A technical analysis of streaming video codecs
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A Technical Analysis of Streaming Video Codecs. Including Current and Emerging Standards. Video Compression Basics. Frames Compression starts with the frames. Each frame can be compressed like any other image. Blocks

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Including Current and Emerging Standards

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A technical analysis of streaming video codecs

A Technical Analysis of Streaming Video Codecs

Including Current and Emerging Standards


Video compression basics

Video Compression Basics

  • Frames

    • Compression starts with the frames. Each frame can be compressed like any other image.

  • Blocks

    • Each frame is broken up into blocks for coding, each codec uses a different scheme in it’s use of blocks. A standard bock size is 8x8 pixels. Other codecs use variable sizes.

  • Spatial Redundancy

    • The concept referring to the fact areas of a frame “look the same” .

    • If a frame has a large uniform area, a codec will encode that area in such a way that all redundant data is removed. This allows for a lower bit rate without sacrificing quality.


Video compression basics1

Video Compression Basics

  • Temporal Redundancy

    • Temporal Redundancy refers to the fact that some areas of a frame remain the same between frames.

    • A codec will only encode the changes between frames and reduce the bit rate by not needing to retransmit the unchanged areas of the frame.

1. Axis Communications. "Video Compression." - Technical Guide. Axis Communications, 2013. Web. 28 Mar. 2013. <http://www.axis.com/products/video/about_networkvideo/compression.htm>.

Illustrated Example of Temporal Redundancy. 1


Advanced compression

Advanced Compression

  • Block Based Motion Compensation

    • Block based Motion compensation takes advantage of the fact that the some parts of a frame can be reused in the next frame even if it has moved in the frame.

    • The trunk of the red car below can be reused from frame to frame, The codec must just code the movement of the block reducing the bit rate.

2. Berkeley Design Technology, Inc. "How Video Compression Works." Berkeley Design Technology, Inc. Berkeley Design Technology, Inc., 15 Aug. 2007. Web. 28 Mar. 2013. <http://www.bdti.com/InsideDSP/2007/08/15/Bdti>.

Illustrated Example of block based motion compensation.2


H 264

H.264

  • High Quality, Low Bitrate.

  • Variable Block Sizes

    • 4x4 to 16x16

  • Calculated Blocks

    • More data calculated = less data transmitted

  • Robust Error Correction

  • More resource hungry

  • Dedicated Hardware required in low power and mobile applications.


Including current and emerging standards

VP8

  • Designed for Web and wide variety of devices

  • Processor-Adaptive Encoding

    • 16 encoding modes based on hardware

  • Temporal Scalability

    • Automatic coding changes based on bandwidth

  • Alternative Reference Frame

    • Higher quality with no additional complexity


Theora

Theora

  • Open Source, BSD Style License

  • Built off of VP3 a predecessor of VP8

  • No license issues

  • No patent issues

  • Slightly lower quality at the same bitrate.

  • FREE!


H 265

H.265

  • Reduced Bitrate by ½ over H.264 keeping quality the same.

  • Builds on H.264

  • Suited for UHD

  • Reduces Bitrate by ½ while preserving quality

  • Very resource hungry

  • Requires dedicated hardware


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