1080 24p vs. 720 24p

G

Girlspitswater

Member
I see a lot of talk regarding shooting 1080 24p vs. 720 24p (or 1080 vs. 720 in general for that matter):

What exactly is the debate?
What is everyone's opinion on this topic?
And lastly, what setting have you all found to be most suited for you?

The HMC should be shipped to my work this afternoon and I am taking this camera on a shoot all next week. Any info to get a head start would be excelent! BIG THANKS everyone!
 
720p is true progressive, meaning that one frame follows the next at 24 or 30 frames a second, up to 60 (slo-mo). Progressively. 1080i is interlaced, with overlapping fields in a pattern that give it that "video" look. Then it goes through an in-camera pulldown to 24p. So 720p, with its own discrete frames, behaves more like film, and is thus preferred by the discerning individual. There's a bunch of details to quibble about but that's the nutshell.
 
I’d like to follow up on this question in the hope of getting some thoughts from the legends like Barry Green and Bob Diaz.

How well does 720p display on consumer 1080i/p HD televisions? Someone in here once wrote that average consumers won’t be able to distinguish a difference. True?

Finally in terms of television (local) production -- what’s the best format option (most versatile for broadcast) for the HMC? I’m gearing up to film two separate pilots (one for local PBS, the other to be pitched to local stations), and if I go with the multiple HMC production option -- what format do you recommend to allow for the best versatility in terms of broadcast distribution? (meaning, the local station doesn’t say “this is nice but we can’t use it”) My guess is 1080/24p. Am I right?

My thanks!
 
Justin Kuhn said:
720p is true progressive, meaning that one frame follows the next at 24 or 30 frames a second, up to 60 (slo-mo). Progressively. 1080i is interlaced, with overlapping fields in a pattern that give it that "video" look. Then it goes through an in-camera pulldown to 24p. So 720p, with its own discrete frames, behaves more like film, and is thus preferred by the discerning individual. There's a bunch of details to quibble about but that's the nutshell.
Click to expand...

HMC150 shoots 1080p as well as 1080i.

Personally, I prefer to work with 720p on the HMC150. It mostly comes down to the codec and bitrate. With the HMC you get 21mbps for both 720p and 1080p. So with 1080p you're compression is higher. However, both start with the same uncompressed image. In the couple of keying tests I ran at both 1080 and 720, when I zoomed in to the same image size, I didn't see much (really any) difference.
 
1920 x 1080p should / does have higher resolution than 1280 x 720p however I cannot see the resolution difference.


P= progressive
I= interlaced


In HD TV you normally get 1080i or 720p. When viewed normally you cannot see much difference but for fast moving -slow motion type things [sports mostly] 720p is better because progressive scans in one line at a time [1, 2, 3, 4, etc.] whereas 1080i scans in odd lines and then even lines [1, 3, 5, 7 etc followed by 2, 4, 6, 8 etc].
Broadcasters can carry more 720p signals than 1080i signals... Or so I'm told.


Progressive gives you 24 frames per second or 30 frames per second or whatever frame rate you have.
Interlaced gives you 60 fields per second [odd lines then even lines].


This odd even stuff gives you [Can give you] jagged lines around the edges of faster moving objects.
You don't have that “issue” with progressive.


One thing I hated about HDV was the 1080i.
I had to de-interlace everything which was an extra step plus you lose resolution when you de-interlace so 1080 is no longer 1080. But that depends on what de-interlacing method you use.


There is so much more to it just as Justin Kuhn said but for me 720 or 1080 as long as there is a “P” at the end.... I okay with it.
 
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Deinterlacing 1080i 24p with advanced pulldown will simply discard the split frame and recombine the others giving you 1080 actual lines of vertical resolution
 
AGMedia said:
I’d like to follow up on this question in the hope of getting some thoughts from the legends like Barry Green and Bob Diaz.

(#1) How well does 720p display on consumer 1080i/p HD televisions? Someone in here once wrote that average consumers won’t be able to distinguish a difference. True?

