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Old September 4th, 2007, 06:51 AM   #1
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XH A1 25f conversion to 24p - is it totally ok?-

Hi,

I'm doing some experiments before starting a HD project with my PAL Canon XH A1.

My idea is the following: I want to shoot in 25f (visually is what I like) and my delivery method is going to be a DVD-R with HD-DVD format.

The only workflow I find is to convert with cineform from 25f to 23,97p and edit in Premiere CS3 a cineform HD 24p project. When I edit then I export to mpeg 2 at 1440x1080 23,97 progressive. The quality is fine but horizontal pans are getting some strobbing (or judder) efect wich are not presenent in the original 25f tape.

Is there any succesful workflow with cineform shooting in 25f to finally get a 23,97 progressive high quality video?

Does cineform support 100% the 25f from PAL Canons? I ask this because HDLINK or Cineform HD presets im premiere only appears the 24f. Is the 25p preset fully ok with 25f?

It's been tested the hdlink conversion from 25p to 23,976p using a 25f source?

I ask this things because spending 499$ is a serious thing for me and I need to be sure that cineform do what I ask here.

Thanks in advance.
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Old September 4th, 2007, 10:03 AM   #2
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We completely support Canon 25F, and the 25p preset is the correct one. We don't need a 25f mode as 25p is the same, whereas 24f and 24p in HDV are slightly different, as one has pulldown and the other doesn't. We can convert 25p/f to 23.976p, without issue. Sounds like everything is working fine. As for horiztonal pans, there a potential judder source in any 24 or 25p production, becareful of your display device, pans may look smooth on your viewfinder, yet appear to judder on the computer monitor, this happens as you computer monitor is refreshing at a different rate. Single step your output to confirm you don't have any missing frames or frame blending.
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Old September 4th, 2007, 02:14 PM   #3
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thanks for the quick answer,

As traditional PAL user I'm not used to concepts like pulldown. I have a last question and it is about this pulldown.

Let's see this scenario:

I have an exported (from Premiere CS3) .avi cineform codec file at 23,97p and I want to make a compliant mpeg2 file for Ulead DVD Moviefactory to create a HD-DVD,

I remember Tom Roper in this forum told me that with his Canon XH A1 (NTSC) he didn't need to convert anything becuase his 24f video file was a 23,97 video in a 60i stream with puldown and this is exactly what Ulead accepts (29,97i or 23,9 in a 60i stream and it's recognized by Ulead as a 29,97 video).

My question is this:

When I create the mpeg2 file (coming from the cineform's avi at 23,97p) what happens to the video when I insert in the encoding a 2:3 pulldown? When I do that the video is theoretically still 23,9 but with the pulldown Ulead sees it at 29,97... Also if I add a pulldow wich would be the right field order (upper or bottom or even it doesn't matter because it's still progressive).

So the question is if make sense or not (loss of quality or loss of progressive) to add 2:3 pulldown to the cineforms 23,97p avi file.

I talk about adding the pulldown beacuse it's not possible to create (with Ulead) a HD-DVD with a 23,97p file (it converts to 29,9 with terrible results).

If someone can answer this questions properly I think I will finally understand the NTSC mysteries.

Thanks again David and congratulations for your great product.
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Old September 4th, 2007, 02:32 PM   #4
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I don't understand why Ulead can't take 23.976p files; pulldown injection should not be required for HDDVD authoring. If you are adding pulldown, go for top field first. Consider a different HDDVD authoring tool.
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Old September 4th, 2007, 02:38 PM   #5
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it does not... (there is a method to patch the mpeg file and fool Ulead changing the header info so Ulead believes that the video is 29,97 when its actually 23,97p)

but what happens to the video when the pulldown is injected?
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Old September 4th, 2007, 03:05 PM   #6
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Quote:
Originally Posted by Sergio Garcia View Post
it does not... (there is a method to patch the mpeg file and fool Ulead changing the header info so Ulead believes that the video is 29,97 when its actually 23,97p)

but what happens to the video when the pulldown is injected?
23.976p become 29.97i -- then you are requiring the player to reconstruct but the 24p for display.
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Old September 4th, 2007, 03:16 PM   #7
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this is what Tom Roper told me about the cineform converversion from 25f to 23.97p. Please tell me if it makes any sense to you:


My opinion from viewing the clip of Palma de Majorca is that the workflow described above is generally successful as a bridge from 25F to NTSC compatible HD-DVD without having Ulead MF6 re-encode it.

But since you already use the XH-A1, I think it would be preferable to have the Canon factory modify your cam to include native 24F mode support. Here's why.

In the conversion from 25 to 24, a non-standard cadence is inserted, something like this 3:2:3:2:3:2:2:2:3. The resultant playback at a 60 hz monitor refresh rate is very good, except for the expected pulldown judder which is not bad.

The problem occurs when you want to eliminate the 24p pulldown judder altogether, which normally is made possible by a monitor that can display frames at a multiple of 24, typically 72hz. Such a monitor will display the pulldown cadence as 3:3:3:3:3, eliminating the judder frame. My 1080p monitor works this way. When you enable the 72 hz mode, if the cadence is standard 3:2 it is decoded to 3:3 for smooth motion handling. But since your cadence has to account for the insertion of an extra frame to maintain 25P timings, it upsets the 72hz mode causing elements of the image to strobe as you're panning the outside of la Seo. Switching off 72hz mode will eliminate the issue of the strobing, but the pulldown judder remains in play. The judder is minor, but you're soliciting critical review here, so I hope you will receive the observation in the helpful spirit it was intended.

If your Canon camera is made 24F enabled natively, your workflow is simplified, and the minor problem of the 25 to 24 timings is discharged. 24F in the XH-A1 is already flagged 29.97, so you don't have to repatch the headers. Ulead MF6 will not re-encode it, since it's already in a compatible form. And since the cadence is pure 3:2, 72hz refresh rate display is free of judder and strobing.

Other than that, your subject matter is interesting, detailed and colorful, the soundtrack emotional and involving. You'll understand my intention is to critique the technical aspects of the workflow itself, not your artistic skills.
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Old September 4th, 2007, 03:56 PM   #8
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The doesn't seem relevent, particularly "In the conversion from 25 to 24, a non-standard cadence is inserted, something like this 3:2:3:2:3:2:2:2:3," that is nonesense. When CineForm converts 25 to 24, we change the presentation rate and remodulate the audio to match. This 4% speed shift is very common for this type of conversion. Now you have 24p signal and can be presented easily on multiple output formats.
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Old September 4th, 2007, 04:34 PM   #9
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ok all clear. Thanks David for your time!
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Old September 6th, 2007, 06:08 AM   #10
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one last question David...

What makes more sense to you: converting during capture from 25p to 23,9p or just capture 25p and do the conversion during the export at the end in a cineform .avi?
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Old September 6th, 2007, 10:38 AM   #11
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Depends on your primary market. If you have more 25p customers, edit in 25p. Reason is the remodulation of audio is hardest to do well for music, whereas voice and wide sound is pretty easy. If you have primarily a 23.976 market, you can convert all you picture and voice elements to 23.976 without any issues, adding music in full quality to your 24p production. If you then need a 25p mix, you may what to relayout your music track for the highest quality. For a fast 24p->25p mix, the audio remodulation in HDlink I think is better than Adobe's and is pretty good.
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