8 bit or 10 bit. My thoughts.

[Rafael Amador]

Very interesting Alister.
I think as well that the AVC-Intra is too short of data rate.
About the "10b recording" I don't know which are the expectations of the people.
There is more improvement going from 420/36Mbps to 422/100Mbps than the one going from 422/100Mbps to 10b Uncompress.
Some people expect the footage already color corrected.
rafael

[Alister Chapman]

Originally Posted by Rafael Amador

Some people expect the footage already color corrected.
rafael

How True!!

You are quite right, the jump from 35Mb 4:2:0 to 100Mb 4:2:2 is really quite dramatic while the step from that to uncompressed 10 bit is really very small and very difficult to see, even after grading.

[Mark Job]

Hi Alister:
You wrote: "How True!!

You are quite right, the jump from 35Mb 4:2:0 to 100Mb 4:2:2 is really quite dramatic while the step from that to uncompressed 10 bit is really very small and very difficult to see, even after grading. "


....It depends on what your presentation medium is. The difference between 100 Mbps Long GOP and 10 bit uncompressed in digital projection on a large screen is significant. This difference is also significant when you output to motion picture film. If you are looking at a TV set then it's not so appearent.

[Alister Chapman]

I disagree. Projection tends to hide any small artefacts. Air currents, suspended particles etc tend to soften the picture by a small amount. It is my personnal experience that I see more issues in an image on a large monitor or TV than projected, even at 4k. I have seen my material projected on many occasions on to some very big screens, including the main theater at IBC and also at NAB and it allways amazes me how good it looks, even 35 Mb footage. Transfered to 35mm the film grain hides even more digital artefacts.

[David Heath]

Originally Posted by Alister Chapman

I have not seen any information to corroborate Panasonics claim that their I frame only codec is 2x more efficient than Mpeg 2.

There are so many variables that I don't think it's possible to claim any single, definitive figure for the improvement factor. Under some circumstances the figure may be better than 2x, under others nowhere near as much. Those variables include the material under compression, and the actual bitrates - compare AVC-Intra v MPEG2 I-frame only at low bitrates and you may get a widely different improvement factor to doing it at high bitrates. Note the EBU did not give detailed results of their tests - only their conclusions, that both XDCAM 422 and AVC-Intra are considered suitable for "future general broadcast HD acquisition".

Note the word "general" - they are not saying that better than either may not be desirable for real top end acquisition (assuming the camera front end is up to it). What they ARE saying is that both AVC-Intra and XDCAM422 are both very good, and trying to argue one is better than the other really is splitting hairs.

And note that the 2x claim infers like-for-like, so AVC-Intra v MPEG2 I-frame only. Generally, we're more likely to be comparing it to long-GOP, with the efficiencies that itself brings (and which vary with GOP length), so in very broad terms, the figures tend to bear out that there's not a lot to choose between AVC-Intra 100 and XDCAM422 OVERALL. That's not to say that one may look better in some circumstances, the other in different circumstances.

Originally Posted by Mark Job

....What an odd conclusion. I guess the EBU didn't try any Primary & Secondary Color Correction then ;-)

What they did do was compress, decompress, then put in a series of shifts so the next compression would differ from previous ones - not just simply recompress the material without alteration. For XDCAM, they additionally made sure that original I-frames recompressed as difference frames, to deliberately tax the codec as much as possible.

As Alister says, this is for acquisition codecs - if you wish to do a lot of post work, then a better than either post codec may well be sensible.

[Mark Job]

Hi David & Alister:
I claim MPEG 4 is better than both the aforementioned codecs and compresses way, way more. In post production one can see a distinct difference between 8 bit and 10 bit acquisition, but I do submit that codec related exccentricities can certainly color, if not mask any advantages provided by 10 bit. I have not seen 4:4:4 12 bit acquisition, but I have been informed the MPEG 4 HDCAM SR codec is stunning. I can tell you the 4:2:2 version of it is stunning as well.

[Perrone Ford]

The SI-2K is 12bit acquisition. The Viper is 10-bit Log, Panalog is 10-bit log (from 14-bit linear), the Arri D21 is 12-bit linear.

Of course, these cameras are in a completely different league than the common "broadcast" cams most likely considered in the EBU test.

[Mark Job]

Hi Perrone & Alister:
My personal application is less broadcast and more Internet and Digital Cinema. I was very surprised by your analysis of large screen projection loss, and what you concluded from this Alister. (??) IMHO, it is precisely the "loss" factor in digital large screen projection, which you described well, that makes the differences between compressed and uncompressed easy to see. Since you're losing so much, you need to originate with as much information as you can possibly squeeze out of your camera.

.....Another reason for uncompressed is because such a signal is inherently less noisy, and when you have to go into a crippled video format like those currently employed on the Internet, then the less noise the better. As I think you pointed out earlier, encoders don't know what to do with noise. Noise in the signal doesn't encode well. Since my Tv series is on the Internet, I want to be able to take steps to improve what I consider to be not very good video quality. At least Adobe Flash and Windows Media Video have been steadily improving to the point where their HD professional codecs are quite acceptable now. I state *acceptable* but not great.

[Aaron Newsome]

Without question, you guys always have the most interesting "conversations" when I'm doing my real job. I miss the best ones for sure. Alister pretty much said it all in the opening post though.

[Mark Job]

Hi Aaron:
Yeah, I'm sort of debating, deliberating, and inquiring because I'm also actively involved in developping my own dream box to capture video my way, so we will see what we can see.

[David Heath]

Originally Posted by Mark Job

I claim MPEG 4 is better than both the aforementioned codecs and compresses way, way more.

I'm not disagreeing with you, but it's necessary to define "better", silly though it may sound.

