Resampling - why and when?

Richard Jones wrote on 2/25/2013, 5:20 AM
I see from this and other forums that many (but not all) people recommend disabling resampling when editing (by R Cl on event, choosing Switches and then pressing the button) although Vegas seems to have Smart Resample enabled as a default. I know that resampling is supposed to reconcile frame rates where they differ but, apart from this, am not sure why or when this needs to be enabled/disabled. Your advice will be welcomed (and if it is not so important, why does Sony have it as a default?). .

What prompted this question is that I am editing cine film that has been professionally converted to AVI (PAL 720 x 576) with frames having been interpolated to bring the frame rate to 25fps from the Super 8 rate of 18 fps. When I view these events on my external monitor they look nice and sharp when being reviewed in the Trimmer but become softer when they are transferred to the Timeline. Is this because of resampling or might there be another reason? (by the way, they look OK when the DVD is made).

Richard

Comments

JohnnyRoy wrote on 2/25/2013, 5:45 AM
> "I see from this and other forums that many (but not all) people recommend disabling resampling when editing (by R Cl on event, choosing Switches and then pressing the button) although Vegas seems to have Smart Resample enabled as a default. I know that resampling is supposed to reconcile frame rates where they differ but, apart from this, am not sure why or when this needs to be enabled/disabled."

Way back in the days of DV before HD was invented, Smart Resample was actually "smart". It would almost always work properly. Yes it would reconcile the differences in frame rates. That's what it's meant to do.

Once HD came along and manufacturer started coming out with cameras that shoot 30.0 fps instead of 29.97 fps or 59.94 fps instead of 29.97 fps the trouble started. Blending frames to go from 30.0 fps to 29.97 fps will produce a ghosty mess. In that case it's best to disable resample and slow the playback rate to 0.999. Likewise blending frames to go from 59.94 fps to 29.97 fps produces horrible ghosting. If "smart" resample was really smart, it would see that one is double the other and simply drop every other frame but it's not that smart; probably because the code hasn't been touched since the DV days.

I'm sure lots of editors would like to see a new feature in Vegas Pro 13.0 be improved "smart" resample that was a lot smarter than what we have today.

> " When I view these events on my external monitor they look nice and sharp when being reviewed in the Trimmer but become softer when they are transferred to the Timeline. Is this because of resampling or might there be another reason? (by the way, they look OK when the DVD is made). "

You answered your own question when you said that it looks OK when the DVD is made. Nothing has changed with the footage. The preview uses reduced accuracy to "preview" the footage. If you change your preview setting to Best(Full) you should see the same quality as on your DVD but it might not play back at full frame rates which is why the preview sacrifices a bit of quality to keep the playback up to full.

~jr
farss wrote on 2/25/2013, 6:32 AM
"What prompted this question is that I am editing cine film that has been professionally converted to AVI (PAL 720 x 576) with frames having been interpolated to bring the frame rate to 25fps from the Super 8 rate of 18 fps."

If you want to do a really good job of this look for posts by JohnMeyer or drop him a PM.
Better results can be obtained by going back to the original frames and then using motion estimation to build new frames to give 25fps. Vegas does none of this, you need to delve into Virtual Dub and/or AVISynth.

If you had the original frames i.e. the post house gave you an image sequence, you could use Twixtor with Vegas to do the frame rate conversion although I suspect JM's techniques to be better and they're free...apart from a bit of a learning curve.

Bob.
Richard Jones wrote on 2/25/2013, 7:05 AM
Thank you jr. That's gone a long way to dealing with my concerns. A couple of follow ups if I may:-

1. I'm still working in SD in PAL land at 25fps but I'm guessing that what you say still holds true.

2. It would seem sensible to disable Smart Resample permanently. Am I right? (If so, I'll buy the Vasst utility to apply it to all of the events).

3. As a supplementary, how does the Reduce Interlace Flicker button in the Switches menu affect things? Would it be sensible to engage this as well? And if so permanently or just on occasions (& which ones)?

