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Having to render after importing from Compressor4

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Edwin Street
Having to render after importing from Compressor4
on Apr 3, 2013 at 4:46:34 pm

Hello,

I convert my DSLR H.264 file to ProRes4444 in Compressor4 and drop it into my timeline in FCP7. It asks me to match the sequence settings with the clip settings and I click Yes. But I have to render a green bar. Does anyone know why this is?

If I use Compressor to convert to ProRes422(HQ) and put that into my timeline, I don't get the green bar...

If I use 5DtoRGB, the ProRes4444 file comes out at a slightly less bit-rate than the Compressor4 ProRes4444 (which is odd), but I can also put this into the timeline without having to render it. It's only the Compressor ProRes4444 that I need to render in the FCP7 timeline.

(I know that it's overkill to use ProRes4444 with a DSLR and I don't normally, but I'm curious to know why I have to render it)

I'm using a MacBookPro 2.4 GHz Intel Core 2 Duo if that helps.


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Shane Ross
Re: Having to render after importing from Compressor4
on Apr 3, 2013 at 5:02:07 pm

[Edwin Street] "I convert my DSLR H.264 file to ProRes4444"

HUGE waste of space. There is absolutely no reason to transcode to ProRes 4444. You won't improve the quality of the image one bit. If you transcoded to ProRes 422...vanilla ProRes...it will look exactly the same as 4444, but take up 1/3 the drive space. Just because the number is bigger and more impressive, doesn't mean it's better.

[Edwin Street] "(I know that it's overkill to use ProRes4444 with a DSLR and I don't normally, but I'm curious to know why I have to render it)"

If you know it, why are you doing it? Even HQ is too much. But, whatever. ProRes 4444 is meant for high high end formats, and for graphics with alpha channels. HIGH data rate. How fast is the drive you are trying to play this from? How is that drive connected to the computer? Are the sequence settings ALSO ProRes 4444?

Stop wasting your time trying to figure out why a codec you really shouldn't be using in the first place, isn't working. Go with what's appropriate and move on.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


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Edwin Street
Re: Having to render after importing from Compressor4
on Apr 3, 2013 at 5:30:29 pm

The reason I'm asking is that I may be shooting on RED a little down the track and I needed a 4444 file to get my head around.

As you mentioned it may be my drive speed and Final Cut trying to render it to a lower bitrate. I'm using my internal harddrive though, for this experiment, but I don't know how many RPM it is.

Yes sequence settings are match to clip settings.

Also, what is an alpha channel? How many channels does ProRes4444 have? and how is this linked with graphics.


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Shane Ross
Re: Having to render after importing from Compressor4
on Apr 3, 2013 at 5:32:51 pm

Alpha Channels are...say you have a graphic image, on black. But you need the black to be transparent, so you only see the graphic image. And embedded alpha cuts out that black, so when you add the logo, all you see is the logo.

I'd use ProRes HQ for RED. Unless you are going to screen on the BIG screen.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


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Edwin Street
Re: Having to render after importing from Compressor4
on Apr 3, 2013 at 5:42:36 pm

Cool, thanks for that. Kind of like layers in Photoshop.

Does ProRes4444 only have one extra layer (Alpha Channel)?

And how can I see this extra channel? Do I need to use Motion or After Effects?


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Shane Ross
Re: Having to render after importing from Compressor4
on Apr 3, 2013 at 5:43:57 pm

I'm not techie enough to answer that.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


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Spencer Averick
Re: Having to render after importing from Compressor4
on Apr 3, 2013 at 6:09:10 pm

It's just the one extra "layer". You can't ever see it because it's invisible, you can only see it in action. If I have a ProRes HQ sequence in FCP of a guy being interviewed, and a graphics guy creates an animated lower third that flys in, he will create a ProRes 4444+ file that I can just add right on top of the video.You can use it for graphics like that or just for very high end data rate video delivery.

It's a hi data rate video that has the option to add an alpha channel if need be. The alpha is the (+).

But like Shane says, if you're editing a RED show you don't want to edit in 4444 (especially with your laptop).
If you're going to the big screen, compress the R3D files to ProRes Proxy or LT for editing, then a colorist will link back to the original RED files before coloring and delivering.
If you're editing a RED show for TV or Web or something, you can probably compress, edit, color, and deliver all in ProRes HQ.
As far as the green render bar, I'm not exactly sure why but you're right it's always like that no matter what in FCP with PR444. Always have a green render, probably because it's just a massive file.


