HDV to SD downconversion - chroma sampling
 

Just want to clarify ...

Is my understanding correct in that shooting in 1080 HDV 24F, and then downconverting to SD with a lossless codec like PhotoJpeg at 100% with something like MPEG Streamclip, would essentially yield 4:4:4 SD video?

I'm thinking of doing this for an upcoming film competition, and will be shooting HDV, but the final delivery format will be DVD. So rather than shooting in the DV mode, in theory, shooting HDV and downconverting to SD with a better codec should provide superior results.

4:2:2 would be sufficient for this, so what codec would you recommend ... DVCPro50, PhotoJPEG (75%-100%), or Apple Uncompressed 4:2:2? I'll be working within Final Cut Pro.

PhotoJPEG@100% is where it's at.

Presumably you're considering this route for considerable post-tweaking or effects once it is SD? Is this a better route than shooting HDV, tweaking/FX in HDV, then either downsampling to SD via a NLE or even using the camera itself to downconvert?

Forgive me, I have nothing to add but I'm very curious about the pros and cons of the workflow you're choosing. I tend to do a lot of post effects work and I'm keen to know what tricks other people are using.

Si

Personally, I think it's best to do it all in an HD format, then downconvert at the end.

He might be wanting to simplify things though for a speedier post process.
Although that's also fairly negligible, given a fast G5 or PC.

Barlow- Just out of curiosity, what is your workflow?

Workflow:

--Shoot HDV and occasionally straight to SDI
--Transcode via SDI or MPEG Streamclip to DVCProHD or PhotoJPEG@75%
--Inverse Telecine 24F clips in Cinema Tools (PITA, but I like true 24p timelines)
--Edit in FCP in either 1080 24p timelines, or standard 1080i
--Export finished QT movies in DVCProHD or PhotoJPEG
--Encode h.264 in 720 or 1080 for HD DVD
--Downconvert to DV50 or PhotoJPEG @100% for SD DVD encoding

Basically, HDV is acquisition only for me. This might change if and when Apple truly supports the H1, but I doubt I'll stop working in intermediate codecs. I think even with true 24p HDV timelines (for 24F stuff) it'll still be overly render heavy but I sure hope I'm wrong.

Does that get you 4:2:2?

Only raw SDI capture...but 4.2.0 from the H1 is plenty good for my needs.

Look at my extremely simple greenscreen shots. There are some uncompressed SDI frames, raw SDI to DVCProHD clips, and m2t's from tape transcoded back to DVCProHD and PhotoJPEG.

Tell me what you think?

www.homepage.mac.com/mrbarlowelton

You are using PAL to get the 4:2:0 then? Just trying to follow along, because this is far different than the old DV stuff. I'm pretty well stuck with weak 4:1:1 as a source file, which certainly doesn't get any better when working on it. Now we have HDV available, and it is supposed to offer far better results, and higher chroma and color.

HDV, in 50hz (PAL spec) or 60hz (NTSC spec) is 4.2.0 color sampling in a 1440x1080 frame. There's still a lot of chroma information and because the resolution is so high, I believe there's a lot more to work with than the SD formats.

I'm not using PAL, I have a 60hz H1.

Thanks for the info, Barlow.

Si

Ok, gotcha now. Thanks :)

Barlow - you are the man.

Right back atcha! :-)

...jus keepin' it real.

Thanks for all your responses. I'm particulalry interested in this, because the final output for this competition will be dvd. In this case, I will shoot HDV, but am planning to do my edit in SD (capture 24F HDV and convert to most likely DVCPro50 or PhotoJPEG (100%) at this point). Since this is a 48 hour film competition, time is of the essence, and I would rather edit in SD to save processing power (despite the fact that I have a G5 Quad).

I also plan to do some heavy color correcting/effects to some of the shots, hence my interest in bringing it to 4:2:2 or 4:4:4 SD. So that's why I just wanted some confirmation on whether HDV 4:2:0 when downconverted to something like DV50 or PhotoJPEG really yields a true 4:2:2 or 4:4:4 SD file. I'm not so much interested in an HD master, as I will need the SD DVD to look the best it can. This is why I am choosing to convert to SD before doing my editing and color correction - for both time and final DVD quality.

I did some quick tests, and I notice that DVCPro50 footage renders about twice as fast as PhotoJPEG(100%) footage, after applying some filter sets. Although, I'd like to try PhotoJPEG for this, I think DV50 may be better in this scenario because of the time restraints to the competition. Thoughts?