You were right about the Preview Setting and it did improve things even though I did have it on Best Auto,

Thank you,

Richard
set wrote on 2/25/2013, 7:26 AM
I guess the media you are edited now is already 25 fps piece as the conversion from 18 fps was already done previously, so if your editing is just cutting, no slow motion or fast motion applied, there will be no differences. For perfect condition, you can try Bob's suggestion above.

I ever mishandled the resampling once, using 50P media (avchd2 camcorders), edit in 25p, render in 25P.
As I leave the Resampling ON, ALL 50P frames is condensed in a 25P, resulting the motion a bit blurred. By turning off on this situation, the rendering process will use needed frames for use in 25P project.
Doing speed differences, and applying slow-motion on interlaced footages, better turn ON smart resample, otherwise you will get flicker...

EDIT: #3 : Reduce Interlace Flicker work best on still images...
If you can have preview output through DV device, to TV, try previewing it, with setting BEST-FULL, so the resolution of preview is the same : 720x576. or, make sample render, especially on high-motion scene, so it is easily seen...

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Richard Jones wrote on 2/25/2013, 7:56 AM
Many thanbks to Bob and Setiawan3D.

Yes. John Meyer made some invaluable comments in the two threads I opened somke time back about transferring cine film to video with or without Telecine - he really is brilliant! This said, I think I'm stuck with the transfers I've had made professionally and generally find them excellent.

I see what you are getting at about the Disabling Interlace Flicker for stills or media generated images but what effect does it have, if any, on normal events and would it cause harm or problems to keep this on all the time?

Richard
farss wrote on 2/25/2013, 1:22 PM
"I see what you are getting at about the Disabling Interlace Flicker for stills or media generated images but what effect does it have, if any, on normal events and would it cause harm or problems to keep this on all the time?"

The Reduce Interlace Flicker switch is there to deal with the problem of Interline Twitter. From my experience it is not a smart switch, it seems to apply some form of crude low pass filter (blur) to all media. Interestingly many Vegas users delivering SD NTSC seem to find the outcome acceptable but SD PAL users (including me) find it reduces resolution too much.

Bob.
Chienworks wrote on 2/25/2013, 2:00 PM
I'm pretty sure that Vegas' resampling and flicker have nothing to do with each other. Neither concept affects the other.

Resampling *only* blends adjacent frames together when the frame rates don't match, and turning off only makes Vegas drop/duplicate frames instead of blending. It shouldn't be related to or have any affect on interlacing, deinterlacing, etc.
Richard Jones wrote on 2/26/2013, 5:02 AM
Thank you Bob and Chienworks. It seems that the right option woi;d be to disable Smart Resample and leave Reduce Interlace Flicker at its default of off. . Do you agree?

Richard
Andy_L wrote on 2/26/2013, 9:47 AM
Can we agree that it's basically never a good idea to let Vegas resample? As others point out, there are other tools that do a much much better job when frame rate conversion is needed, and when it's not needed, Vegas still tries to resample by default in many cases.

It's not a feature: it's a bug.
wwjd wrote on 2/26/2013, 10:14 AM
I don't know the tech side, but whenever I forget to turn it off, it makes a smeary mess of everything. It is the ONE big thing I don't like about Vegas. I mean, how easy it would be to just have it default to off, or give us the option in preferences to change it.
Leaving it on, and wrecking most everyone's renders? In a VIDEO program??? HELLO Programmers?
Chienworks wrote on 2/26/2013, 11:54 AM
Well, i would think that *MOST* of the time, people aren't changing the frame rate. The have projects in which the source, project, and output all have the same frame rate. In that case, Vegas doesn't bother resampling. That you have projects that require it is rare in the overall scheme of Vegas usage.
amendegw wrote on 2/26/2013, 12:03 PM
Here's a thread from about a year ago that might shed some light on this subject: Whither Smart Resample

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farss wrote on 2/26/2013, 12:15 PM
"It seems that the right option woi;d be to disable Smart Resample and leave Reduce Interlace Flicker at its default of off. . Do you agree?"

I've very rarely needed to change the defaults Vegas uses.
As all my footage is 25fps and I'm deliver 25fps then Smart Resample is smart enough to do nothing.
Reduce Interlace Flicker by default is Off and I always leave it that way

Bob.