You bring up an interesting point about changing codecs. Even with tape I found when I scope the Avid out directly I can run my Tek scope alarms at 0% area setting and not log errors. If I instead I scope the output of the HDCam or HDCamSR deck I have to set the area parameter in the for gamut to 1% or the alarms light up like Christmas time. My understanding is the compression and then subsequent enhancement circuits on the decks cause tiny specular errors that trigger the scope alarms.
You mention changing codecs as causing shat seems to be similar issues. I have found just taking a 23.976 file in dnx220X and other resolutions and adding pulldown will also start the scope flagging errors. IIRC even just doing a mixdown in avid and going into a 59.94 project with the motion adapters added the exact same video essence and codec that played in the 23.976 project without alarm at 0% suddenly shows alarms when the pulldown is being added. I'm not sure why this happens but it does.
Perhaps the motion adapter isn't clean in some form. I do know if I take color bars signal from 23.976 and bring that into a 59.94 project I get jiggy jaggies in the waveform display but if I import the exact same test pattern still while in the 59.94 project the resulting bars are clean of the jiggy jaggies. I assume the same is happening to the video following the same path. If I use Adobe Media Encoder to add the pulldown it the resulting file still seems to display the alarm issues so I don't really know if it's the Avid time warp jiggy jaggies or something in the nature of adding pulldown. For the life of me I don't understand how adding pulldown should change to video in a manner that suddenly triggers the scope alarms for gamut.
---In Avid-L2@yahoogroups.com, <pat@...> wrote :
A proper grade is key to ensuring levels are legal to start with of course. Then avids safe color limiter with 422 selected (no point in legalising with it not working its hardest) but experience shows some content xan still be illegal even with the safe color limiter applied. That then needs manual correction.
The change in codec is often the issue so dnx185x to AVC intra as we need to gor UK deliverables can throw an issue.
We have tge AQC of the final output as a check for Gamut errors and more and an eyeball QC of the final timeline with scopes etc as the human check.
Worth noting that there are alternatives to the safe color limiter that offer more broadcast options like R103 and even soft clippers. Be good if the Avid safe color limiter was upgraded to offer similar options. And even better if it had a mode that could do the limiting so that the codec change to follow was safe as well.
Pat from his mobile.
Posted by: bigfish@pacbell.net
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