1 / 12

# lns arithmetic for mpeg encoding using a fast dct - PowerPoint PPT Presentation

LNS Arithmetic for MPEG Encoding Using a Fast DCT. Jie Ruan and Mark G. Arnold. LNS (Logarithmic Number System). Represents a number by a sign bit and an exponent to a certain base (b). S. Exponent (n-1 bits). F (Precision). Properties of LNS. Large dynamic range

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

## PowerPoint Slideshow about 'lns arithmetic for mpeg encoding using a fast dct' - albert

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

### LNS Arithmetic for MPEG Encoding Using a Fast DCT

Jie Ruan and Mark G. Arnold

• Represents a number by a sign bit and an exponent to a certain base (b)

S

Exponent (n-1 bits)

F (Precision)

• Large dynamic range

• Easy for multiplications, divisions and exponentiations

• Additions are not linear operations for LNS

• Cost of adders is exponential to word length

• Has advantages at low precisions.

Logb(XY)=logbX+logbY

The cost is a fixed-point adder

More complex process than multiplication

E.g., when calculating logb(X+Y), (x=logbX, y=logbY)

Calculate z=x-y

Table-lookup sb(z)=logb(1+2z)

Logb(X+Y)=y+sb(z)

LNS Arithmetic Units

• RGBYUV

• Motion Estimation

• Discrete Cosine Transform (DCT)

• Variable Length Coding

2 Dimensional 8x8 DCT

• Berkeley MPEG Tool is a software to perform MPEG encoding and decoding, written in C language.

• The DCT function is modified to accommodate LNS features.

• At F=4, a visually acceptable precision

10-bit LNS

16-bit Fixed-point

64-bit Floating-point

Hardware implementation for DCT

• NxN 2 Dimensional DCT

• Usually performed through 2 rounds of 1-D N-point DCT, with an NxN buffer

• Less hardware and simpler data input arrangement than direct 2-D implementations

• Chen’s 1-D DCT algorithm

• Directly factorizes the DCT matrix

• 16 multiplications

Comparison Hardware cost for Chen’s algorithm, at F=4

• At low precisions LNS is a good way for DCT in MPEG, compared to Fixed-point

• shorter word length

• less area

• Comparable visual result

• LNS is a good alternative for MPEG encoding