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Rafael Amador
Re: Having to render after importing from Compressor4
on Apr 3, 2013 at 7:18:08 pm

Edwin,
Make sure is not the audio what has to be rendered.

[Edwin Street] "As you mentioned it may be my drive speed and Final Cut trying to render it to a lower bitrate. I'm using my internal harddrive though, for this experiment, but I don't know how many RPM it is.

Yes sequence settings are match to clip settings."

No.
Prores444 is fully supported for RT.
In a low performance system could play choppy, but would never needs rendering.

[Spencer Averick] "As far as the green render bar, I'm not exactly sure why but you're right it's always like that no matter what in FCP with PR444. Always have a green render"
No here, on my 5 years old MBP.
rafael


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Joseph Owens
Re: Having to render after importing from Compressor4
on Apr 4, 2013 at 5:16:29 pm

[Edwin Street] "Does ProRes4444 only have one extra layer (Alpha Channel)?
And how can I see this extra channel? Do I need to use Motion or After Effects?"


The 4's are sampling channels. 4444 can carry four streams of image information -- RGBA or Y'CbCrA.
Your green bar might mean that you are carrying RGB in the 4:4:4 tables, which might give FCP some issues. Unfortunately there are no flags in the ProRes4444 codec to explicitly state what it is, exactly, that is being transported. RED usually exports into PR4444 as RGB.

There are ways to examine the alpha channel, if it exists. In FCP's Viewer, you will notice three buttons imbedded in the center along the top frame. The one on the right has a "cornerframe" icon. Clicking on it will reveal some options -- Overlays, wireframes, and "RGB", "Alpha" and "RGB&Alpha". RGB, of course, shows you your color picture. Alpha will show you your key-holdback, and RGB&Alpha will give you a sense of how the alpha will interact with the foreground picture elements to punch-through a background. Its a red/monochrome representation.

Most compositing software has to be able to show you the alpha channel, extract it, modify it, and re-embed it.

jPo

"I always pass on free advice -- its never of any use to me" Oscar Wilde.


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Rafael Amador
Re: Having to render after importing from Compressor4
on Apr 5, 2013 at 2:08:13 am

[Joseph Owens] "Your green bar might mean that you are carrying RGB in the 4:4:4 tables, which might give FCP some issues. Unfortunately there are no flags in the ProRes4444 codec to explicitly state what it is, exactly, that is being transported"
You are right Joseph.
We had this discussion long ago.
The problem is that there is no way to control which Prores444 flavor (RGB or YCbCr) we get on exporting.
I understood that applications that render in RGB (AE, SHAKE,..) export RGB and so applications rendering in YCrCb (FC) export YcrCb.
It seems that Compressor do it on RGB.
rafael


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Edwin Street
Re: Having to render after importing from Compressor4
on Apr 5, 2013 at 9:29:12 am

Thank you all for your help.

If I open the Compressor4 exported ProRes4444 file in Media Info it shows this:
Chroma subsampling : 4:4:4

If I open the 5DtoRGB exported ProRes4444 file in Media Info it shows this:
Chroma subsampling : 4:2:2

If I open the Quicktime exported ProRes4444 file in Media Info it shows this:
Chroma subsampling : 4:2:2

Is the FCP timeline Chroma subsample : 4:2:2 and is this why I am having to render the Compressor4 file and not the others?

Why do different programs export with different chroma subsamples if it's the same codec?

Why do they use the numbers 4 and 2 to represent a channel?

I've been editing for a long time but never been able to understand different channels and colours, thanks.


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Rafael Amador
Re: Having to render after importing from Compressor4
on Apr 5, 2013 at 11:00:08 am

[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:
http://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


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Edwin Street
Re: Having to render after importing from Compressor4
on Apr 5, 2013 at 2:24:43 pm

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:
http://mediainfo.sourceforge.net/en

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


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Rafael Amador
Re: Having to render after importing from Compressor4
on Apr 5, 2013 at 2:52:10 pm

[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


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Edwin Street
Re: Having to render after importing from Compressor4
on Apr 5, 2013 at 3:42:14 pm

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?


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Rafael Amador
Re: Having to render after importing from Compressor4
on Apr 5, 2013 at 4:12:18 pm

[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


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