BIT RATE & QUALITY (R-D) Coding bit rate(R) vs. Picture quality(D) R-Q and D-Q functions(R(q),D(q)) charact
erize the R-D behavior. R-D functions. (R-D curves) Adjust the quantization setting and control
the R and D. Optimal Scaling for Best D(q) or R(q)
ρ DOMAIN R-D ANALYSIS
ρ: percentage of zeros among the quantized coefficients. (with a quantization parameter q)
ρ monotonically increases with q.– R(q) R(ρ), – D(q) D(ρ), – ρ domain R-D analysis
BIT RATE
R(q) = Qz(q) + Qnz(q)– Qz(q) : total bits required for representation of
all zero coefficients– Qnz(q) : total bits required for representation o
f non-zero coefficients
SCALING & R-D
Under Certain Quantization Parameter q:– Small scaling High compression ratio– Large scaling High image quality
Given a Quantization Parameter q and a Bit-rate R, We Can Find the Optimal Scaling for Best Image Quality.
OPTIMAL SCALING
Quality Function : D(k, q) Bit-rate Function : R(k, q)
Where q is the size of Scalar Quantization step(fixed), k is the scaling factor of wavelet high frequency subband (variable).
Cost Function F(k) = F(D(k), R(k))
FUTURE WORK
Find The Cost Function of SQ Accurately. Use SPIHT Model Instead of SQ. Modify SPIHT. (Probably)
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