GH4 10bit 444 gh4 help

mr bill said:
How do you get 444 out of a GH4?
Click to expand...

GH4 4K 4:2:0 has enough chroma information to create a 4:4:4 version when down sizing the 4K to 1080 HD, but the CODEC you use to down size has to be smart enough to turn the 4K 4:2:0 into 1080 4:4:4.
 
You don't need to install anything from Cineform. You do need the latest version of PP or after effects - CC 2015.

Overall the tutorial is very good. The only thing I disagree with is setting Max Render Quality and Frame Blending. Do NOT check those boxes. They add nothing and can make things worse.
 
Jim Simon said:
You don't need to install anything from Cineform. You do need the latest version of PP or after effects - CC 2015.
Click to expand...

If you are working with a non CC 2015 version of PP or AE you will need to install the free GoPro Studio. ( this also applies to older versions of Sony Vegas Pro and Apple FCPX )
 
TheDingo said:
GH4 4K 4:2:0 has enough chroma information to create a 4:4:4 version when down sizing the 4K to 1080 HD, but the CODEC you use to down size has to be smart enough to turn the 4K 4:2:0 into 1080 4:4:4.
Click to expand...
Do you have any example files to illustrate what you're saying ..as I might misunderstand you. If you say you can turn basically anything into a 10 bit 4:4:4. ....and it just doesn't look like it originated from a 10 bit 4:4:4 ...I agree with you.
If you claim there is no difference between a 10 bit UHD 4:4:4 downscaled to 10 bit 1080 4:4:4 ...and 8 bit UHD 4:2:0 downscaled to 10 bit 1080 4:4:4 ...with the software of your choice …I would really like to see some example files that back this up.
 
bunk said:
Do you have any example files to illustrate what you're saying.
Click to expand...

Not off hand. This was a very big deal last year after the GH4 camera started to ship, and some people noticed that certain shots of the sky would band when originally shot as 1080 HD 4:2:0, but if you shot the same sky as 4K and then down sized to 1080 HD the banding was gone. This triggered a big debate on several different websites and lots of samples were kicked around, including a sample by DVX's very own Barry Green which showed the higher chroma resolution when down sized to 1080. At one point one of the original software coders who created the Cineform CODEC chimed in and confirmed that if done properly you could theoretically obtain 1080 4:4:4 from a 4K 4:2:0 source. ( the Cineform CODEC appeared to be one of the few CODECs that was retaining the 4K color info when downscaling to 1080 HD )

I've never seen any samples where original 1080 4:4:4 footage was compared with the 4K 4:2:0 footage down sized footage of the same subject matter, so I'm taking it on faith that it can be equivalent to 4:4:4, but it would be interesting to compare. I guess the key issue is having a camera that can shoot 1080 4:4:4 internally ?
 
I thought this technique was debunked when the GH4 first shipped?

When I first read this thread, I thought, ah maybe its something CINE codec is doing to retain the subsampling, but then I read the same is true if applied to the ProRes Codec.

I'm confused - so is it a codec specific thing, or a Adobe Media Encoder specific thing?
 
TheTrickster said:
I'm confused - so is it a codec specific thing, or a Adobe Media Encoder specific thing?
Click to expand...

The 4K 4:2:0 format records the same amount of color information as 2K 4:4:4, so it all comes down to what software is doing the actual down size from 4K to 2K and if it is preserving all the color data from the 4K file when it creates the 2K file. It appears that the Cineform CODEC does this when it down sizes, and it's certainly possible that other CODECs could do the same thing. It all depends on how they were coded.
 
the 4:4:4 thing has always been true. The only people trying to debunk it are those who don't really understand whats going on. Anytime you take 4:2:0 and reduce the size by 1/4 (1/2 vertical and 1/2 horizontal) you will be left with 4:4:4. Doesn't matter if its 8k to 4k, 4k to HD or HD to SD.

Think of it like a five gallon bucket of apples. Say that five gallon bucket is only half full. If you dump the two and a half gallons of apples into a two and a half gallon bucket you now have a two and a half bucket that is full of apples.

Chroma subsampling is not really a bad thing and it stills carries the stigma it once had with 4:1:1 interlaced DV footage. Its really just about ratios of color to luma and if you have a ratio that is smaller but then make the video itself smaller you bring that ratio back to a solid level. Don't think of it as resampling the color as much as we are actually just throwing out the extra luma pixels so the chroma and luma now match. There is a bit more complex science going on because of how image processing works but in all reality thats what is going on here. You sacrifice the 4k luma resolution to match the luma and chroma pixels at HD resolution.

