Panasonic pre-NAB press release: AJ-PX5000G P2 & MicroP2 AVC-Ultra camera

[Barry_Green]

... and I have now received confirmation -- AVCI-100 at 1080/60p is, indeed, 200 megabits per second, as verified by the head of the engineers at the Panasonic factory.

AVC-Intra, being designed as a professional master-quality codec, has consistent performance frame-to-frame regardless of the number of frames per second. The actual bitrate per second can vary if the # of frames vary, but the quality of the frame will be absolutely consistent regardless of the frame rate. 1080/60p takes up twice as much bitrate as 1080/30p (or 1080/60i). That's why AVC-I is named as having a "class" of performance. AVCI-100 is not a strict 100 megabits per second, it's "class 100", which is not as high quality as "class 200" would be. The number ("100" in AVCI-100) refers to the bitrate at standard HD sizes -- either 1080/60i (or 30p) or 720/60p. So AVCI-200, in 1080/60i, will be 200 megabits per second; for AVCI-100 in 1080/60i, it's 100 megabits per second. For other frame rates the actual bitrate per second will be proportionally affected by the number of frames. AVCI-200 at 1080/30p would be 200 megabits per second; 1080/24p would be 160 megabits per second, and 1080/60p would be 400 megabits per second. Similarly, for AVCI-100, 1080/24p is 80 megabits/sec, 1080/30p or 60i is 100 mbps, and 1080/60p is 200 mbps.

So, harddrive, your assumption was incorrect. If you've made this speculation on any other forums, it sure would be nice of you to go back and correct that so that the misinformation is countered and false rumors don't gain any traction.

 

[jdv]

1080 60p at 28000 USD? How is it exciting? Or am I missing something?

Tend to agree with this feeling. While the new tech/codec looks interesting, most TV stations (and even reality shows) are cutting budgets left and right. It's small sensor size would seem to eliminate it from most narrative work. It's price isn't attractive - and that's before having to invest in/commit to P2 cards. AVCI-100 at 1080/60p at 200 megabits per second is a nice feature, but one hardly useful for most ENG type work.

Again, interesting stuff. However it's tough to see why any station not already invested in P2/Panny would be buying, particularly at that price point. But I have no idea what the relative age of the Pannys already out in the field is - perhaps there is a built-in demand for this camera. It is without a doubt a sweet looking thing, and with it's slo-mo capacity, it might find a place in sports TV.

 

[harddrive]

You're making an assumption that may not be warranted. I haven't heard them say that 1080/60p will devote half the bitrate. The number in the name of the codec has traditionally been associated with the bitrate, but that is not a set thing with their AVC. Instead they refer to the AVC modes as a "class", such as "class 200" or "class 400". ........... And using that as a model, I believe AVCI-100 1080/60p will likely take up 200 megabits -- exactly the same amount of space per frame as all other AVCI-100 modes.

Again, you're assuming. I am assuming that it will indeed maintain the number of bits per frame of all other AVC-Intra 100.
....................

Well, again, I submit that you are misreading it. If you read it again with the idea that the bitrate is fixed per frame, it all starts to make sense. It's saying that it *can* record Class 200, but not 1080/60p in Class 200.

In which case it would appear my reservations are unfounded - if AVC-Intra 100 at 1080p/60 does indeed use 200Mbs, then any concerns about compression per frame being compromised are not valid. But whilst all your references to "class" (not bitrate) do indeed lead what you say to make perfect sense, then surely you must agree it's confusing terminology? I know I'm far from the only person to have thought (incorrectly it would seem) "AVC-Intra 100" equates to a nominal 100Mbs bitrate, period. The sentence I commented on in the press release was "will record in full-resolution, 10-bit 1080/60p (in AVC-Intra100)." and I suspect many people will (like me) have read that to mean "it will record 1080p/60 at a bitrate of about 100Mbs"?

I even looked AVC-Intra up in wikipedia which says "nominally 100 Mbit/s, size of each frame is fixed" - isn't it reasonable (even if I now realise wrong!) to take that to mean "AVC-Intra 100 always has a bitrate of around 100Mbs and each frame within a file has the same size as all the others"? I'd suggest ""nominally 100 Mbit/sat 30fps, size of each frame is fixed and independent of frame rate" as a less ambiguous wording?

Barry, I'm not arguing with the technicalities of what you're saying - quite the opposite - thank you for clearing the "class100", "class 200" matter up. But.... don't you think it's confusing terminology? Perhaps it would be better if you wrote their press releases!

Taking it further, then is it correct to assume that in the 50Hz world, and a 25fps framerate, the bitrate is then around 83.3Mbs? Because if so, that is far from common knowledge and I suspect will surprise a lot of people - it has been very widely assumed and written that for 25fps AVC-Intra100, the bitrate was 100Mbs. Or is it a different per frame figure between 50hz and 60Hz frame rates?

 

[Barry_Green]

It is confusing. I didn't get it at all when they kept using "class" last year at NAB. It's only now, with the unveiling of 60p within the existing codec, that I finally have grasped what it was they were talking about, and why they felt it necessary to add the word "class" in the first place.

Now that I know how it works, now I know why they had to differentiate it with a class. However, I suggest that the problem of confusion with the "class" is that they chose a number that does have a correlation with bitrate. If they instead had just called it "Class 1" and "Class 2" and "Class 3", that would probably have been vastly more comprehensible than calling it "Class 100", "Class 200", and "Class 444" (or whatever the top-end version is going to be called).

