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Discussion Groups | Speech Coding | p++ in Fixed Point??

Technical discussions related to Speech Coding (all itu and other vocoders, ACELP, CELP, AMR, etc)

  

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p++ in Fixed Point?? - aditya_naidu1 - Apr 27 2:25:00 2005





Hello all,

Thank You for help and useful tips.
Is there any special way for implementing variable increment in fixed
point such as p++;

for eg.

plc[i]+=(*p0)*a;
p++;

or this can be left as such?
because p++ is euqivalent to p=p+1.Shouldnt this cause a prob if 'p' is
in a different representation format(say Q2.13).

Thanks
Aditya





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Re: p++ in Fixed Point?? - Arvind - Apr 27 9:14:00 2005

Assume p is x.y format. Then p++ is 
p = p+ ((1<<y)-1)
 
if p saturates(max value of x.y reached), change Q-format of p to x+1.y-1 by scaling down.
 
Enjoy
A

aditya_naidu1 <a...@pmail.ntu.edu.sg> wrote:


Hello all,

Thank You for help and useful tips.
Is there any special way for implementing variable increment in fixed
point such as p++;

for eg.

plc[i]+=(*p0)*a;
p++;

or this can be left as such?
because p++ is euqivalent to p=p+1.Shouldnt this cause a prob if 'p' is
in a different representation format(say Q2.13).

Thanks
Aditya


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Re: p++ in Fixed Point?? - Steve Holle - Apr 27 10:32:00 2005


What would you increment by? I would suggest p += x with x being
your increment value.
At 12:25 AM 4/27/2005, aditya_naidu1 wrote:
>Hello all,
>
>Thank You for help and useful tips.
>Is there any special way for implementing variable increment in fixed
>point such as p++;
>
>for eg.
>
>plc[i]+=(*p0)*a;
>p++;
>
>or this can be left as such?
>because p++ is euqivalent to p=p+1.Shouldnt this cause a prob if 'p' is
>in a different representation format(say Q2.13).
>
>Thanks
>Aditya
Steve Holle
Link Communications, Inc.
1035 Cerise Rd.
Billings, MT 59101
sholle@shol...



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Re: p++ in Fixed Point?? - Andrew Nesterov - Apr 27 20:22:00 2005



> Date: Wed, 27 Apr 2005 06:25:45 -0000
> From: "aditya_naidu1" <adityanaidu@adit...>
>
> Is there any special way for implementing variable increment in fixed
> point such as p++;
>
> for eg.
>
> plc[i]+=(*p0)*a;
> p++;
>
> or this can be left as such?
> because p++ is euqivalent to p=p+1.Shouldnt this cause a prob if 'p' is
> in a different representation format(say Q2.13).

As you said, p++ is equivalent to p = p + 1, where p and 1 are integers.
This means that if the variable represents a fixed point Q3.12 value,
p++ increments the LSB, which is equial to 2**(-13). If a 1.0 was to be
added to a Q2.13 value, the Q2.13's 1.0 has to be written as 0x2000
or 8192 decimal.

Regards,

Andrew




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