The end format doesn't matter as long as it is capable of holding better than 4:2:0. Cineform, ProRes, 4:2:2 50mbit mpeg2, DNXHD, DVCPROHD, ect doesn't really matter as long as that format can hold 4:2:2 or 4:4:4. The software that does the down conversion doesn't matter as much either although you may get more accurate results from other programs. This is because when you take an image made up of pixels and scale it down the software creates all new pixels based on an average of the pixels around it. Some methods of down scaling may lead to better results such as bi-cubic or gausian. Sharper methods of down conversion attempt to sharpen edges so they may not be as good. You always get 4:4:4 but how those new 4:4:4 pixels are created could make the edges easier or harder to deal with and look less natural.
 
Also, with the modern algorithms, 4:2:2 is almost as good as 444. One of the secrets to Alexa is that it shoots a 2880x1620 pixel image in 16:9 (4.6 MPX) for 1080p downconversion and 4:2:2 in 1080p is 2.1 MPX + 1.05 + 1.05 = 4.2MPX.

F65, a $60,000 camera, has a 17.6 MPX sensor, which shoots 4K in 4:2:2 (8.8 + 4.4 +4.4 = 17.6). 8.8 MPX 4K is 4:2:0 and, after debayering, the final res is between 1,500 and 1,700 lines.
 
DLD said:
F65, a $60,000 camera, has a 17.6 MPX sensor, which shoots 4K in 4:2:2 (8.8 + 4.4 +4.4 = 17.6). 8.8 MPX 4K is 4:2:0 and, after debayering, the final res is between 1,500 and 1,700 lines.
Click to expand...

Guess I don't understand?

The F65 I have sitting next to me uses a CMOS sensor not a Bayer, and shoots 16-bit linear raw. Although you can shoot HD in 12-bit or 10-bit 4:4:4, or 10-bit 4:2:2
 
David W. Jones said:
Guess I don't understand?

The F65 I have sitting next to me uses a CMOS sensor not a Bayer, and shoots 16-bit linear raw. Although you can shoot HD in 12-bit or 10-bit 4:4:4, or 10-bit 4:2:2
Click to expand...
F65 has what Sony describes as "Q67" (quality or quantity at 67%, as it were). It doesn't have the standard Bayer pattern but it's a Bayer sensor nonetheless. The difference is that the pattern is diagonal rather than square. Its sensor has 20 MPX, 17.6 MPX of which are used for 4K acquisition, giving it a 4:2:2 color space (ARRI Alexa65 uses the same basic formula but on a much larger MF size sensor and at a much higher price of ~ $300,000, though it's available as a rental only). To go full RGB/non-Bayer, a 4K camera would have to have (8.8 x 3) 26.4 MPX. I expect the next generation of pro cameras to have just that.
 
Last edited:
is the BlackMagic 4K sensor Bayer style? I read it is global shutter, and thought maybe it was a different setup
 
wwjd said:
is the BlackMagic 4K sensor Bayer style? I read it is global shutter, and thought maybe it was a different setup
Click to expand...
Any sub-RGB sensor (defined as quoted resolution times three, making it 6.3 MPX for 1080p and 26.4 for 4K) with have a Bayern pattern sensor and, not so surprisingly, there are very few true RGB cameras out there. F35 was one (and it was a 1080p CCD, not a CMOS sensor, and it cost $250,000 when it was announced at the end of 2008) and F23 another.

After the high end pro gear moved toward 4K, I don't recall seeing a 4K RGB camera. Red Dragon and Weapon 6K is 19 MPX, which once again, can deliver a 17.6 MPX 4:2:2 4K image.
 
Here is a link to a 4:4:4 PNG (in 1920x1080) - I presume using this as a 'clip' we can test different Media Encoders / Codec's / NLEs to see what they are doing when when downscaling from 4K 4:2:0, obviously this would have to be upsized in some way to 4k - but its a baseline to see what 1080 4:4:4 should look like...

chroma-small-2ygo6v.png

http://www.abload.de/img/chroma-large-29ooi6.png

No idea, if this is helpful or not.
 
You must log in or register to reply here.
Back
Top