I'm using EditStudio but I don't think my problem relates specifically to the application; I'm posting here because I'm not sure quite what the root of the problem is.

I find that whenever a clip is rendered in an editing suite (i.e. passed through a codec again because an efffect is applied) the resulting AVI shows a very marked degrading of image quality. I realise that multiple passes through any "lossy" codec will have a theoretical impact on quality, but discussions elsewhere ( eg on Adam Wilt's DV site) seem to detect only marginal effects, whereas what I see is a serious "mosaic-ing" or "band-ing" effect which rather undermines any benefit I get from applying the post-process in the first place..

It's difficult to talk qualitatively, so I've put some images up in my web-space which illustrate what I'm talking about.

http://www.wjm.clara.net/dv/rendering.html


In these examples, I'm just applying a tiny effect to a region not included in the portion of the image I've extracted, so the re-rendering should be trying to replicate the original exactly. But the effect is that the 16-pixel blocks, which I realise are an inevitable part of the DV algorithm, become seriously exaggerated with each rendering pass.

[I accept too that you shouldn't ever render the source more than once, even if you apply several effects to it - but with even one pass the effect is visible (in the movie as well as in the stills), and I include examples of multiple passes for even greater clarity.]

I note that EditStudio calls DirectX codecs - and I do see that my system loads QDV.DLL when a clip is inserted, which seems right (?) - but I also see that the only DV Codec referenced under "Multimedia" (in my Windows ME "System" display) is Adaptec's DVSoft. I've seen discussions elsewhere that suggest this codec (which probably came with MGI VideoWave, packaged with my Firewire card) might be undesirable. How can I tell if the Adaptec codec is, in fact, being called - and would there be any significant difference anyway?

I'm sure that quality shouldn't be compromised in this way (should it?) - is there anything I can do to get to the bottom of this, or resolve it?