Media signal Media format Last updated on June 15, 2010 Doug Young Suh [email protected].
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Transcript of Media signal Media format Last updated on June 15, 2010 Doug Young Suh [email protected].
Go to basics“I learned everything in Kindergarten.”
What did I learn in Kindergarten for video coding?
• Probability theory, linear algebra, sampling theory
Media signal
AD conversion
Analog = continuous time + analog
Digital = discrete time + digital
Media signal
Sampling and human-being
Low freq.
High frequency
440Hz, A, Ra
Do-Re-Mi-Pa-Sol-Ra-Si-Do
Media signal
Quantization
Analog digital
Analog : infinite number of valuesDigit-al : finite number of values
Media signal
Quantization and de-quantization
Loss of information, but acceptable accuracy
Media signal
Image Resolution
Original image :256*256, 8bits
128*128, 8bits
256*256, 4bits
Media signal
Color representation
CameraLinearMatrix
A to DConverter
G
R
B
C b
Y
C r
RGB cf) rectangular coordinate
YCbCr (YUV) cf) polar coordinate
Red (255,0,0)
Blue (0,0,255)
Original Red Green Blue 4:4:4
Y U V
U, V no high freq. 4:2:2 4:2:0
Color representation
Media signal
RGBYCbCr Y = 0.29900R+0.58700G+0.11400B Cb = -0.16874R-0.33126G+0.50000B Cr = 0.50000R-0.41869G-0.08131B
YCbCrRGB R=1.00000Y+1.40200Cr G=1.00000Y-0.34414Cb-0.71414Cr B=1.00000Y+1.77200Cb
Color conversion 1 to 1 mapping
Media signal
Color conversion 4:4:4 1+1+1
4:2:2Horizontally 2:1 subsampling
4:2:0 1+1/4+1/4
Most popular Amount ½
Video formats
QCIF CIF(352x288) 4CIF QVGAVGA(640x480)SXGA(1280x1024)
Networked Video
VLCQ DCT
MotionEstimation
+
FrameMemory
Original Video
Encoded Bitstream
Video encoding
IQ
IDCT
Motion vector
2-3 2-22-1