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Old March 7th, 2005, 07:12 AM   #1
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Is anyone aware that the Panasonic AJ-HD1200A deck (the DVCPROHD deck everyone uses to get footage into FCP) COMPRESSES the video that goes out the firewire port? 24p DVCPROHD 720p video is only 5.6mb/sec (less than double that of DV)

Here's a screencap from Quicktime (video is from a Panasonic-provided AccessHD DVDROM that is chock full of DVCPROHD video and a FCP project)
http://www.ultimind.net/dvcprohd.jpg

Another "gotcha" about DVCPROHD is that, in camera, Panasonic HD cameras are recording 960x720 to tape...NOT 1280x720. Refer to Andrew Balis' "Working With Panasonic HD and Final Cut Pro HD" article on Kenstone.net
http://www.kenstone.net/fcp_homepage...low_balis.html

So the combination of recording 960x720 internally to tape (being stretched to 1280x720 on output), 5.6mb/sec data rate, and the DVCPROHD codec all point to this new HDX100 EASILY being able to record to MiniDV tape with the DVCPROHD codec. Roughly 40minutes on a 60min DV tape.

I think 60p at the same datarate would be pushing it quality-wise, but 30p doesn't sound out of the question...perhaps 30min recording at 30p and 40min at 24p?
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Old March 7th, 2005, 07:49 AM   #2
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The AJ1200 deck doesn't add any extra compression on firewire output. DVCProHD is always 100mbs, but on capture, you can remove the extra frames that it records to embed the 24 frames in the 60 frames it always records, leaving you with 40mbits of data a second rather than 100mbits.

Yes, the DVCProHD Varicam records 960x720, just like HDCAM records 144x1080 instead of 1920x1080.

The end results look very nice though - it's a combination of compromises just like any other camera out there.

Can you push DV tape to record >25mbits without errors or issues? Don't know. But it seems that tape is dead anyway....

Graeme
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Old March 8th, 2005, 05:58 AM   #3
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<<<-- Originally posted by David Valencic :

So the combination of recording 960x720 internally to tape (being stretched to 1280x720 on output), 5.6mb/sec data rate, and the DVCPROHD codec all point to this new HDX100 EASILY being able to record to MiniDV tape with the DVCPROHD codec. Roughly 40minutes on a 60min DV tape. >>

But several things about his argument that you have not taken into consideration.

1. It takes 16 record heads working in pairs to record and DVCPROHD signal. They cost $800 per pair.

2. To record DVCPROHD on a metal evaporated tape would not be within the SMPTE standard. The DVCPRO formats are on Metal Particle tape.

3. Lastly if we dealt with the first two issues and did the recording on mini-DV, a 1 hour DV tape would be 15 minutes.

Those three arguments, rule out the mini-DV as being a viable way to record the DVCPROHD signal.

Hope that helps,

Jan
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Old March 8th, 2005, 02:43 PM   #4
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By the way, just for clarification:

"24p DVCPROHD 720p video is only 5.6mb/sec (less than double that of DV)"


That should actually be 5.6MB (megabytes, not megabits) per second. A small detail I know, but just didn't want anyone getting confused.
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Old March 8th, 2005, 03:18 PM   #5
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David,

How exactly is an anamorphic recording a "gotcha"?
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Old March 8th, 2005, 03:30 PM   #6
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Considering full-frame HD specifications call for square-pixels with a 16:9 AR- thus a frame size of either 1280x720 or 1920x1080 - I would take the anamorphic pixel AR's of DVCPRO HD as a definite, albeit understandable, "gotcha".
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Old March 8th, 2005, 05:07 PM   #7
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... and yet, just about every format that records HD employs the same "gotcha" -- HDCAM records at 1440x1080, HDV records 1440x1080... so why is it a "gotcha"?
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Old March 8th, 2005, 05:17 PM   #8
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I guess I'll have to go re-read my white papers now that I've learn how the Varicam deceived me.

But first, I have to go call the director of the last film I shot and tell him that he's been duped.

All joking aside, these cameras do deliver full frame 1280x720 and 1920x1080 HD. They are just recording it anamorphicly. Just like a DSR500 or any other currently available native 16/9 digital camera.

