EX1 XDCAM EX vs. ProRes footage - added noise during conversion? - Page 2 at DVinfo.net

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Sony XDCAM EX Pro Handhelds
Sony PMW-300, PXW-X200, PXW-X180 (back to EX3 & EX1) recording to SxS flash memory.


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Old April 4th, 2010, 04:00 AM   #16
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Hey Ryan,
This has happened to me in exactly the same way and I stopped using ProRes because of the noise with the conversion using compressor. I don't know what is happening as PR supposed to be a clean compression but the extra noise has killed this for me.
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Old April 4th, 2010, 08:55 AM   #17
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How about giving Cineform a shot? It is a true intermediate codec that uses wavelet compression versus ProRes which uses the older DCT style compression.

I dont really use ProRes much, but I am always suspect of Compressor. I've even seen weird results that I dont like.
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Old April 4th, 2010, 12:56 PM   #18
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Alister, would it be beneficial to record 10bit from a camera like the new PMW EX 350?
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Old April 4th, 2010, 02:25 PM   #19
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The 350 is very clean so there may be a small benefit for recording 10 bit, but it will depend on many factors including the gamma you use and it's not going to be a big benefit, you'll probably still find camera noise the limiting factor in grading. You really want a noise figure better than 60db to really take advantage of 10 bit.
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Old April 4th, 2010, 05:55 PM   #20
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Quote:
Originally Posted by Tim Kolb View Post
I think that it's 8 bit vs 10 bit that may be the visual difference here... It's been a tactic of high end post guys for some years to add noise to 8 bit footage to make it seem a bit deeper.

8 bit needs to do a fair bit of 'rounding' and what many of us see as being 'clean' footage is actually footage of objects that have more texture and variation than we have color precision to faithfully capture with 8 bits of color depth. Compression definitely accentuates

Compressed 10 bit footage can definitely seem more 'noisy' than 8... I've done some recording comparisons between 8 and 10 bit external devices fed via SDI...and I've seen what I believe you're seeing.
Maybe itís more a question of being able to see more of what the camera actually sees with 10 bit over 8 bit than 10 bit actually making the imagine noisier which just doesnít sound right. But I guess thatís the same thing you just said.


Quote:
Originally Posted by Tim Kolb View Post
10 bit is still preferable for any compositing work...those minor tonal variations are a huge help in selling an effect in cases where using 8 bit footage would cause the grayscale to collapse and posterize...
Itís more than preferable really. Itís basically a must! Reason why I couldnít understand when Alister said he could pull a cleaner key from 8 bit 4:2:0 long-GOP over 10 bit 4:2:2 I-frame.
But itís not only compositing. There are many benefits to be had in doing post in 10 bit.

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Originally Posted by Cris Daniels View Post
How about giving Cineform a shot? It is a true intermediate codec that uses wavelet compression versus ProRes which uses the older DCT style compression.
Yep, I prefer Cineform over Prores. I think it has a higher quality.
But on a Mac Prores has some workflow advantages.

Quote:
Originally Posted by Alister Chapman View Post
The 350 is very clean so there may be a small benefit for recording 10 bit, but it will depend on many factors including the gamma you use Ö
Yeah, Iím using STD3 on the EX1 when shooting green screen. The cine gammas do all sorts of funky things you want to avoid when shooting for green screen, like lifting the mid tones etc.

