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Edit Comment Close Premium member Presentation Transcript MPEG: A Video Compression Standard for Multimedia Applications: MPEG: A Video Compression Standard for Multimedia Applications Václav Hlaváč CTU Prague, hlavac@cmp.felk.cvut.cz Initial material were slides of Didier Le Gall, Worcherster Polytechnic Institute.Introduction: Introduction 1980’s technology made possible full-motion video over networks Television and Computer Video seen moving closer (Today, Sony and Microsoft are squaring off) Needed a standard Often, triggers needed volume production Ala facsimile (fax) Avoid de facto standard by industry 1988, Established the Motion Picture Experts Group (MPEG) Worked towards MPEG-1 Primarily video but includes audio (MP3)The Need for Video Compression: The Need for Video Compression High-Definition Television (HDTV) 1920x1080 30 frames per second (full motion) 8 bits for each three primary colors (RGB) Total 1.5 Gb/sec! Cable TV: each cable channel is 6 MHz Max data rate of 19.2 Mb/sec Reduced to 18 Mb/sec w/audio + control … Compression rate must be ~ 80:1!Compatibility Goals: Compatibility Goals 1990: CD-ROM and DAT key storage devices 1-2 Mbits/sec for 1x CD-ROM Two types of application videos: Asymmetric (encoded once, decoded many times) Video games, Video on Demand Symmetric (encoded once, decoded once) Video phone, video mail … (How do you think the two types might influence design?) Video at about 1.5 Mbits/sec Audio at about 64-192 kbits/channelRequirements: Requirements Random Access, Reverse, Fast Forward, Search At any point in the stream (within ½ second) Can reduce quality somewhat during this task, if needed Audio/Video Synchronization Robustness to errors Not catastrophic if some bits are lost Lends itself to Internet streaming Coding/Decoding delay under 150 ms For interactive applications Ability to Edit Modify/Replace frames Relevant Standards: Relevant Standards Joint picture Experts Group (JPEG) Compress still images only Expert Group on Visual Telephony (H.261) Compress sequence of images Over ISDN (64 kbits/sec) Low-delay Other high-bandwidth “H” standards: H21 (34 Mbits/sec) H22 (45 Mbits/sec)MPEG Compression: MPEG Compression Compression through Spatial TemporalSpatial Redundancy: Spatial Redundancy Take advantage of similarity among most neighboring pixels Spatial Redundancy Reduction: Spatial Redundancy Reduction RGB to YUV less information required for YUV (humans less sensitive to chrominance) Macro Blocks Take groups of pixels (16x16) Discrete Cosine Transformation (DCT) Based on Fourier analysis where represent signal as sum of sine's and cosine’s Concentrates on higher-frequency values Represent pixels in blocks with fewer numbers Quantization Reduce data required for co-efficients Entropy coding CompressSpatial Redundancy Reduction: Spatial Redundancy Reduction Zig-Zag Scan, Run-length coding “Intra-Frame Encoded”Question: Question When may spatial redundancy reduction be ineffective? What kinds of images/movies? Answer: Answer When may spatial redundancy elimination be ineffective? High-resolution images and displays May appear ‘coarse’ What kinds of images/movies? A varied image or ‘busy’ scene Many colors, few adjacent Loss of Resolution: Loss of Resolution Original (63 kb) Low (7kb) Very Low (4 kb)Temporal Redundancy: Temporal Redundancy Take advantage of similarity between successive framesTemporal Activity: “Talking Head” Temporal ActivityTemporal Redundancy Reduction: Temporal Redundancy ReductionTemporal Redundancy Reduction: Temporal Redundancy ReductionTemporal Redundancy Reduction: Temporal Redundancy Reduction I frames are independently encoded P frames are based on previous I, P frames Can send motion vector plus changes B frames are based on previous and following I and P frames In case something is uncoveredGroup of Pictures (GOP): Group of Pictures (GOP) Starts with an I-frame Ends with frame right before next I-frame “Open” ends in B-frame, “Closed” in P-frame (What is the difference?) MPEG Encoding a parameter, but ‘typical’: I B B P B B P B B I I B B P B B P B B P B B I Why not have all P and B frames after initial I? Question: Question When may temporal redundancy reduction be ineffective?Answer: Answer When may temporal redundancy reduction be ineffective? Many scene changes High motionNon-Temporal Redundancy : Non-Temporal Redundancy Many scene changes vs. few scene changes Non-Temporal Redundancy : Non-Temporal Redundancy Sometimes high motionTypical MPEG Parameters: Typical MPEG ParametersTypical Compress. Performance: Typical Compress. Performance Type Size Compression --------------------- I 18 KB 7:1 P 6 KB 20:1 B 2.5 KB 50:1 Avg 4.8 KB 27:1 --------------------- Note, results are Variable Bit Rate, even if frame rate is constantMPEG Today: MPEG Today MPEG video compression widely used digital television set-top boxes HDTV decoders DVD players video conferencing Internet video ... MPEG Today: MPEG Today MPEG-2 Super-set of MPEG-1 Rates up to 10 Mbps (720x486) Can do HDTV (no MPEG-3) MPEG-4 Around Objects, not Frames Lower bandwidth Has some built-in repair (header redundancy) MPEG-7 New standard Allows content-description (ease of searching) MP3, for audio MPEG Layer-3MPEG Tools: MPEG Tools MPEG tools at: http://www-plateau.cs.berkeley.edu/mpeg/index.html MPEG streaming at: http://www.comp.lancs.ac.uk/ FFMPEG http://ffmpeg.sourceforge.net/index.org.html You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.
