Cypress DCT-1D Betriebsanweisung PDF herunterladen (Seite 52)

CHAPTER 4. LAB TASK 2 - DESIGN A JPEG ACCELERATOR

shifting 17 steps:

Y [u, v] = round



(A[u, v] − 8192 · δ[u, v]) · R[u, v] · 2

−17









−96 −3 0 0 0 0 0 0

−24 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0

−2 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0







, (4.3)

which left only four non zero coefﬁcients.

4.6.2 Design of a hardware accelerator for quantization

The following piece of code in jcdctmgr.c in jpegfiles calculates the quantization

of one block. Instead of division multiplication with the reciprocal is used.

Listing 4.4: C code for quantization in jcdctmgr.c.

i n t r e c i p r o c a l s [ ] = {2 0 4 8 , 29 7 9 , 3277 , 20 4 8 , 136 5 , 819 , 64 3 , 53 7 ,

2731 , 27 3 1 , 2341 , 17 25 , 1 2 60 , 5 65 , 54 6 , 5 9 6 ,

2341 , 25 2 1 , 2048 , 13 65 , 8 1 9 , 57 5 , 475 , 585 ,

2341 , 19 2 8 , 1489 , 11 30 , 6 4 3 , 37 7 , 410 , 529 ,

1820 , 14 8 9 , 88 6 , 58 5 , 482 , 301 , 318 , 42 6 ,

1365 , 9 3 6 , 5 9 6 , 5 1 2 , 4 0 5 , 31 5 , 290 , 356 ,

669 , 5 12 , 4 2 0 , 3 7 7 , 3 1 8 , 2 7 1 , 273 , 324 ,

455 , 3 56 , 3 4 5 , 3 3 4 , 2 9 3 , 3 2 8 , 318 , 3 3 1 } ;

. . .

f o r ( i = 0 ; i < DCTSIZE2 ; i ++) {

r v a l = r e c i p r o c a l s [ i ] ; / / 16 b i t

s i g n e d temp = w o rks p a ce [ i ] ; / / 16 b i t s i g n e d

temp = temp ∗ r v a l ;

i f ( temp & 0 x10000 ) {

temp = temp >> 1 7 ;

temp += 1 ; }

e l s e

temp = temp >> 1 7 ;

c o e f _ b l o c k [ i ] = ( s h o r t ) temp ; / / 16 b i t s i g n e d }

. . .

Preparation task 9

Design a HW Quantization unit (Q2 in Figure 4.1), that calculates exactly the same

values as the code in Listing 4.4. Instantiate your Q2 unit and modify the code in

listing 4.4. We propose that Q2 should be able to quantize 2 numbers per clock cycle.

1 2 ... 47 48 49 50 51 52 53 54 55 56 57 ... 81 82

Kommentare zu diesen Handbüchern

Keine Kommentare

Cypress DCT-1D Betriebsanweisung Seite 52

Kommentare zu diesen Handbüchern

Verwandte Produkte und Handbücher für Nein Cypress DCT-1D