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Originally Posted by Alister Chapman View Post
One thing to consider is that the footage from an EX1 is border line with regard to getting any advantage from 10 bit recording as the noise level of the camera is greater than the 10 bit quantization level, so there is little to nothing to be gained by using 10 bit over 8 bit for capture with an EX1 (or any other camera with a 54db or worse noise figure).
Well, but itís not that 10 bit is worse than 8 bit. Whatever small gains it may produce, even if thatís the case, small gains is better than no gain. Besides, 10 bit seldom comes alone. If we were talking 10 bit 4:2:0 long-GOP over 8 bit 4:2:0 long-GOP I could see. But 10 bit is normally at least 4:2:2 and normally not long-GOP. Just leaving long-GOP land when you are talking about green screen and compositing in general is a Godsend. When you add 10 bit + better color resolution (4:2:2) + no long-GOP, itís hard to say I would rather shoot HDV/XDCAM for green screen and compositing.
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Old April 5th, 2010, 03:03 AM   #21
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Quote:
Originally Posted by Michael Maier View Post
Well, but itís not that 10 bit is worse than 8 bit. Whatever small gains it may produce, even if thatís the case, small gains is better than no gain. Besides, 10 bit seldom comes alone. If we were talking 10 bit 4:2:0 long-GOP over 8 bit 4:2:0 long-GOP I could see. But 10 bit is normally at least 4:2:2 and normally not long-GOP. Just leaving long-GOP land when you are talking about green screen and compositing in general is a Godsend. When you add 10 bit + better color resolution (4:2:2) + no long-GOP, itís hard to say I would rather shoot HDV/XDCAM for green screen and compositing.
With an EX1 there is nothing to be gained from 10 bit, yes 4:2:2 will give an advantage, but you have to trade that off against the added complexity of capturing to 10 bit and the size of the files generated. It won't suit everyones workflow, but given the choice I too would prefer 4:2:2 at a higher it rate over EX 35Mb/s. That's why I use a NanoFlash at 100Mb/s. To get similar performance from ProRes you need to use HQ which generates much larger files, which slows down my end to end workflow and makes project backups larger. If you shoot progressive the difference between 4:2:0 and 4:2:2 is tiny, you are only gaining an increase in vertical chroma resolution, a decent keyer should easily be able to extrapolate that from a 4:2:0 progressive signal and most keyers don't just work off the chroma, it is a combination of chroma and luma. At the end of the day getting the lighting right is going to make a far greater difference than whether you are using native EX or something else.


Please don't mix HDV and XDCAM in the same sentence, they are very different, they use different mpeg profiles, different frame sizes and bit rates. It's like saying a Ferrari and a Ford are the same as they both run on petrol. The quality difference between HDV and XDCAM is significant.

When I did my original tests I found ProRes to be noisy, both converted files and direct HDSDi captured files exhibited more noise than the native EX1 or XDCAM HD files. I was using a Blackmagic card for capture, it is possible that this is not the best solution for ProRes capture. Certainly the uncompressed capture files were a lot cleaner. To date I have not seen anything yet to make me change that view, but I have not looked into it closely.
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Old April 5th, 2010, 08:34 AM   #22
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"Yep, I prefer Cineform over Prores. I think it has a higher quality.
But on a Mac Prores has some workflow advantages."


Well I'm in it for the higher quality, thats is what this whole thread is about after all.... I can only think of one advantage of Pro Res from a workflow standpoint and that is not a good enough reason to work with Pro Res for me. And I can think of some disadvantages of Pro Res as well, since a huge percentage of post facilities and VFX studios use Windows or Linux boxes.
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Old April 5th, 2010, 08:50 AM   #23
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Quote:
Originally Posted by Michael Maier View Post
Maybe itís more a question of being able to see more of what the camera actually sees with 10 bit over 8 bit than 10 bit actually making the imagine noisier which just doesnít sound right...

I couldnít understand when Alister said he could pull a cleaner key from 8 bit 4:2:0 long-GOP over 10 bit 4:2:2 I-frame...

Well, but itís not that 10 bit is worse than 8 bit. Whatever small gains it may produce, even if thatís the case, small gains is better than no gain....Just leaving long-GOP land when you are talking about green screen and compositing in general is a Godsend. When you add 10 bit + better color resolution (4:2:2) + no long-GOP, itís hard to say I would rather shoot HDV/XDCAM for green screen and compositing.
I don't think in the EX1's case that it's a matter of what the camera "sees" being more intricately represented so much as what the camera is 'putting out' for signal. Alister's point is that many of these smaller cameras (I am an EX1 owner myself and really like that camera BTW) have a relatively high signal to noise ratio. It's part of the tradeoff in coming up with an inexpensive, small camera with a small sensor that puts out full HD resolution. I think Alister's point is that 10 bit is likely to represent this noise much more faithfully than 8...