85VideoCompress Malden Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINTLite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 296 Category: Education License: All Rights Reserved Like it (1) Dislike it (0) Added: February 27, 2008 This Presentation is Public Favorites: 0 Presentation Description No description available. Comments Posting comment... By: kamalja (32 month(s) ago) can i hav this presentation plzz Saving..... Post Reply Close Saving..... Edit Comment Close Premium member Presentation Transcript MPEG: A Video Compression Standard for Multimedia Applications: MPEG: A Video Compression Standard for Multimedia Applications Václav Hlaváč CTU Prague, hlavac@cmp.felk.cvut.cz Initial material were slides of Didier Le Gall, Worcherster Polytechnic Institute.Introduction: Introduction 1980’s technology made possible full-motion video over networks Television and Computer Video seen moving closer (Today, Sony and Microsoft are squaring off) Needed a standard Often, triggers needed volume production Ala facsimile (fax) Avoid de facto standard by industry 1988, Established the Motion Picture Experts Group (MPEG) Worked towards MPEG-1 Primarily video but includes audio (MP3)The Need for Video Compression: The Need for Video Compression High-Definition Television (HDTV) 1920x1080 30 frames per second (full motion) 8 bits for each three primary colors (RGB) Total 1.5 Gb/sec! Cable TV: each cable channel is 6 MHz Max data rate of 19.2 Mb/sec Reduced to 18 Mb/sec w/audio + control … Compression rate must be ~ 80:1!Compatibility Goals: Compatibility Goals 1990: CD-ROM and DAT key storage devices 1-2 Mbits/sec for 1x CD-ROM Two types of application videos: Asymmetric (encoded once, decoded many times) Video games, Video on Demand Symmetric (encoded once, decoded once) Video phone, video mail … (How do you think the two types might influence design?) Video at about 1.5 Mbits/sec Audio at about 64-192 kbits/channelRequirements: Requirements Random Access, Reverse, Fast Forward, Search At any point in the stream (within ½ second) Can reduce quality somewhat during this task, if needed Audio/Video Synchronization Robustness to errors Not catastrophic if some bits are lost Lends itself to Internet streaming Coding/Decoding delay under 150 ms For interactive applications Ability to Edit Modify/Replace frames Relevant Standards: Relevant Standards Joint picture Experts Group (JPEG) Compress still images only Expert Group on Visual Telephony (H.261) Compress sequence of images Over ISDN (64 kbits/sec) Low-delay Other high-bandwidth “H” standards: H21 (34 Mbits/sec) H22 (45 Mbits/sec)MPEG Compression: MPEG Compression Compression through Spatial TemporalSpatial Redundancy: Spatial Redundancy Take advantage of similarity among most neighboring pixels Spatial Redundancy Reduction: Spatial Redundancy Reduction RGB to YUV less information required for YUV (humans less sensitive to chrominance) Macro Blocks Take groups of pixels (16x16) Discrete Cosine Transformation (DCT) Based on Fourier analysis where represent signal as sum of sine's and cosine’s Concentrates on higher-frequency values Represent pixels in blocks with fewer numbers Quantization Reduce data required for co-efficients Entropy coding CompressSpatial Redundancy Reduction: Spatial Redundancy Reduction Zig-Zag Scan, Run-length coding “Intra-Frame Encoded”Question: Question When may spatial redundancy reduction be ineffective? What kinds of images/movies? Answer: Answer When may spatial redundancy elimination be ineffective? High-resolution images and displays May appear ‘coarse’ What kinds of images/movies? A varied image or ‘busy’ scene Many colors, few adjacent Loss of Resolution: Loss of Resolution Original (63 kb) Low (7kb) Very Low (4 kb)Temporal Redundancy: Temporal Redundancy Take advantage of similarity between successive framesTemporal Activity: “Talking Head” Temporal ActivityTemporal Redundancy Reduction: Temporal Redundancy ReductionTemporal Redundancy Reduction: Temporal Redundancy ReductionTemporal Redundancy Reduction: Temporal Redundancy Reduction I frames are independently encoded P frames are based on previous I, P frames Can send motion vector plus changes B frames are based on previous and following I and P frames In case something is uncoveredGroup of Pictures (GOP): Group of Pictures (GOP) Starts with an I-frame Ends with frame right before next I-frame “Open” ends in B-frame, “Closed” in P-frame (What is the difference?) MPEG Encoding a parameter, but ‘typical’: I B B P B B P B B I I B B P B B P B B P B B I Why not have all P and B frames after initial I? Question: Question When may temporal redundancy reduction be ineffective?Answer: Answer When may temporal redundancy reduction be ineffective? Many scene changes High motionNon-Temporal Redundancy : Non-Temporal Redundancy Many scene changes vs. few scene changes Non-Temporal Redundancy : Non-Temporal Redundancy Sometimes high motionTypical MPEG Parameters: Typical MPEG ParametersTypical Compress. Performance: Typical Compress. Performance Type Size Compression --------------------- I 18 KB 7:1 P 6 KB 20:1 B 2.5 KB 50:1 Avg 4.8 KB 27:1 --------------------- Note, results are Variable Bit Rate, even if frame rate is constantMPEG Today: MPEG Today MPEG video compression widely used digital television set-top boxes HDTV decoders DVD players video conferencing Internet video ... MPEG Today: MPEG Today MPEG-2 Super-set of MPEG-1 Rates up to 10 Mbps (720x486) Can do HDTV (no MPEG-3) MPEG-4 Around Objects, not Frames Lower bandwidth Has some built-in repair (header redundancy) MPEG-7 New standard Allows content-description (ease of searching) MP3, for audio MPEG Layer-3MPEG Tools: MPEG Tools MPEG tools at: http://www-plateau.cs.berkeley.edu/mpeg/index.html MPEG streaming at: http://www.comp.lancs.ac.uk/ FFMPEG http://ffmpeg.sourceforge.net/index.org.html