MPEG4 specifies many different subsets - including AVC-Intra, itself a specific of MPEG4 Pt 10 or H264 - see H.264/MPEG-4 AVC - Wikipedia, the free encyclopedia .

And you have to specify bitrate. It shouldn't cause any surprise that MPEG2 at a high enough bitrate will outperform MPEG4 at a much lower bitrate.

But what is likely is that an MPEG4 variant will offer comparable quality to MPEG2 at a lower bitrate, so in that respect it may well be seen as more efficient. But it comes at a price - and that tends to be complexity, more difficult and requiring more power to code/decode. Hence, better in terms of bitrate efficiency, worse in terms of editability.

[Mark Job]

Hi David:

You wrote: "But what is likely is that an MPEG4 variant will offer comparable quality to MPEG2 at a lower bitrate, so in that respect it may well be seen as more efficient. But it comes at a price - and that tends to be complexity, more difficult and requiring more power to code/decode. Hence, better in terms of bitrate efficiency, worse in terms of editability."

......Try 1.5 X that of MPEG 2 in terms of quality enhancement (Compared to Long GOP) @ a little less data rate (I don't know how much less yet, but it is less. I do know you can cram so much more data on a memmory card with it however.) I don't know anything about MPEG 4's editability. I do know there is a royalty to pay to the MPEG consortium *IF* we elect to offer any sort of MPEG 4 compression in our box. We pay more again if we offer built in DVD image authoring (MPEG 2 Again). We don't pay anything if we go uncompressed ! ;-)

.....We're including an above average data processing chip in our box, because we literally want it to handle complex instruction sets for things we can't even figure out how to program yet (Which is allot of things actually), at as rapid a speed as possible.

......The XDR/Nano is a complex and unusually sophisticated system when you think of it, because the designers made it to run all kinds of operations and programs they can keep on adding to at a later date. I don't know how many programs the XDR and Nano can hold in their memmory, but in theory, I suspect the software engineers can just keep on going for quite sometime adding new programs to their manufactured units until an internal memmory limit or a hardware limitation is reached. This is really a very fascinating way to design and build something. If you consider there probably is no 100 % foolproof way CD could of programmed everything possible into these units before an initial release anyway, so they would need to have a way to desin and impliment based on user feedback.

[Alister Chapman]

With regard to projection. My observation is that projection often hides small nuances and artifacts that are more visible on a large LCD or Plasma screen monitor. Now I am not saying that starting out with a better image is in any way less desirable when projecting, simply that projecting is not as tough a test as of image picture quality as some may think. That's my opinion at least, based on actual observation of my own material on both large screen (60") monitors and projected at both 2k and 4k onto 30ft screens.

Codec decoding is a very important issue when choosing codecs for professional video applications. I believe the way the RED system works with its convoluted post production workflow is it's biggest downfall. Certainly RED can produce stunning pictures but very few producers want to deal with the cumbersome workflow. I have several Sony HXR-MC1 mini cams. These use AVCHD which is a type of Mpeg 4. Working with the files from these cameras is a complete PITA. Yes there are advantages in terms of file size and on a mini cam being able to have small files and thus small amounts of storage is essential. But even though it means more complexity and a second box I use the NanoFlash as a recorder whenever I can as the Mpeg 2 files are so much easier to deal with in Post. It's also a happy bonus that the picture quality is better, but then the Nano runs at a higher bit rate so thats expected.

You can argue over the numbers, figures and bitrate and the intricacies of all the various codecs forever and it's often an interesting debate. My observations in my original post were based on my real world experience working with products that are available now. Right now I believe that the NanoFlash is sitting in the sweet spot of size, usability, compatibility and picture quality. I could quite easily record 10 bit uncompressed from my cameras, but the files would be massive with all the storage and handling implications that brings. But visually the difference between acquiring at 100Mb/s 8 bit and uncompressed 10 bit is just about invisible. Even after heavy post work, provided in the studio I do any renders at 10 bit the difference is so tiny that it gives me no desire to have to deal with bigger files or slower codecs for acquisition.

One observation I have is that as a FCP user I find the Apple ProRes HQ codec rather disappointing. It seems to be fairly noisy and for my broadcast productions I am now rendering to uncompressed and this is giving me a cleaner picture.

[David Heath]

Originally Posted by Alister Chapman

You can argue over the numbers, figures and bitrate and the intricacies of all the various codecs forever and it's often an interesting debate. My observations in my original post were based on my real world experience working with products that are available now.

The point is that the numbers generally back you up - providing you look at the whole subject, and not just focus on one factor - such as 10 bit. I fully agree with what you say.

Two things can give contouring/banding in a post workflow - insufficient bitdepth or too much compression. The first seems intuitive, the second much less so. What it means is that 10 bit is only really worthwhile if it doesn't compromise the overall compression.

[Mark Job]

Originally Posted by Alister Chapman

I could quite easily record 10 bit uncompressed from my cameras, but the files would be massive with all the storage and handling implications that brings. But visually the difference between acquiring at 100Mb/s 8 bit and uncompressed 10 bit is just about invisible.

....Hi Alister: Yeah, in your application, but not in mine. In Internet Web Encoding (Which is more of an art than it is an exact science), starting post from an uncompressed source and rendering to an uncompressed source if you require rendering (As I think you have already found out for yourself) yields a much cleaner delivery than working from a compressed source. In our web site, you can double click on the screen and stream full screen. This is programmed as a dual purpose. If you have a laptop or desktop with an HDMI output which can connect to your large HD flat screen TV, then when you stream my production you are receiving Blu-ray quality audio and video. We are going to start to use Apple's Soundtrack Pro, because it allows us to mix, monitor and build a true Dolby Digital 5.1, which we will encode to stream straight from our website for the audio portion of our video streams.