Official OPPO BDP-93 Owner's Thread - Page 906 - AVS Forum
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post #27151 of 27161 Old Yesterday, 01:01 PM
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Originally Posted by wmcclain View Post
The choice is there to accommodate possible flaws in the way the display handles color spaces. If your video looks good to you, then the selection won't matter.

If you'd like to test the alternatives yourself, Spears & Munsil have an article showing how to do it with their calibration disc.

-Bill
Thanks Bill. I have the S&M disc - will check it out. The PQ looks terrific BTW - just wondering what the differences are and why. I have flicked between the different choices and can’t see any real difference in PQ - although I did think that the red jacket Aaron Cross wears at the beginning of The Bourne Legacy looked more 'red' with RGB and a little 'orangey red' with the other choices, but that could just be me.
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post #27152 of 27161 Old Yesterday, 01:12 PM
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Originally Posted by kbarnes701 View Post
Thanks Bill. I have the S&M disc - will check it out. The PQ looks terrific BTW - just wondering what the differences are and why. I have flicked between the different choices and can’t see any real difference in PQ - although I did think that the red jacket Aaron Cross wears at the beginning of The Bourne Legacy looked more 'red' with RGB and a little 'orangey red' with the other choices, but that could just be me.
"Why" is fading into the mists of time. It had to do with conserving bandwidth in the mid-20th century.

Here is a background article: http://en.wikipedia.org/wiki/Chroma_subsampling

The BDP-83 FAQ had this old entry which may still be applicable: What if I want to set the color space manually?

-Bill

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post #27153 of 27161 Old Yesterday, 01:17 PM
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Originally Posted by kbarnes701 View Post
Hi guys. I wonder if someone could give me a heads-up with this question: I have an Oppo 93 and it feeds an Epson 5030 PJ via a Denon X5200W. In the Oppo settings I can choose 4:4:4 or 4:4:2 or RGB to send to the Epson. Does it matter which I choose, and why? And which is best? I am currently using RGB and all seems to be OK, but this is something I have never thought about until recently when someone asked me "why RGB?" and I realised I had no real idea. Thanks.

I looked in the FAQ linked on P1 of the thread and it says to use 4:4:4 but doesn't explain why or what this setting does that the others don't
You might wish to ask this in the dedicated thread for your PJ model. A properly set up display with no processing bugs will look the same regardless. Unfortunately that type animal is too rare in the wild. It may also depend on what other settings you have enabled in the display. IOW, one type of motion processing might show color space errors more than another - which is why its best to consult the experts on that particular display.
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post #27154 of 27161 Old Yesterday, 02:44 PM
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Originally Posted by wmcclain View Post
"Why" is fading into the mists of time. It had to do with conserving bandwidth in the mid-20th century.

Here is a background article: http://en.wikipedia.org/wiki/Chroma_subsampling

The BDP-83 FAQ had this old entry which may still be applicable: What if I want to set the color space manually?

-Bill
Thanks again Bill. Off to read...
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post #27155 of 27161 Old Yesterday, 02:45 PM
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Originally Posted by rdgrimes View Post
You might wish to ask this in the dedicated thread for your PJ model. A properly set up display with no processing bugs will look the same regardless. Unfortunately that type animal is too rare in the wild. It may also depend on what other settings you have enabled in the display. IOW, one type of motion processing might show color space errors more than another - which is why its best to consult the experts on that particular display.
They sent me here! I need to do more reading about it - thanks for the pointers.
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post #27156 of 27161 Old Yesterday, 05:33 PM
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Originally Posted by kbarnes701 View Post
Thanks Bill. I have the S&M disc - will check it out. The PQ looks terrific BTW - just wondering what the differences are and why. I have flicked between the different choices and can’t see any real difference in PQ - although I did think that the red jacket Aaron Cross wears at the beginning of The Bourne Legacy looked more 'red' with RGB and a little 'orangey red' with the other choices, but that could just be me.
RGB has a Red, Green, and Blue value for each and every pixel. Equal values of R, G, and B give you a shade of gray between Black and White. YCbCr has a gray scale, luminance value (confusingly labeled Y) and two color difference values telling how much Blue and Red respectively to add to, or subtract from, that gray scale to get the desired color. For example, subtract ALL the Blue and Red from the specified gray scale and you get Green of the desired brightness.

RGB would seem to be the most intuitive way to do this, so what's up with YCbCr? Well that has to do with the physical reality that human eyes can sense fine spatial detail in grays more readily than in color. The human eye sees gray in higher detail resolution.

This fact has been used since the dawn of color video to reduce the amount of data needed to encode a frame of video. In the days of early broadcast TV that was necessary to keep the radio frequency bandwidth down to a reasonable size so you could get enough broadcast TV channels crammed into the frequencies reserved for TV broadcasts. In the case of standard DVD discs (and now Blu-ray) it has to do with reducing the amount of space a movie would take up on the disc, and, even more important, the data bit rate necessary to read that movie off the disc.

The trick that's used on SD-DVD and Blu-ray discs is to discard the color information for every other pixel -- both horizontally and vertically. That is done even before the video data is fed into a video compression scheme like MPEG. The compression scheme FURTHER reduces the data you need to store by recognizing that most of the time adjacent frames of video are very similar to one another. If you can figure out how to record just the differences, it takes less space.

If you think about it, throwing away the color information can't be done in RGB. Why? Because each of the three components, R, G, and B, describing a pixel include information BOTH on its color and on its gray scale brightness. But YCbCr is tailor made for this trick because all of the gray scale information is in the Y component, and all of the color information is in the Cb and Cr components.

