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Re-linking AMA transcoded clips vs. straight imported clips

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Jennifer Jones
Re-linking AMA transcoded clips vs. straight imported clips
on Mar 23, 2012 at 1:42:31 am

Hi guys, this may have been covered earlier, but I couldn't find the answer.

Basically, I'm starting a project for which I have the time to do a straight import of all the (Canon 7D) footage. (We don't start editing for several weeks). We will be editing on two systems, so we'll import (or transcode) on one system, and copy the media (and project) to the second, and re-link.

Initially, I'm inclined to just do a straight import of the 7D .mov(s) rather than transcode, to avoid possible AMA / relink issues.

So, my question is, if I do a straight import (rather than an AMA transcode), will I have difficulty re-linking to the media on the second system once we've copied it over? Or, is the re-linking process the same weather or not you transcode or import.

Grateful for any advice,
Jennifer


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Michael Phillips
Re: Re-linking AMA transcoded clips vs. straight imported clips
on Mar 23, 2012 at 1:54:30 am

Having the bin relink to the imported or transcoded media (DNxHD media) is the same regardless of method. AMA will give you more relink flexibility later such as from sequence. Also, AMA transcode is much faster than import.

Michael

Michael Phillips


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Jennifer Jones
Re: -linking AMA transcoded clips vs. straight imported clips
on Mar 23, 2012 at 12:02:18 pm

Ok. Thanks, Michael.


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Hans Sieber
Re: -linking AMA transcoded clips vs. straight imported clips
on Mar 24, 2012 at 9:05:47 am

I can only second what Michael said. BUT there´s one thing to be aware of. Using AMA on H264 clips results a picture with a gamma shift. If your material is rather light this might not pose a problem, but if your´re working with night shots you`ll be crushing your blacks.
AMA is still under construction...


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Michael Phillips
Re: -linking AMA transcoded clips vs. straight imported clips
on Mar 24, 2012 at 11:21:55 pm

If you see gamma changes it is usually associated with having Perian or other QT codec helper installed that interferes with the decode process. Remove that and things will get more manageable. Also, in v6 (I think 5.5) QT via AMA offers "levels" control. Right click on one or more source clips, then right click and select "source settings" In there you will have 3 options:

Scale to video levels (16-235)
Expand to graphics levels (0-255)
Do nothing

Canon HD-DSLR records in 601 color space full range (0-255). If finishing for broadcast, I would suggest selecting "scale to video levels". You have a histogram available in that window that will let you know what the range is and whether it falls into the 16-235 video levels (the two gray bars). Once you transcode, those levels are baked in to the REC 709 DNxHD codec.


Michael

Michael Phillips


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Jennifer Jones
Re: -linking AMA transcoded clips vs. straight imported clips
on Mar 25, 2012 at 2:18:51 pm

Good to know - Thanks, again.


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Hans Sieber
Re: -linking AMA transcoded clips vs. straight imported clips
on Mar 27, 2012 at 8:48:36 pm

Sorry been on a tough job the last days. Michael I don`t think tha the gamma shift I´m talking about is a result of wrong mapping (full range /video range) nor its perian. I tested this on several systems PC/MAC. On version 2. Adrenaline up to 5.5. I always get the same result. A gamma shift every time I´m using a non Avid or strictly RGB (Animation) codec. I did test this by exporting colour bars qusing a QT container with e.g. H264 codec. Open it with AMA and you`ll get the gamma shift. It´s confusing me for more than 2,5 years...


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Jane wagner
Re: -linking AMA transcoded clips vs. straight imported clips
on Apr 26, 2012 at 2:23:22 pm

Hi Hans,

I would love to know more about the gamma shift. We are starting post on a long form doc. currently shooting with the 7D and wanting to do AMA Link then transcode at a lower resolution for 'offline' then consolidate to a higher resolution for online. But should we do this by importing at a lower resolution then consolidating re importing at the finishing res? Any input would be greatly appreciated. On a related but slightly different note, we are thinking of not doing Raid arrays but going with JBOD for more flexibility with large quantities of media. Any thoughts on this and speed with HD footage?

[Hans Sieber] "A gamma shift every time I´m using a non Avid or strictly RGB (Animation) codec. I did test this by exporting colour bars qusing a QT container with e.g. H264 codec. Open it with AMA and you`ll get the gamma shift. It´s confusing me for more than 2,5 years..."


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Hans Sieber
Re: -linking AMA transcoded clips vs. straight imported clips
on May 3, 2012 at 8:08:04 am

Hi Jane,

been away for some time on a job. So sorry for the delay in answering you. Personally I would import at DNXHD36 for Offline then batch import the locked piece with a online coedc of your liking. AMA changes teh luma values in your H264 QT as I stated in my post. I`ve not found a way around the porblem other than going the import way.
But maybe thats not a problem for you. If your footage is not low level footage you could live with the shift (which also pushes your blacks down). Just do a test import of a clip and then also AMA link it. There you`ll see what is happening. But if you´re shooting with hight contrast or night shots you´ll loose substantial information in your blacks.
Concerning your Raid question I would never do a large project in the JBOD style. You´ll have no backup once a disk crashes. Too risky for my liking. Regarding speed, it depends on the chosen codec. IF you plan to finish in e.g. DNxHD 220 you need serious perfomance. No way to do that with JBOD. For Offline it should work speedwise.

Hope I could be of some assistance.

Cheers
Hans


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Jane wagner
Re: -linking AMA transcoded clips vs. straight imported clips
on May 3, 2012 at 2:14:39 pm

Hi Hans,

Thanks so much for your detailed response. I was thinking of using 0 raid drives, and then cloning them for a back up copy, plus this will give an extra set of media for possible use by the AE. Any thoughts on raid 0? I will do a test with the import vs AMA link.

Best,
Jane


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Hans Sieber
Re: -linking AMA transcoded clips vs. straight imported clips
on May 3, 2012 at 9:46:46 pm

Hi Jane,

I´m not the expert on hardware but if I´m getting you right, you want to create a software Raid 0 inside your machine? And then clone the raid to another raid, presumably Raid 5? Software raids are not nearly as stable as hardware raids. I´ve no experience with such raids concerning stability and performance with large projects. You´ll have a hard time keeping the second set up to date with incoming material. But that´s just a side thought. I would think about getting a professional hardware raid. If you buy a pro Raid you´ll have less hassle in the end. It costs but might save your soul...:)

Cheers Hans


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