jsynthlib-devel

[Jsynthlib-devel] FW: Re: What is the JSL way to deal with negative param values?

[Steven S. <ste...@co...>]

Methinks this went to the wrong list

 

  _____  

From: Steven Schmidt [mailto:ste...@co...] 
Sent: Monday, March 28, 2005 10:36 AM
To: 'jsy...@li...'
Subject: Re: What is the JSL way to deal with negative param values?

 

I've been casting it as a byte and while it seems to work up to a point -
I'm not getting the negative values to display.  
I thought it should work the way I'm doing it, but it stops at zero.  Please
have a look at this snippet and make recommendations if you can:
The purpose of this method is to subtract the max value for the widget if
the param value is greater than the max value.
 
public static SpinnerWidget dynaSpinner(String label, IPatch patch, int min,
int max, int base, 
                       IParamModel pmodel, ISender sender) { 
        String pt = patch.getByteArray().toString();
        
        int rawval =   pmodel.get();
        int prelimval = (byte)pmodel.get()+ max & 0x7F;
        System.out.println("rawval:"+ rawval+"  prelimval:"+prelimval);
        if (rawval > max)  { 
               base = -max;
               System.out.println("      BASE:"+base + "     The
math:"+(prelimval + base));  
               SpinnerWidget spinner = new SpinnerWidget (label, patch, min,
max, base, pmodel, sender);
        }
        SpinnerWidget spinner = new SpinnerWidget (label, patch, min, max,
base, pmodel, sender);
        
        return spinner;
        }
 
}
This outputs:

rawval:126  prelimval:10

      BASE:-12     The math:-2
-2 is the correct value, but the spinner widget actually displays a '0' -
apparently getting stuck at 0.
Help!!!
 
Bill Zwicky wrote:
> Note that this goofiness is on top of the fact that your synth has 
> probably scrambled the bytes a little to get around the restrictions of 
> the sysex message.  So you need to deal with that, on top of dealing 
> with signed bytes.

 

 

Re: [Jsynthlib-devel] FW: Re: What is the JSL way to deal with negative param values?

[Bill Z. <wrz...@po...>]

Steven Schmidt wrote:

> I’ve been casting it as a byte and while it seems to work up to a point – I’m not getting the negative values to display.     
>
> I thought it should work the way I’m doing it, but it stops at zero.  Please have a look at this snippet and make recommendations if you can:   
>
> The purpose of this method is to subtract the max value for the widget if the param value is greater than the max value.   
>
You realize that "the math" prints get()+max-max, which is the same as 
rawval? So if rawval has the right value, then you don't have a problem. 
What is the value for min and max? If max is less than zero but the 
spinner control itself won't go negative, then we have a bug. Try using 
a SliderWidget, I know those work.

-Bill

Re: [Jsynthlib-devel] FW: Re: What is the JSL way to deal with negative param values?

[Steven S. <ste...@co...>]

Bill Zwicky wrote:

> Steven Schmidt wrote:
>
>> I’ve been casting it as a byte and while it seems to work up to a 
>> point – I’m not getting the negative values to display.    
>> I thought it should work the way I’m doing it, but it stops at zero.  
>> Please have a look at this snippet and make recommendations if you 
>> can:  
>> The purpose of this method is to subtract the max value for the 
>> widget if the param value is greater than the max value.  
>
> You realize that "the math" prints get()+max-max, which is the same as 
> rawval? So if rawval has the right value, then you don't have a 
> problem. What is the value for min and max? If max is less than zero 
> but the spinner control itself won't go negative, then we have a bug. 
> Try using a SliderWidget, I know those work.
>
> -Bill

Yes - min val is less than zero and the spinner won't go negative, 
although it does go negative in other instances.
This:

addWidget(p21_osc18va, new SpinnerWidget("**Tune", patch, -1200, +1200, 
-128,
                new TritonMultiCompModel(patch, 311, 1,1200), new 
TritonSender(311)), 3,
                8, 1, 1, 15);

displays the correct value of -5 for the MSB/LSB combo of  7f 7b
(I haven't looked at why I had to subtact 128 (base val) to get it 
right, but that's a suspiciously even number)
So, have we a bug?  I'll try a slider and see if I have the same problem 
and report back.

Re: [Jsynthlib-devel] FW: Re: What is the JSL way to deal with negative param values?

[Bill Z. <wrz...@po...>]

Steven Schmidt wrote:

> displays the correct value of -5 for the MSB/LSB combo of  7f 7b
> (I haven't looked at why I had to subtact 128 (base val) to get it 
> right, but that's a suspiciously even number)
> So, have we a bug?  I'll try a slider and see if I have the same 
> problem and report back.
>
Are the bytes still correct when the spinner reads -129?

In a sysex message, the high bit must always be zero, and (I'm guessing) 
your synth simply sticks the remaining 14 bits together to form a 
number.  7f 7b is
  0111 1111 0111 1011
and if we drop the high bits and regroup the nybbles, we get
  11 1111 1111 1011
If you add 5 to that, you get zero.  So 7f 7b is exactly -5 in 14 bits.  
(If you're running Microsoft Windows, you can try this with the included 
calculator; it can handle both hex and binary.)

-Bill

Re: [Jsynthlib-devel] FW: Re: What is the JSL way to deal with negative param values?