I don't understand the shock and feelings of deceit that is usually expressed when people discover this.
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Old March 8th, 2005, 05:35 PM   #9
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<<<-- Originally posted by Barry Green : ... and yet, just about every format that records HD employs the same "gotcha" -- HDCAM records at 1440x1080, HDV records 1440x1080... so why is it a "gotcha"? -->>>

My reasoning for this being that a certain amount of up-sampling will be involved when displaying DVCPRO HD at full-frame HD resolutions, which invariably degrades the quality. Conversely, when recording from the Varicam or Cinealta directly through the SDI outputs, you are indeed getting the full frame.
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Old March 8th, 2005, 07:41 PM   #10
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Yes, but that same amount of upsampling happens with HDCAM and with HDV and with just about every method of recording HD that I can think of. Record to tape on a $100,000 F900 CineAlta and it'll do the same thing.

So why single out DVCPRO-HD? They all do it.
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Old March 8th, 2005, 07:52 PM   #11
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<<<-- Originally posted by Barry Green : Yes, but that same amount of upsampling happens with HDCAM and with HDV and with just about every method of recording HD that I can think of. -->>>

The direct-to-disk systems such as the Viper do not upsample, and neither does the Ikegami camera which records directly to the DNxHD format.

<<<-- So why single out DVCPRO-HD? They all do it. -->>>

I wasn't singling it out, as it's the only format we are currently discussing in this thread. It's a necessary evil of the codec, and I deem it mentionable because DVCPRO HD's upsampling is the most significant compared to the other formats.
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Old March 8th, 2005, 08:38 PM   #12
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Upsampling? Hmmm.

If I shot 35mm with an anamorphic lens, and then projected that film through a lens stretching it back out to the proper geometry, would that be upsampling?

If we're going to get picky about square pixels, the Viper is a bad camera to bring up. The Viper groups pixels together to get different aspect ratios... Up to 5 pixels grouped together for some aspect ratios! Does that count as conforming to the "square pixel HD specifications"?
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Old March 8th, 2005, 08:53 PM   #13
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<<<-- Originally posted by Brad Abrahams : <<<-- Originally posted by Barry Green : Yes, but that same amount of upsampling happens with HDCAM and with HDV and with just about every method of recording HD that I can think of. -->>>

The direct-to-disk systems such as the Viper do not upsample, and neither does the Ikegami camera which records directly to the DNxHD format.

What is the DNxHD format camera? You have lost me here. And what is the cost of that camera?


<<<-- So why single out DVCPRO-HD? They all do it. -->>>

I wasn't singling it out, as it's the only format we are currently discussing in this thread. It's a necessary evil of the codec,

If it is the "evil" if you call it that, but but I feel that it is better termed a compromise, known by both parts and we agree.

Best,

Jan
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Old March 8th, 2005, 09:06 PM   #14
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<<<-- Originally posted by Jon Fordham :If I shot 35mm with an anamorphic lens, and then projected that film through a lens stretching it back out to the proper geometry, would that be upsampling?>>>

As I'm sure you're aware, film is a completely different beast. In this thread we're discussing digital, where every pixel counts. Any way you slice it, a 33% loss of horizontal pixels is worth mentioning.

<<<--The Viper groups pixels together to get different aspect ratios... Up to 5 pixels grouped together for some aspect ratios! Does that count as conforming to the "square pixel HD specifications"?--->

I'm aware of some of the funkier pixel arrangements in the Viper Cam, but if you read through the white papers, you'd realize that when dealing with the native 16:9 AR you are not losing any horizontal resolution.
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Old March 8th, 2005, 09:11 PM   #15
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<<<--What is the DNxHD format camera? You have lost me here. And what is the cost of that camera? -->>>

Press release for the DNxHD camera here:

http://www.ikegami.com/Avid_NLTek.html

"Chief among these products is the new Editcam HD camcorder, the recording section of which utilizes the Avid DNxHD high-quality mastering codec to deliver HD resolution, full-raster (1920 by 1080) images..."

<<<--If it is the "evil" if you call it that, but but I feel that it is better termed a compromise, known by both parts and we agree. -->>>

I agree it is necessary, and fully understand why it is necessary, however it does not negate the reservations I have for the format.
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