lossy compression -- why can't I get an answer from editors

M

Marshallarts

Well-known member
Not sure why I can't get a clear answer from my editor friends about this. It almost seems this is something noone is really concerned about with video, although in still photography this is practically the most irreverent of all taboos.......

Lossy compression ( http://en.wikipedia.org/wiki/Lossy )

Can someone please give me an answer to the lossy compression issue while importing from DV to FCP with the intention of outputing to create a DVD?

The other day an editor friend suggested I take a DVD dub of a miniDV tape and use it to cut my reel. I can definitely do this. But I was confused why an editor would be so 'cool' with doing it this way. Hasn't the DVD already gone through a few generations of lossy compression?

Doesn't FCP (or equivalent) "uncompress" the media while editing at times in order to edit it, and then "recompress" it (after rendering or simply just to get it back on the hard drive edited). And since the media is going to put output to DVD doesn't that create another Lossy factor of resaving it in another fashion after it was compressed?

Wouldn't one want to preserve the highest possible state of the media and output with the least possible degradation by lossy compression? I know there are many different video codecs to consider here, but there must be an agreed upon procedure as far as inputing, editing, then outputing in a way that lessens any negative side-effects.

Can someone please explain this to me?
 
Let me expand on my example.

I know FCP and other NLE simply make an EDL of the cuts/transitions it needs to make. But since the media was taken from a Lossy format wouldn't it be re-saved lossy in the output? And then when going to DVD isn't that another lossy re-save?

Since all video is digital and is sampled to some degree, isn't it all lossy? (i.e. is there a .tiff or lossless equivelent to video?)
 
there are lossless formats to work in... but they don't really apply to your situation. going from DVD to editing and back to DVD will introduce some degredation. if you have the source on miniDV, just import that and work with it... don't use the DVD copy.
 
yeah, i was surprised one would suggest to import from the DVD. It's an obvious no-no to anyone with basic knowledge in photography not to use the lossy format. No idea why this issue isn't brought up more.

But more importantly. Can someone explain the best protocol to avoid lossy compression? I would also like the explanation of DV > DVD and the lossy issues involved.
 
Marshallarts said:
Not sure why I can't get a clear answer from my editor friends about this...
Click to expand...
Complete ignorance. Unfortunately the new breed of editors have no clue about quality, they can't read a waveform or vectorscope and they think that the videos on youtube look great. Is that clear enough?

Marshallarts said:
Can someone explain the best protocol to avoid lossy compression?
Click to expand...
Don't shoot and edit on DV. DV video is compressed during acquisition, aprrox. 5:1. This is compounded by further recompression during the editorial process where titles, effects and color correction cause the signal to be recompressed. The bottom line on keeping a clean signal throughout the production pipeline is a matter of economics. An uncompressed workflow can easily exceed $100,000 whereas a DV based workflow can be had for less than $10,000.

If the footage you want to include in your reel is DV then a DV file of that footage should work just fine. There's nothing to be gained by converting the file to an uncompressed QT or uncompressed AVI.

Marshallarts said:
I would also like the explanation of DV > DVD and the lossy issues involved.
Click to expand...
DVD is a delivery format not an archive or source format. DVD's are encoded using MPEG 2 compression. The amount of degradation is dependent on the settings used for compressing the data. Even at the best settings a DVD will never look as good as the source file.
 
Simply put: If you want to avoid compression, always work in the same format you shot in.

However, I have seen video ripped from DVDs and although this is not Ideal, if you must do it you can achieve acceptable results.
 
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