Creative COW SIGN IN :: SPONSORS :: ADVERTISING :: ABOUT US :: CONTACT US :: FAQ
Creative COW's LinkedIn GroupCreative COW's Facebook PageCreative COW on TwitterCreative COW's Google+ PageCreative COW on YouTube
AJA:AJA io ForumAJA Kona ForumAJA Xena ForumAJA io TutorialsAJA Kona TutorialsAJA Xena TutorialsAJA

HD and SD output at 24 fps

COW Forums : AJA Kona - Mac

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
Share on Facebook
Tom CarlsonHD and SD output at 24 fps
by on Aug 10, 2008 at 7:24:28 pm

I am using a Kona 3 card to play back HD 1920 X 1080 Apple Photo - JPEG material at 24 fps. We have successfully done this to an HD projector and HD plasma display. The sync is good and the picture looks great at 1080 psf 24 fps. We want to simultaneously output SD to our NTSC monitors. To get good SD picture, we must change the engine for the project to 1080 psf at 23.98, and set the SD downconversion to 525 29.97 fps. That works and we get good picture out of both the SD and HD outputs. The problem is that when we do that, we are running too slowly by .1%. Is there any way to run HD and SD simultaneously at 24 fps? We are very close, other than that pesky speed issue.

By the way, we use Virtual VTR as our playback "machine." It chases 24 fps time code.

Tom Carlson


Return to posts index
Reply   Like  

Michael SacciRe: HD and SD output at 24 fps
by on Aug 10, 2008 at 11:05:11 pm

The question is going to be, can your NTSC monitor accept a 23.98 singnal? Most cannot.



Return to posts index
Reply   Like  

Tom CarlsonRe: HD and SD output at 24 fps
by on Aug 10, 2008 at 11:27:02 pm

Thanks, Michael. Actually, the Kona 3 creates a 29.97 SD output if you set the main engine to HD 23.98 and downconvert. It's very slick and allows you to view on both an HD monitor and an SD NTSC monitor simultaneously. The problem is that we can't set the engine to HD 24 fps and downconvert in the same way to get a NTSC output. The Kona won't allow it. So, since I've set the Kona 3 main engine to 1080 psf 23.98 and the stage is running at 24 fps, there is a slight speed differential. We lock in the right spot and chase, but over time there is a .1% drift (about 2 frames a minute). That's the usual pulldown differential. For now, I think I'll need to run a second system for SD, and leave the Kona to play the HD at 24 fps, unless I can figure out how to fix this. Maybe a Canopus Box or a Mojo SDI.

Any other thoughts?

Tom



Return to posts index
Reply   Like  


gary adcockRe: HD and SD output at 24 fps
by on Aug 11, 2008 at 1:50:37 pm

[Tom Carlson] " Is there any way to run HD and SD simultaneously at 24 fps?"

No

since NTSC is 29.97 drop frame- it would take a dedicated hardware to handle the timebase conversion in realtime- FCP cannot do this, and Kona tools only compensate for the addition and removal of pulldown- not a timebase conversion.

Most all HD and DI postproduction is done at 23.98 vs 24.0 for this very reason

gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows
Inside look at the IoHD




Return to posts index
Reply   Like  

Tom CarlsonRe: HD and SD output at 24 fps
by on Aug 11, 2008 at 2:40:50 pm

Thanks Gary. I am using this on a scoring stage, and our composer is working at 24 fps throughout his process to match the speed of the Avid files we get from editorial. At 24 fps, it's easy to pass material back and forth without having to resort to OMF's or do speed conversions. That way, everyone is running at 100% speed. The feeling is that it would be pretty disruptive to change to a pulldown rate on the stage, so we will be working at 24 fps for now. I've been trying to figure out a way to do this for a while now. On the last couple of pictures, we've only had Avid SD 24 fps picture and used the output from the computer DVI and a little $20 box from apple that converts DVI to NTSC. Doesn't look great, but at least it got us through in sync. The Mojo SDI is supposed to be able to take 24 fps files and play them back to an NTSC monitor in sync, but I haven't seen what the quality is like yet. They must be dropping frames to do this.

Hmmm. I wonder if I used a program like Combustion or AE and did a speed bump up to 24.024, then played the SD files back with a downconversion to 29.97 fps on a separate system...Of course, the easiest solution would be to get rid of the SD monitors on the stage and just play everything at HD 24 fps. And the search continues...

