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Canon XL H Series HDV Camcorders
Canon XL H1S (with SDI), Canon XL H1A (without SDI). Also XL H1.


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Old September 23rd, 2005, 08:07 AM   #1
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24F cadence... any clues?

Given that the 24F is supposed to be better tha the Z1's CF24, how will it be encoded to the 60i stream.

Will there be a 2:3:3:2 cedence in addition to 2:3, or will it be output as a true 24 fps file?

I wonder because I got the feeling that the Z1's attempt to do create a 2:3 cadence caused compression artefacts. I got the feeling that jumping between interlaced and un-interlaced frames within a 15 frame GOP pushed the codec a little.

Dylan.
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Old September 23rd, 2005, 08:20 AM   #2
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Hi Dylan,

I scrolled through the XL H1 menu options last week pretty thoroughly. Indeed there is an option to select 2:3 or 2:3:3:2 for 24F. Keep in mind those were pre-production MT samples though.
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Old September 23rd, 2005, 08:35 AM   #3
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the 2:3:3:2 cadence is good news, though I'm still concerned. I did get the feeling that having one interlaced frame would sort of reverberate through the compression GOP - it seems to on the Z1.
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Old September 23rd, 2005, 09:52 AM   #4
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Quote:
I got the feeling that jumping between interlaced and un-interlaced frames within a 15 frame GOP pushed the codec a little.
According to David Newman - who has the best technical understanding of the HDV MPEG-2 GOP compression I know of - the FX1/Z1U is always "flagged" as an interlaced stream - regardless as to whether the data is progressive or something else.

I've never noticed any obvious compression artifacting in CF24 footage above what I would experience with CF30 or 60i.

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Old September 23rd, 2005, 11:02 AM   #5
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Yes, I'm surprize the camera offers 2:3:3:2 as is doesn't need it for HDV. Although it may have marketing value as many do assume incorrectly that it will impact compression quality. However 2:3:3:2 will be handle to support the DV mode, which is helped by this field structure.
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