data rate at 1080 same as 720?

D

dktanner

New member
Hi guys, I am new to this forum.
Here's my problem.
My camera tutor is trying to convince me to shoot a short film on the af 100 in 720p, because he say's the school doesnt have a lot of hard drive space and the short film is more about practise. I'd like to shoot at the highes No I think that the data rate (which is quite low anyway) is the same in 1080 and 720.
I looked it up on the panasonic website and found this diagram.(u have to scroll down a bit to see it)...

http://pro-av.panasonic.net/en/af100/feature03.html

if so, how come the data rate is the same. I'm assuming my camera teacher thinks if i shoot at 720 that'd be half the amount of data...

I would apreciate your help:-)
 
Maybe your tutor isn't so concerned about the camera files but more the files that are created after transcoding. In FCP there is difference between ProRes at 1920x1080 and ProRes 1280x720.

Still a bit tight. Buy yourself a firewire drive and manage your own data.
 
Agree, a 1TB drive goes for nothing these days.
Keep in mind, a USB drive isnt recommended for editing off of. So get a Firewire Equipped drive.
I am not all that familiar with the AF100, but with my GH2... the stock settings for 720p uses a lower bit rate then the higher 24MB data rate for 1080p.
 
they both have the same bitrate but if like gary said it is being trnascoded, 720p would be smaller. otherwise avchd they both will be the same
 
I edit from Lacie Rikiki 1TB USB drives a lot when I'm using my MBP, I used to be sceptical about USB too but had no problems in a year of using them pretty heavily,
usually a good deal cheaper than FW too, don't get a G-Tech mini FW drive whatever you do, had 2 fail on me! one twice after the drive was replaced under waranty, so I guess thats 3 fails
 
The AF100 records PH mode at 21 to 24mbps, regardless of whether it's 1080 or 720. You get higher quality at 1080/24 than you do at 1080/60i, and you get higher quality at 720/24 than you do at 720/60. And you'd get higher compression quality but less resolution at 720/24 than at 1080/24.
 
I didn't know that was the case Barry, it's very similar to the Sony XDCAM codec in the respect that the bitrate stays the same regardless of framerate or frame size. This makes me more likely to shoot 720 where resolution isn't as big of a deal. I kind of wish I knew that earlier.
 
The more I think about it the more I want to shoot 720 for the quality benifit. I used to shoot 720p DVCPROHD with my HVX200 and HPX170 all the time, and that bitrate is 40mbps I-frame. 21-24mbps Long GOP is pretty close if not better equivilant wise to 40mbps I-frame.
 
Sony's XDCAM and Panasonic's AVCCAm do have a lot of structural similarities -- they're both long-GoP IBP 8-bit 4:2:0 codecs. AVCCAM is h.264/mpeg4 vs. XDCAM's mpeg2, but in general overall codec type they do behave generally similarly.

You'll see more of a quality difference between 1080 and 720 on an AF100 or AC160/130 than you would on an HMC150, because there's substantially more detail in the 1080 modes of the newer cameras, and therefore the compression will have to work that much harder in 1080 mode.

If you don't need 1080 res or variable frame rates and you want the least-compressed footage, that's what 720/24 is for.

On the HPX170 I actually advised that the best quality comes from 1080 mode instead of 720. Reason being, *because* the HPX170's chip block didn't deliver a fully-saturated 1920x1080 frame, the 1080 recordings were more detailed and less compressed than the 720 recordings. The space savings on the HPX170 were substantial, 40mbps instead of 100mbps, but the image quality difference wasn't as big as the size difference. Even so, 1080 was the least-compressed and highest-detailed mode on the HPX170.

On the new full-raster AVCCAMS (meaning, not the HMC150) the 720/24 version is the least compressed, although the detail difference between 1080 and 720 is pretty substantial -- you give up a lot of detail from 1080/24 down to 720/24 on the AC130/AC160. Not quite as much on the AF100 since it resolves a little bit less than the 130/160.
 
Brian@202020 said:
The more I think about it the more I want to shoot 720 for the quality benifit. I used to shoot 720p DVCPROHD with my HVX200 and HPX170 all the time, and that bitrate is 40mbps I-frame. 21-24mbps Long GOP is pretty close if not better equivilant wise to 40mbps I-frame.
Click to expand...
There are many things that go into that evaluation beyond bitrate. The AVCCAM will be 1280x720, whereas the HPX170's 960x720, so the AVCCAM footage can be sharper. But, the HPX170's rendering 4:2:2, so it will have nearly twice as much color resolution as the AVCCAM cameras. As for compression quality, if both were AVC, then 40mbps I-frame might be about on par with 21mbps of long-GoP, but since you're comparing 2001-era DV-based compression against 2011-refined AVC/H.264 I would think that on raw compression capability the AVCCAM would return superior results so long as the codec doesn't get overloaded.
 
Yeah Barry I'm aware of the other benifits and drawbacks you listed for both codec. In 1080 I personally think the benifits of the 80mbps 24p DVCPROHD footage out way the benifits of the 21-24mbps AVCCAM 1080 footage. 720 is a different story, and I can't wait to test out the 720p AVCCAM on a few jobs and hopefully reap the benifits I was unaware of.
 
No pixels are being skipped, but the way it's being downconverted from 1080p->720p in realtime is creating some extremely mild moire patterns. The chips are always scanned at 1080p all the time, there is no pixel-skipping or line-skipping or pixel-binning or any of that hoohah going on.
 
So this has me confused a little...On the AF100 1080p 24p looks worse than 720p 24p? I am shooting a lot of projects in the next few weeks one being a short film which will be playing at fests and the other are weddings and such. So far I have only shot 1080 24 and have loved the footage. How would i benefit shooting 720?
 
There isn't a substantial difference, and no I wouldn't say the 1080/24 looks "worse" than 720/24. It's simply a case of -- there is no free lunch, there's always a tradeoff. In 1080/24 you get substantially more detail and more resolution. In 720/24 you get less detail and less resolution, but the compression can therefore be "cleaner" (fewer compression artifacts).

Fact of the matter is that most people never notice or see any compression artifacts in most footage anyway, so as a practical matter for most people it's a non-issue. It's just a tidbit for that 5% who are going to be pushing the camera to its limits -- if you're in a situation where the codec might be taxed beyond its ability to cope, the 720 mode can be pushed further than 1080 can before compression artifacts become visible.
 
What happens to the bitrate when we record (1) 1080 or (2) 720 via the SDI to say (1) KiPro or Samurai, or (2) Blackmagic uncompressed?
 
Until you have time to mull over the different benefits of resolution/bit rate. I suggest u get urself a good HD, and shoot the highest quality/settings. Unless your shooting slow mo stuff, stick with the frame rates - multiples of 24.
I think we can all agree 1080p looks the best, and in post you can downsize it to 720...giving you a finer grain and less noise.
 
AlmaVideo said:
What happens to the bitrate when we record (1) 1080 or (2) 720 via the SDI to say (1) KiPro or Samurai, or (2) Blackmagic uncompressed?
Click to expand...
When recording to ProRes or uncompressed via SDI you loose the benifits of 720, but when recording to the Nanoflash the benifits of 720 still exists. The Nanoflash records to a modified codec that has similar bitrate qualities to the AF100 just at a way higher bitrates.
 
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