HDV to SD vs SD specifications.

Laurence wrote on 11/18/2005, 10:45 AM
I've done a number of projects with my VX2000 camera that ended up in SD 16:9 anamorphic DVD format. Now that I have an HDV camera (an HVR-A1), I'm noticing that DVD's in exactly the same format look much sharper. I'm trying to analyse exactly why that is technically. Maybe someone can verify or improve my logic or add insight.

VX2000:

* Shoots 4:3 footage with even and odd lines averaged for an extra 6db of gain.

* Thus 4:3 footage equals 480/2 or 240 lines of vertical resolution.

* Letterboxing and expanding this to a 16:9 format means that these 240 lines of resolution are actually reduced to 180 lines. These 180 lines are interpolated to 480 lines, but this merely fills out the frame and the perceived resolution is still 180 lines.

* VX2000: 500 lines of horizontal resolution.

* VX2000 shoots in a 4:1:1 colorspace. The DVD's mpeg encoding uses a 4:2:0 colorspace. Thus video shot with my VX2000 ends up being viewed on DVD in the lower resolution in the equivalent of 4:1:1: colorspace.

HDR-A1:

* After downrezzing, the converted HDV footage contains 480 unique lines of vertical resolution in the 16:9 aspect ratio.

* Horizontal resolution: 720 lines.

* Colorspace if you render directly to MPEG 2 is 4:2:0.

Thus the actual qualities of footage shot with each camera, when viewed on a SD 16:9 anamorphic DVD are as follows:

VX2000: 500 x 180 with 4:1:1 colorspace

HDR-A1: 720 x 480 with 4:2:0 colorspace

That is a HUGE difference. Am I misconstruing something or are my figures correct?

Comments

Laurence wrote on 11/18/2005, 11:17 AM
Another thing: Since 1080i downrezzed to 60i doesn't have any even/odd line averaging going on, isn't it just as sharp now resolution wise as 24p? In the past I always preferred 24p to 60i because the picture clarity was more important to me than smooth motion. With downrezzed HDV, I find I really like 60i. You get both clarity and smooth motion.