The final verdict re: 720p vs 1080p

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Phil1076

Well-known member
Taking the following points into consideration:

1. AVCHD is a fixed size codec
2. I will not be doing any keying
3. I will not be broadcasting
4. I'm not interested in pixel peeping


Is it fair to say that 720 24p will yield less noise than 1080 24p on this camera due to less compression?
 
I think it's hard to be definitive because it depends on what you are shooting, and you also need to differentiate between noise from the sensor and artefacts generate by the codec.

The codec only has limited space and noise is harder to compress than a clean image, so in that sense, some of the noise (and details) may get smoothed out as you stress the codec more, on the other hand artefacts introduced in order to compress the larger frame, and to most people this can look like noise.

A final verdict is 'it depends' ;)

Perhaps it would be better to address your situation from another angle. If you are not going to be doing any keying, not going to be broadcasting in full HD (720p uprezes quite nicely, especially with a kiss of Neat Video) and don't bother pixel peeping, then shoot 720p all the time. It will save on hard disk space if you need to transcode, will be much easier on your NLE and you really don't lose that much anyway.

When ever I am using the HMC and shooting for DVD rather than Blu-ray I shoot at 720p. End of story.
 
Barry suggests the colours are better in 1080i mode but on the other hand, the resolution of 1080i is only marginally higher than 720p in the execution of the HMC150.
 
Well I would assume that higher resolution - more chroma samples recorded. Not that the colors are "better" per se, but you might have a little more latitude in post working at 1080 pixels.
 
I would expect latitude to be a function of the CCD and lens more than the codec. (Assuming 4 bits for luminance, which is the standard for all codecs.)
 
Can you elaborate? I read the "more chroma samples" thing a few weeks ago. What does this translate to in the real world?

Assume I do wedding videos and I output to both BD and DVD.
 
hendosan said:
Well I would assume that higher resolution - more chroma samples recorded. Not that the colors are "better" per se, but you might have a little more latitude in post working at 1080 pixels.
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Exactly. It's not that the colors are "better", but that there's more sampling per luma, and therefore the colors are going to be represented more accurately. On the HMC150, you get a total real-world resolution of about 1440 x 810 out of the chipset, so that'll give you a little bit sharper images in 1080 vs. 720, but you get a LOT more chroma sampling in that 1080 frame (960x540 vs. 640x360 in720p) so you have almost the same luma resolution, but well over twice as much chroma information.
 
Jim Simon said:
I would expect latitude to be a function of the CCD and lens more than the codec. (Assuming 4 bits for luminance, which is the standard for all codecs.)
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I'm sure that's not what hendosan meant. I'm sure he was meaning that you had more flexibility in post because you had more accurate color sampling and 2.25x as much chroma information.
 
Phil1076 said:
So what's the final verdict? Will I get less noise/grain shooting in 720 24p vs. 1080 24p?

Assume I do wedding videos and I output to both BD and DVD
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I'm afraid you will really have to do your own tests rather than rely on people who don't shoot weddings and/or ship both DVD & Blu-ray. Weddings are somewhat different to most people shooting shorts, features, adverts, promotions etc because (as you know) at weddings we can't stop the show and setup another light or two because it would look better. Unless you had time to prepare a room, you get what you get and fix it in post.

The scene settings used in camera can make a huge difference, making each of 720/1080 look better or worse than each other. Look at the detail and coring settings as well as the gamma.

I've shot both 720p and 1080p for weddings and delivered both DVD and Blu-ray too. My strategy is simple. If the couple only want DVD then shoot 720p, because it's much easier on the editing system and the final render time is a LOT shorter if you are adding effects, noise reduction (Neat Video) and color grading. Since time is money, the render time alone can make a big difference. We are talking several hours, not minutes and seconds.

If you are shooting for Blu-ray than 1080 is 'probably' the better choice. I say 'probably' because the HMC is not true 1920x1080 and I've taken 720p footage and washed it through Neat Video to clean things before uprezing to 1080p and it looks gorgeous on a large screen TV from Blu-ray. Most people won't tell the difference between the 720 and 1080 from an HMC if it's processed correctly, compressed for Blu-ray then played on a large TV - especially if they don't have them side by side to compare!

So, while there are some minor resolution differences, there is extra chroma sampling in 1080 mode etc, I'm not sure you will see enough difference if it's intended for TV playback (even in HD) rather than the big screen.

There is no definitive answer and the final verdict you are looking for will vary from person to person based on what they shoot and how it's delivered. Sorry!
 