(#2) Finally in terms of television (local) production -- what’s the best format option (most versatile for broadcast) for the HMC? I’m gearing up to film two separate pilots (one for local PBS, the other to be pitched to local stations), and if I go with the multiple HMC production option -- what format do you recommend to allow for the best versatility in terms of broadcast distribution? (meaning, the local station doesn’t say “this is nice but we can’t use it”) My guess is 1080/24p. Am I right?

My thanks!
Click to expand...


(#1) My own feelings are that a 1.5x increase (1280 x 1.5 = 1920 and 720 x 1.5 = 1080) would not be noticed by most. This assumes normal shots and not blue/green screen work.


(#2) First, HD TV in the USA is broadcast as 720/60p or 1080/60i. In the case of 720/60p, one could broadcast a 720/30p or 720/24p video and it would be laid on to a 60p output. With 720/30p every frame would be shown twice in the 60p output. The 720/24p would be shown in a 2:3 (twice followed by the next frame three times) output. The 1080 follows much the same rules, except the output is 60i.

While a 1080i station could up-res a 720p video, but chances are they would like to have it in full 1080 resolution. On the other hand, a 720p station could down-res a 1080p video.

This leaves you with a choice, shoot 1080/24p for a film look OR 1080/30p for a video look.

I know that the idea of 24p is popular, but the lower frame rate does not work as well as the higher frame rate with rapid movement. The 30p does offer the higher frame rate and is better for faster movement, but will lack the film look that people may want. I wish I had a simple answer to this choice.


COMPRESSION RATIOS:

Last night I thought to see what the compression ratios were for the different resolutions and frame rates. Now this information can be misleading, because it's only good when we are comparing the same CODEC. Even different compressions using the same system, but different CODECs have no real comparison, because the different CODECs may produce different quality compressed videos.

(h_Res x v_res x frame_rate x 12_bits_per_pixel) / output_bits_per_second = compression_ratio : 1

1080/30p = 35.5:1
1080/24p = 28.4:1

720/60p = 31.6:1
720/30p = 15.8:1
720/24p = 12.6:1

Interlaced generates addition load for the CODEC, making things worse, so these numbers can't show the additional load:

HM Mode 1080/60i = 43.9:1
HG Mode 1080/60i = 57.4:1
HE Mode 1080/60i = 93.3:1 (In this mode the resolution is 1440 x 1080)

In the 720/24p mode the compression ratio is so low, Panasonic could have used M-JPEG and it would have worked. The bottom line is that with AVCHD, you are VERY unlikely to generate any motion artifacts no matter what you shoot at 720/24p. If anyone can generate motion artifacts, I'd sure love to see what the heck you are shooting!

Even at 720/30p, the compression ratio is so low you would have to work VERY hard to find something that could produce motion artifacts.

As the compression ratio gets higher and higher, the risk of a motion artifacts increases. However, this depends on what you are shooting. Using a different camera with a different H.264 CODEC, guys playing basketball shot at 60p did not show any major artifacts with a compression ratio of 31:1, but did show some motion artifacts at 30p and a compression ratio of 50:1. Then again, neither the 31:1 nor the 50:1 videos showed any motion artifacts with slow moving subjects.

In the case of the HMC-150, one would need to run tests at the different resolutions and frame rates to see where fast action might cause motion artifacts.


Bob Diaz
 
Thanks for the info guys thus far. I'm not concerned/confused between Progressive and Interlaced, The concern I have reached is the questions whether I should shoot 720p or 1080p. 1080 in theory should be great quality, although there is arguments out there questioning that with the MHC such as what Kurtmo said...

"With the HMC you get 21mbps for both 720p and 1080p. So with 1080p you're compression is higher. However, both start with the same uncompressed image."

Bob's comment is very though with great info. Please correct me if I'm wrong (new to compression ratios) Bob and others, but is it correct say the lower the compression ratio, the higher the image quality for that codec?

For Example, when comparing:

1080/24p = 28.4:1
and
720/24p = 12.6:1

720/24p is a lower compression ratio, therefor a higher image quality or am I way off in left field on this one?

Thanks again guys.
 
