Sunday, August 3, 2014

Re: [Avid-L2] Is there a new BlackMagic Desktop Video Driver that eliminates the 1 Frame offset on Digital Cut?

 

In looking at the template for Model    SRW-5500 there is already a line for:

SBVStartFieldOffset    1

Do I leave this line in the text file as well? 

Is it possible to duplicate the existing .txt file and change the model name from SRW-5500 to something like SRW-5500BM to distinguish it from the normal template that works correctly with the nitrisdx? 

Does the parameter you mention changing allow for negative numbers as well if I wanted to tweak something the other way.

Is this parameter changing the relationship of the actual timeline rolling relative to the edit strobe sent to the SR deck?  My concern is that now the deck edits on the correct field it's the timeline rolling that appears to be off.  It sounds like this tweak will accomplish the desired result.  I'll try it tomorrow.



---In Avid-L2@yahoogroups.com, <bogdan_grigorescu@...> wrote :

Go to: /Applications/Avid Media Composer/SupportingFiles/Machine_Templates  
add the following line to the template : SBVSTARTFRAMESOFFSET 1 

cheers,
BG
Finalé Editworks | Post Production Facility in Vancouver, Canada





From: "John Moore bigfish@... [Avid-L2]" <Avid-L2@yahoogroups.com>
To: Avid L2 <Avid-L2@yahoogroups.com>
Sent: Saturday, August 2, 2014 7:44 PM
Subject: [Avid-L2] Is there a new BlackMagic Desktop Video Driver that eliminates the 1 Frame offset on Digital Cut?

 
I know I've read here that there is a bug with Blackmagic's Video Desktop Driver for their cards when used with Avid.  I have an SRW-5500 and after using my Nitris DX I decided to test my BlackMagic SDI card that I purchased for Resolve.  It is outputting a Frame late as has been posted on this forum before.  In my case I'm using a Keyspan, the older model, that is frame accurate with my Nitris DX on my MacPro 12Core OS 10.8.5 SNDX V6.5.4.  Because it is outputting a frame late an insert edit starts with a frame of black.  This info was mentioned in earlier threads.  I have to find another vtr cable to try controlling the deck through the blackmagic card's RS-422 port to see if that is any different.  I doubt it will be.  I'm on BlackMagic Video Desktop 9.7.7.  I will check there site to see if there are any revisions that may correct the issue.

It seems to me given this behavior it is very similar to FCP 7 with a Kona 3 and being set to Sony preset A which rolled the timeline 1 frame late.  Given I'm using a Keyspan that is frame accurate with the NitrisDX but a frame late with the BlackMagic SDI card as the output I think it's logical to assume that the BlackMagic card is buffering the Avid output by a Frame.  Thus the timeline is actually rolling at the right time relative to the SRW-5500 going into record the Blackmagic card is causing a 1 frame delay of the output signal so the black frame avid holds on output until it rolls the timeline is caught in the BM SDI cards frame buffer/processing when the vtr actually goes into record thereby accounting for the black frame at the insert edit point. 

How can anybody work this way with Avid products.  I haven't checked capture frame accuracy yet but that will be my next step.  Is there any kind of offset setting like aja products offer that I could tweak this.  The Avid timeline needs to roll one frame earlier to account for the video delay the BM card is causing.

I am basing this on my experience with processing delays in other devices and my tests with FCP.  The frame buffering may not be the real issue but it sure acts like a frame buffering.  Given the card looks like it can perhaps do cross converts etc...  I would think it would have to have the whole frame into it's buffer before it could process and converted frame on output but perhaps I'm wrong on that.  It just all seems like a one frame DVE delay happening like the good ole linear days only then the switcher output wasn't black before rolling.
 
John Moore
Barking Trout Productions
Studio City, CA
bigfish@...


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