Weird PTT issue

filmy wrote on 8/29/2003, 7:49 PM

I have somewhat resolved this but I wanted to post to see if anyone else has seen this -

I converted a 30i over to 24p. The conversion went fine, no issues at all. I did one PTT with no problems. While outputting I noticed a few things that I needed to fix, titles and such. So I went back to the "masters" and fixed only those sections. Now one of these was the opening titles - I fixed that section only and re-rendered out at 24p the exact same way I have done everything else.

Now comes the weird part, and for a while extremely frusterating part. I wait the 45 minutes for the audio to re-render out to the *.W64 format. Now when that is done the countdown screen pops up. I hit record on my decks and let 'er rip. About 10 seconds or so into the opening there is a glitch - the picture stutters, audio drops out...sync is lost. It catches up in about another 10 seconds or so. Not acceptable by any means. So I stop and go into the project and double check everything - it is all fine. So I try again. Same thing. I change the location of the pre-render save locations and try again. After another 45 minutes - same bloody thing.

So I try a PPT with just this section - same thing. I try 24p PPT with both 2-3-3-2 and 2-3 and both have the same issue - the glitch occurs at the same spot. So I edit out the audio on the timeline to be sure it isn't that. Keep in mind it was the image that I needed to correct, not the audio, so I still had the orginal audio. So I cut out the orginal audio and put in the audio form the new render. Same glitch, same spot - no change.

After 4 hours of starting to feel VV is "sucking" I come to the conclusion something must be wrong with the file. So I re-render a new version. Now come to today - I take this new version and load it up. I try just the start so I don't have to go through the 45 minute audio renders - and guess what? Same freaking issue. New file but same glitches at the same exact points.

This time I try some other testing methods - I play the file from the media pool. Plays fine. I open the capture mod and load up the new file in that, going out via firewire. I hit play and guess what? File plays perfect. So I open up the file I had tagged as "NG" - it too plays perfect. So now I am seeing this is some sort of PTT/VV Timeline issue that is only affecting this ONE FILE!!!

I went through every setting I could think off for the time line - Resample off, audio settings, temp file settings, field settings. I even opened a new project and loaded just that one clip onto the timeline and did a PTT - every time, no matter what - same glitches, same locations. So I moved the file to another hard drive thinking it might be the hard drive. No change - same issue.

So as a final test I re-rendered the 24p file, rendered using the 2-3 pulldown, using the 2-3-3-2 pulldown. (So it went - 30i > 24p 2-3 > 24p 2-3-3-2) Guess what? File plays perfect now on PTT.

So problem solved - but here is what I just do not get - Every other file in this 70 minute project is rendered at 24p with 2-3 and PTT with 2-3-3-2 and there are no issues at all. So why did this one single file have these problems? Why did this one file have to be rendered out again with 2-3-3-2 in order for it to PTT with no glitches?

(And one final thing before someone starts telling about what the manual says - yes, I read it and yes I did follow what it says. These are final renders, no other editing is being done so per the manual 2-3 for the final product. It also says to use 2-3 for the final PTT when you are finished but I have found if I use the 2-3 setting for PTT it does nothing but glitch, so I have to use the 2-3-3-2 setting. Either way PTT for everything but this one file was fine.)

Comments

filmy wrote on 9/2/2003, 8:47 PM

Well now - the plot thickens. I am doing my PTT. About 20 minutes or so into it a small section looses sync, but only for a few seconds. I let it go just to see. All goes well until about 01:02:00;00 into it - than this happens: interview fine, cut to 'action' loose sync and stutter; interview fine, cut to action loose sync and stutter; interview fine, cut to 'action' loose sync and stutter; and so on. It does this on every single non-interview edit until the end of the film. It did not do this on the first PTT I did. All of these end files have remained the same. Could the 'edited in' fixes at the start cause this? Read on.