It's a bit more complex than that.

In general, the lower compression ratio is better, because the compression noise is less, BUT we reach a point where the compression noise can not be seen and going to a lower compression ratio does not appear to improve the image.

The problem with video compression is that it's hard to put a finger on how much can you get away with. The more random the changes, the more the risk of seeing compression noise. Crank the gain to +18dB and the random noise patterns from the CCDs will really cause havoc and increase the risk of compression noise. Fast action, like with sports, can increase the risk for seeing compression noise.

If at all possible, shot some test shots of the things you want to produce and see if any of the footage shows any hint of compression noise or not.


FYI:
I'll be off-line for 2 weeks because I'm going on a trip and won't have any internet access during that time. I hope that if you have more questions, either someone else can help, or you can afford to wait 2 weeks.

Best Wishes,

Bob Diaz
 
I just gotta say Bob is the man. He always takes time out of his day to write an essay if need be to help a stranger out ^_^
 
Dear Mr. Diaz,

My thanks for your very thoughtful response. Your insights are very helpful, and I thank you.

My concern with 30p with the HMC is that it isn’t native -- it’s one of those “pulldown” deals. Combined with what I’m assuming is a 60 interlaced stream in the 1080 mode -- I’m thinking this means I’d be back in the HDV world being required to “remove pulldown” and “deinterlace.”

I’m not really looking for the “movie” look, rather the most versatile production option for television. This thinking brings me to either the 720/60p or 1080/24p.

From these two choices -- 60p is preferred, but the question then goes to that “up-rez” thing regarding stations/televisions. Meaning, does 720 look bad on a 1080 set? Is something filmed in 720 already obsolete, or will it be in two years?

The traditional view, obviously, is that “up-rez” sucks and should be avoided at all costs. Accordingly, this dumps me back on the 1080/24p doorstep.

Another option is to dump the HMC altogether and go with the AG-HPX170. I’ve been testing these models side by side these past few weeks and the bottom line is that if you have even modest post production capabilities -- the functionality and price difference (in terms of spending more on P2 cards than on the actual cameras) renders the HMC a spectacular option and the HPX an awful option. I’m also convinced P2 will be entirely obsolete in two or so years -- bringing the entire logic of a full scale P2 investment into question.

SO -- following this line of thinking -- and assuming that interlaced material is not ideal -- we come back to the 1080/24p or 720/60p question. In my case, the choice of format truly effects investments in productions -- and that’s why I ask for the thoughts of the pros, and am grateful for insights shared.

Thanks!
 
BobDiaz said:
(#1) My own feelings are that a 1.5x increase (1280 x 1.5 = 1920 and 720 x 1.5 = 1080) would not be noticed by most. This assumes normal shots and not blue/green screen work.


(#2) First, HD TV in the USA is broadcast as 720/60p or 1080/60i. In the case of 720/60p, one could broadcast a 720/30p or 720/24p video and it would be laid on to a 60p output. With 720/30p every frame would be shown twice in the 60p output. The 720/24p would be shown in a 2:3 (twice followed by the next frame three times) output. The 1080 follows much the same rules, except the output is 60i.

While a 1080i station could up-res a 720p video, but chances are they would like to have it in full 1080 resolution. On the other hand, a 720p station could down-res a 1080p video.

This leaves you with a choice, shoot 1080/24p for a film look OR 1080/30p for a video look.

I know that the idea of 24p is popular, but the lower frame rate does not work as well as the higher frame rate with rapid movement. The 30p does offer the higher frame rate and is better for faster movement, but will lack the film look that people may want. I wish I had a simple answer to this choice.


COMPRESSION RATIOS:

Last night I thought to see what the compression ratios were for the different resolutions and frame rates. Now this information can be misleading, because it's only good when we are comparing the same CODEC. Even different compressions using the same system, but different CODECs have no real comparison, because the different CODECs may produce different quality compressed videos.

