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Posted by Frank on 10/05/06 11:38
On Sat, 28 Jan 2006 08:58:51 -0500, in 'rec.video.production',
in article <Re: HDV capture on under-powered PC>,
Ty Ford <tyreeford@comcast.net> wrote:
>On Sat, 28 Jan 2006 01:06:36 -0500, Frank wrote
>(in article <ed0mt1lmmbls31cmnejgrauvr5gl2nm413@4ax.com>):
>
>> Yes, 25 Mbps in the case of 1080i HDV. 720p HDV is 19.7 Mbps, however.
>
>Hi Frank,
Hello Ty. I frequently read your articles on iCOM Mag.
>Thanks for the math lesson! :)
Just trying to be accurate. We don't want to mislead the newbies, not
to mention that Google Groups will archive this stuff for the next
four-thousand years. :)
>When you're talking about HDV at 19.7 Mbps, is that an HDV camera shooting in
>DV mode or in HDV mode?
I was referring to an HDV (High Definition Video) camcorder shooting
in HDV mode, although all existing HDV products also support DV
(Digital Video) mode.
>I thought 720 was DV and not HDV.
Sounds like you're thinking of, for example, NTSC DV or NTSC
DVD-Video, both of which have a frame size of 720 pixels wide by 480
lines high.
The HDV format comes in two very different and distinct flavors, for
lack of a better word, known as HDV1 (or HD1) and HDV2 (or HD2).
HDV1, which is employed by all JVC HDV products, has a
display/presentation frame size of 1280 pixels wide by 720 lines
(pixels) high. These frames are acquired and displayed progressively,
hence the use of the term 720p to describe the HDV1 format. For
acquisition purposes, the HDV1 format has a frame size of 1280 x 720.
The HDV1 format is therefore described as using square pixels.
HDV2, as employed by all Sony and Canon HDV products, has a
display/presentation frame size of 1920 pixels wide by 1080 lines
(pixels) high. These frames are acquired and displayed interlaced with
two fields per frame, hence the use of the term 1080i to describe the
HDV2 format. For acquisition purposes, the HDV2 format has a frame
size of 1440 x 1080. The HDV2 format is therefore described as using
non-square pixels.
The ATSC (Advanced Television Systems Committee) has defined a large
number of High Definition TeleVision (HDTV) formats but, fortunately
for all of us, only two are in common use - 720p and 1080i - which
dovetails nicely with the two different flavors (or sub-formats, if
you prefer that term) of HDV.
720p HDV, because of its smaller frame size, only requires a data
transfer rate of approximately 19.7 Mbps (mega bits per second).
1080i HDV, with its larger frame size, requires a higher data rate of
approximately 25 Mbps (mega bits per second), similar to the DV
format.
NTSC DV would be classified as a 480i format.
The numbers - 480, 720, and 1080 - refer to the number of scan lines,
not to the number of pixels (picture elements) per scan line.
>Confused in Baltimore,
No reason to be confused in Baltimore, which many years ago I used to
frequently pass through in a tunnel on the drive from Newark, NJ to
either Washington, DC or Rockville, MD. I never really got to see very
much of Baltimore itself, aside from that tunnel. :)
>Ty Ford
Regards,
--
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/
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