XH-G1/S - HD-SDI 60i output at 24F

[Alex Lafkovici]

Hello,

I have a question about the HD-SDI output of the XH-G1/s cameras when the camera is set to 24F.

So far I've been using the cameras in HD-SDI - 60i mode - with a Panasonic AVHS-300G video switcher - sending the video out live in 60i, and also capturing/recording from the HD-SDI in 60i.

My question is whether I can capture/record in 24F (I will use real-time 2:3 pull-down when capturing) and at the same time send out the video live in 60i?

I've read that when he XH-G1 cameras are set to 24F, the HD-SDI output is still 60i (which is compatible with the AVHS-300G switcher), and that the 24F flag is just carried within the standard 60i signal.

Does this mean that the HD-SDI - 60i - signal is a normal 60i that I can send out live when the camera is in 24F mode -- no frame doubling or anything? -- Then at the same time, I can capture/record this signal in 24F using pull-down?

Sorry if this is an amateurish question -- since I usually film live, I've never gone much into the 24F features of these camera and I'm not very knowledgeable about it. But I'm starting to think that having a 24p recording may simplify creating dvds, bluray, etc.. so I'm wondering if I can pull this off...

Any advice is appreciated, thanks so much,
Alex

[Simon Wood]

If you are using a HD/SDI recorder then you can usually capture the frame rate if it is set up to do so.
I use a Nanoflash, and this records the 25 frame rate through some internal wizardry (even though my camera, an XLH1, outputs 50i through the HD/SDI out).

Presumably some of the newer recorders can do this, though that would have to be confirmed with your specific camera.

Possibly some capture cards could do this too.

[Alex Lafkovici]

Thanks Simon,

I have a capture card which will capture the 24F footage at 24p (using 2:3 pulldown).

What I'm more concerned about is the 60i footage which is going out live -- as is.

Is the 60i coming out from the HD-SDI a true 60i when the camera is set to 24F? -- Or is there frame doubling or other type of stuff going on, making it unwatchable to the viewers which are going to be watching this recording live?

[Simon Wood]

I believe the output of the HD/SDI is 60i no matter which framerate is selected.

[Alex Lafkovici]

Wow.. ok.

I think I may try this workflow out then. Go live with 60i, but record at 24p.. interesting.

One of the pitfalls of recording at 24F will be a reduced resolution -- of about 10% - if I remember Tom Roeper's imatest trial correctly... But it may be worth it just to simplify workflow, avoid the deinterlacing for dvds & all that.

Thanks Simon.

So once the material is captured with the 2:3 pulldown, I'll have the file in 24p? -- I can just drop it on a 24p timeline?

[Simon Wood]

Originally Posted by Alex Lafkovici

So once the material is captured with the 2:3 pulldown, I'll have the file in 24p? -- I can just drop it on a 24p timeline?

You know I'm not sure - I've only worked in PAL land, and 50i to 25f is easier I guess. The Nanoflash spoils me; as it takes all of the thinking out of the equation!

You should run some tests with your capture card with the camera set at 60i and then at 24f and see what the difference would be both with and without the pulldown.

I believe the G1 has embedded flags in the HD/SDI stream which cards like the AJA Kona can read easily.

[Alex Lafkovici]

Thanks Simon -- I just did a trial, and it seems to work.

I do have an Aja Kona capture card -- so that is capturing the video with 2:3 pulldown, resulting in a 24p file.

The live video is also going out at 24 frames progressive, even though the video is wrapped in 60i format -- it is 24p, it looks like 24p.

The Pansonic AVHS300G video switcher supports "1080i-59.94i" and the HD-SDI output of the Xh-G1/s is 60i (even though it's really 24p wrapped in 60i), so the HD-SDI 60i video format works with the switcher!

If the HD-SDI output would have been a true-24p output, I don't think it would work with the video switcher, since the switcher does not support 24p. So this is an interesting advantage of these cameras -- being able to go live at 24p with any HD video switcher.

Thanks for all the help - It's good to know this is an viable option, now we just have to decide if we want to film this way. My admiration goes to film-makers who film in 24p -- as soon as I move the tripod or zoom in, I can see the judder! It must take a lot of skill to film well at 24 frames progressive.

Another disadvantage of the 24p would be the 10% resolution loss our camera takes -- but making progressive dvds and blurays results in higher quality discs (easier mpeg-2 encoding for progressive projects) and a more universal format.... I'll have to think about this now....

Thanks for all the help!

[Simon Wood]

Originally Posted by Alex Lafkovici

I do have an Aja Kona capture card -- so that is capturing the video with 2:3 pulldown, resulting in a 24p file.

Another disadvantage of the 24p would be the 10% resolution loss our camera takes -- but making progressive dvds and blurays results in higher quality discs (easier mpeg-2 encoding for progressive projects) and a more universal format.... I'll have to think about this now....

I read somewhere here that AJA actually worked with Canon on getting those flags embedded in the G1, so you have a good setup there. Great to hear it is working out as planned.

You have to slow your movements a bit more when you're shooting progressive (there are some calculations available on the internet somewhere for 35mm film cameraman showing how fast they could actually move and pan). You might also want to experiment with your shutter speeds to see what works best with your lighting set-up.

Best of luck!