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Kid Vid Tape Recorder Options\Help Needed


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#26 alex_79 OFFLINE  

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Posted Sat Apr 13, 2019 5:31 AM

I found this recording of the complete "harmony smurf" tape on youtube:

https://www.youtube....h?v=xNAYdOSi3aA

 

It's recorded with both channels mixed, but apparently the data only happens in between songs, so it would be easy to recreate the "stereo" tracks for use on a real Kid Vid module from that.

It uses a single audio frequency, so it reminds morse code more than FSK when you hear it...

The "data" channel only contains 3100Hz tones of varying length.

There's a preamble which I guess is used to identify what tape is being played:

preamble_harmony_smurf.png

Attached File  preamble_harmony_smurf.wav   166.29KB   6 downloads

 

 

then a single tone of about 0.166 sec at the end of each track (a NTSC frame is 0.0166 sec, btw)

end_of_track.png

Attached File  end_of_track.wav   55.13KB   2 downloads

 

 

and finally another sequence which is repeated a few times to indicate the end of the tape.
end_of_tape.png

Attached File  end_of_tape.wav   1.41MB   3 downloads
 



#27 Thomas Jentzsch OFFLINE  

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Posted Sat Apr 13, 2019 5:42 AM

Did you not know this? Or does it not help?


Edited by Thomas Jentzsch, Sat Apr 13, 2019 5:42 AM.


#28 alex_79 OFFLINE  

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Posted Sat Apr 13, 2019 5:59 AM

Those files only contain the music, not the data track (I guess that part was hardcoded in z26)


Edited by alex_79, Sat Apr 13, 2019 6:00 AM.


#29 BigO OFFLINE  

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Posted Sat Apr 13, 2019 8:59 AM

I found this recording of the complete "harmony smurf" tape on youtube:

 

[...]
It uses a single audio frequency, so it reminds morse code more than FSK when you hear it...

Interesting. Conversion to a digital signal may be fairly easy. 

My first guess would be that the longer intervals are the beginning of a frame or the beginning of a message. 

Somebody who's good at disassembly can probably spot the detection of similar patterns being looked for by the code. 

 

Somebody with a Kid Vid, a digital storage Oscilloscope and a tape deck could lay up the digital signal out from the Kid Vid next to the audio track to see if there's a direct one-to-one correlation between "tone present" and a digital 1 or 0 from the Kid Vid digital output..

 

I wonder if the decoding could be as simple as amplifying and rectifying the signal with a filter capacitor to smooth the output. The output doesn't have to be ripple free and super clean. It just has to stay above and below the digital logic thresholds for the duration of a bit. Seems like a scheme like that would be appropriate to the time period.

 

An op-amp comparator set up with an appropriately low reference voltage could probably crank out a 90% duty cycle square wave from a sine wave. Again, a little filtering to keep the signal from dipping too low in the "off" times might work.

 

Hearing the "sound" of the KV digital output could tell how sophisticated the demodulation is.

 

Just throwing out some thoughts that anyone is free to run with if they so choose. 

 

As ridiculous as it might be, I wouldn't put it past somebody around here to eventually do a homebrew Kid Vid compatible game. :)



#30 BigO OFFLINE  

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Posted Sat Apr 13, 2019 9:02 AM

I found this recording of the complete "harmony smurf" tape on youtube:

https://www.youtube....h?v=xNAYdOSi3aA

Okay, a few seconds of listening to that and I totally understand TJ not wanting to listen to those tapes again. 



#31 Shawn OFFLINE  

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Posted Sat Apr 13, 2019 2:27 PM

If these could be found out it would be interesting to add a simple title screen menu to the Bears (or even Smurfs) to choose which of the 3 games to play. The Smurfs already has the means to start the games by holding reset and using difficulty switches but it would be much easier with an on screen menu. That is way beyond anything I could do though. Hacking away at the physical tape deck and cartridge is about my limit. The software side of things I'm at a loss, you guys are the big wigs in that department.  This way everyone could have a shake at playing it on real hardware without a $200+ kidvid, $50 for Smurfs or another $200+ for the bears. That is if you can even find them with the tapes.



#32 BigO OFFLINE  

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Posted Sat Apr 13, 2019 5:28 PM

If the tape you mentioned earlier is in your possession, you might try ripping it to an MP3/WAV/whatever and posting it up. Somebody might run with it.

Maybe somebody can identify the serial communication protocol. That might be enough to get somebody interested in pursuing an adapter or a solid state Kid Vid emulator.

 

The hardware side should be doable if somebody wanted to build a solid state Kid Vid emulator. There are cheap MP3 modules and Arduinos out there. With those in hand, it's just a simple matter of programming. ;)



#33 Thomas Jentzsch OFFLINE  

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Posted Sun Apr 14, 2019 11:03 AM

If these could be found out it would be interesting to add a simple title screen menu to the Bears (or even Smurfs) to choose which of the 3 games to play. The Smurfs already has the means to start the games by holding reset and using difficulty switches but it would be much easier with an on screen menu. That is way beyond anything I could do though. Hacking away at the physical tape deck and cartridge is about my limit. The software side of things I'm at a loss, you guys are the big wigs in that department.  This way everyone could have a shake at playing it on real hardware without a $200+ kidvid, $50 for Smurfs or another $200+ for the bears. That is if you can even find them with the tapes.

But then you would miss the true, original experience. :)



#34 Shawn OFFLINE  

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Posted Sun Apr 14, 2019 1:32 PM

But then you would miss the true, original experience. :)

 

I totally agree. You can have rips of the audio to play as you game in that situation but I would prefer the original experience if possible.



#35 Shawn OFFLINE  

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Posted Sun Apr 14, 2019 1:33 PM

If the tape you mentioned earlier is in your possession, you might try ripping it to an MP3/WAV/whatever and posting it up. Somebody might run with it.

Maybe somebody can identify the serial communication protocol. That might be enough to get somebody interested in pursuing an adapter or a solid state Kid Vid emulator.

 

The hardware side should be doable if somebody wanted to build a solid state Kid Vid emulator. There are cheap MP3 modules and Arduinos out there. With those in hand, it's just a simple matter of programming. ;)

 

Tape is at a friends house. I will have it in the future though.



#36 Shawn OFFLINE  

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Posted Mon Apr 15, 2019 1:23 AM

I'm starting to consider buying another kidvid and doing a tear down to see what exactly the differences are between it and a vanilla tape deck.






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