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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Compression Artifacts

Don't get me wrong, I'm still a big fan of the camera, I just don't think the argument of "yes there are artifacts, but they're not *that* bad and are acceptable for most people so don't worry about it", doesn't fit with the philosophy of Red and what is being done.

I'd also like to hear if anyone has any guidelines for getting the most out of the compression, in terms of lighting, exposure, composition, camera settings, etc. It seems that people are getting wildly different results, but does anyone have any specifics of the strengths and weaknesses of the codec?
 
Of course bluring/denoising blue channel is just a workaround.
But if you want 4k stored on cf you need to compress the data significantly. And they did it nearly 1:10. Red calls it visually losless. I will call it great images, mostly visually losless for not pros. But sometimes you will see artefacts. That´s fact.
Redteam is damn good, but they´re still from earth, managing data with without being really magic.
It will be better with raw-port. It could be better with higher datarates stored on hdd.
Maybe I´m wrong in near future. Maybe the new daughterboard will fix it. Maybe they will do it in new redcode without touching datarates.
But if, I will call them the codecsorcerers from outer space or - let me think a while - keeping simple by calling them codecgods.

Just in case --> anyone here wanna pray with me twice a day towards lake Forrest?
 
Ben, can you post up the r3d file? I'd like to run some tests out of redcine with the original.
 
With the atmospheric contrast loss and it being almost exclusively in the blue channel the only thing I could think of doing to possibly bring up the noise floor and extract some more data out of it would be to try using some CTB filtration and opening up the lens a bit more.
 
I´m wondering about knowone recognized these artecacts before. Do you remember the hdr.tiff from evin? has been from february `07. Look at this great image -
and after that mind this part of same pic showing wavelat scars in blue channel. (8x zoomed)
This is how they did the incredible small datarate.

And btw I didn´t realize it either. Laguun showed me these bluescars...
 
TAFKAR said:
I´m wondering about knowone recognized these artecacts before. Do you remember the hdr.tiff from evin? has been from february `07. Look at this great image -
and after that mind this part of same pic showing wavelat scars in blue channel. (8x zoomed)
This is how they did the incredible small datarate.

And btw I didn´t realize it either. Laguun showed me these bluescars...
Click to expand...

That blue channel CU is very disappointing but why would there ever be a reason to look at an image above 100% magnification except for pixel by pixel retouching.

I would love to see the color image at full 4K res to compare it to the blue channel sample.
 
Doesn't the sample aerial image look very soft? Or is that just normal for motion picture helicopter shot? I would think the less sharp an image is, the more artifacts you may get as the software is tying to find detail to render? I would love to hear an experts input on this.
 
There's another thread discussing this issue here:

http://www.reduser.net/forum/showthread.php?t=6346

that includes some pretty good images of the problem. Although the thread starts to wander, and at times breaks up into bouts of spasmodic defensiveness. (I honestly don't understand why technical discussion should provoke such defensiveness in some folks. If we talk about these things, they'll get fixed - or at least we'll generate workarounds. Everybody loves the camera - just chill out.)

I'm going to have to weigh in on the "yes, I've seen it" side. It's definitely noticeable - particularly with tungsten-balanced lighting, mostly in the blue, some in the red, and in areas of low detail (which is, paradoxically, high detail - due to noise... i.e. your eye is going to pick out noise/grain more easily over a smooth surface). And it's definitely visible in motion as well, contrary to what some have suggested.

The thing that really gets me is the *size*. Check out post #8 in the thread above, in the upper-right corner over the blurry background. I'd think that sensor noise would be pretty high frequency - it surprises me that the codec responds with artifacts of that size. Then again, I stopped taking math classes as soon as I was allowed to.

In motion (RGB), it appears as a subtle crawling/pulsing in the luminance of the image. And I think this is the crux of the problem... i.e. film can get plenty grainy in the blue channel as well - but it's an organic effect that we're all used to. Compression / video noise artifacts just look weird.

I'm not sure either of the workarounds already suggested are ideal: 1) blur the blue channel (will piss off the compositors), 2) shoot everything daylight balanced (will piss off DP's and/or producers), 3) wait for uncompressed RAW output.

But I'm hoping with further discussion, we'll come up with something. (I will say, a selection of data rates/compression ratios in the future would be, in the vernacular, "dopesauce". Be great to just crank the rate when necessary.)
 
Maybe there could be both; SP 27MB/s and HQ 40MB/s.
Click to expand...

I like the idea of different data rates, but one bottleneck might be CF at this point. The RED drive probably has higher bandwidth capacity in RAID0, but is more sensitive to bumpy enviroments.

Does 2k use the 27 MB/s data rate? If so, a test between 4k and 2k would be worthwhile.

This might be an area where someone could develop some algorithms for post to improve the quality or reduce noise. I am not a fan of noise reduction myself, but people use it all the time. a SCATCH plug-in anyone?
 
Would it help to reduce blue and red noise by using filters to correct the white balance before it hits the sensor? (Like CTBs and stuff like that)
 
It's not very practical for typical scenarios where you'd use tungsten lighting (night interiors and night exteriors), except for bluescreen shots.

The general consensus is that 320 ASA is the native speed of the sensor, so an 80A blue filter would knock this down to nearly 80 ASA, not very practical for your typical night interior scene with tungsten lamps. And of course using a higher ASA rating to compensate sort of defeats the point if you're trying to reduce noise.

I'd say that you're going to have to light night interiors scenes like you'd normally do on film -- with smaller tungsten lamps to match tungsten practicals in the scene, at a reasonable ASA level (320 to 500 ASA) so the light levels are not unrealistic nor overpower the natural ambience -- and deal with any noise level in the blue channel in post somehow if you find it to be a problem. Blue correction filters or blue gels is not really a good idea, not if you're trying to light a night interior scene naturalistically.
 
Re: Redcode data rates: I don't know what the current firmware does, but based on Jim's two dragster R3D files posted a few weeks ago, I measured:

A001_C006_071102_001.R3D "Drag2" 2k 16:9 72 fps (526 frames)
Data rate: about 263 kB/frame, or 6 MB/sec at 24 fps

A003_C007_071105_001.R3D "Drag1" 4k 2:1, 23.98 fps (236 frames)
Data rate: about 1047 kB/frame, or 24 MB/sec at 24 fps

This is based on my analysis of the R3D files using a hex editor. The size of image frames within those R3D files is an integer multiple of 512 bytes (padded out with 0x00 bytes). The frame size is variable, but not by much: for example, with the 2k res file, most frames are exactly 263 kB, and the smallest frame is 245 kB.

When you think about it, a 4k 2:1 image is 8 Mpixels with 12 bits per pixel. When the output file is only 1 MB in size, that's quite a bit of compression (12:1).
 
I think, the problem we´re talking about only gets weight when using full 4k for mastering. If you downconvert 4k in 2k you will not see anything of these problems.
In my mind right now we have only two solutions:
downconvert 4k to 2k makes sense nearly most of times,
if you really need 4k, denoising blue is the way to fix it.
It´s only a workaround for now, maybe red will get it done someday.

btw: ok, have been late with the scars. Got the message :greedy:
 
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