Image Processing Reference
In-Depth Information
Adobe After Effects help with this problem. At the high end, professional users deploy
tools such as Discreet Combustion and Pinnacle Commotion. All of these tools offer other
useful capabilities as well.
Comparing Video with Film as a Source Input
When Hollywood movie films are broadcast on TV, the frame rates have to be adjusted so
that the picture is played at a different frame rate. Film runs at 24 frames per second and
opening the shutter twice for each frame reduces the flickering.
This is close to the frame rate of European broadcast systems, but it is a long way
from the right frame rate for TV systems in the United States.
To change the frame rate without using the digital interpolation techniques is quite
tricky, so a mechanical means of accomplishing this was developed that is called 2-3 or
3-2 pulldown. It is done differently for 60 Hz and 50 Hz field rates. (Chapter 4 discussed
film formats and examined pulldown and telecine systems.)
Up-Rated Scanning
Some TV sets have a built-in frame store that is loaded with new pictures at a rate of 25 or
30 times per second. The output delivers the video to the screen at a 100 Hz frame rate.
This significantly improves the viewing experience. The frame store also provides scaling
and aspect-ratio correction. The digital scaling sometimes introduces subtle artifacts into
the picture that are similar to those caused by over-compressing the source material.
Scanning Modes
In the descriptions of the different image sizes, terminology such as 1080i or 1080p is used
to describe two alternative line-scanning patterns for HDTV. Standard definition (SDTV)
generally has just an “i.” This indicates whether the line scanning is interlaced or pro-
The future of video everywhere is progressive, not interlaced.
-Ben Waggoner, 2004
This is certainly true, and the European Broadcasting Union ( EBU ) predicts that between
2009 and 2015, progressive HD-compatible displays will probably outnumber interlaced
SDTV receivers.
Tests with H.264 and WM9 encoders prove that they both encode progressively
scanned video with a better efficiency (compression ratio) than they do interlaced video.
The delivery of progressively scanned content is preferable because it is easy to cre-
ate interlaced material from it but much harder to go the other way. In any case, it is
convincingly argued by the EBU that putting expensive and very-high-quality interlaced-
to-progressive conversion equipment at the broadcaster's head-end installation is far
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