FORUMS: list search recent posts

Downconvert 1080i25 to 576p25

COW Forums : Broadcasting

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
Tom Alesch
Downconvert 1080i25 to 576p25
on Jan 21, 2009 at 12:18:41 pm

Hey,
we are doing a project that was shot on XDCAM HD in 1080p25 (for the progressive look) intended for DVD PAL 16:9 release (that is 720x576 at 25fps, played back as 1024x576 for the 16:9 ratio).

Accidentally some of the material was shot 1080i50. I imagine that it should be possible to downconvert it to 576p25 without any significat loss of quality compared to the downconverted 1080p25 material, but I don't know how to do it. Our players converter (Sony PDW-F70) only delivers 576i50 from the 1080i50.

I think about exporting the material as a tiff sequence, resize it in photoshop by 50% to 540x960 (every second field will be gone, so it will be progressive) and than resize by 106.67% to get a 576x1024 resolution, which will by squeezed at import to our AVID Meridien (SD) to 576x720. But this will take lots of time. Maybe anyone knows another solution...?

By the way, I'm really curious to know how the F70 manages to get that good looking 576i from 1080i. Seems not to be an easy calculation to me...

Tom


Return to posts index

Dino Sanacory
Re: Downconvert 1080i25 to 576p25
on Jan 21, 2009 at 6:51:28 pm

Photoshop probably wont work quite like that. Chances are the resize will be interpolated from the whole frame which will mix the two interlaced fields together. This could still leave interlace artifacts. I would use After Effects.

Once the HD clip is in After Effects, interpret footage as upper field. This removes a field from the material. You are now at half resolution, but half resolution HD (similar to your Photoshop thinking). Place the clip in a 720 by 576 at 25 fps comp and scale to fit. Output with fields set to none. You now have a progressive standard def clip.

You mention working on a Meridien system and the PDW-F70. You make no mention of how you would get the material as HD for your photoshop process. Depending on your workflow, there may be other options.





Return to posts index

Tom Alesch
Re: Downconvert 1080i25 to 576p25
on Jan 21, 2009 at 7:29:23 pm

Thanks for your help. I think photoshop would work, but AE sounds indeed more appropriate. To do the captureing I want to use the Sony XDCAM Transfer software.

Well, you're speaking of other options. Indeed, I have accesss to a Final Cut Studio 2 (just never worked on it myself so far), and some weeks before the deadline for this project my boss will have upgraded our AVID to MC Nitris DX. I didn't mention that because I have to be sure right now there is a solution, and for me, being sure involves I can try it out myself. But probably I would trust you if you claim that there is an all ready preset for what I need in new AVID software :-)



Return to posts index


Dino Sanacory
Re: Downconvert 1080i25 to 576p25
on Jan 21, 2009 at 10:15:23 pm

With a newer version of Media Composer there is the possibility to have mixed resolution media in the timeline. That is, both HD and SD. For a project like this, you could just work entirely HD and then transcode the final sequence to SD if that is what is required for delivery. This way you still have an HD copy should there be a use for it down the line. I don't think Avid makes any distinction between the media as progressive or interlace. the project choices have more to do with processing than the media format. (Something that has to be tested of course.)

Within the Avid there is the FluidMotion effect. This is pretty good at taking interlace to progressive. Simply effect any clips in the final sequence that don't conform to the desired format.

I might be able to offer several workflow options but the right choice is driven by your particular situation and limited by what can actually be communicated in an internet forum. If you happen to be located in the New York area (with the delivery being PAL, I'll guess no), I am available as a consultant.



Return to posts index

Tom Alesch
Re: Downconvert 1080i25 to 576p25
on Jan 22, 2009 at 4:35:20 pm

Thanks again Dino,
I'm confident now that there will be some way to get the expected results.
Just can't ask you as a consultant, I'm located in Europe... :-)

Tom



Return to posts index

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
© 2017 CreativeCOW.net All Rights Reserved
[TOP]