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Blu-Ray with CBR through Compressor ?

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Thomas Helm
Blu-Ray with CBR through Compressor ?
on Apr 2, 2013 at 6:57:39 pm

Hello everybody,

I'm new here - so please don't hurt me ;-)

I have a film that I need to bring on a Blu-Ray for a festival-screening.

The infosheet from the festival says, that the Blu-Ray must have a CBR at 30 Mbit (including sound). I talked to the festivals tech-guy and he said, that CBR is the most stable, that is why they don't want VBR (appearently the ups and downs in the variable bitrate make a Blu-Ray unstable... at least that's what he said).

Since I have the project (ProRes 4444) in Final Cut, I thought I send it through compressor, build the Blu-Ray in Encore, make a discimage and burn that in Toast.

BUT... there is no CBR option in Compressor for h264... or at least I can't find it anywhere. There is one for Mpeg2, but the festivals tech-guy told me that the quality will be much worse. I would prefer the modern codec too - but not with a VBR.

How would you go about to make a h264 with a CBR in an apple environment... I know that Quicktime pro can do that (http://digitalcontentproducer.com/videoencodvd/revfeat/h264_mac_0907//index1.html), but then I don't have an m2v for Encore and I want to prevent too much recompressions/calculations.

Any suggestions - thought ?

Regards - Thomas


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Mark Spano
Re: Blu-Ray with CBR through Compressor ?
on Apr 2, 2013 at 8:07:06 pm

[Thomas Helm] "I talked to the festivals tech-guy and he said, that CBR is the most stable, that is why they don't want VBR (appearently the ups and downs in the variable bitrate make a Blu-Ray unstable... at least that's what he said)."

Yeah sure, this guy's a peach. H.264 VBR is what makes Blu-ray look so good. CBR is generally a waste of bit rate. But, you gotta give them what they want…

[Thomas Helm] "Since I have the project (ProRes 4444) in Final Cut, I thought I send it through compressor, build the Blu-Ray in Encore, make a discimage and burn that in Toast."

Sounds like a plan. I do this all the time (of course with VBR)

[Thomas Helm] "BUT... there is no CBR option in Compressor for h264"

For Compressor to encode H.264 for Blu-ray, it only allows for VBR encoding (which is what you have found, and no, you are not missing it)

[Thomas Helm] "How would you go about to make a h264 with a CBR in an apple environment"

Well, since you intend on using Encore for authoring, I assume you also have Adobe Media Encoder. This can encode H.264 with CBR at high bit rates for Blu-ray. Roll your own custom preset to look like this:





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Thomas Casque
Re: Blu-Ray with CBR through Compressor ?
on Apr 2, 2013 at 8:29:39 pm

Great - thanks for the speedy reply Mark !

You are right I have the media encoder from adobe - but I never looked into it before - looks like a neat little program :-)

So I will give out a prores 4444 from FCP and import it into adobe media encoder. Kind of done...

But another thing is, that I need to interlace my 25p project. Looks kind of simple at the first glance. Just hit interlaced and select upper or lower field order...

Noobie question: How was that again with the field order and interlaced material... lower field for PAL and upper field for NTSC - or is this kind of irrelevant for Blu-Rays?


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Mark Spano
Re: Blu-Ray with CBR through Compressor ?
on Apr 2, 2013 at 8:44:36 pm

[Thomas Casque] "But another thing is, that I need to interlace my 25p project. Looks kind of simple at the first glance. Just hit interlaced and select upper or lower field order..."

I would first ask the projection if they can use 25 fps. Some projection can only use 24 or 23.976 fps.

If you want to make the Blu-ray with 25i, when you go to output your ProRes 444 from FCP, first duplicate your master sequence, and go to Sequence Settings, change field order there. It will not change any clips in your sequence, just duplicate each frame into two fields on output. The render will take a bit longer to export since it's creating fields where there were none, but it's not doing any motion interpolation, just duplication, so it should be easy. Definitely check this file (on a broadcast monitor) once you've output it. It should (for all intents) look identical to your 25p master.

[Thomas Casque] "How was that again with the field order and interlaced material... lower field for PAL and upper field for NTSC - or is this kind of irrelevant for Blu-Rays?"

That's SD talk. In HD, all interlaced material is Upper Field First.



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Thomas Casque
Re: Blu-Ray with CBR through Compressor ?
on Apr 2, 2013 at 8:55:37 pm

The projectionist said 24p or 50i is what is possible.

Since I don't have the time to have the 5.1 sound changed to 24 fps professionally, I thought I would go with the interlaced option.

But 25i ? I thought 25p equals 50i - since two half-images per frame ?!?

I had originally planned to do the interlacing just like you described now. So last question: Do you think fcp will do just as well with the interlacing as the adobe media encoder ? The adobe environment looks much more promising... but maybe that is just because of the ancient finalcut7 interface ;-)


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Mark Spano
Re: Blu-Ray with CBR through Compressor ?
on Apr 2, 2013 at 9:23:43 pm

[Thomas Casque] "But 25i ? I thought 25p equals 50i - since two half-images per frame ?!?"

Nomenclature - it's confusing. I always try to write so that the number represents frame rate, and have the letter designate whether it's interlaced or progressive.

25i = 25 frames per second = 50 fields per second.

50i = 50 frames per second = 100 fields per second = does not exist.

If the projectionist said 50i he probably meant 25 fps interlaced. Double check with him.

[Thomas Casque] "Do you think fcp will do just as well with the interlacing as the adobe media encoder ?"

Definitely use FCP to create the interlacing. FCP is good at the dumb tasks, so duplicating frames into fields is fine in FCP. Then your Media Encoder only has to worry about taking each field and encoding into H.264.



