Mpeg family
- 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. 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. VIDEO COMPRESSIONVIDEO COMPRESSION ? Why do we use compression?Why do we use compression? – Temporal RedundancyTemporal Redundancy – Spatial RedundancySpatial Redundancy time x y
- 4. Two Stage Coding ProcessTwo Stage Coding Process Stage 1 Stage 2
- 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. 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. 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 ?
- 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. 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. 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. 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. Some MPEG-4 Video FeatureSome MPEG-4 Video Feature ? SegmentationSegmentation ? SpriteSprite ? TrackingTracking
- 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. 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