I don't have a solution but I've seen issues with speed ramped 23.976 clips in a 59.94 timeline when the offline was done with SD transcodes of the material with an added tape name. It seems even if the original material is 23.976 once a tape name is added when Avid transcodes to SD media it thinks the media came from a tape of the 30 origin, like the traditional telecine workflow before we had 23.976 tape machines. The result is confusion in the motion effect. I would see the time code in the motion effect window that did not match the time code in the timeline. The resulting speed ramps had to be manually adjusted.
I'm not sure this is your issue but it's possible the migration of the FCP timeline into Avid added tape names or somehow confused Avid as to the actual frame rate and time code base of the clips.
Also when the anchor points on the motion effect are not the first frame, which happens a lot when you start slipping clips once they are cut in that can exacerbate this issues in my experience.
I think of it like might have drop frame time code but for some reason in the motion effect it's counting like non drop so the numbers drift off. This is not exactly what happens but it's something like that under the hood.
None of this explains things shifting when rendered but maybe there is some interaction.
---In Avid-L2@yahoogroups.com, <CraigACM@...> wrote :
I've run into some vexing problems with 25i footage in a 23.98 timeline.
We are re-conforming a 90 minute documentary shot in 2006 on three early HD formats: Varicam 720p/23.98; HDV 1080i/25i; and HDV 1080i/59.94. Back then, it was all converted to 23.98 Standard Def Widescreen DVCam and edited in Final Cut. The edited master file is ProResHQ 720x480 Anamorphic 23.98 used to encode for DVDs.
Now we've been asked to re-conform a 1920x1080 version using the original sources. I successfully imported the Final Cut timeline into the Avid (7.0.4.3) and have cut the SD ProRes master file into the sequence as a visual reference for sync. The soundtrack is locked and will not change.
Batch capturing the Varicam was not a problem, but there were timecode shifts in all the HDV footage because of the frame rate conversions. So it was a laborious process to find, capture and line up those shots. My process was to selectively capture HDV via firewire into either a 25i or a 59.94i project. Then, bring those clips into the 1080/23.98 project and eye-ball match to the ProRes reference. Superimposing the ProRes track I was initially pleased at how well Avid's motion effect matched with the original frame rate conversion. In many cases the registration was perfect frame for frame. In other clips, there would only be a few frames each second that drifted out of registration but it was good overall.
Several days later, after working on other areas of the program, the following problems cropped up:
I suddenly realized that all my HDV footage was wildly out of sync with the visual reference – like 6 or 7 frames off. And I was unable to adjust these HDV clips or even move them to a different video track. The HDV clips still showed the green dot motion effect, but timewarp couldn't modify or render them. I couldn't even duplicate the sequence. Each attempt to modify produced an error message: "Tracks have incompatible edit rates." Yet, all the other non-HDV footage behaved normally, and I could even re-cut the same HDV footage into the timeline on other tracks.
Fortunately, I found an earlier version of the sequence that had all the HDV footage in place and that sequence did not present the error. I decided I should immediately do a mixdown of the HDV clips to lock-in the frame rate conversion and make everything an edit-friendly codec.
That's when I discovered that IN MOST CASES, the mixdowns do not match the motion effected HDV clip. They are not in sync – the first frame is usually shifted by one frame. And the rendered motion is blurry, an apparent blending of adjacent frames rather than the clean progressive frames that appear prior to mixdown. BUT… on several clips, the Mixdowns were a perfect match of the original clip with the motion effect, even on shots with a lot a motion in them! What a mind-f**k!!
I've tried several things: rendering the motion effect first; selecting adaptive deinterlace source; and promoting the timewarp to try different combinations of settings/rendering. But they all change the clips for the worse. I tried mixdowns of a sequence of clips and doing each clip individually; I tried starting the mixdowns on different frames to see if there was some magic cadence at work. I've tried transcoding the clips to ProRes but that has the same result (in fact, on the clips that did mixdown correctly, the transcode was not as good). I even discovered that if you copy and paste one of the green dot clips, then render or adjust a setting in Timewarp, and then remove that effect so that it is back to a clip with just a green dot, it will be out of sync with the original clip – the start timecode has shifted.
If anyone has worked through similar problems, would greatly appreciate your input on how to bake-in a decent looking frame rate conversion.
Thanks,
Craig Mikhitarian
ACM Productions, Ltd.
Posted by: bigfish@pacbell.net
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