Having to render after importing from Compressor4

[Rafael Amador]

[Edwin Street] ” file in Media Info it shows this:”
which “Media info’ are you talking about?

To undesratnd Chroma Subsampling, please have a look to this article of G. Nattress:
https://www.nattress.com/Chroma_Investigation/chromasampling.htm

In short:
– 444 there is no subsampling; Each pixel has his own Y + Cb + Cr information.
– 422; Each pixels has his own Y information, but only one every two pixels has Cb and Cr information.
– 411/420; Each pixel has his y information, but only one every 4 pixels has Cb and Cr information.

Chroma subsampling can only exist in YUV (YCrCb).
Chroma subsampling is not possible in RGB, because there are not chroma channels.

rafael

[Edwin Street]

Thanks for the link to that page it was a good read but I found it a little outdated as it talks mostly about DV and Betacam although the introduction about chroma sampling was great.

I’ve done some playing around and exported the timeline with the compressor version and it turns out that the timeline is Chroma subsampling : 4:4:4
So why I have to render is still a mystery to me.

The program I use is this:
https://mediainfo.sourceforge.net/en

On PC it’s free but on Mac you get it from the Mac App Store for 99c

[Rafael Amador]

[Edwin Street] “Thanks for the link to that page it was a good read but I found it a little outdated as it talks mostly about DV and Betacam although the introduction about chroma sampling was great.”
You are right, the article is old, but the patterns of chroma haven’t changed.

[Edwin Street] “So why I have to render is still a mystery to me.”
i’ve been making a couple of tests exporting PR444 from Compressor, and i don’t get any color bar.

One question: Do you have the “Frame Control ON” in Compressor?
If you don’t , make a test with Frame Control ON.
Compressor works only in 8b when frame Control is not ON.
rafael

[Edwin Street]

I’ve tried with Frame Controls on and off and get the same result. Green render bar.

What do you mean by “Compressor works only in 8b when frame Control is not ON.” ?

Do you mean 8-bit? With frame controls off, it just selects the options automatically for you instead…

How does that make a difference?

[Rafael Amador]

[Edwin Street] “What do you mean by “Compressor works only in 8b when frame Control is not ON.” ?”
Right that.
Compressor works in Floating Point only when Frame Control is ON.
I’m not sure how that would affect a plain transcoding, but any resizing, de-interlacing or retiming will be done in 8b unless Frame Control is ON. That means that any 10b stuff that you process must be done in such way, otherwise the footage will be crunched to 8b.
That’s up to the Compressor manual.

I’ve never used the “Frame Control AUTO”, because I have no idea when will be ON or OFF.
rafael