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Posted by My Name Is Nobody on 11/05/07 18:33
"Frank" <frank@nojunkmail.humanvalues.net> wrote in message
news:2toti3ppffr99of3d354238ccak4icgrmh@4ax.com...
> On Mon, 05 Nov 2007 04:17:33 GMT, in 'rec.video.production',
> in article <Re: Canon HV-20 wins 2007 award as "Best HDV Camcorder">,
> "My Name Is Nobody" <nobody@msn.com> wrote:
>
>>OK so, please explain why an HDV signal is referred to as both 1440x1080
>>and
>>1920x1080? I seem to have missed some distinction.
>
> As explained to you by several others, 1080i HDV (and HDCAM and XDCAM
> HD as well) is stored (written to magnetic tape in HDV and HDCAM or
> burned to optical disc in XDCAM HD) in an anamorphically squeezed,
> non-square pixel, 1440 by 1080 form. At display time, that 1440 by
> 1080 frame is expanded to 1920 by 1080. That's the distinction.
>
> In the case of 1080i HDV, the 1440 by 1080 frame size was chosen so
> that the video data rate could be set the same as DV25 (approximately
> 25 Mbps), thus allowing the use of existing DV tape cassette transport
> mechanisms. This allowed the cost to be kept down, and allowed
> products to come to market sooner.
>
> Storing full-raster 1920 by 1080 frames at a data rate of only 25 Mbps
> would have resulted in the need to compress the video so much that it
> would have visually been unacceptable. As it is, 1080i HDV video
> compression is right on the edge.
>
> The difference between a full-raster, square pixel, 1920 by 1080 frame
> (2,073,600 pixels) and an anamorphically squeezed, non-square pixel,
> 1440 by 1080 frame (1,555,200 pixels) is a 25 percent data reduction.
> It was easier to keep to the 25 Mbps data rate with this 25 percent
> reduction (having 25 percent fewer pixels to compress).
>
> Storing 1440 by 1080 frames, rather than full-raster 1920 by 1080
> frames, results in a quality loss (in terms of horizontal resolution),
> but that's the way it is. Besides, it had already been an accepted way
> of life with the HDCAM format, so a precedent had been set.
>
> If you want full raster (square pixel) HDV, then you must use JVC's
> 720p flavor of HDV, where a full 1280 pixel by 720 pixel frame size is
> stored.
>
> The AVCHD format is different. The format supports both 1920 by 1080
> and 1440 by 1080. Some camcorders implement one and some implement the
> other (and some implement both depending upon the recording mode
> setting you choose), so read the specs carefully if this of concern to
> you.
>
> Also, if you purchase a 1920 by 1080 AVCHD camcorder and plan to edit
> your footage, be certain that the NLE you plan to use supports 1920 by
> 1080 files. Some of the original programs that claimed to support
> AVCHD editing only supported the 1440 by 1080 flavor and not the 1920
> by 1080 flavor. This wasn't a problem in the beginning, when all 1080i
> AVCHD camcorders were storing 1440 by 1080 frames, but now that
> full-raster 1920 by 1080 products are available, it's a consideration.
>
> Non-square pixel digital video formats, whether over-sampled or
> under-sampled, have been with us for some time now. The two most well
> known examples are NTSC DV, over-sampled and stored to tape as 720 by
> 480 frames but displayed at 640 by 480, and PAL DV, which is stored to
> tape as anamorphically squeezed 720 by 576 frames but displayed at 768
> by 576.
>
> --
> Frank, Independent Consultant, New York, NY
> [Please remove 'nojunkmail.' from address to reply via e-mail.]
> Read Frank's thoughts on HDV at http://www.humanvalues.net/hdv/
> (also covers AVCHD and XDCAM EX).
Thank you Frank, This is the "information" I was missing in enough detail
for someone not all ready familiar with it to get the picture.
I bought the HV20, for the camera, not because I was worried about
"full-raster 1920 by 1080", obviously, I didn't know what that was. It was
only after I started very successfully editing/creating 1440x1080 videos
with Sony Vegas Movie Studio Platinum 7.0, then later Adobe Premiere Pro CS3
that I (mistakenly) thought the software wasn't equal to the Camera, and
speaking directly to someone at Canon only reinforced that misunderstanding.
So it has been stuck in my craw ever since, well, until now. :-)
Now I will say, Canon having a "perhaps" full-raster 1920 by 1080 capable
sensor on the HV20 then "down converting" to non-square pixel, 1440 by 1080
format to store only to be expanded "unconverted" back to 1920 by 1080 to
display seems rather silly.
The films are still breathtaking...
Thanks again
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