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720/24p @ 59.94 to 29.97 Downcovert Image Stutter
I’m editing DVCPROHD 720/24p in 59.94 and downconverting to Betacam 10bit Uncompressed in 29.97 keeping the image letterboxed in 4X3. The problem I’m having is that the image stutter is increasing after the downconvert to the point it’s a problem on all pans and tilts. The method I’m using to downconvert is . . . . Exporting the project as a quicktime file in 720/59.94 then importing the file into a new 10 bit uncompressed time line and rendering the file. This method works to maintain the letterbox and allows me to output to my Betcam deck, but increases this motion artifact on the pans/tilts. I’m using a AJA IO. Does anyone have any ideas about how I can minimize the stutter or do I have to reshoot these scenes in 60p?
Bill Paris
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7 Replies
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Betacam SP is not 10 bit so why even do this?
Were you referring to digi betacam instead?
Tony Salgado
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Tony,
The AJA IO has a US BETACAM NTSC 10bit Codec which is what I’m using on all my SD Projects.
Bill Paris
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Don’t listen to Tony, he’s busting your chops. Work in 10 bit if you want to, the only thing you’ll lose is drive space. People will argue with you until the cows come home about how there’s no technical advantage, but if that’s your method, stick with it. It’s like people saying it’s silly to shoot and post in HD when all you need is an SD master. I disagree. When you start with more information, you will get more information on the output.
Your method of downconverting is not really downconverting. You are using quicktime to do a some sort of rescale and frame interpolation. you should really use hardware to do a proper downconvert in real time. A kona 2 or 3 card, or a KOna LH or LHe card will do this in hardware, in real time with great quality. You do not need to reshoot. You said the you are working 720p24 in 59.94 anyway. That means you are working in 60p.
Hope this helps.
Jeremy
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Jeremy,
Thanks for the information and the insights into the problem I’m encountering. I’ll purchase a Kona Card asap, in the meantime I went ahead and re-shot the images (Artists Paintings) using a faster frame rate (60p vs 24p) in the camera (HVX200). As a short term solution I’ll use Quicktime to get the project out on tape, but re-output when I get the card installed. Thanks again for your help!
Bill Paris
ps. Regarding 10 bit vs 8 bit I obviously agree with you.
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I’m having a similar issue downconverting some fast-motion sports video shot at 720p 60p to beta SP using a Kona LH.
Can someone post a quick workflow for doing this that eliminates the stutter? I’m doing an easy setup in FCP using NTSC uncompressed 8 bit, puitting the 720P clips on that NTSC timeline and rendering.
What should the sequence settings be?.
What does the following really mean? “You said the you are working 720p24 in 59.94 anyway. That means you are working in 60p.” If its a 720p24 clip, how do you work in 59.94?
Thanks for any insight.
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It has to do withe how the image is recorded. It is called 720p24 over 60 in which there are 24 frames recorded with pulldown in a 60p cadence. If you understand how 24p gets recorded into NTSC, it is a very similar process. When you record 24pN (or native) then only the 24 frames get recorded and there is no 60p.
Now, you are not using the downconvert function on your Kona properly. This is a real time function and there’s no rendering needed. What you need to do is start with your 720 sequence. Open the Kona control panel and set your secondary format to 525i29.97. Then select the output you are coming out of (which in your case is probably the analog component output). When you select that output, change the setting from primary (which should be 720p59.94) to secondary (525i29.97). GO back to FCP and hit play. Now your image 720p sequence is being downconverted in real time to your Beta.
Jeremy
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Jeremy,
Thanks! The downconvert to beta looks great- perfectly smooth. Its nice not to have to render- I guess in thinking about it- it makes sense that the Kona board should handle this no problem.
Thanks again
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