X-simon
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Mar 11, 2001, 10:10 AM
Post #3 of 3
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Re: DV - NTSC compressor lossy?
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To answer your question specifically, yes the DV codec is lossy.
It uses two compression schemes.
One is to convert the RGB signal into a 4:1:1 signal. This is similar to the component digital of professional broadcast (4:2:2) but has less color resolution.
But the killer step is that (unlike D1 which stops at the 4:2:2) it then applies a compression similar to JPeg.
Think of creating a pristine image (call it A) in photoshop, and then saving out the image as a Jpeg (call it B) at say 75% quality.
Jpeg is lossy, so next time you read B in to photoshop, it will not be quite the same image A you had originally.
Now save out this Jpeg image B with a new Jpeg compression applied on top, as image C. Image C will not quite be image B, which was not quite image A.
The more times you do this, the further away you get.
Instead of saving out uncompressed images to maintain quality, try a codec that saves them as YUV. This is like the 4:2:2 standard of digital. Also try to find a codec that marries this with a run length of other lossless compression on-top.
Without taking such measures, your video will certainly degrade.
Depending on the codec in use though you can recompress anywhere from around 5-10 times without too much loss in quality.
Hope that helps
Simon
: I do alot of editing in premiere and After effects. I edit and compress a piece of footage several times over and over. Am I loosing quality if I keep exporting out movies using the DV-NTSC compressor? Does this codec recompress and degrade the quality?
: Also I tried exporting footage uncompressed but the files became outagiously big.
: Thanks
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