EmbDev.net

Forum: FPGA, VHDL & Verilog fixed point precision


Author: Abdallah      (Company: Home) (my_name)
Posted on:

Rate this post
0 useful
not useful
Peace!
I want ask about the number of bits shoud I use in an fixed_point number 
to obtein the good precision, precision of distance eclidean.
some detail:
I want to determine an vector of foor element VECT[MOY1,MOY2,MOY3,MOY4], 
each element is the moyen of one quart of matrix of (64*64), the matrix' 
element value varies (0-255)'''it's pixel valor'''
--> the result of division (MOY1=SUM/Nbits) has 8 bits in the integer 
part;
Question: how many bits of fractional part shout I use to get the good 
result (result of euclidean distance between two vector 
VECT1[MOY11,MOY12,MOY13,MOY14] and VECT[MOY21,MOY22,MOY23,MOY24])..
thank you....peace:

Author: Duke Scarring (Guest)
Posted on:

Rate this post
0 useful
not useful
Abdallah      wrote:
> about the number of bits shoud I use in an fixed_point number
> to obtein the good precision
You have to define the precision. Independed if you use fixed point or 
integer number format.

The number of bits depends on your dynamic range:
http://en.wikipedia.org/wiki/Dynamic_range

Roughly: NoBs = SNR / 6

eg.: 16 Bit = 96 dB / 6

Duke

Author: Markus W. (elektrowagi78)
Posted on:

Rate this post
0 useful
not useful
Why would you consider to be the DR at 16 Bits not to be 96dB but 
96dB/6?

Author: ... (Guest)
Posted on:

Rate this post
0 useful
not useful
You wanted a GOOD precission in the result, right? then divide it by 6 
:-)

Author: Duke Scarring (Guest)
Posted on:

Rate this post
0 useful
not useful
Markus Wagner wrote:
> Why would you consider to be the DR at 16 Bits not to be 96dB but
> 96dB/6?
Read carefully:
 number of bits * 6 dB = dynamic range

Reply

Entering an e-mail address is optional. If you want to receive reply notifications by e-mail, please log in.

Rules — please read before posting

  • Post long source code as attachment, not in the text
  • Posting advertisements is forbidden.

Formatting options

  • [c]C code[/c]
  • [avrasm]AVR assembler code[/avrasm]
  • [vhdl]VHDL code[/vhdl]
  • [code]code in other languages, ASCII drawings[/code]
  • [math]formula (LaTeX syntax)[/math]




Bild automatisch verkleinern, falls nötig
Note: the original post is older than 6 months. Please don't ask any new questions in this thread, but start a new one.