[Steven S. <ste...@co...>]

Bill Zwicky wrote:

> Steven Schmidt wrote:
>
>> displays the correct value of -5 for the MSB/LSB combo of  7f 7b
>> (I haven't looked at why I had to subtact 128 (base val) to get it 
>> right, but that's a suspiciously even number)
>> So, have we a bug?  I'll try a slider and see if I have the same 
>> problem and report back.
>>
> Are the bytes still correct when the spinner reads -129?
>
> In a sysex message, the high bit must always be zero, and (I'm 
> guessing) your synth simply sticks the remaining 14 bits together to 
> form a number.  7f 7b is
>  0111 1111 0111 1011
> and if we drop the high bits and regroup the nybbles, we get
>  11 1111 1111 1011
> If you add 5 to that, you get zero.  So 7f 7b is exactly -5 in 14 
> bits.  (If you're running Microsoft Windows, you can try this with the 
> included calculator; it can handle both hex and binary.)

Do you know of an existing editor that works in this manner?

Re: [Jsynthlib-devel] FW: Re: What is the JSL way to deal with negative param values?

[Bill Z. <wrz...@po...>]

Steven Schmidt wrote:

> Do you know of an existing editor that works in this manner?

What part is giving you trouble?  Are you familiar enough with binary 
and boolean math to work through this?  Here are some links with an 
excessive amount of detail:

http://mathforum.org/dr.math/faq/faq.bases.html
http://mathforum.org/library/drmath/view/54311.html
http://mathforum.org/library/drmath/sets/select/dm_twos_complement.html

The "twos complement" link is most relevant, as it explains how negative 
numbers work.  I can't find a good, decisive tutorial on binary math, 
but if you search around that site, you should be able to find answers.

Anyway, to answer your question, my own Casio CZ editor is reasonably 
similar.  You need to chop your numbers into 7-bit chunks, and the CZ 
works with 4-bit chunks.  The math is the same, only the constants 
differ. I've pulled all the code into a common superclass:
    synthdrivers/CasioCZ1000/CZModel.java

-Bill

Re: [Jsynthlib-devel] FW: Re: What is the JSL way to deal with negative param values?

[Bill Z. <wrz...@in...>]

I apologize for the ridiculous lateness of this; I just discovered it 
had never been sent. I hope it's useful to someone.


Steven Schmidt wrote:
>  I've been casting it as a byte and while it seems to work up to a point -- I'm not getting the negative values to display.     
>  I thought it should work the way I'm doing it, but it stops at zero.  Please have a look at this snippet and make recommendations if you can:   
>  The purpose of this method is to subtract the max value for the widget if the param value is greater than the max value.   
Why would you do that? I'm having trouble figuring out what your code 
sample is doing, so I'll pull some explanations out of thin air, and 
hope something applies.

There are *three* data formats you need to think about when building 
your editor:

1. The GUI format. What is the range you want to present to the user? 
For example, my Casio CZ has a detune parameter that ranges from -47 to 
+47, so I use a slider with exactly that range.
2. The binary format. How does your synth represent a value as bits? For 
the detune parameter, the CZ uses one bit to represent sign, and 7 bits 
for the absolute value.
3. The sysex format. The upper bit of each byte in a sysex cannot be 
used, so usually there's an extra encoding applyed to expand the binary 
format so that it skips those useless bits. The CZ simply uses the 
lowest 4 bits of each byte, so after step two, I chop the data into two 
nybbles, and store them in consecutive locations in the sysex.

When we say "bytes are signed numbers", we're talking about the sysex 
format (level 3), and the tricks involved in getting data into and out 
of the sysex byte array. The IParamModel, on the other hand, converts 
between levels 1 and 2. To use my CZ example again, DetuneModel.get() 
returns an integer in the range -47 to +47, and DetuneModel.set() 
accepts the same.

http://mathforum.org/library/drmath/sets/select/dm_twos_complement.html

>      
>  public static SpinnerWidget dynaSpinner(String label, IPatch patch, int min, int max, int base,    
>                         IParamModel pmodel, ISender sender) {    
>          String pt = patch.getByteArray().toString();   
>             
>          int rawval =   pmodel.get();   
>          int prelimval = (byte)pmodel.get()+ max & 0x7F;   
>          System.out.println("rawval:"+ rawval+"  prelimval:"+prelimval);   
>          if (rawval > max)  {    
>                 base = -max;   
>                 System.out.println("      BASE:"+base + "     The math:"+(prelimval + base));     
>                 SpinnerWidget spinner = new SpinnerWidget (label, patch, min, max, base, pmodel, sender);   
>          }   
>          SpinnerWidget spinner = new SpinnerWidget (label, patch, min, max, base, pmodel, sender);   
>             
>          return spinner;   
>          }   
>      
>  }   
>  This outputs:   
>
> rawval:126 prelimval:10
>
>        BASE:-12     The math:-2     
>  -2 is the correct value, but the spinner widget actually displays a '0' -- apparently getting stuck at 0.   
>  Help!!!   
>      
>  Bill Zwicky wrote:   
>  > Note that this goofiness is on top of the fact that your synth has    
>  > probably scrambled the bytes a little to get around the restrictions of    
>  > the sysex message.  So you need to deal with that, on top of dealing    
>  > with signed bytes.   
>