Understanding Macroblocks

1
Understanding Macroblocks
2
What is a Macroblock?
16 pixels

• The basic building block of a video image
• A macroblock is 256 square pixels
• 16 vertical by
• 16 horizontal
• Video conferencing images are made from dynamic
  macroblocks
• 720p HD is defined as
• 1280 horizontal pixels
• 720 vertical pixels
• Video conferencing should support 30fps for
  business quality motion handling

16 pixels
Macroblock
3
Dynamic Macroblocks Needed for 720p, 30fps?

• How many dynamic macroblocks per second does an
  HD video conferencing system need to encode and
  decode?

1280h x 720v 921,600 pixels per frame 921,600
16h 16v 3,600 macroblocks per frame 3,600 x
30 108,000 macroblocks per second
108,000 macroblocks/second
4
What Does TANDBERG Provide?

• TANDBERG cannot code and decode full HD video due
  to limited dynamic macroblock (video building
  blocks) capability

• Limited macroblock capability forced TANDBERG to
  non-standard (lower resolution, non-HD) formats
  where they could dynamically code and decode at
  30fps

Fully Dynamic Video at 30fps
HD Standard
Non-Standard
720p
Maximum Dynamic Macroblocks
448p
400p
5
Video Formats and Dynamic Macroblock Requirements
6
Static Macroblocks

• Static Macroblock technology was developed by
  Polycom
• This technology was designed to improve frame
  rates for content sharing, where images had small
  changes
• Reducing the dynamic macroblocks reduces the
  workload placed on the codec.
• If you are struggling to achieve higher frame
  rates, this is one way to push up that number.
• However, this comes at a price. When you rely on
  static macroblocks and real motion takes place,
  the video quality suffers with video blurring,
  blocking and unnatural motion caused by drops in
  frame rate

7
TANDBERG and Static Macroblocks

• Makes their frame rate statistics look higher
  when there is very little motion
• Environments with motion suffer as frame rates
  drop
• People moving in the video image
• Camera movements (panning, tilting, zooming)
• Switching to alternate video sources (DVD, VCR,
  2nd camera)
• TANDBERG systems will not negotiate with other
  vendors that support full dynamic macroblocks
• Why? Codec is underpowered to deliver true HD
  (108,000 macroblocks per second) and can not
  fully code and decode
• Will force real, dynamic HD systems to drop down
  to 4CIF or lower where they can handle dynamic
  decode

8
Summary

• High definition video conferencing is a very
  specific science and well-defined
• TANDBERG does not meet this definition
• In order to compensate for not delivering true,
  dynamic HD, TANDBERG uses Static Macroblocks to
  reduce workload on its video conferencing codecs
  and claim higher frame rates
• Polycom HDX 9000 solutions deliver true HD at
  30fps, even in highly dynamic environments