Tom Carlson



Return to posts index
Reply   Like  

gary adcockRe: HD and SD output at 24 fps
by on Aug 11, 2008 at 3:52:11 pm

[Tom Carlson] "Hmmm. I wonder if I used a program like Combustion or AE and did a speed bump up to 24.024, then played the SD files back with a downconversion to 29.97 fps on a separate system...Of course, the easiest solution would be to get rid of the SD monitors on the stage and just play everything at HD 24 fps. And the search "

Output QT Ref files and conform them in CT to be 23.98- it will take but a few seconds - then they will playback with pulldown added for NTSC.




gary adcock
Studio37
HD & Film Consultation
Post and Production Workflows
Inside look at the IoHD




Return to posts index
Reply   Like  


Tom CarlsonRe: HD and SD output at 24 fps
by on Aug 11, 2008 at 4:47:59 pm

Output QT Ref files and conform them in CT to be 23.98- it will take but a few seconds - then they will playback with pulldown added for NTSC.

Hi Gary,

So, if I conform them to 23.98 in Cinema Tools, won't that make them play too slowly if everything else on the stage is referenced to 24 fps? To get simultaneous output of HD and SD, I'll need to set the Kona 3 to 23.98, which was causing both the HD and SD to play too slowly when we tried that before. Does Cinema Tools actually do something to the files so that they will play in sync, once conformed to 23.98 and played with the 23.98 Kona 3 setting? All of the pre-records are still playing at 24 fps. I realize I may be asking for the impossible here.

Tom



Return to posts index
Reply   Like  

Will FilesRe: HD and SD output at 24 fps
by on Oct 21, 2008 at 7:17:57 pm

What you're describing is actually standard practice in most feature dubbing stages. What we normally do is prepare everything at 100% speed (24fps @ 48k) but then pull the WHOLE mix stage down to 29.97 / 23.98 / 47.952k. That is, we pull the audio AND the video AND the timecode down by that old .1% NTSC pulldown. This effectively keeps all the elements in perfect sync, and allows us to use mixing consoles, outboard gear, and video equipment that only operate in the 29.97 TC world. I realize it seems a little archaic and overly complicated, but it's actually very straightforward in practice. Once the mix is finished, the final master will be in perfect sync when you play it back at 48k with 24fps picture (AKA film).



Return to posts index
Reply   Like  

Ramona HowardRe: HD and SD output at 24 fps
by on Oct 21, 2008 at 8:06:07 pm

Will,

Happy to hear someone really understood the rambling.

Archaic is not a bad thing, especially if you can't get a real answer as to how the many applications out there are handling this type of stuff and if they are doing it correctly. Makes you realize shortcuts are not always a good thing.

Cheers,
Ramona



Return to posts index
Reply   Like  


Tom CarlsonRe: HD and SD output at 24 fps
by on Oct 21, 2008 at 8:51:33 pm

Thanks Will and Ramona for the responses,

I am very familiar with pulling down picture and track by .1%. We do this all of the time on the dubbing stage.

The problem is, we are running the scoring stage at 100% 24 fps and everything is running at that speed. The composer is bringing in a lot of material using Logic, which does not function at pulldown sampling frequencies. So the only way to deal with this in standard definition is to run Virtual VTR and output through the DVI port to a computer-type or HD monitor, or run a Canopus box (poor quality). The third alternative, and one that we ended up using on our last scoring session, was to get our hands on HD material. We played that out of a Pixus at HD. Simultaneously, we used an Aja convertor box to down-rez to standard definition for the NTSC monitors on the stage. With a multisync monitor NTSC, everything played beautifully and in sync at 100%.

We can play the 24 fps SD files at 23.98 and uprez to HD, but that doesn't take care of the NTSC monitors and also does not run at the correct speed. What would be ideal for situations where we just have SD monitors, would be to have a setting in the Kona that would allow us to output from a 24 fps SD QT file to NTSC. Period. I know it's very non-standard, but that would be simplest.

Thanks to all that have "given this a think."

Tom Carlson



Return to posts index
Reply   Like  

Ramona HowardRe: HD and SD output at 24 fps
by on Aug 13, 2008 at 7:25:56 pm

Tom,

This requires an audio rate conversion, which is part of our 3.0 series for Rave, so yes this is very possible using AJA hardware and an app that supports it.

The difference is that Rave works with native DPX files.

Cheers,
Ramona
Rave information can be found at http://www.spectsoft.com



Return to posts index
Reply   Like  

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
Share on Facebook


FORUMSTUTORIALSFEATURESVIDEOSPODCASTSEVENTSSERVICESNEWSLETTERNEWSBLOGS

Creative COW LinkedIn Group Creative COW Facebook Page Creative COW on Twitter
© 2014 CreativeCOW.net All rights are reserved. - Privacy Policy

[Top]