Lns arithmetic for mpeg encoding using a fast dct
Download
1 / 12

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


  • 250 Views
  • Uploaded on

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

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

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


An Image/Link below is provided (as is) to download presentation

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 logarithmic number system l.jpg
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 l.jpg
Properties of LNS

  • 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.


Lns arithmetic units l.jpg

Multiplication

Logb(XY)=logbX+logbY

The cost is a fixed-point adder

Addition

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


Major parts of mpeg encoding l.jpg
Major parts of MPEG Encoding

  • RGBYUV

  • Motion Estimation

  • Discrete Cosine Transform (DCT)

  • Variable Length Coding


2 d discrete cosine transform l.jpg
2-D Discrete Cosine Transform

2 Dimensional 8x8 DCT


Berkeley mpeg encoder l.jpg
Berkeley MPEG Encoder

  • 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.


Visual effect of mpeg encoding with lns dct l.jpg
Visual Effect of MPEG Encoding with LNS DCT

  • At F=4, a visually acceptable precision

10-bit LNS

16-bit Fixed-point

64-bit Floating-point



Hardware implementation for dct l.jpg
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

    • 26 additions


Compares lns dct with fixed point dct l.jpg
Compares LNS DCT with Fixed-point DCT

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


Conclusion l.jpg
Conclusion

  • 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


ad