Or, if they wanted to correlate to bitrate, maybe they should have chosen a number that corresponds with the bitrate PER FRAME, not the bitrate per second... So AVCI-100 could have been "Class 3300" (3300kbps per frame) and AVCI-200 could have been "Class 6600" or whatever...

But, the precedent was set back in the late '90's with DVCPRO25 and DVCPRO50 and later DVCPRO100, so while hindsight might be great and Monday-morning quarterbacking is all fine and dandy, it's too late and we're stuck with the names they've given it. And yes, it's confusing and will take some education on their part.

Taking it further, then is it correct to assume that in the 50Hz world, and a 25fps framerate, the bitrate is then around 83.3Mbs?

No.

Or is it a different per frame figure between 50hz and 60Hz frame rates?

Yes. It is definitely 100 mbps in the 50Hz world. Because there are fewer frames, they get to use use milder compression in the 50Hz world. Fewer frames per second left them with extra bits, so they used those bits to increase resolution. In AVCI-100, they use all the bandwidth available to them, and that would mean that you folks actually get better performance (milder compression) than we get. To verify, I just ran off two recordings in AVCI-100, one in 720/60p and one in 720/50p, and the resulting file sizes were almost identical.

 

[harddrive]

It is confusing. I didn't get it at all when they kept using "class" last year at NAB. It's only now, with the unveiling of 60p within the existing codec, that I finally have grasped what it was they were talking about, and why they felt it necessary to add the word "class" in the first place.

I feel a lot better to hear you say you yourself have only just grasped what is being referred to! It's very good to get it clarified, though - maybe should be a "sticky" somewhere? Maybe someone could also get the wikipedia entry updated and clarified?

Now that I know how it works, now I know why they had to differentiate it with a class. However, I suggest that the problem of confusion with the "class" is that they chose a number that does have a correlation with bitrate. If they instead had just called it "Class 1" and "Class 2" and "Class 3", that would probably have been vastly more comprehensible than calling it "Class 100", "Class 200", and "Class 444" (or whatever the top-end version is going to be called).

Agree 100% with all that.

Or, if they wanted to correlate to bitrate, maybe they should have chosen a number that corresponds with the bitrate PER FRAME, not the bitrate per second... So AVCI-100 could have been "Class 3300" (3300kbps per frame) and AVCI-200 could have been "Class 6600" or whatever...

After your first post, that had crossed my mind as well, but reading what you say below about the 50Hz world that would mean "AVC-Intra class 100" would translate to one thing in the US, another in Europe. Maybe that wouldn't be such a bad idea though.....? I may be misremembering, but I have a feeling that AVC-Ultra was originally going to mean what "class200" means now - so AVC-Intra would always mean 3300kbs per frame, the number then accurately always defining actual overall bitrate.

But, the precedent was set back in the late '90's with DVCPRO25 and DVCPRO50 and later DVCPRO100, so .......

I may differ with you on the subject of precedent. The three examples above all did have exactly those bitrates (largely because they were initially tape based, based on 25Mbs, and doubling was the easiest way to engineer a higher format), so haven't we got used in Panasonic nomenclature to the number defining the bitrate? You may point to 720/p24 when solid state came along (with 40Mbs), but in general didn't that get referred to simply as "DVCPRO HD"? That's why reading "AVC-Intra 100" in the press release made me think (yes, wrongly) it was a 100Mbs system being talked about.

..........while hindsight might be great and Monday-morning quarterbacking is all fine and dandy, it's too late and we're stuck with the names they've given it. And yes, it's confusing and will take some education on their part.

And all I can say to that is that you're right! Unfortunate, but we're stuck with the given nomenclature.

Yes. It is definitely 100 mbps in the 50Hz world. Because there are fewer frames, they get to use use milder compression in the 50Hz world. Fewer frames per second left them with extra bits, so they used those bits to increase resolution. In AVCI-100, they use all the bandwidth available to them, and that would mean that you folks actually get better performance (milder compression) than we get. To verify, I just ran off two recordings in AVCI-100, one in 720/60p and one in 720/50p, and the resulting file sizes were almost identical.

And again, thanks for the clarification. That is what I had thought when I put "it has been very widely assumed and written that for 25fps AVC-Intra100, the bitrate was 100Mbs.". But of course it does mean that at 25fps there are about 4000kbs allocated per frame, at 30fps 3300kbs, as you say above.

Which raises an interesting practical point. General advice for programming destined for markets in both 50Hz and 60Hz territories is to shoot in the one which covers the majority of likely use, and probably to go for either 24p or 25p as that can be relatively easily changed from one to the other by a 4% speed up/slow down. Bearing the above comments about bitrates in mind, then if your end market is 50:50, they become an argument in favour of producing in 25p and obtaining the 24p by the slow down, rather than the other way round. The 25fps mode will have considerably milder compression per frame than 24fps.

 

[Barry_Green]

That may indeed be a viable option. I would think someone would have to run some serious side-by-sides to see if there's a noticeable difference; I'm betting it'll be pretty minor if noticeable at all since Panasonic markets AVCI as "master quality", but if there is a difference, I would suspect that the 25p version would be slightly cleaner.