I shoot everything at 1080 24p or 30p. Only exceptions are sports, where 60p comes in nicely, and when I need to slomo. DVD output doesn'lt get upressed for editing. I just edit RT in Edius. On the fence about upressing for HD output (when using a NLE like Edius since I can setting render quality to be higher res than the source footage when doing CC, etc.).
 
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The Blu-Ray spec allows 1280x720 24p without issue. There is no need to up-res to 1080 and the difference between 1080 and 720 (as many people on the net have pointed out) is not noticeable unless you're going to a truly huge screen.

Since 1920x1080 is more than twice the pixel count of 1280x720, and AVCHD is a fixed length codec (21Mbps+3Mbps sound), I would assume that 720 would show much less compression artifacts. I haven't really had a chance to try it out to be honest. I work ever day until 5pm (by which time it's dark outside) and my 9 month-old is quite the hand full. I will try to make time this weekend.
 
1080 24p/30p is roughly the same amount of data as 720 60p.

As for comparing 1080 24p/30 to 720 24p/30p. I thought there was an in depth comparison buried somewhere on dvxuser that showed 1080 24p/30p to be better than 72024p/30p.
 
Phil1076 said:
Since 1920x1080 is more than twice the pixel count of 1280x720, and AVCHD is a fixed length codec (21Mbps+3Mbps sound), I would assume that 720 would show much less compression artifacts.
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That's not a valid assumption though -- I know, I've been there. :)

It would only be true if the 1920x1080 was fully and thoroughly saturated with detail to the same degree as the 1280x720 is. And on an HMC150, that's not the case. The HMC150 has a little more detail, but not a lot more, spread out over 2.25x as much space. AVC is an extremely intelligent codec, and it doesn't waste its bandwidth, it knows how to deal with it.

I originally thought as you did, that the 720p mode must be cleaner, but after using it for a while I switched my tune and decided that 1080p is really the way to go, giving you the most detail, much more color information, and if there's a penalty in terms of compression artifacts it's pretty darn minimal.

However, I still maintain that if you want the "live" look, 720/60p is just much preferable over 1080/60i, no doubt about that!
 
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Denwa said:
1080 24p/30p is roughly the same amount of data as 720 60p.
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True, but ... here's where it gets maddening -- even though it's the same number of pixels, that doesn't mean it would compress the same. AVCHD is a long-GoP codec, meaning that it not only compresses spatially (as in, 1280x720) but it also compresses temporally, compressing the changes between frames. If very little changes from frame to frame, the codec can be astonishingly efficient. If a tremendous amount of change happens from frame to frame, the codec will be taxed considerably harder. In 24p, much more changes, frame-to-frame, than it does in 60p. Yes there's more frames per second, but if they're not changing much, there's very little penalty. In the end, the same amount of motion will happen in 24p or 60p (meaning, the same amount of motion is happening in front of the camera) and it'll need to be recorded; in general they both do pretty well, but I would expect 720/24p with a 1/48 shutter to be a little cleaner than 60p at 1/60th. More of the motion would be under motion blur at that point, and therefore be easier to compress.
 
Phil1076 said:
The Blu-Ray spec allows 1280x720 24p without issue. There is no need to up-res to 1080 and the difference between 1080 and 720 (as many people on the net have pointed out) is not noticeable unless you're going to a truly huge screen.
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Yep, I fully understand the specs, but once in a while you have a picky customer that comes back and says that the BD player said 720p but they want the 'full HD' version, meaning 1080p and not 720p. I've had one such customer, so I made them a 1080p version and they went away happy.

BD is a bit of a sore topic with me at the moment. I've been struggling to get Encore to make me a particular BD for a WEEK now. It's keeps crashing! Arrgghh!
 
OK, that makes sense (no.. it does..really!). :)

I know that data sizes for upressed footage from AVCHD to Avid DNxHD, tend to be the pretty similar for 720-60p and 1080-30p (or was it 24p..er close enough).

Barry_Green said:
but I would expect 720/24p with a 1/48 shutter to be a little cleaner than 60p at 1/60th. More of the motion would be under motion blur at that point, and therefore be easier to compress.
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In your above post are you comparing 720 24p to 720 60p in regards to being cleaner or 1080 24p to 720 60p?
 
That above post was referencing 720 vs. 720, saying that the additional frames of 720/60p would probably tax the codec a little more than the variation between frames of the 24p, when specifically factoring in that the 1/48 shutter would probably let that motion blur out a bit.
 
Exact said:
I've been struggling to get Encore to make me a particular BD for a WEEK now. It's keeps crashing! Arrgghh!
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been there before... i feel your pain.

I shoot everything at 720p (although I've only recently got the HMC151) as my tests showed very little difference when burned to bluray and none when burned to DVD
 
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