DV PAL capturing question
 

Hi there,

So, I've got a question that has been bugging me for some time, and having read through lots of forums I can't seem to get to the bottom of it.

When I record my video (on a PD 170P) I record in DVCAM and the aspect ratio is 4:3, right, unless of course I select the 16:9 option. On importing to FCP, I select the DV PAL 48 kHz setting and ensure that my sequence settings are the same. So far, so simple. However, on looking at the details of the capture preset, the frame size is automatically at 720x576 with an aspect ratio of CCIR 601/DV PAL (5:4).

But there is an alternative setting on the drop down menu that gives me the option of CCIR 601 PAL Sq. (4:3) and a frame size of 768x576.

Now, when I keep the original preset 5:4 ratio in the capture settings, it looks fine during play back but when actually capturing the image looks slightly stretched. But, having captured it looks fine in the viewer.

So, although it's not causing me an actual problem right now, I am still entirely confused, and want to get to the bottom of this - should I change the setting to CCIR 601 PAL Sq. (4:3)? Why is the preset 5:4? And why isn't it a problem? Many thanks to anyone who can put my admittedly a little pedantic mind at rest!

Just to be clear: are you shooting NTSC and importing into a PAL timeline? If so that's why things are being "stretched" because there is a slight size difference between the PAL and NTSC standards.

However if you're shooting with a PAL camera then the PAL settings should match.

The answers to questions like this are right at your fingertips; from the FCP6 built-in users manual:

It's just the shape of the pixels in CCIR 601. Nothing to worry about, FCP can handle it.

Hi Robert - I am shooting in PAL, so it's nothing to do with a conversion issue. It's more that I don't understand the significance of CCIR 601 - what is it and why are the pixels different sizes?

Liam - It hasn't been causing me any probs, I'm just puzzled - why is it being sqeezed to 5:4 during capture, but then expanding?

I've noticed that there's an option in FCP in the viewer size drop down that is "Show as square pixels" that is automatically selected. When I untick it, the image becomes 5:4 - squished!

Is there a good reason - tv compatibility or something - that it is captured with the 720x576 CCIR 601 (5:4) not the 4:3 option?

It is a bit acedemic, but still intriguing me.

768x576 is picture defined with square pixel.
it is an obsolete standard, since DV, everything is based on 720x576 with rectangular pixel.
it does not change the way image is displayed (it is still 4:3) as long the pixel ratio is properly set.
today the only other format to have square pixel is 1920x1080 and 1280x720.
all other format PAL DV, NTSC DV, HDV, PAL and NTSC wide screen have rectangular pixel.
this means the actual apparence of the video in a square pixel screen (like your computer) will look wrong (call it anamorphosed) if the player is not correcting it.

Thanks Giroud, that was exactly the answer I was looking for. Is CCIR 601 a reference to the size/type of pixel then? It basically is, or at least defines, the pixel ratio?

Cheers,

Matt.