So I took one section and tested it - same thing that I first described. So I just cut to the chase with this - Following SoFo's 30i > 24p instructions to a tee. Create a new 24p project. Load up just this problem section. Set Deinterlace to Blend. Disable "resample". Render as 24 (2-3-3-2) and PTT with 24 (2-3). The same scene now looks too "real" with the Blend setting and PTT does not work with a 2-3 setting. All it does is stutter non stop and looses sync. So I test PTT with the 2-3-3-2 and it works fine. This is all from the timeline of VV now, not outputting with anything else. So the bottom line, here are the settings that work best for me look wise: Deinterlace - OFF or NONE. Smart Resample - ON. Now as for the PTT - as I said everything I already rendered at 2-3 plays back fine via the capture mod or from the media pool. I also tried Premiere and WinDV and the files also play back fine. So this is for sure a VV PTT/Timeline issue and for some reason it only affects certian sections and/or scenes. If I render these problem scenes at 2-3-3-2 and also PTT with 2-3-3-2 they work fine. So out of an almost 70 minute film about 2 - 3 minutes worth of material will not play back correctly during a PTT via the VV timeline unless they are re-rendered using the 2-3-3-2 setting. And a PTT with the 24p 2-3 setting never works no matter what. IT just plays like stop motion or a flip card book with no audio.

So what is up? Any thoughts? Comments from SoFo? I think this is somehow an audio issue. Printing back to tape via the capture module, WinDV or Premiere does not force a re-render of audio to the *.w64 format. Doing a PTT from the timeline forces all the audio to re-render. It seems to me that for whatever reason the audio is loosing sync and the picture is trying to slow down to allow the audio to re-sync itself. I say this because the audio, in all cases, stops and then a fraction of a second later the picture starts to slow down until both audio and video lock back up.

vitalforces wrote on 9/2/2003, 9:59 PM

Feel free to disregard this, as I am no expert by any means. But borrowing from a pattern I saw on other posts--what kind of video card do you have, and does it (a) have current drivers, and/or (2) did you uninstall any program lately that might have yanked out part of either your video graphics drivers or your directX?

SonyDennis wrote on 9/3/2003, 9:04 AM

filmy:

If your system can (usually) print 24p to tape using 2-3-3-2 pulldown, but generally can't do it using 2-3 pulldown, I'd say that it's on the hair edge of being able to create pulldown on-the-fly. What speed CPU and hard disks are you using?

A while back, I did a timing test, to see how pulldown method affected performance. 2-3 pulldown is harder to remove while reading, and harder to insert during rendering. On an unoptimized Dell P3/800, here's what I saw:

CPU utilization:

Reading 2-3-3-2 while printing 2-3-3-2: 40%
Reading 2-3 while printing 2-3-3-2: 60%
Reading 2-3-3-2 while printing 2-3: 70%
Reading 2-3 while printing 2-3: 80%. At this point, the output got behind and started dropping frames.

So, you can see it uses a lot more CPU to read and write 2-3 pulldown, and once your machine is past it's limit, your lose sync and drop frames.

2-3-3-2 pulldown should always be used for source media and pre-renders. With the Panasonic AG-DVX100, shoot in "24p Advanced" mode.

2-3 pulldown (because it looks smoother) should always be used for final rendered output only.

I'd recommend rendering your project to 24p DV using 2-3 pulldown, and then use the capture/print tool to print the rendered file to tape. That way, the pulldown is being adding during the render and not during the print. The capture/print utility will see the file as a regular 60i DV file.

///d@

filmy wrote on 9/3/2003, 6:46 PM

Thanks for the response Dennis.

>>>2-3 pulldown (because it looks smoother) should always be used for final rendered output only.<<<

This was the concept I was going on when I rendered everything using 2-3. I wasn't planning on editing anything until I found the few minor issues. Even then I rendered out the fixes using 2-3 because no further work was being done on them. However from the timeline the PTT at 2-3 just has never worked. Only 2-3-3-2. The only reason I have had to re-render anythng with 2-3-3-2 is because it fixes those issues in those sections I mentioned.

So here is a question - why can the rendered 2-3 files play out fine in everything but the timeline? As it is I thought that VV was less CPU intensive than other NLE's and simply placing files onto the timeline and doing nothing to them i would think is not very intensive at all and I would think it is even less intensive for a PTT...I mean other than the rendering of the audio to the *.w64 format. I guess my question is sort of like this - What is the main difference between loading the exact same file(s) onto the VV timeline and loading them into the capture mod for output. (And I mean playback only wise - not editing wise)

I agree with the 2-3 render and output via the capture/print tool because the files do play perfect that way, however, as I mentioned, I had some minor adjustments to do. The thing I still find strange is the fact that output was fine the first time. Making these adjustments seemed to do something and the fact that these errors happen in the exact same spot makes me wonder how it can be a CPU related issue when it is not random - in other words if the stutters and audio drops happened in random sections I would hit myself in the head and say "Doh! CPU issue - makes sense" but because it happens at the exact same spot, even if that file was the only thing on the timeline, it makes me think it is something else and that is why I thought of the audio.