I think there are some caveats involved here...I've seen 10 bit uncompressed from my EX1 and that stuff looks great (I'd have to rent hard drive space from the defense department to edit 10 bit uncompressed HD everyday, but...it looked very good). Once you start to have compression enter the picture, I think that has an impact on this issue as well.

Long GOP vs I frame for compositing depends on how good the codec is, and how well the compositing app handles it. It's not as if there are 'partial' frames that you can't composite of course...each frame is fully decoded and then the composite executes on that raster. I think when many of us think "Long GOP" we think of low bitrate files like you would see on a consumer DVD or in a web video. Long GOP alone doesn't determine quality level.

As far as 8 bit 4:2:0 vs 10 bit 4:2:2...and pulling a 'cleaner key'...

I think this needs to be placed in the context of lower end cameras with higher signal to noise ratios...as mentioned. If a 10 bit 4:2:2 clip has a compression scheme that accentuated some of that noise, you may end up seeing pixels of varying color on a greenscreen background resulting from noise that is now causing slight deviations in the chroma hue and luma info. In order to knock that background out, you need to create a 'wider bite' to make sure all the slight variations are included in the color you're 'knocking out' whereas 8 bit might have simplified that area, imaging what appears to be a more 'consistent' set of hue, saturation and luma values...in some cases 'less' is 'more'.

Also...4:2:0 vs 4:2:2 is a separate factor from 8 bit vs 10 bit. As far as 4:2:0 is concerned in general, I've puled keys from HDV. Is it ideal? Certainly not, but I think that many people somehow think that 4:2:0 keys like 4:1:1 (DV), and that really isn't true.

4:2:2 does up the density of color difference samples in the image and gives you an advantage over 4:2:0, but I think you also need bitrate to increase to realize any really serious gains as well. XDcam at 35 Mbit/s keys better than HDV because it's full raster (1920 vs 1440) and it has a 60% data rate increase. Both are 4:2:0, it's true, but at the end of the day, throwing more bits at it may not seem very 'sexy' or 'technical' but sometimes 'more' is simply...more.

In this discussion, the specifics are getting a little blended together...the actual range of formats and specifications you could be referring to within this realm of an '8 bit 4:2:0 Long GOP vs 10 bit 4:2:2 I-frame' discussion are many, and you have three factors that all change independently...and then you add different compression schemes on top of that with constant vs variable bitrate and DCT vs Wavelet transforms...

8 bit 4:2:0 Long GOP-

19 Mbit XDcam
25 Mbit HDV (not full raster)
35 Mbit XDcam
(also AVCHD falls in here at several bitrates)

8 bit 4:2:2 long GOP-

50 Mbit XDcam
100 Mbit MPEG2 (CD Nano)
140 Mbit MPEG2(CD Nano)
160 Mbit MPEG2 (CD Nano)

8 bit 4:2:2 I frame-

100 Mbit DVCProHD
135 Mbit HDcam
(these two tape formats are considered per manufacturer spec of course)
160 Mbit MPEG2 (CD Nano)
220 Mbit MPEG2 (CD Nano)

Also, several NLE manufacturers such as Avid, AJA, BlackMagic, Grass Valley have their own codecs that would fit in here...

10 bit 4:2:2 I-frame-

100 Mbit AVC Intra (Panasonic)
~36 Mbit ProRes 422 (Proxy)
~100 Mbit ProRes 422 (LT)
(and just 'ProRes' which has "significantly lower data rate than HQ" ...)
~220 Mbit ProRes 422 (HQ)

CineForm also belongs in here, with variable bitrates and several quality levels

Several different NLE codecs would also be in this list from Avid, AJA, BlackMagic, Grass Valley, etc.


...so which two are you comparing? The problem with discussions like these is that there are too many factors that get lumped together. The bottom line is that image specification is a game of inches. Lots of nuance here... Black and white conclusions are tougher to come by in the real world than they are on the sales brochures.

:-)
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