Downconverted HDV does yield 4:2:2 or 4:4:4 SD

M

mgalvan

Well-known member
So I've done my testing today on some HDV 24F to various SD codecs for higher chroma resolution in SD. My results ... downrezzing HDV 4:2:0 to a SD codec does retain the full color information the codec is capable of ...

I took the same clip and downconverted to DV, DVCPro50, and PhotoJPEG (at 100%). THen I brought it into Final Cut Pro (with each clip in their own respective timelines with the same properties as the clips themselves) and looked at the individual Cr and Cb channels of each clip in a side by side comparison. And sure enough, the PhotoJPEG had the same chroma res as its luma res. The DvcPro50 file was 4:2:2 and the DV 4:1:1. I did apply the same various filter sets to each of the clips and rendered ... the PhotoJPEG and DVCPro50 held up much cleaner than the DV clip.

And to finally confirm my tests, I took the DV compressed clip and bumped it up to DVCPro50 and dropped it side by side with my "native" DVCPro50 clip. After looking at the individual Cr and Cb channels again, the DV-to-DVCPro50 clip, showed the same chroma resolution of the DV clip, even though it was encoded up to DVCPro50, proving that your footage isn't any better than the highest compression scheme it has gone through.

This is great, as I never expected this kind of SD workflow from my H1. You really can get 4:2:2 or even 4:4:4 (or at least close to it) by downconverting HDV to the right SD codec. THis is great for any work I put out on DVD. Thanks for everyone's insight on this.
 
So are you leaning towards PhotoJPEG now? It'll give you the most resolution both spatially and in chroma for SD. 854x480 with 4.4.4 or very close to that would make a pretty darn good SD master for encoding widescreen DVD's.
 
Although I would like to use PhotoJPEG, I think I'll be using DVCPro50 because it'll give me realtime playback on my production monitor (I currently don't have a card for my G5 Quad), plus the DVCPro50 renders a little faster ... time is of the essence for this upcoming project.

On another note, I did notice that the 854x480 PhotoJPEG was slightly wider than the anamorphically stretched DV50 and DV footage. Is the horizontal res really 854?
 
Look at anamorphically stretched DV50. In QT player if you have an "unsqueezed" frame in full 16x9 it should be 854x480 resolution. With PhotoJPEG or animation codec it's square pixel so you preserve a little more resolution. No need for anamorhphic stretching of the image with a funky pixel aspect ratio. If your PhotoJPEG stuff looked wider than the anamorphic DV50 it could be that you exported the PhotoJPEG with that res and anamorphic pixels or your DV50 only played in a 4x3 frame.

Ah well, good luck with your project. I'm sure with this SD downconverting technique it will look pristine either way.
 
Nope, just 4.2.0...the point is that you'll have better colors and a better core image in SD before you encode to DVD.
 
There are higher levels of MPEG-2 that can support 4:2:2, but the most commonly used are for DVD and broadcast and HDV, and those are all 4:2:0.
 
You must log in or register to reply here.
Back
Top