(h_Res x v_res x frame_rate x 12_bits_per_pixel) / output_bits_per_second = compression_ratio : 1

1080/30p = 35.5:1
1080/24p = 28.4:1

720/60p = 31.6:1
720/30p = 15.8:1
720/24p = 12.6:1

Interlaced generates addition load for the CODEC, making things worse, so these numbers can't show the additional load:

HM Mode 1080/60i = 43.9:1
HG Mode 1080/60i = 57.4:1
HE Mode 1080/60i = 93.3:1 (In this mode the resolution is 1440 x 1080)

In the 720/24p mode the compression ratio is so low, Panasonic could have used M-JPEG and it would have worked. The bottom line is that with AVCHD, you are VERY unlikely to generate any motion artifacts no matter what you shoot at 720/24p. If anyone can generate motion artifacts, I'd sure love to see what the heck you are shooting!

Even at 720/30p, the compression ratio is so low you would have to work VERY hard to find something that could produce motion artifacts.

As the compression ratio gets higher and higher, the risk of a motion artifacts increases. However, this depends on what you are shooting. Using a different camera with a different H.264 CODEC, guys playing basketball shot at 60p did not show any major artifacts with a compression ratio of 31:1, but did show some motion artifacts at 30p and a compression ratio of 50:1. Then again, neither the 31:1 nor the 50:1 videos showed any motion artifacts with slow moving subjects.

In the case of the HMC-150, one would need to run tests at the different resolutions and frame rates to see where fast action might cause motion artifacts.


Bob Diaz
Click to expand...

I think that using compression ratios is missleading. Remember that this is a long GOP format so each frame is stored only as the difference between it and the previous frame. It is not like an intra frame compression format where each frame stands on its own.

In laymans terms, at 30p you have twice the elapsed time per frame compared to 60p, so the change in the image will be greater as more will have happened in that extra time. Therefore you have more image changes to compress for each frame of 30p or 24p than for each frame of 60p.

I am not saying that this cancells out the theoretical compression ratio advantage completely, but it will do to a significant extent. This means that the 60p image shouldn't be much different in quality. It also has double the frame rate which is an improvement in 'time resolution'.

Stuart
 
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AGMedia said:
My concern with 30p with the HMC is that it isn’t native -- it’s one of those “pulldown” deals. Combined with what I’m assuming is a 60 interlaced stream in the 1080 mode -- I’m thinking this means I’d be back in the HDV world being required to “remove pulldown” and “deinterlace.”
Click to expand...
No, none necessary. It's recorded with the progressive flag set so your footage should be treated as progressive. I don't know why they don't just call it "native" 30p, because it acts like it.

I’m not really looking for the “movie” look, rather the most versatile production option for television. This thinking brings me to either the 720/60p or 1080/24p.
Click to expand...
Well... if it's for the "television" look, then 720/60p or 1080/60i. If it's for the "movie" look, then 720/24p or 1080/24p. 30p gives you problems when you want to convert to PAL frame rates. 60i/60p/24p all convert better to 50/25p than 30p does.

From these two choices -- 60p is preferred, but the question then goes to that “up-rez” thing regarding stations/televisions. Meaning, does 720 look bad on a 1080 set?
Click to expand...
720/60p converted to 1080/60i looks a lot better than 1080/60i converted to 720/60p.

Is something filmed in 720 already obsolete, or will it be in two years?
Click to expand...
ABC, FOX, and ESPN all broadcast exclusively 720p, and will likely continue to do so. In fact, I went through my cable channels looking at all the high-def channels. I think the grand total was 17 were 1080i, and 11 were 720p. That's a full 40% of the high-def channels on Time Warner Cable broadcasting 720p!

No doubt that eventually, someday, 1080p will be the future. But 720p has a lot to recommend it right now.

The traditional view, obviously, is that “up-rez” sucks and should be avoided at all costs. Accordingly, this dumps me back on the 1080/24p doorstep.
Click to expand...
Well, yeah, but... there's not much more detail in the HMC150's 1080/24p mode, over its 720/24p mode. You're pretty much squeezing out all the camera can deliver when using the 720 mode. And the compression is more efficient in 720 mode. So for those reasons I recommend 720 on an HMC150 as its "sweet spot".

the functionality and price difference (in terms of spending more on P2 cards than on the actual cameras) renders the HMC a spectacular option and the HPX an awful option.
Click to expand...
Well, based on a strictly cost-opinion, the HMC150 is much less expensive. But it doesn't do a lot of things the 170 does - like variable frame rates, or standard-def recording, or HD-SDI, or live video streaming, or time lapse, etc. It's not quite apples to apples there.

