Last updated on June 15, 2010 Doug Young Suh suh@khu.ac.kr Media format Last updated on June 15, 2010 Doug Young Suh suh@khu.ac.kr Media signal
Go to basics “I learned everything in Kindergarten.” What did I learn in Kindergarten for video coding? Probability theory, linear algebra, sampling theory
AD conversion Digital = discrete time + digital Analog = continuous time + analog Digital = discrete time + digital Media signal
Sampling and human-being Sampling theory (Nyquist theory) Sampling frequency fs > 2fmax Speech 8kHz > 2 X 3.2kHz Audio 44.1kHz > 2 X 20kHz Video Temporal : 24Hz (movie), 60Hz (TV) Spatial 440Hz, A, la Low freq. Do-Re-Mi-Pa-Sol-Ra-Si-Do High frequency Media signal
Quantization Analog digital Analog : infinite number of values Digit-al : finite number of values Media signal
Quantization and de-quantization Loss of information, but acceptable accuracy Media signal
Audio Speech: 8kHz sampling Х 8bits/sample = 64kbps 압축 10kbps CD quality: 44kHz sampling Х 16bits/sample Х 2(stereo) 1.544Mbps 압축 128kbps or 256kbps MP3
Image Resolution Spatial resolution: 256*256, 8bits Temporal resolution: 24Hz, 60Hz, etc. (fps: frames per second) 128*128, 8bits 256*256, 4bits Media signal
Color representation RGB cf) rectangular coordinate YCbCr (YUV) cf) polar coordinate Red (255,0,0) Blue (0,0,255) Media signal
Color representation Original Red Green Blue 4:4:4 Y U V U, V no high freq. 4:2:2 4:2:0
Color conversion 1 to 1 mapping 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 Media signal
Color conversion 4:4:4 1+1+1 4:2:2 Horizontally 2:1 subsampling 4:2:0 1+1/4+1/4 Most popular Amount ½ Media signal
Video formats QCIF CIF(352x288) 4CIF QVGAVGA(640x480)SXGA(1280x1024)
Video encoding 2-1 2-3 2-2 DCT Q VLC IQ IDCT Original Video Encoded + DCT Q VLC Encoded Bitstream IQ Motion Estimation Motion vector Frame Memory IDCT Networked Video