.

I was also able to get in touch with the guy who wrote the FW for the synth tha I'm looking at, he too gave me some good advice.

If you find the tools, please post links, but don't go to a lot of trouble. It's not an urgent project.

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cappy2112



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PostPosted: Fri May 25, 2018 9:53 am    Post subject: Reply with quote  Mark this post and the followings unread

Blue Hell wrote:
Well you would first want to know if it in fact is Frequency Shift Keying by looking at the signal in the time (as a wave) and in the frequency domain (as a spectrum plot, or FFT plot) ... audacity could help you with that.

Then when it is FSK .. what you could do is make a couple of filters to filter out the frequencies you are interested in, then do amplitude tracking on the outputs of the filters and when they go over a certain threshold value you could assume that frequency to be present.

This simple approach may not be sufficient though, depending on how fast the signal changes frequency. There are better ways to do it, but more complicated of course.

You should do a google for FSK decoding in software .. but first study the signal to see what it actually is. That, or get a specification.


Thanks Jan.

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cappy2112



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PostPosted: Fri May 25, 2018 10:59 am    Post subject: Reply with quote  Mark this post and the followings unread

MusicMan11712 wrote:
I helped out someone a couple of years ago, by reading some Casio CZ-5000 cassette data and trying to reconstruct them. I know there are some tools out there for deciphering FSK data cassettes. I might have explored a software solution (converting the decoded tones) into hex data [e.g., sysex] and might have found some resources. Ultimately, I used some audio tools to play the data into my CZ-5000 and re-saved the data as an audio file direct to sound card (eliminates tape noise).

If you want, I can try to find the resources I used and post them in this thread. Maybe they will be helpful. I do recall there was more done with FSK-type stuff in recent years, but the stuff from the 80s which was more basic met my needs.

Steve


I'm sure this will be useful to help correlate the output of my software.
http://www.winradio.com/home/fskdecoder.htm

I still need to find the algorithms used for demodulation though

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MusicMan11712



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PostPosted: Fri May 25, 2018 8:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

cappy2112 wrote:
I'm sure this will be useful to help correlate the output of my software.
http://www.winradio.com/home/fskdecoder.htm

I still need to find the algorithms used for demodulation though


That looks like an excellent tool, though based on what I remember from my research it looks like it is based on more recent uses of FSK.

Out of curiosity, what gear are you working with? If its 80s gear, I believe FSK was much simpler than the newer stuff.

Steve

I know I had other links, but this is the one that got me started: http://r-massive.cellarseer.com/casio-rz-1-mt-jack/
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cappy2112



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PostPosted: Fri May 25, 2018 11:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

MusicMan11712 wrote:
cappy2112 wrote:
I'm sure this will be useful to help correlate the output of my software.
http://www.winradio.com/home/fskdecoder.htm

I still need to find the algorithms used for demodulation though


That looks like an excellent tool, though based on what I remember from my research it looks like it is based on more recent uses of FSK.

Out of curiosity, what gear are you working with? If its 80s gear, I believe FSK was much simpler than the newer gear./[/url]


An Oberheim Xpander

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