Lecture-13 - Lecture-13 Model-base Video Compression JPEG...

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1 Lecture-13 Model-base Video Compression JPEG Baseline Coding • Divide image into blocks of size 8X8. Level shift all 64 pixels values in each block by subtracting 2 n-1, (where 2 n is the maximum number of gray levels). Compute 2D DCT of a block. Quantize DCT coefficients using quantization table.
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2 JPEG Baseline Coding Zig-zag scan the quantized DCT coefficients to form 1-D sequence. Code 1-D sequence (AC and DC) using JPEG Huffman variable length codes. JPEG BLOCK DIAGRAM DCT Q VLE VLE -1 Q -1 DCT -1 image Encoded image Decoded image
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3 JPEG Original 64K 13K 5K Difference MPEG-1 Encoder DCT - DCT Q DCT -1 Q -1 + Motion Estimat Frame Mem-1 Frame Mem-2 Motion Compenst Input Image inter intra Motion Vectors TO VLC Reconstrd Image Predicted image Prediction error Rate control ‘0’
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