720 vs. 1080 – HDX900 DVCPRO-HD

[Tom Krohn]

I too, have been under the impression that 720-59.94P would be prefered to shooting 1080-59.94i when using the HDX-900. Recently I’ve been asked to shoot at 1080. My concern is that the clients are expecting 1080P and that the HDX-900 is outputting 1080i.

My question is, when the Camera System is set to 1080-59.94i and the Camera Mode is set to 24P or 30P, am I essentially capturing at 1080P? Or is it still recording and outputting an interlaced signal that may have frames that are made up of non-identical fields(pull-down), and with less vertical resolution(at least where there’s motion in the frame) than material recorded at 720-59.94P?

Any guidance is appreciated.

TK

[John Sharaf]

Tom,

The HDX900 in 1080 mode writes progressive frames at 24, 25 and 30 fps and interlace at 50 and 60, the same as other multispeed 1080 cameras like the Sony F900. I don’t believe you’re offered 59.94/60p in 1080 only in 720. The difference is that it always records at 30 frames/60 fields per second and therefore includes the 3:2 pulldown. The slight advantage to using the 1080 mode, even though it’s a native 720 imager is that the horizontal resolution of the recording is 1440 vs. 960, as both 720 and 1080 suffer some horizontal downrez.

JS

[Tom Krohn]

Thanks John. That helps. To be clear though….

…HDX-900 in System Mode 1080-59.94i and Camera Mode 30P, I’m recording progressively in 1080, and there’s no pulldown per se because it’s 30 progressive frames over what is essentially a 30 frame/60 field system?

But that’s not the same as 1080P. Can 1080P only be achieved by using a camera with a native 1080 imaging device?

And finally, again just to be clear, you think that any loss of vertical resolution in 1080i vs 720p is negligible relative to the increase in horizontal resolution?

Again, thanks!

TK

[Kenny Kato]

I can share what I know and hope this will help.

Let’s go over spec of DVCPRO HD format itself.

DVCPROHD (Some say DVCPRO 100) will prefilters the 720p image from the DSP to a recorded size of 960×720.

and 1080i is prefiltered to 1280×1080 for 59.94i
and 1440×1080 for 50i

To maintain compatibility with HDSDI, DVCPRO HD unsamples during playback.

so, as above, it’s not true 1280×720 or 1920×1080 once it is recorded.

let’s talk about HDX900’s 720 to 1080 process.
resolution upsampling is processed at DPR of camera.
This is before prefiltering of VTR section.

How it is upsampled:
1280×720 -> 1920×540 (Odd Frame)
1280×720 -> 1920×540 (Even Frame)

1280×720(1/60sec)x2 image is sampled to 1920×1080(1/30sec).
time duration is merely few lines and it is virtually undetectable.
This is reason why you’ll get 1920x 1080 from HDSDI out.
Connect to HDCAM-SR and you’ll get best possible image from this camera.

When you set to 1080/30P or 24P, upsampled interlace image will be processed in similar way like Sony’s Psf.

Cheers!

[Nick Teti]

So the Panasonic HDX900 in 1080 mode. Does it output 1920x 1080 out of the HDI-SDI port? Thanks for your help, Nick, mister photon media