Question re resampling quality setting

eclipse · Post by **eclipse** » Thu Sep 03, 2009 1:23 am

In Video Studio 9, I am editing DV AVI clips. The edits consist of nothing other than trimming the clips and adding transitions. I am then saving the edited clips for archival purposes as DV-AVI files, using the "same as project settings" option. Under these circumstances, does the "resampling quality" setting under the edit tab of preferences affect the quality of the edited files?

Post by **Ken Berry** » Thu Sep 03, 2009 1:32 am

In my view, no -- because DV/AVI only has one set of properties (apart from Type 1 and 2 distinctions); and is, moreover, largely lossless.

Trevor Andrew · Post by **Trevor Andrew** » Thu Sep 03, 2009 11:26 am

Hi

and I don¡¦t think the quality slider is available when using DV-Avi files

eclipse · Post by **eclipse** » Thu Sep 03, 2009 1:47 pm

Ken -- thanks. That is comforting, although the "in my view" equivocation is a bit disconcerting. Is there a way to know for sure?

Trevor -- are we talking about the same setting? I didn't see a quality slider for the resampling setting, only choices of good, better and best. I am not referring to the quality slider for compression that has quality on one end and speed on the other.

Also, I used to have a pdf of the full (200+) page manual for VS9, but can no longer find it online. Is it still available?

Trevor Andrew · Post by **Trevor Andrew** » Thu Sep 03, 2009 3:52 pm

Hi eclipse

Sorry for that, I had assumed the quality /speed slider.

To be honest I don¡¦t really know what the Good, Best and Better choices are referring to.
But I wouldn¡¦t have thought this setting had any bearing on the rendering quality?
More likely the preview playback quality, but I just don¡¦t know.

VS 9 Manual

Patches and Updates
http://www.corel.com/servlet/Satellite/ ... 7911963266

Follow the link for VS 9.0
Manual should be at bottom of Pdf list.

If you cannot find, give me an e-mail, I have a copy. (218 pages)

eclipse · Post by **eclipse** » Thu Sep 03, 2009 8:15 pm

Thanks for the link. The manual has this to say about the resampling setting: "Resampling quality: Specifies the quality for all effects and clips. A higher quality results in better video reproduction but takes longer to render. Choose Best if you are preparing for final output. Choose Good for fastest operation." Unfortunately, it does not answer the question as to whether it affects the saved video file under the conditions described in my first post, but it does suggest that it affects something other than still images and more than just the preview window.

Post by **Ken Berry** » Thu Sep 03, 2009 9:55 pm

The "in my view" related to the two qualifications I added: the Type 1 and 2 distinction would not affect the quality of the video. Type 2 DV captures the video and audio in two separate channels but in the one single stream. Type 1 captures video and audio as a single channel and stream. But the properties for both are the same.

The real qualification is the fact that DV is "virtually" lossless. As you would be aware, DV is a compressed format, about five times compressed from 'raw' AVI. (Raw AVI runs to about 65 GB per hour, while DV takes up 13 GB per hour.) Now any compression involves a little loss in quality, but this varies according to the algorithms used for the codecs. With mpeg, the loss is comparatively large and cumulative from render to render, though the human eye might only begin to perceive it after two or three renders. However, there are tests which indicate there are real losses after just one render. But with DV, the loss is minute and will not be perceived by the human eye until it has been rendered many more times than is conceivable in a normal editing project.

And heck, I am a lawyer and we congenitally never say an outright 'yes' or 'no' to anything!!

eclipse · Post by **eclipse** » Wed Sep 09, 2009 3:20 am

Just for kicks, I took a short DV clip and saved the video file twice (using "same as project settings" and with no edits whatsoever), once with the resampling quality setting on "better" and the other with it set to "best." I timed both, and with it set to "best" it took substantially longer (40sec vs. 25sec.). I really need to get a definitive answer on this, because I saved over 20 hours of home videos for archival purposes using the "better" setting. If the "best" setting makes a perceptible difference, I am willing to redo it all. But obviously I don't want to do this if it's a waste of time. Again, I do not understand what resampling quality means in the context of simply re-saving a DV video to which nothing has been done other than chopping it into scenes, trimming out a bit of garbage, and adding transitions between the scenes. But clearly the disparity in rendering time means something is different.

Black Lab · Post by **Black Lab** » Wed Sep 09, 2009 3:37 am

If the "best" setting makes a perceptible difference, I am willing to redo it all.

So does it? You only mention the time difference, not the quality. If time matters, and the quality is close or no different, then I would think Better would be best.

eclipse · Post by **eclipse** » Wed Sep 09, 2009 3:56 am

Well, my untrained eyes can't really tell a difference on a monitor. But there might be a difference that is in fact subtle and perceptible. And time isn't an issue -- preserving the original video in the best quality possible is the objective. If it takes longer, so be it. And I'm curious -- if the test clip is being re-saved same as project settings with no changes whatsoever, what exactly is happening during the 25 or 40 seconds that it is rendering?

Black Lab · Post by **Black Lab** » Wed Sep 09, 2009 12:57 pm

Then if time is not an issue I don't know what all the fuss is about. Set it to Best and get to work.

eclipse · Post by **eclipse** » Wed Sep 09, 2009 4:17 pm

What I meant was that rendering time isn't an issue. I have over 20 hours of analog video that has been converted to DV, edited on VS and then saved as DV, with the resampling quality set to "better." The time issue is that I don't have to do all that over (which would require recapturing the analog video) if it isn't worth it. I guess what really I'm looking for is information as to precisely what this setting does. Based on some reading on resampling in the jpeg context, I have a hunch that it may relate to when there is a change in resolution when saving the video file (e.g. going from 352 x 480 to 720 x 480), but I don't know this. Even if that were the case, there is no change in resolution when rendering since the file I'm working with is 720 x 480 and is being saved as 720 x 480. Yet, as mentioned earlier it still took 25 or 40 seconds to render a 2 minute clip that had no edits, so something is going on during that period.

Black Lab · Post by **Black Lab** » Wed Sep 09, 2009 5:05 pm

Well I guess what you need to do is take one of those tapes that you already converted using "Better" and do another conversion using "Best". Then you are comparing apples to apples. You have the final say as to whether the quality is any different. If it is not, then your work is done. If it is, then you have to decide if it is worth the time and effort to re-convert.