4:2:2 vs 4:2:0 example; 4:4:4 would be even nicer...

[Piotr Wozniacki]

Just for comparison sake, I have blown up a very small fragment of the same scene, recorded both on my EX1 SxS card (using the 35 Mbps, 4:2:0 codec), and on my nanoFlash (50 Mbps, 4:2:2).

One can easily see how the vertical color resolution is doubled in the latter case. But looking at the picture, I've dreaming of how nice the full 4:4:4 color would look - while 4:2:2 removed all the vertical jaggies at the red flower edge, the horizontal edge is still ugly...

Well, it's nice to dream, isn't it :)

[Mark Job]

Hi Piotr:
The Nano Flash recorded still looked significantly superior to the 4:2:0 in terms of both color and resolution. However, both images looked really bad ! Could you post uncompressed .Tiffs to this thread (Sorry, I don't know if this web site can handle Tiffs but it's worth a try). I don't know to what degree the .png stills are affecting the image quality.

EDIT: Piotr, what resolution was the RED camera shooting the flowers at ? 2K, 3K, 4K ?

[Dave Sperling]

Or maybe just show us a still of the full frame from either EX1 or Nano to get an idea how much you've blown this up?
Thanks for posting the pictures!

[Andrew Stone]

Piotr good discussion topic. Ultimately, topics like this can lead to better use of the nanoFlash.

Just on an anecdotal level (which all of our comments will be without using scopes and such) I find pros and cons in the image quality of both.

Focusing on the nanoFlash image, it should be emphasized that this is a 50Mbit image and as such it is dealing with more color (chroma) information in that bit range which could account for the clearly visible mosquito noise in the darker portions of the image.

I think it would be more instructive to do a series of shots at various bitrates. What this tells me, in a practical sense, as I do a lot of low light work that I should be using higher bitrates than 50Mbits if I expect that I will have to grade in a serious manner in low light situations.

It will be interesting to see if we can determine what factors go into creating mosquito noise.

-Andrew

[Piotr Wozniacki]

Gentlemen,

In this little ad hoc example, I didn't want to compare bit rates, but color resolution. Perhaps it will suffice to say that both pictures are some 427x240 pixels fragments, blown up to the full 1920x1080 size.

[Andrew Stone]

Piotr I don't believe you can leave bitrates out of the discussion as the bitrate determines the amount of color mangling that occurs with the source. If you are using 50Mbit on 422 color and 35 Mbit on 420 then your result is going to be relatively close as the 50Mbit crunching has to deal with more source data than the 35 Mbit. Providing a higher bitrate image would allow a better "triangulation" to figure out what is playing into the various kinds of distortion that are being introduced.

-Andrew

[Piotr Wozniacki]

Andrew,

True, but no bitrate will change the color subsampling method; with 4:2:2 only the vertical color resolution is doubled compared to 4:2:0 (see the graphics in http://dougkerr.net/pumpkin/articles/Subsampling.pdf).

[Peter Moretti]

Right, I'm sure that the higher bit rates look better. But this wasn't meant to be an exhaustive test, just an experiment to show how much 4:2:2 really helps.

[Piotr Wozniacki]

Originally Posted by Andrew Stone

Focusing on the nanoFlash image, it should be emphasized that this is a 50Mbit image and as such it is dealing with more color (chroma) information in that bit range which could account for the clearly visible mosquito noise in the darker portions of the image.-Andrew

Andrew and Peter,

You're absolutely right the darker portions of the 50/422 image show a little less mosquito noise around edges than the 35/420 version does. And this is where the higher bitrates, available with the nanoFlash, really shine!

Having said that, I have deliberately compared two images, created with more or less the same effective bitrate (50 Mbps at 4:2:2 isn't really much more than 35 Mbps at 4:2:0, considering it must compress larger amount of the color information). So it's good to know that even in this scenario, there is less mosquito noise in nanoFlash files - at 180 (280), it would probably be virtually invisible.

Originally Posted by Peter Moretti

Right, I'm sure that the higher bit rates look better. But this wasn't meant to be an exhaustive test, just an experiment to show how much 4:2:2 really helps.

[Dan Keaton]

Dear Piotr,

I think this is a very interesting and informative discussion.

