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Old May 25th, 2005, 08:13 AM   #1
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Best way to downconvert HDV?

Is there any quality difference between these two methods of downconverting?
1) Downconvert right out of the camera/deck and capture in DV, then dupe onto DVD.
2) Capture in HDV and downconvert from the editing system to DVD.
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Old May 25th, 2005, 08:34 AM   #2
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With the FX1, you can literally set the firewire to output to HDV or DV. Set it to DV in the menu and capture in DV mode onto your NLE.

The HD10 allows you to do a downconvert (or upconvert) by using video and audio cables to another deck or camera. You can go 1080i, 480i or 480p (or no conversion).

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Old May 25th, 2005, 08:51 AM   #3
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There is a significant quality difference.

Rendering from HDV (1440x1080 4:2:0 15-GOP MPEG-2) to DVD (720x480 4:2:0 MPEG-2) will yield much better results than rendering to DV (720x480 4:1:1 DV) and then to DVD. Not only does the DV render introduce extra artifacts at the 720x480 level associated with DV compression, but it also requires two colorspace conversions (unless you're working with PAL - in which case DV is also 4:2:0).

Here's the trick though, converting HDV to uncompressed SD for a DVD-render, or exporting from HDV directly to DVD is non-trivial.

-Steve
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Old May 25th, 2005, 08:58 AM   #4
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Quote:
Originally Posted by Steven White
Here's the trick though, converting HDV to uncompressed SD for a DVD-render, or exporting from HDV directly to DVD is non-trivial.
When you say converting HDV to uncompressed SD, do you mean via analog component cables?
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Old May 25th, 2005, 09:18 AM   #5
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No - I simply mean capturing the MPEG-2, and rendering it to an uncompressed file on down-conversion - retaining as much color information and resolution as possible in the process.

I see no benefit to capturing an "uncompressed SD signal" out of the analog outputs of the camera after recording HDV to tape. I don't know if the camera outputs uncompressed on SD component out before DV compression on down-convert - but in principle, capturing the MPEG-2 TS does not degrade the digital source on tape, while capturing the analog out will introduce conversion errors and noise.

Capturing uncompressed SD output live increases the operating cost, the necessary amount of hardware, and decreases the portability of the camera.

My suggested workflow for 1080i (to maximize quality) is:
- Shoot 1080i HDV (to tape)
- Capture 1080i HDV to M2T or a (virtually lossless) digital intermediate (i.e., Cineform)
- Place 1080i in a 1440x1080, 59.94 fps timeline, and deinterlace (upper fields first, highest quality available) to 1080p60
- Render 1080p60 to 720x480p60 uncompressed (4:4:4)
- Render 720x480p60 to 720x480i60 uncompressed (4:4:4)
- Compress uncompressed 720x480i60 to DVD MPEG-2.

If working with 1080p30 (i.e., Cineframe30 mode)
- Shoot 1080p30 HDV
- Capture 1080p30 HDV to M2T
- Place in 1440x1080 29.97 fps timeline
- Render to 720x480p30 uncompressed
- Compress to progressive DVD

In my experience, these operations can be precisely done in After Effects. Getting fields to behave appropriately in Premiere Pro doesn't seem to work as well.

-Steve

Last edited by Steven White; May 25th, 2005 at 10:04 AM.
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Old May 25th, 2005, 09:50 AM   #6
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Quote:
Originally Posted by Steven White
My suggested workflow for 1080i (to maximize quality) is:
- Capture 1080i HDV to M2T or a lossless digital intermediate (i.e., Cineform)
Cineform is not lossless.
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Old May 25th, 2005, 10:03 AM   #7
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Obviously not. But for this purpose, and most, if not all purposes, save perhaps advanced keying, it's really dang close.

I've edited my post to clarify.

-Steve
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Old May 25th, 2005, 10:08 AM   #8
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I'm confused--you want to do uncompressed?

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Old May 26th, 2005, 12:33 AM   #9
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>>> you want to do uncompressed?

Er, no ... he wants to make a DVD.
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Old May 26th, 2005, 05:54 PM   #10
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Simpler Workflow??

Steven
What about the following workflow for SD DVD:
Capture m2t from camera (4:2:0), convert to Cineform CFHD (4:2:2), edit the project in CFHD, render the timeline to 720x480 m2v (4:2:0), author the DVD. What would be the disadvantage of this pathway??
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Old May 26th, 2005, 06:44 PM   #11
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Quote:
render the timeline to 720x480 m2v
There's no real difference between this work flow and the one I suggested above in an ideal world. However, my experience so far has been that Premiere Pro does not handle this step very well - it has the tendency to bugger the fields or simply ignore them.

I just deconstructed SD renders to ensure proper handling of the fields, before doing the render to m2v.

-Steve
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Old May 26th, 2005, 10:43 PM   #12
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Steven
Does the field order need the be reversed in the process of going from HDV (m2t) to m2v DVD (I'm thinking HDV is upper first--is DVD mpeg lower first, like NTSC DV)?? Or is it just something buggy about Premiere's ability to transcode CFHD to m2v aside from field order issues?
Thanks
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Old May 27th, 2005, 02:33 AM   #13
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Alternative Route

If Premiere cannot reliably convert CFHD to m2v DVD, I was considering another possible route:
Capture m2t into Premiere, convert and edit in CFHD, recompress the timeline back to m2t-as if you were going to export back to HDV tape- then use other software such as Canopus Procoder 2 to convert the m2t to m2v DVD. Has anyone done anything like this??
Bob
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Old May 27th, 2005, 08:43 AM   #14
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Thats what I do. Edit everything in CFHD, then as a final step convert to SD DVD using Procoder. I add a bit of temporal smoothing filter and gamma adjustment during that compression - the advantage of that workflow being that I can store the unfiltered master for future use.

Works fine.
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Old May 27th, 2005, 09:13 AM   #15
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Quote:
Does the field order need the be reversed in the process of going from HDV (m2t) to m2v DVD (I'm thinking HDV is upper first--is DVD mpeg lower first, like NTSC DV)
When I rendered the 480p60 to 480i60 I made the field order lower field first just to be sure. I didn't do an experiment with upper field first, so I don't know if it would playback properly or not.

-Steve
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