On Sat, 07 Apr 2001 16:05:13 GMT, Howard Ring wrote:

>I see a slight color shift in the 10th gen picture, but not much
>else different. In the 5th gen pictures, the MainConcept and Canopus
>look pretty close to the originals, but the Quicktime shifts somewhat
>towards green. The DVSoft and MS each shift pretty badly towards green.
>So, is color shifting the only real loss in cycling through a CODEC, or
>can I expect to see detail loss too? I thought there were compression
>schemes that could do 4 or 5 to 1 lossless compression. Were one of
>these used for DV?

Hmmm... In my sample, you are right - the only loss at the
10th generation is a slight increase in color impurity; but
in the QT sample at the other URL, there is considerable
color smearing and loss of resolution obvious; in the
DVSoft sample, there is a green-shift and darkening
only (both can be compensated for with filtering); with
the MS codec there is bad vertical-banding; with the
MainConcept, the results appear as good as with the Raptor
codec (and render times are about as low). Either the
Raptor or MainConcepts codecs could be safely used for
five generations of renderings, I think, but I would
avoid using the DVSoft for multiple generations, and
I would avoid using the versions tested of the MS and QT
codecs for ANY editing involving rendering - these were
unacceptable...

>> Yes, but depending on the quality of the DV-codec, you may,
>> or may not, need to worry about the number of rendering
>> generations while editing. See these for multi-generation
>> examples (though it has been pointed out that some of the
>> codecs used in the second URL have been improved):
>> http://www.David-Ruether-Photography.com/original_vs_10th-gen.htm
>> and:
>> http://members.home.net/dgcom/MiniDV/DVcompressors.htm
>> Not all DV-codecs are created equal...
>> DR