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Thomas Casque
Re: Blu-Ray with CBR through Compressor ?
on Apr 2, 2013 at 9:36:20 pm

Okay great - I'm on my way !

THANKS A WHOLE LOT for the quick and competent help !

Kind regards from Berlin - t


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Thomas Casque
Re: Blu-Ray with CBR through Compressor ?
on Apr 2, 2013 at 9:43:59 pm

Okay great - I'm well on my way now.

THANKS A WHOLE LOT for the quick and competent help !

Kind regards - t


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Rafael Amador
Re: Blu-Ray with CBR through Compressor ?
on Apr 3, 2013 at 2:37:15 am

[Mark Spano] "If you want to make the Blu-ray with 25i, when you go to output your ProRes 444 from FCP, first duplicate your master sequence, and go to Sequence Settings, change field order there. It will not change any clips in your sequence, just duplicate each frame into two fields on output. The render will take a bit longer to export since it's creating fields where there were none, but it's not doing any motion interpolation, just duplication, so it should be easy. Definitely check this file (on a broadcast monitor) once you've output it. It should (for all intents) look identical to your 25p master."
No need to do nothing on FC with the Prores444 master.
In the Media Encoder set 25fps/Upper first.
The master is Progressive, so no problem to interpret it as upper or lower.
rafael


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Mark Spano
Re: Blu-Ray with CBR through Compressor ?
on Apr 3, 2013 at 3:38:39 am

Are you sure Rafael? The Blu-ray spec I have says 25p is not able to be encoded on disc. Unless you're saying that Media Encoder will automatically do the duplication from frames to fields, but then why bother chancing it when you know FCP will do that without issue?



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Rafael Amador
Re: Blu-Ray with CBR through Compressor ?
on Apr 3, 2013 at 5:11:10 am

Hi Mark,
The advantage of Progressive stuff is that can be interpreted as Progressive, Upper or Lower without problem.
Is just about reading the pictures lines in the order you want. It always looks like Progressive,

[Mark Spano] "The Blu-ray spec I have says 25p is not able to be encoded on disc."
You are half right.
BR encodes 1080p stuff as Interlaced (PSF). The Progressive picture is compressed and streamed as it was interlaced.
Is not a big deal. i just about making the system to read odd-lines first, then even-lines instead of line by line.
The picture doesn't lose his progressive nature on display.

That counts for all 1080p25/30 stuff.
When you shoot 1080p25/30, the camera HD/SD-SDI is putting out 1080i25/30. Is the old story of the "Progressive Segmented Formats".
This simplifies the systems allowing to use a single protocol (interlaced) for both materials.
rafael


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Mark Spano
Re: Blu-Ray with CBR through Compressor ?
on Apr 3, 2013 at 2:24:29 pm

Rafael,

I understand how PsF works. What I'm saying is why bother guessing that Media Encoder *might* translate P into PsF, when you already know that FCP will do it? What if Media Encoder decides to do some interpolation to get there instead of simple duplication? I could test this, for sure, but since you need the intermediate file anyway (coming out of FCP), why not just make that PsF (upper field) and eliminate the variables?



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Rafael Amador
Re: Blu-Ray with CBR through Compressor ?
on Apr 3, 2013 at 3:52:35 pm

[Mark Spano] "What I'm saying is why bother guessing that Media Encoder *might* translate P into PsF, when you already know that FCP will do it? "
Could be done in FC, but that will means to lose one generation (rendering), when you just need to read the Prores444 file as Upper instead of Progressive.

Is when we make the H264 that the master neds to be processed as Interlaced instead of Progressive.
Two reasons:
- In a 420 codec, the Chroma is is processed different when the file is Interlaced or progressive.
- The H264 needs to be flagged as Interlaced (Upper first) to match the BR standard.

And is not if Media Encoder "might" translate P in to PSF. Media Encoder will do it. Just set SOURCE: 25fps Progressive, and OUTPUT: 25fps Upper First.
Compressor would do the same.

[Mark Spano] "What if Media Encoder decides to do some interpolation to get there instead of simple duplication? I could test this, for sure, but since you need the intermediate file anyway (coming out of FCP), why not just make that PsF (upper field) and eliminate the variables?"
There is not line interpolation or duplication going on. There is not de-interlacing or re-interlacing.
Is just that the progressive frame (Line 1, 2, 3, 4,..) will be read and streamed sequential:
- Odd lines (Upper field) first, so: Line 1, 3, 5,..
- Even lines (Lower field) after; Lines 2, 4, 6,..
All the lines of your master will be there.
rafael


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Mark Spano
Re: Blu-Ray with CBR through Compressor ?
on Apr 3, 2013 at 3:56:34 pm

[Rafael Amador] "Could be done in FC, but that will means to lose one generation (rendering), when you just need to read the Prores444 file as Upper instead of Progressive."

No generation loss, since there's no master yet. The export from FCP is creating the master.

[Rafael Amador] "And is not if Media Encoder "might" translate P in to PSF. Media Encoder will do it."

OK - this was what I was referring to by saying "sure I could test it". You tested it and it works - I have not since I haven't had the reason to test. I was just offering a method I knew was accurate and foolproof, without speculating if another workflow would work.



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Rafael Amador
Re: Blu-Ray with CBR through Compressor ?
on Apr 3, 2013 at 5:02:08 pm

[Mark Spano] "[Rafael Amador] "Could be done in FC, but that will means to lose one generation (rendering), when you just need to read the Prores444 file as Upper instead of Progressive."

No generation loss, since there's no master yet. The export from FCP is creating the master."

If the footage is progressive, needs to be rendered to be exported as Interlaced.
Only if BEFORE EDITING, the footage is checked as Interlaced in the Browser and edited on an Interlaced sequence won't need rendering.
Rafael


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