OT: ProRes White Papers

What is with Apple? I need some info on the prores codecs, so I go to Apple's website, search prores, click links for the prores white papers... and get taken to a sell-sheet for FCP X. They're not bailing on prores, too, are they?

Here are the questions I'm trying to get answered: a) ProRes is billed as a lossy format for post production but not for delivery. If you're going to edit in it, you're already throwing away whatever the codec squeezes out of the frame; you're not going to get it back, so why can't you deliver in it? b) Does anyone here use prores 4444 to deliver for film-out?

Tom: If you still need it, I've uploaded the white paper.

ProRes compressed 4:2:2 is not great for post production effects such as keying. This isn't simple generation-to-generation recompression, but differencing, etc. ProRes compressed 4:4:4 isn't perfect for this either. Better use an uncompressed 4:4:4 codec for this. 4:4:4:4 with an alpha channel. 10-bit or 12-bit depending on what you've got.

For delivery on the other hand, image appearance is all that matters and ProRes compressed 4:2:2 is fine. (If the horizontal luminance resolution is visually adequate then half as much horizontal chrominance resolution is visually adequate.) You must decide if your image quality and the destination warrant HQ.

Dennis Couzin
Berlin, Germany

Thanks much for this!

On page 10, Apple states: "...The data rates shown on the bar chart above are for ?full-width? (1920 x 1080) HD frames at 29.97 frames/sec. The Apple ProRes family also supports the 720p HD format at its full width (1280 x 720). In addition to full-width HD formats, Apple ProRes codecs support three different ?partial-width? HD video formats used as the recording resolutions in a number of popular HD camcorders: 1280 x 1080, 1440 x 1080, and 960 x 720. While Apple ProRes formats can encode image frames of any dimensions, only the SD, partial-width HD, full-width HD, and 2K frame sizes are supported for real-time editing in Final Cut Pro."

Am I reading this correctly to mean that ProRes is real-time for the 720p flavor of HD, as well as 1920x1080? Anyone know this, for certain?

Yes for certain

I use and have used all the above in FCP in realtime. It really does work (if your Mac meets the minimum the system requirements for ProRes).



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Thanks, Ben. Can Prores proxy and Prores 4444 co-exist in the same timeline, with real-time performance, or will one or the other have to render? This is an animated project and I'd like to use prores proxy for low-res renders, then start adding HQ or 4444 as we start getting finals. (And proxy files are not, in fact 'proxies', right? They're actually self-contained?)

i'd do some tests, Tom.

i've been working with ProRes LT down-converts from ProRes 4x4 Alexa files.
my non-scientific observation is that the LT was taking longer to render than the 4x4
my guess is it takes longer to render the more compressed codecs.

so Proxy may not gain you any render advantage, PLUS for graphics it might not look too great.
try the other ProRes flavours, they are all very band-width efficient. even 4x4

(and yes ProRes "Proxy" is self-contained)


nick

[I use and have used all the above in FCP in realtime. It really does work (if your Mac meets the minimum the system requirements for ProRes).]

I concur, I am enjoying full raster HD 8-bit (standard quality) ProRes422 on a 2.26 Mhz Mac Pro 8-core. Multiple streams, no rendering.

Imagine this in 64-bit! On FCP 8.

- Loren

Today's FCP 7 keytip:
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ProRes are all 10 bit codecs. My guess is that ProRes LT takes longer to render because of the dithering that is required to make the video still look good at that level of compression, while ProRes proxy doesn't have it because it was meant to be a proxy codec.

Dennis, what do you mean by differencing as opposed to loss via re-compression?



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And yea, to work with different ProRes codecs in the same timeline, go to sequence settings and switch render precision to 8 bit yuv. This increases RT performance. You will eventually have to render to your sequence codec.



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"My guess is that ProRes LT takes longer to render because of the dithering"

make sense, thanks for that Strypes

Gerard-

[ProRes are all 10 bit codecs.]

They are?

- Loren

Today's FCP 7 keytip:
Summon your Video Scopes with Option - 9 !

Your Final Cut Studio KeyGuide? Power Pack
with FCP7 KeyGuide --
now available at KeyGuide Central.
www.neotrondesign.com

Yes. This is one of the differences between DNxHD and ProRes. DNxHD came out years earlier, so it was 8 bits, with 10 bit support added in much later only for the HQ (DNxHD 220x/185x).



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I was under the impression that the standard quality versions were always 8-bit. Huh!

- Loren

Today's FCP 7 keytip:
Summon your Video Scopes with Option - 9 !

Your Final Cut Studio KeyGuide? Power Pack
with FCP7 KeyGuide --
now available at KeyGuide Central.
www.neotrondesign.com

Apple says that they are 10 bit and tests indicate that they are 10 bits. I've heard that rumour quite a lot- that HQ is good for high bit depth acquisition sources. Compeletely false.

The difference is in how much data the codecs throw out. HQ throws away less, SQ more and LT even more (but it may use dithering or some fancy prefiltering to improve visual quality), and proxy is the most compressed codec in the Prores family. Use HQ if you can, although the difference between HQ and SQ is barely perceptible.



www.strypesinpost.com

Quote
strypes
what do you mean by differencing as opposed to loss via re-compression?

Something I learned from you! 4:2:2 chroma subsampling looks fine because the eye can't resolve chroma nearly as well as luminance. But effects such as keying do not work like the eye. They generate boundaries from chroma, and where these boundaries disagree with luminance boundaries the differences stand out in the composite.

Apple's white paper does say as much on page 7: "This minimal chroma subsampling has traditionally been considered adequate for high-quality compositing and color correction, although better results can be achieved using 4:4:4 sources."

The white paper's later pages on Quality concentrate on generational losses due to re-compression, and someone reading the conclusions on page 15 might not appreciate that for some effects HQ 4:2:2 is just as good as 4:4:4:4, but for other effects not.

Dennis Couzin
Berlin, Germany

Ah, I remember that part... We were looking at the changed values after compressing to ProRes. I'm just taking it as part of the compression pipeline that ProRes uses. It's hard to really know what is going on in ProRes.

Whether you use 422 or 444 depends on your source. If your source is 4:2:0 or 4:2:2, it does not matter whether you use ProRes 422 HQ or 444, just that you are wasting drive space with 4444 because it has to store those extra 0:2:2 samples which did not exist in the source.



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