Mpeg family

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Mpeg family

  1. 1. VIDEO COMPRESSION &VIDEO COMPRESSION & MPEGMPEG 0992970-0992970- 楊凱翔楊凱翔 0992969-0992969- 林江瑜林江瑜 0992965-0992965- 連重凱連重凱
  2. 2. OutlineOutline • VIDEO COMPRESSIONVIDEO COMPRESSION – VIDEO CODING BASICSVIDEO CODING BASICS – MOTION COMPENSATIONMOTION COMPENSATION • MPEG FAMILYMPEG FAMILY – MPEG-1 VIDEO standardMPEG-1 VIDEO standard – MPEG-2 VIDEO standardMPEG-2 VIDEO standard – MPEG-4MPEG-4 – H.264H.264 – MPEG-7MPEG-7
  3. 3. VIDEO COMPRESSIONVIDEO COMPRESSION • Why do we use compression?Why do we use compression? – Temporal RedundancyTemporal Redundancy – Spatial RedundancySpatial Redundancy time x y
  4. 4. Two Stage Coding ProcessTwo Stage Coding Process Stage 1 Stage 2
  5. 5. Reducing TemporalReducing Temporal RedundancyRedundancy • Segment a frame into macroblocks, notSegment a frame into macroblocks, not search by pixelssearch by pixels • Output energy( bit rate) is increased withOutput energy( bit rate) is increased with the degree of temporal redundancythe degree of temporal redundancy • Interframe coderInterframe coder ( only use temporal( only use temporal redundancy reduction)redundancy reduction)
  6. 6. Reducing Spatial RedundancyReducing Spatial Redundancy • Using DCT codingUsing DCT coding • Intraframe coderIntraframe coder (use only spatial(use only spatial redundancy reduction, only for currentredundancy reduction, only for current frame)frame) • Hybrid( intra-/ inter - frame) coding methodHybrid( intra-/ inter - frame) coding method
  7. 7. Motion CompensationMotion Compensation • Often used andOften used and developed bydeveloped by MPEG familyMPEG family • 將相鄰的將相鄰的 frameframe 中中 出現的移動物件進出現的移動物件進 行互相補償的過程行互相補償的過程 ,因為該物件移動,因為該物件移動 範圍不大且形狀在範圍不大且形狀在 短時間內不易變動短時間內不易變動 • It is preceded byIt is preceded by motion estimationmotion estimation Motion Vector Search Range Current Frame Reference Frame Ω
  8. 8. MPEG-1 IntroductionMPEG-1 Introduction • DCT for intra- and inter- framesDCT for intra- and inter- frames • Block-based motion compensationBlock-based motion compensation • Huffman CodingHuffman Coding • Source input format : YUV, why not RGBSource input format : YUV, why not RGB • Y : luminance component(Y : luminance component( 亮度亮度 )) • U(Cb), V(Cr) : color difference orU(Cb), V(Cr) : color difference or chrominance componentchrominance component (色差)(色差)
  9. 9. MPEG-1 Picture TypeMPEG-1 Picture Type • Intra-Picture( I )Intra-Picture( I ) • Predicted- Pictures( P )Predicted- Pictures( P ) • Bidirectional-Predicted-Picture( B )Bidirectional-Predicted-Picture( B )
  10. 10. MPEG-2MPEG-2 • 與與 MPEG-1MPEG-1 通用通用 • Difference from MPEG-1Difference from MPEG-1 – 好很多的畫質好很多的畫質 – 更多的輸入格式更多的輸入格式 ( ex: RGB, more YUV form)( ex: RGB, more YUV form) – 在雙向傳輸時有較短的在雙向傳輸時有較短的 delay timedelay time – Higher bit rateHigher bit rate – We can adjust our pictures qualityWe can adjust our pictures quality
  11. 11. MPEG-4MPEG-4 • 針對整合多媒體、通訊、電腦之應用上,具體內針對整合多媒體、通訊、電腦之應用上,具體內 容則是以內容為基礎容則是以內容為基礎 (Content-based)(Content-based) 的應用上。的應用上。 • 將影片區分為前景及背景將影片區分為前景及背景(( Object-BasedObject-Based )),只,只 要記錄動態圖像的軌跡即可,因此在壓縮量及品要記錄動態圖像的軌跡即可,因此在壓縮量及品 質上,能較質上,能較 MPEG-1MPEG-1 及及 MPEG-2MPEG-2 來得更好,每秒來得更好,每秒 動態資料處理速率彈性更大。動態資料處理速率彈性更大。
  12. 12. Some MPEG-4 Video FeatureSome MPEG-4 Video Feature • SegmentationSegmentation • SpriteSprite • TrackingTracking
  13. 13. MPEG-1 vs. MPEG-2 vs. MPEG-4MPEG-1 vs. MPEG-2 vs. MPEG-4 一般解析度 最大解析度 一般資料量 最大資料量 Mpeg-1 Mpeg-2 Mpeg-4 3Mbps 80Mbps 5~10Mbps 0.88Mbps 6.5Mbps 1.38Mbps 720X576 1920X1152 352X288 720X576 720X576 352X288
  14. 14. MPEG-1 vs. MPEG-2 vs. MPEG-4MPEG-1 vs. MPEG-2 vs. MPEG-4       影像規格影像規格 Mpeg-1Mpeg-1 Mpeg-2Mpeg-2 Mpeg-4Mpeg-4 壓縮能力壓縮能力 中中 中中 強強 檔案大小檔案大小 中中 大大 小小 影像品質影像品質 可可 很好很好 可至很好可至很好 網路傳輸網路傳輸 勉強勉強 不可能不可能 最佳化 最佳化 

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