GH2 GH2 422 hack?
- Thread starter CColton
- Start date
Shame. Thanks!
blazer003
Well-known member
GH1 can record 4:2:2 at 720p in MJPEG mode (with the hack), and the colors are impressive. It's the main reason I still have my GH1, and I get more comments on how awesome the footage looks when I use 720p 4:2:2 than when I use higher resolution AVCHD of GH1 or 2. The resolution may be better, but the average person like how the colors pop.
Personally, I have never been able to see any difference between turning 4:2:2 on or off. I understand that it is supposed to be useful for green screen I just have never seen any side by side evidence of that. Do you have any comparisons that show the exact same things recorded side by side with and without 4:2:2.
I guarantee I can tell the difference between 1080p GH2 footage and your 720p 4:2:2 MJPEG footage even if they both recorded the exact same thing.
blazer003
Well-known member
I don't have any side by sides, haven't done any definitive tests and admittedly I didn't use the MJPEG option often before the hack, but I can say that I believe that to my eye the MJPEG has better color information than AVCHD. Whether it's the hack or not, I don't know. Maybe I'll do some tests, or I'm sure others have at other points.
If you compare the two side by side, the 1080p looks better in terms of resolution but I do find that I have more latitude to work with in color correction and in general the colors just look better/more real when I use MJPEG. It's a different looking image, but to my average audience (a church congregation of 1500) I seem to always get a few comments about how good the video looked when I use the MJPEG to film something. It's happened twice with the pastor as well, when he came up to me and said "The video looked especially good today," and both times it happened to be things I had shot in MJPEG MOV for ease of editing purposes as I was working with an older portable system, and the MJPEG MOVs are much easier for Adobe CS4 to handle.
So, it's by no means definitive, and I only use it from time to time because I feel like shooting in 720p isn't as good, but people seem to like it.
If you compare the two side by side, the 1080p looks better in terms of resolution but I do find that I have more latitude to work with in color correction and in general the colors just look better/more real when I use MJPEG. It's a different looking image, but to my average audience (a church congregation of 1500) I seem to always get a few comments about how good the video looked when I use the MJPEG to film something. It's happened twice with the pastor as well, when he came up to me and said "The video looked especially good today," and both times it happened to be things I had shot in MJPEG MOV for ease of editing purposes as I was working with an older portable system, and the MJPEG MOVs are much easier for Adobe CS4 to handle.
So, it's by no means definitive, and I only use it from time to time because I feel like shooting in 720p isn't as good, but people seem to like it.
I would agree that the colors are different for MJPEG vs. AVC-HD. The only thing I haven't seen a difference in is the 4:2:2 vs. not 4:2:2 MJPEG. I can't tell the difference visually between those two. I am sure you can pull them apart color by individual color and tell the difference though.
ulisses
Well-known member
How do you add the extra color data from 4:2:0 to 4:2:2 or even 4:4:4 ? I understand it wasn't encoded by the camera.
Barry_Green
Moderator
You can't quite get 4:2:2 720p just by resizing a 1080p image. But you could get basically 4:4:4 when resizing to SD.
The idea here is that in a 1920x1080 image, you have 960x540 chroma (color samples). So if you downconverted the whole image to 960x540 or smaller, you should be able to apply that color sampling across the whole frame, and end up with effectively a 960x540 (or smaller) 4:4:4 image...
But in 720p, for 4:2:2, you'd need 640x720 of chroma info. 960x540 doesn't really get you there. You have more than enough horizontal, but not nearly enough vertical color sampling to make a 4:2:2 720p image.
The idea here is that in a 1920x1080 image, you have 960x540 chroma (color samples). So if you downconverted the whole image to 960x540 or smaller, you should be able to apply that color sampling across the whole frame, and end up with effectively a 960x540 (or smaller) 4:4:4 image...
But in 720p, for 4:2:2, you'd need 640x720 of chroma info. 960x540 doesn't really get you there. You have more than enough horizontal, but not nearly enough vertical color sampling to make a 4:2:2 720p image.
Only if you had access to the uncompressed YCC data before the AVCHD encoder did its job. For that, you'd need the HDMI/SDI output of the AF100, which is already in 8-bit 4:2:2 format.
The main advantage of the hacked GH1's 4:2:2 MJPEG format is the relatively light compression it can use. To make the most of this for green-screen work, I recommend the 75Mbps 4:2:2 MJPEG HD mode found in the Peak Reliability Patch:
75Mbps GH1 Peak Reliability Patch V2
This MJPEG patch is optimized for a custom frame size of 1536x864, which I found to be the largest frame size the GH1 could reliably handle. Since green-screen shots are typically composited into external background footage, the non-standard frame size is not a problem. In practice, you want to shoot the green-screen footage at the highest available resolution so you can make your matte as fine as possible.
Zephyrnoid
Veteran
Yes. The colors in certain flavors of MPEG 4 (AKA MJPEG) do look better than AVCHD but that's where it ends.