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What are the strengths and weaknesses of HDV?
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From Larry Jordan's FinalCut Pro newsletter:

HDV Strengths

For a relatively small amount of money, you can shoot an HD picture. You also have a variety of frame rates to select from, including 23.98, 25, and 29.97. Some cameras offer additional rates beyond these three. And, the default aspect ratio for HDV is 16:9.

In brief, HDV?s strength is its low-cost, HD images.

HDV Weaknesses

However, on the negative side, the weaknesses of HDV are:

  • The HDV image is 1440?1080, which does not precisely match either the 720p or 1080i format.
  • HDV is enormously compressed, creating the possibility of significant motion artifacts when the camera is moved, or zoomed, quickly.
  • HDV uses MPEG-2 compression, the same as a DVD. This compression groups several pictures into a ?group of pictures,? called a GOP, rather than each picture being it?s own entity. 1080i HD groups 15 images into one GOP. 720p groups 6 images into one GOP.
  • This GOP method of compression means that HDV is not accurate for timecode or frames when capturing or outputting. (Editing HDV inside FCP is frame-accurate, however.)
  • HDV uses extreme color sampling, resulting in very, very poor color keying, color correction, or compositing results. (HDV uses 4:2:0 color sampling, the same as a DVD. Here?s an article that explains it in more detail.)
  • HDV renders take about six times longer than DV. This is actually a result of rendering the larger HD image, versus an SD image; still, this will take longer than you expect.
  • HDV needs to be conformed, or rebuilt, into a consistent GOP structure before it can be output to tape or exported to a file. This conforming can take an exceedingly long time. (For instance, conforming a 30 second sequence consisting of five shots, took over 10 minutes on my PowerBook. Conforming a complex hour-long sequence could take several hours on a G-5.)
  • HDV can only use Print to Tape, not Edit to Tape, due to the timecode inaccuracies of HDV.

For these reasons, I am no longer the fan of HDV that I used to be. What I?ve discovered is that we need to separate how we CAPTURE the image from how we EDIT the image.

Last update: 03:18 PM Tuesday, March 21, 2006

 



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