In your example, I calculate that this is 22.2222% of the entire image, or approximate a 450% zoon (if I calculated correctly). I base this on your reporting that the image area is 427x240 and the original image was 1920 x 1080.

Alister Chapman has posted on this blog, an analysis of Sony's 35 Mbps 4:2:0 versus 50 Mbps 4:2:2. He concludes that the compression ratio is about the same.

I think it be worthwhile to show what is possible with the tools that you already have.

Thus, I feel that one could record using I-Frame Only, at 220 Mbps or 280 Mbps I-Frame Only and then zoom in to check the quality. One could compare this to 35 Mbps 4:2:0, or 50 Mbps 4:2:2 or anything else they desire.

[Mark Job]

Hi Friends:
Very interesting discussion. What about the difference in *Quantization* between the way MPEG 2 @ 4:2:0 (Probably also 1440 x 1080 pixels ??) color space is being encoded versus Full Raster HD 1920 x 1080 pixels @ 4:2:2 color space MPEG - 2 at 50 Mbps ? I have seen 25 Mbps HDV Mpeg - 2 .m2t files with only 1440 x 1080 pixels look visually free of Mosquito noise and blocking artifacts, while I've seen 35 Mbps MPEG - 2 not look as good. Can we ascertain what the Quantization factors are from the two examples ? My point being there are other factors which can be colouring what we are seeing here. EDIT: Data rate isn't everything, but it certainly is an important factor of course.

[Dave Sperling]

Hi Mark,
Remember, there are 2 different 35 Mbps codecs - both 4:2:0.
The one for the EX cameras is 1920x1080, the one for the PDW-355 series disc cameras is 1440x1080.
Also, I believe both the 35 Mbps codecs are VBR, as opposed to the 25 Mbps HDV codec and 50 Mbps XDcam422 codec which are both CBR.
Just more variables for the equation...
At least we all seem to agree that the 100 Mbps (and higher) Nano recordings look better than the lower bit rate camera-based ones!

[Mark Job]

Originally Posted by Dave Sperling

Hi Mark,
Remember, there are 2 different 35 Mbps codecs - both 4:2:0.
The one for the EX cameras is 1920x1080, the one for the PDW-355 series disc cameras is 1440x1080.
Also, I believe both the 35 Mbps codecs are VBR, as opposed to the 25 Mbps HDV codec and 50 Mbps XDcam422 codec which are both CBR.
Just more variables for the equation...
At least we all seem to agree that the 100 Mbps (and higher) Nano recordings look better than the lower bit rate camera-based ones!

...Hi Dave: Yes indeed, you'e absolutely right :-) Also, HDV MPEG 2 m2t file quality can vary in quality from camera to camera as well @ 25 Mbps encode rate. The one in the Canon XL H1 camcorder is truly excellent, but I understood it to be a VBR encoder, and it was for this reason that it was above average. Perhaps Dan or Chris Hurd would know what kind of MPEG - 2 encoder is in the XL H1 ? Dan I thought the Sony XDCAM HD 4:2:2 hardware encoder CD uses in the XDR & Nano Flash was a VBR encoder ? (I hope I'm not transversing private corporate information asking about this ?)

[Dan Keaton]

Dear Mark,

JVC used what has become to be known as HDV 1, 18.7 Mbps (I think)

Sony and Canon used 25 Mbps, known as HDV 2 (as far as I remember).

I do not know if HDV 2 is VBR or CBR.

I do know that our 50 Mbps 4:2:2 and above Long-GOP codecs are CBR (Constant Bit Rate).

Our I-Frame Only and 18 and 35 Mbps codecs are VBR.

[Piotr Wozniacki]

Originally Posted by Dan Keaton

I do not know if HDV 2 is VBR or CBR.

Dan,
The HDV as used in Sony camcorders is 25 Mbps CBR.

Mark,
You're right that even the same standard (like the said 25 Mbps 420 HDV) can be implemented better or worse. One of the examples of very poor implementation of that codec has been the Sony's V1 camcorder, which - particularly in its 25p version - suffered from many artifacts (macroblocking, mosquito noise, and some peculiar phenomenon known as "oil pain effect"). It was also very easy to "break"...I owned that camera, and sold it away as soon as the EX1 was announced.

I'm very happy now with the excellent XDCAM EX 35 Mbps VBR codec of the EX1, but even more so - with the codec options offered in Convergent Design recorders!