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Vste r2


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  • -Video compression refers to reducing the quantity of data used to represent video images and is a straight forward combination of image compression and motion compensation -There are no magic settings that fit all projects. Major factors that dictate the need and amount of compression depend on your delivery method and your audiences connection speed and hardware. As well the content within the video has a major factor on compression settings.
  • . Video compression, like data compression, is a tradeoff between disk space, video quality and the cost of hardware required to decompress the video in a reasonable time. However, if the video is over compressed in a lossy manner, visible (and sometimes distracting) artifacts can appear.
  • Similarities can thus be encoded by merely registering differences within a frame (spatial) and/or between frames (temporal). Spatial encoding is performed by taking advantage of the fact that the human eye is unable to distinguish small differences in color as easily as it can changes in brightness and so very similar areas of color can be "averaged out. With temporal compression only the changes from one frame to the next are encoded as often a large number of the pixels will be the same on a series of frames. Interframe compression uses one or more earlier or later frames in a sequence to compress the current frame, while intraframe compression uses only the current frame, which is effectively image compression
  • There is no simple answer to these settings unfortanityly. Different video requires different styles of compresion. There is always a trade off of somekind. Depending on your audience may change your technique
  • NTSC was designed to utilize the limited bandwidth into homes for broadcast video, this standard was developed around 1950 and slightly modified for color in the 1960’s. This standard will cease to be used in Feb 2009 due to advancements in Digital video. Interlaced shows odd lines then even lines sequentially and human eyes combine the two fields into one image. @ 29.97 Progressive scan takes more bandwidth, every frame is shown in it’s entirety which is closer to film in nature. All video should be de-interlaced before compressing. The reason being is when you lower frame rates on the video Interlaced images will show artifacts
  • This should be an example of Compressing but leaving it interlaced
  • I n telecommunications and computing, data rate is the number of bits that are conveyed or processed per unit of time. The bit rate is quantified using the 'bits per second’ ‘kilobites per second’
  • Make the size of the video smaller to compensate and gain some quality If video won’t play smoothly maybe data rate is too high.
  • This example is keyframe every 5 frames
  • Adjusting by halfs because of the complexities involved with figuring out which frames to drop
  • Size the video is going to be on the screen not the size of the file.
  • Transcript

    • 1. Video Compression Making BIG files small
    • 2. What is Video Compression
      • Most video compression is lossy, i.e. it operates on the premise that much of the data present before compression is not necessary.
      • For example, DVDs use a video coding standard called MPEG-2 that can compress ~2 hours of video data by 15 to 30 times while still producing a picture quality that is generally considered high quality for standard-definition video
      • Video Compression is a trade off between video quality, disk space, and hardware needed for decompression
    • 3. More about compression theory
      • Video data contains spatial and temporal redundancy.
      • Spatial Data= Difference within frames
      • Temporal Data = Difference between frames
      • Interframe vs intraframe compression.
    • 4. What went wrong?
    • 5. What was wrong with that video?
      • Interlaced
      • Data rate - 300kbs
      • Key frame - every 150f
      • Frame rate - 15fps
      • Quality Settings - High
      • Codec - H.264
      • Size Ratio 480 x 360 - 4:3
      • 2MB Original-165MB
    • 6. Interlaced VS Progressive
      • NTSC = 29.97 interlaced frames of video per second
      • Interlaced=image is broken into odd and even lines
      • Progressive scan means every frame is the entire image
    • 7. Interlaced compression artifacts
    • 8. What is Data Rate?
      • Data Rate is the number of bits that are conveyed or processed per unit of time
      • Data rate is synonymous with bit rate.
      • While often referred to as "speed", Data rate does not measure distance/time but quantity/time
      • Data rate includes video and audio combined
      • Video(300kbs) + Audio(128kbs)=
      • Total Data Rate(428kbs)
    • 9. Data Rate
      • Data rate greatly impacts quality of the video as well as size. I usually start with the automatic settings built into most current programs. Rule of thumb 300kbs for med-high bandwidth streaming 100kbs for dial up.
      • -Some computers cannot handle higher data rates
      • -Think about how your audience will retrieve your video and let the software do the work
    • 10. Key frames
      • In video compression, a key frame is a frame that contains the entire image
      • Difference frame or in-betweens contain only important info to fill in the gaps between Key Frames
      • Think of an image of a person walking in front of a wall. To show motion only the person needs to be redrawn as the wall stays the same.
    • 11. Key frames
    • 12. Key frames
      • More action needs more key frames
      • Running video looks better at a setting of every 60 frames
      • Fish still looks good at every 150 frames
      • Always adjust key frames when compressing
    • 13. What is Frame Rate
      • The frame rate is the number of frames per second displayed during the video.
      • More frames do not necessarily make the video look better, due to the limitations of the human eyes and brain to process all of the data
      • Basically, a frame is the same as a still picture
    • 14. Frame Rate
      • Most camcorders record at 30fps
      • Progressive mode is usually 24fps
      • Film is 24fps
      • NTSC is 29.97fps and Pal is 24fps
      • Adjust by halfs 30-15fps 24-12fps
    • 15. Quality Settings
      • The quality factor of encoded video streams is a rough measurement of video encoding quality expressed in bits per pixel.
      • Most programs let you adjust compressor quality
      • Start low and work up
    • 16. Codec
      • A video codec is a device or software that enables video compression and/or decompression for digital video.
      • Co = Compressor / Dec = Decompressor
      • Most widley used codec currently for video is H.264 (MPEG4 Ver10)
      • Other examples, H.261, MPEG-1 thru 4, H.263, DivX, Xvid, WMV and the list goes on and on
    • 17. Size
      • This greatly impacts file size and quality
      • Try 480x340 for 4:3 SD
      • 480x270 for 16:9 HD
      • NTSC is 640x480
    • 18. Audio Settings
      • Always set to mono, at this level of compression you gain little from stereo
      • Encode using AAC
      • Set to 22.050khz
      • Set target bit rate to 48kbs
    • 19. Looking Good!
      • Progressive
      • Data rate - Auto
      • Key frame - every 60f
      • Frame rate - 15fps
      • Quality Settings - Med
      • Codec - H.264
      • Size Ratio 480 x 360 - 4:3
      • 8.6MB Original 165MB
    • 20. Looking Good!
    • 21. Sample Video Comparison
      • Interlaced
      • Data rate - 300kbs
      • Key frame - every 150f
      • Frame rate - 15fps
      • Quality Settings - High
      • Codec - H.264
      • Size Ratio 480 x 360 - 4:3
      • 2MB Original-165MB
      • Progressive
      • Data rate - Auto
      • Key frame - every 60f
      • Frame rate - 15fps
      • Quality Settings - Med
      • Codec - H.264
      • Size Ratio 480 x 360 - 4:3
      • 8.6MB Original 165MB
    • 22. What programs can I use?
      • Sorenson Squeeze
      • Flash Media Encoder
      • Quicktime Pro
      • Compression is built into ,most major editing packages I.E. Final Cut, I-movie, Adobe Premier
    • 23. File Types
      • Flash FLV
      • Quicktime MOV
      • Realplayer .ra, .rax, .rv., .rvx, .rm, .rmx, .rmj, .rms
      • Windows Media Formats .asf, .wma, .wmv, .wm
    • 24. Thank You For Coming
      • Now for Examples
      • [email_address]
      • [email_address]