No doubt that for a personal user, home enthusiast, or a "closed shop", the HMC150's price advantage over the HPX170 is quite compelling. But if you need to integrate with the broadcast/P2 world, you might see some significant advantages with the 170.

I don't know if that's your business though. I'm just pointing out that both products exist for a reason, even as similar as they are. The choice between them should be relatively easy, once one assesses what's truly important to them then one or the other should emerge as the obvious choice.

I’m also convinced P2 will be entirely obsolete in two or so years -- bringing the entire logic of a full scale P2 investment into question.
Click to expand...
"entirely obsolete"? When 85% of Europe's broadcasting infrastructure has switched to P2? When P2 is the overwhelming choice for broadcasters worldwide? I don't think it's going anywhere anytime soon.

What I do see is that its appeal to direct end customers will probably dip, as AVCHD grows in prominence. P2 never made the best choice for, say, a wedding shooter... but recording 3 hours on a $100 card is far more attractive and that's what AVCHD can do. So I think P2 will likely migrate up into being more specifically used by broadcasters and higher-end production houses, whereas SDHC/AVC-HD will take over with the smaller organizations.
 
Hi
If I am shooting primarlly for the web, and looking for the highest resolution on the web, would I want to shoot 1080P because I don't have to deal with the TV broadcast issues?
 
sagedrummer said:
Hi
If I am shooting primarlly for the web, and looking for the highest resolution on the web, would I want to shoot 1080P because I don't have to deal with the TV broadcast issues?
Click to expand...
Well, broadcast is just one part of the issue. For web, any progressive format should work well if you can match your target framerate. One of the points of this debate is that 1080 will not give you higher quality (and can arguably be worse). Also, I have yet to see anything over 720p used for the web anyway. The only point I see in using 1080p is if you have trouble editing 720p in your workflow (which many have due to current software issues).
 
mcsmooth said:
The only point I see in using 1080p is if you have trouble editing 720p in your workflow (which many have due to current software issues).
Click to expand...

If you can't edit 720p, you probably will have more trouble editing 1080p.

If you are shooting for web use, 720p sounds like the best choice as it is the size and frame rate a good website would be displaying e.g. (Vimeo), and you would not need to further compress it, except for the down compression going from master to web stream. Since you are compressing downward and not upward, you should retain the best parts of the master.
 
Thanks for all the responses, it seems like 720P is the way to go, at least if I am shooting primarily for the web. There are instances where it may be watched on a TV but I think I would be safe with 720P with that anyway.
 
Green Hornet said:
If you can't edit 720p, you probably will have more trouble editing 1080p.
Click to expand...
My statement was misleading, but that is true in regards to computer load. What I meant is that some NLE's are not fully compatible with 720p modes. This is the first camera to implement the feature (even though it is in the spec), so I guess it was expected. If you are transcoding, it probably isn't an issue.
 
sagedrummer, if you are shooting primarily for the web, then 720p is the way to go.

I have a 152, so my 720p options are 25 and 50fps. 60fps is absolutely fantastic for movement, the reason why the sports channels use it, but 50fps is very close (I shoot exercise and gym environments in the present work context, with a lot of rapid movement).

I recommend 720p simply because it upscales and downscales (which you will need) beautifully.

Tangential to the OP's question, but worth considering in these discussions is the in any comparison between 1080i ("full" HD) and 720p, is the Kell factor. A 1080i picture has about the same final resolution as 720p (assuming Kell factor of 0.7; others here might offer a different percentage reduction), and (personally) for the motion and scaling reasons mentioned, I think 720p is the right choice. The 150 series does this really really well, IMHO. cheers, kl
 
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