Some explain the pixel stuff to me please.

DavidBeier

DavidBeier

Veteran
Ok, I'm aware that the HVX200 actually has 960x540 chips that are pixel shifted to a resolution of 1440x810 which are then converted to either 1920x1080 or 1280x720. Now I just read that the image is actually 960x720 in 720 resolution. What exactly does this mean? Is this the case of all DVCProHD cameras? Is this the case with HDV? How does 960x720 translate into 1280x720 when displayed?
 
The only HD format in common/mass use that records "full raster" is HDV 720p.

HDCAM is nominally 1920x1080, but it downrezzes/subsamples/prefilters to 1440x1080 before recording.

So does HDV: 1920x1080 gets recorded at 1440x1080.

So does DVCPRO-HD: 1920x1080 gets recorded at 1440x1080 (Europe/50Hz) or at 1280x1080 (US/60Hz).

In 720, DVCPRO-HD gets prefiltered from 1280x720 down to 960x720.

The pixels are stored anamorphically and are expected to be expanded back to the full size upon playback.
 
Difference between DVCPROHD 720P and HDV 720P

luma 960*720 (691 200) vs 1280*720 (921 600)
chroma 480*720 (345 600) vs 640*360 (230 400)
 
Barry_Green said:
In 720, DVCPRO-HD gets prefiltered from 1280x720 down to 960x720.

The pixels are stored anamorphically and are expected to be expanded back to the full size upon playback.
Click to expand...

I think I have a fair understanding of pixel aspect ratios... Those pixels can think they're whatever shape they want to be, but at the end of the day you have 960 pixels of horizontal information that is saved. You can't have more because that's the literal size of the image. You can force them square and they'll "appear" to be 1280, but you haven't gained resolution, just stretched it out to make the image look correct. ...am I wrong on that part...?
 
Just remember that the quality of the image isn't only resolution. In HDV you get 1280x720, but in DVCPROHD you have to stretch the 960x720 to 1280x720 in post. BUT... in HDV you've got 4:1:1 color and in DVCPROHD you've got 4:2:2 color. So... one third less horizontal resolution but double the color.
 
andy_starbuck said:
Just remember that the quality of the image isn't only resolution. In HDV you get 1280x720, but in DVCPROHD you have to stretch the 960x720 to 1280x720 in post. BUT... in HDV you've got 4:1:1 color and in DVCPROHD you've got 4:2:2 color. So... one third less horizontal resolution but double the color.
Click to expand...

Don´t like to splitt hair but its actually just 50% more color due to that chroma is based on the luma and because the luma is greater on HDV we end up with more chroma thanks to that.
 
Ryan_W said:
I think I have a fair understanding of pixel aspect ratios... Those pixels can think they're whatever shape they want to be, but at the end of the day you have 960 pixels of horizontal information that is saved. You can't have more because that's the literal size of the image. You can force them square and they'll "appear" to be 1280, but you haven't gained resolution, just stretched it out to make the image look correct. ...am I wrong on that part...?
Click to expand...

So something shot with the same CCDs, same lense, ect, in DVCProHD is going to look blurrier or have less detail than the exact same thing put on an HDV tape? Once again, out of curiosity, why does DVCProHD, supposedly a superior recording medium with much less compression, do this?

Does the Varicam or Cinealta also compress the pixels like the HVX200 in 720p?
 
The Varicam uses the same format so yes.

HDCAM shoots in 1080P With 1440*1080 and chroma 480*1080 (3:1:1)

HDCAM SR Shoots 1080P with 1920*1080 and chroma 1920*1080 (4:4:4)
 
Isnt 3:1:1 a misnomer - color space is relative to itself, not to full resolution so 3:1:1 means for every color pixel there is 3 lumas - thats not correct - its still 4:1:1
 
Well if thats the case then NTSC DV in WideScreen would just be 5:1:1.

The color is relative to the luma, not the pixel aspect ratio.
 
HDCAM *is* 3:1:1. 480 chroma samples per line, 1440 luma samples per line, one chroma sample for every three luma samples.

It's not a case of the "3" meaning 3/4 luma sampling, although there are those who will argue that point. It's a case of that HDCAM (and, near as I can tell, only HDCAM) uses actual 3:1:1, which is exactly halfway between 4:1:1 and 4:2:2.
 
Well, it's a weird situation because in the end all formats will output in either 1280x720 or 1920x1080, so absolute color resolution is of cause relative to these 2 output format and not the internal pixel format.
But thats not what the X:X:X is about, it's all about the internals.
 
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