DV compression during output.

[Deadzone]

This is a topic I have heard a lot about and would like a definitive answer to. First of all, what do people mean when they say that DV footage is compressed? I heard it was something to the ratio of 6:1. Does that mean for every six pixels available only one gets recorded? Also, people tell me that when DV goes into FCP there is no loss in quality if imported at full resolution. However, When the movie is output back to DV tape will it suffer due to the DV compression? I ask because I have a friend who output his movie and deleted the media only to find out there was a mistake in the movie. Now all he has is the DV tape. If he imports the movie back into FCP then outputs it again to DV tape will there be a loss in quality because of the compression. Thanks in advance for any information.

 

[Scottdvx100]

Re: DV compression during output.

Most video (and still) formats use compression. There are many methods of doing compression. In the case of DV it analyzes square chunks of the image in 8x8 pixel blocks (?) and attempts to reproduce that with minimal bits of information. DV also records in 4:1:1 color space. That means it puts higher priority and sampling on lumanence than on color to reproduce what it needs to for the eye. If you look at the pixels, red and blue will be rectangular and take up 2 pixel positions.

If you import and export to DV just as a pure edit then there will be no loss.
It's essentially doing a pure copy of digital data.
If you manipulate (including color correction) any scenes then they will require re-compression which may result in a slight loss. Usually not visible unless you re-import, re-export a few times.