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Old May 6th, 2010, 09:19 AM   #1
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can someone please explain these recording specs?

These are specs for the HPX-170: 1080/60i (30p over 60i, 24p over 60i, 24pA over 60i)

I don't understand what "30p over 60i" or "24p over 60i" means.

thanks!
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Old May 6th, 2010, 09:44 AM   #2
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Hi Dina:

It's a bit complicated to understand but it all goes back to the codec. DVCPRO HD uses 1080 60i as a transport stream for all variations of 1080. In other words, the camera is photographing and imaging a progressive signal and flagging the appropriate frames for 24p, 24pA and 30P but but those progressive images are recorded within a 1080i stream.

It is very similar to how the DVX100 works. The DVX100 is an NTSC/PAL camera, correct? So how does it record in 24p or 30p in an interlaced format like NTSC or PAL? Simple, it images and records progressive signals into a 480i interlaced NTSC output. You then use various software methods if you need to extract a true progressive only stream like Cinema Tools in FCS. But as far as the look, which is generally what most people are concerned with, the footage looks progressive, even while playing back in an interlaced NTSC/PAL stream.

With the 170, if you record 1080 30p, you just use it by editing the 60i. If you shoot 24p, you can use Cinema Tools or the DVCPRO HD frame removal feature in FCP or something similar to it if you don't use FCP to remove the extra frames. The smart format to shoot, in my opinion, is 1080 24pA. If you shoot this format, the frames to be removed are already flagged and FCP will remove them upon log and transfer so you end up with 1080 24p without any further processing necessary. I shot a film last year with the AG-HPX170 using 1080 24pA. It was exhibited in the IMAX Theater in Copenhagen through a 4K data projector and it looked great, very cinematic even though 1080 is low resolution for an IMAX venue.

All of this is a bit confusing if you are not technical and has led to a lot of people saying over the years that the DVCPRO HD cameras don't record true progressive, which is incorrect. But a lot of this is also legacy from the DVCPRO HD codec, which, while still a very good and effective codec, it outdated and has been surpassed by AVC INTRA.

Last edited by Dan Brockett; May 6th, 2010 at 10:29 AM.
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Old May 6th, 2010, 10:11 AM   #3
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...and to add to Dan's excellent explanation,

There are some configurations where the camera images a certain frame rate and progressive, but the system of transmitting the material has certain limitations. HDcam's data rate and frame protocol were developed so that existing facilities could use the serial digital infrastructure they were using with SD for instance.
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