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Mpeg family

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Mpeg family Mpeg family Presentation Transcript

  • VIDEO COMPRESSION & MPEG 0992970- 楊凱翔 0992969- 林江瑜 0992965- 連重凱
  • Outline
    • VIDEO COMPRESSION
      • VIDEO CODING BASICS
      • MOTION COMPENSATION
    • MPEG FAMILY
      • MPEG-1 VIDEO standard
      • MPEG-2 VIDEO standard
      • MPEG-4
      • H.264
      • MPEG-7
  • VIDEO COMPRESSION
    • Why do we use compression?
      • Temporal Redundancy
      • Spatial Redundancy
    time x y
  • Two Stage Coding Process Stage 1 Stage 2
  • Reducing Temporal Redundancy
    • Segment a frame into macroblocks, not search by pixels
    • Output energy( bit rate) is increased with the degree of temporal redundancy
    • Interframe coder ( only use temporal redundancy reduction)
  • Reducing Spatial Redundancy
    • Using DCT coding
    • Intraframe coder (use only spatial redundancy reduction, only for current frame)
    • Hybrid( intra-/ inter - frame) coding method
  • Motion Compensation
    • Often used and developed by MPEG family
    • 將相鄰的 frame 中出現的移動物件進行互相補償的過程,因為該物件移動範圍不大且形狀在短時間內不易變動
    • It is preceded by motion estimation
    Motion Vector Search Range Current Frame Reference Frame
  • MPEG-1 Introduction
    • DCT for intra- and inter- frames
    • Block-based motion compensation
    • Huffman Coding
    • Source input format : YUV, why not RGB
    • Y : luminance component( 亮度 )
    • U(Cb), V(Cr) : color difference or chrominance component (色差)
  • MPEG-1 Picture Type
    • Intra-Picture( I )
    • Predicted- Pictures( P )
    • Bidirectional-Predicted-Picture( B )
  • MPEG-2
    • 與 MPEG-1 通用
    • Difference from MPEG-1
      • 好很多的畫質
      • 更多的輸入格式 ( ex: RGB, more YUV form)
      • 在雙向傳輸時有較短的 delay time
      • Higher bit rate
      • We can adjust our pictures quality
  • MPEG-4
    • 針對整合多媒體、通訊、電腦之應用上,具體內容則是以內容為基礎 (Content-based) 的應用上。
    • 將影片區分為前景及背景 ( Object-Based ) ,只要記錄動態圖像的軌跡即可,因此在壓縮量及品質上,能較 MPEG-1 及 MPEG-2 來得更好,每秒動態資料處理速率彈性更大。
  • Some MPEG-4 Video Feature
    • Segmentation
    • Sprite
    • Tracking
  • MPEG-1 vs. MPEG-2 vs. MPEG-4 3Mbps 80Mbps 5~10Mbps 0.88Mbps 6.5Mbps 1.38Mbps 720X576 1920X1152 352X288 720X576 720X576 352X288
  • MPEG-1 vs. MPEG-2 vs. MPEG-4       最佳化  不可能 勉強 網路傳輸 可至很好 很好 可 影像品質 小 大 中 檔案大小 強 中 中 壓縮能力 Mpeg-4 Mpeg-2 Mpeg-1 影像規格