Explain "True 480p Progressive Mode"

[Hugh DiMauro]

I am reading the specs for the Z1U which says:

"480p True Progressive Mode for Gorgeous Standard Definition Imagery."

Is that a real progressive mode or pixel shift that Canon does? I thought the Z1U didn't have a progressive scan bone in it's body.

Can somebody tell me if it is true progressive scan?

[Boyd Ostroff]

I'm guessing they achieve this by downsampling the HD image. In other words, if your CCD has at least 960 vertical pixels and shoots at 60i then it's reading 480 pixels into each of the video fields so the camera could average the data from each field and have a 480p image.

[Boyd Ostroff]

BTW, where did you see those specs? I'm looking at the PDF brochure from a couple months ago. There is a table titled "Recording, Playback and Down-conversion modes." They do NOT list 480p as a recording mode, but as a playback/down conversion mode (for both 4:3 and 16:9 BTW).

According to this table, the only way to get 480p is to record in HDV and then output the signal as analog component. The table indicates that firewire, composite and s-video do NOT work in this mode. So basically it would let you connect to a monitor for viewing, or to a capture card that can handle 480p. You would not be able to send the 480p signal via firewire to your NLE directly from the camera.

Or at least that's what this table indicates. Maybe someone with an actual camera can confirm this?

[Rob Lohman]

If they simply toss one field (1080 -> 540) and add some cropping
you get a true progressive signal.

[Luis Caffesse]

It's listed here in Sony's specs for the camera.


Under "Recording Features" it lists:

"Switchable 50i/60i recording in HD and SD to support world markets.
480P true progressive mode for gorgeous standard definition imagery"

But when you look at the "Specifications" page, it only says:

"Scanning system - 1080/60i, 1080/50i (switchable)"


So I would guess that Boyd and Rob are right.
They are probably achieving the 480P by downsampling the HD image.

Could someone tell me if this is actually being laid down to tape, or is it just on output?

Sony has 480P listed under their "recording features," but it wouldn't be the first time
a manufacturer listed some misleading specs.

Just curious.

[Boyd Ostroff]

Sony's brochure is very specific in saying that there is no 480p recording mode, just 480i and 1080i. The progressive output is only available when playing back 1080i recorded footage through the component outputs. Here's the table which explains this from page 5 of their brochure: http://www.greenmist.com/misc/z1.jpg

[Chris Brook]

I think we have a case of "creative/marketeer-itis".

A recording feature is that footage shot can be played back in 480p.

It's times like this I know I did the right thing getting out of advertising !

... or maybe I'm wrong and at NAB they'll demonstrate a firmware update to show it and this is a case of the marketing department getting too quick fingered. But I wouldn't but a one pence bet on it

[Luis Caffesse]

"The progressive output is only available when playing back 1080i recorded footage through the component outputs"

Thanks for the link Boyd.

Now, not to get too geeky...because I know that in the end it doesn't really matter, but just out of curiousity.

Is the 480P that is being downsampled from an HD image equal to a "True" 480P image taken off progressive scan chips?

Like I said, I'm just curious from a technical standpoint.
I know that in the end it's the perception that matters.

[Rob Lohman]

Let's turn this around. If you shoot 1080i, capture that you can
downsample this yourself (in the computer) to 480p, or better
yet you get:

720 x 540 PROGRESSIVE at the original pixel aspect ratio, OR
960 x 540 PROGRESSIVE at 1.0 pixel aspect ratio

Both are still in 16:9 screen aspect ratio