Roland SR-JV flash? (or: encryption from hell.....)

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ledan
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Roland SR-JV flash? (or: encryption from hell.....)

Unread post by ledan »

Roland SR JV Expansion
Roland SR JV Expansion
roland_sr_jv.png (447.99 KiB) Viewed 4754 times
Hi,

It did always strike me as odd (well, not from Rolands POV of course) that no-one did any serious attempts in releasing a sr-jv flash ram card that was user editable by some means (much like some manufacturers did in the past). Of course, i remember reading something about the format used also being encrypted in some way which might explain the lack of such projects.

But what really stops anyone from doing this? Is it purely crypto algorithms from hell or is it merely legal issues?


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Re: SR-JV flash? (or: encryption from hell.....)

Unread post by tux »

I'm fairly sure it's not encrypted but rather compressed, but of course compression can be just as hard to figure out if you don't know what compression is being used or if it's not a standard compression but something proprietary.

Has anybody every done a dump of a SR-JV card?
That would be the first step to start deciphering the format.


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My Yamaha synths: RM50, TG77, TG500, CS6R (with PLG150-AN and PLG150-DX)
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Re: SR-JV flash? (or: encryption from hell.....)

Unread post by ledan »

Hi Tux,

i think you are onto something for sure. I have googled around a bit and found the web pages of Don Solaris over att www.donsolaris.com (i have his soundset in my Blofeld also) and he describes it like this:

"Companding compression
Both the JD and Super JV series use a companding form of waveform compression often expressed with 1:2 waveform ratio. Here is how it works. Once the waveforms are sampled at the factory, they are being dynamically compressed and converted to 8 bit. The reason why they are compressed prior to that is to preserve low level information and somehow increase the dynamic range of this 8 bit file. At that stage they are put into machine’s ROM. Once the machine boots up it will load a waveform, convert it to 16 bit and apply dynamic expansion. Essentially the same thing what a compressor and expander that you have in your rack do. This way a compression of 1:2 waveform ROM has been achieved. This dates back into days when memory was very expensive, and manufacturers were looking way to squeeze as much as possible into fixed ROM space. Companding was on of the options where for every 16 bits of input, you would use only 8 bit to store them, yet with some tricks “preserve” the data.

The question now arises: does that make Super JV and JD series 8-bit machines? Well technically speaking no. These are not just plain 8 bit samples in the ROM but 8-bit companded samples. It makes a difference, because prior to being played, their original 16 bit dynamic range is partially restored. It should also be noted that this is the stage were a lot of “magic” is happening. By that i mean Roland’s (probably) custom algorithms to make these waveforms sound so musical and rich in sound. If it is the most simple μ-law companding algorithm, then hats off to Roland, they did a pretty good job. I haven’t meet a person that doesn’t like the sound of Super JV series and they would hardly believe these originate from 8 bit samples."

So compressed for sure.


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Re: SR-JV flash? (or: encryption from hell.....)

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Suggest it to Brian as a potential project :) Between us we cracked the SY Wave Card format (Brian - hardware, me - sound format).


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Re: SR-JV flash? (or: encryption from hell.....)

Unread post by ledan »

Hi Derek,

I'll ask him. Thx.

oh, btw... what the two of you concocted and made a reality must be the most well known "secret" in the history of synths actually :-D ;-) Luckily for the entire SY-community i should say. But what you did, a secret???? I would rather say that "Yamaha SY" + "custom waveforms" in the encyklopedia will have both of your pictures next to it 8)


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Re: SR-JV flash? (or: encryption from hell.....)

Unread post by Derek »

Thanks.

It was a really interesting challenge that would not have started without Brian going into the hardware reverse engineering, but I was happy to play my part.

Over the years I have developed an eye for reverse engineering Yamaha file structures, but this ROM based format was challenging compared to having a synth to hand where you could change a parameter, save the file, compare against your baseline file in a hex editor to see what changed, and keep repeating. It was compounded by some strange parameters in the way the samples were tuned, but I think we got a good understanding to the point where people can create their own Wave Card files for loading into a WaveBlade. :)


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Re: Roland SR-JV flash? (or: encryption from hell.....)

Unread post by beebeedee »

hey, i got as far as dumping a ROM, but its looks like its encrypted: i couldn't see any ascii text or discernible structure.

Roland developed a custom Chip for the XP series, so its very likely they put the encryption on the chip.

also: those 40 pin molex connectors are rare as rocking horse poop.


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Re: Roland SR-JV flash? (or: encryption from hell.....)

Unread post by shadowmask »

This sounds interesting. Can you upload the ROM Dump somewhere?

Brian


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Re: Roland SR-JV flash? (or: encryption from hell.....)

Unread post by bnz99 »

Is anyone interested in figuring this out as well? I have been working with the romulator and was able to identify and alter a patch name, but there are definitely some challenges involved.


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