So, for example, you can throw away half the color information across a line of video by recording it like this: Y, Cb, Y, Cr, Y, Cb, Y, Cr.... Each pixel gets a Y value but only every other pixel gets a Cb value -- with the skipped pixel getting a Cr value instead.

The digital video format used on discs is called YCbCr 4:2:0. That format throws away half the color information BOTH horizontally (as just described) AND vertically. In current SD-DVD and 1080p Blu-ray players, the player will not output that YCbCr 4:2:0 coming off the disc without reconstituting some or all of the missing color information first. That process is called color up-sampling. If only the vertical information is reconstituted, the result is called YCbCr 4:2:2 (with each line of video looking like that example just above). If both the vertical and horizontal information is reconstituted, the result is called YCbCr 4:4:4 -- with a Y, Cb, and Cr value for every pixel. Don't bother worrying what those numeric codes actually mean -- it's not important. It's just jargon.

NOTE: 4K video standards do allow the player to output YCbCr 4:2:0 -- just the way it comes off the disc. The OPPO 103D and 105D players will upscale to 4K and can output that as 4:2:0 to an appropriate display, which allows them to output 4K/60 video even using their HDMI v1.4 hardware.

Reconstituting the missing color information is a type of scaling -- very much like upscaling 480p SD resolution to 1080p HD -- except in this case it is just for color. The missing color information is permanently lost of course -- it isn't on the disc to begin with. What happens is that a best guess of the correct color is made by applying math to the data that actually IS on the disc.

RGB format necessarily also has color information for every pixel, so it is basically the same as YCbCr 4:4:4.

The things to keep in mind are:

1) The "missing" color information really isn't on the disc. It was permanently discarded in the process of encoding the transfer to put on the disc. To get to YCbCr 4:2:2, YCbCr 4:4:4 or RGB output, color interpolation math has to be applied to the data that IS on the disc. It doesn't matter what format the player is asked to use for output. The "real" color information coming off the disc is always the same limited subset, and the 4:2:2, 4:4:4, or RGB output are always "color up-sampled" from that.

2) Before the pixels can light up on your display a complete color has to be determined for each and every pixel. That means "color up-sampling" *HAS TO HAPPEN* at some point between the disc and the pixels on screen. So if the player is asked to output 4:2:2, then some later device -- perhaps the TV itself -- has to finish the job of raising that further to 4:4:4.

Again, the original content information -- i.e., what's being played off the disc -- is the same regardless. And if the color space math is done correctly, these different formats *SHOULD* produce the identical picture on your TV. However real-world TVs often have quirks that make them work better with one format over another. There's no logic to this, so the only way to know if that's true about YOUR TV is to try the different formats and see for yourself if you can detect an improvement. If you can NOT see a difference between the formats, then be happy. That's the way it is SUPPOSED to work.

---------------------------------------------------------

Video for home theater also includes some extra "headroom" range which makes video processing math work better because it doesn't have to worry about a hard cutoff in the data values at Black and White. So some data range is reserved for Blacker Than Black pixel values at one end and for Peak White pixel values at the other end.

So for example, the gray scale range (with Deep Color OFF) is defined as 255 steps, with the values from 0-15 being the Blacker Than Black values, 16 being defined as Black, 235 being Reference White, and the values from 236-254 being the Peak White values. (255 is a reserved value, making 256 values in all -- which can be represented in 8 bits.)

This is how YCbCr 4:4:4 and YCbCr 4:2:2 both work, and it is *ALSO* how "RGB Video Level" works.

"RGB PC Level" works differently. It has Black defined as 0 and Reference White defined as 254. Thus there is no data range for either the Blacker Than Black or the Peak White values. This comes from how computer graphics and video games talk to displays. Since the video imagery is being created on the fly in the computer, WITHOUT ANY SUBSEQUENT PROCESSING, there's no need to reserve the "headroom" values at either end. But if you convert home theater video content to RGB PC Level you have just "stretched out" its data range -- more data steps than were expected between Black and Reference White. That leads to rounding errors which show up on screen as banding. The bottom line is that you don't use "RGB PC Level" for output unless you are connecting to a computer-style monitor that simply can't handle any of the other 3 choices correctly.

------------------------------------------------------

Deep Color refers to the number of data bits used to represent each pixel. The "normal" representation for all current forms of home theater media is Deep Color OFF -- which means 8 bits for each of the 3 components (e.g., RGB or YCbCr), and thus 24 bits per pixel. Deep Color 30 bit means 10 bits per component and Deep Color 36 bit means 12 bits per component.

But all of the CONTENT is only 8 bits per component! So that means all you can do with 10 or 12 bit Deep Color representation is carry the low order rounding bits that come out of the video processing. Allowing those rounding bits to travel across the HDMI cable to the next device might possibly produce better results, but since they are MERELY rounding bits, the degree of "better" must necessarily be subtle, possibly even vanishingly so.

But once again, some displays have quirks that make them work better with one Deep Color choice than another. If you see a big improvement with one Deep Color choice then you have found a bug in how your display handles the other choices. (Rounding bits don't produce "big improvements".) If you can't spot ANY improvement using Deep Color 30 or 36 bit, then leave Deep Color OFF. Why? Because that reduces the data rate the HDMI cable has to carry, which means you are less likely to suffer HDMI handshake issues or data dropouts.

NOTE: Some displays are known to accept 30 or 36 bit video but trim off the extra bits on input and work with just the regular 24 bits. This is not really as cheap as it sounds, because pixels in current consumer displays can't really render the full color resolution implied by 30 or 36 bit video data. So some trimming is going to happen regardless before the pixels light up. Better displays will do their internal processing with more bit-width, and only trim the results of that down to what the pixels can render. The point here is that it's not all that uncommon to have a display that accepts 30 or 36 bits but doesn't produce a better picture than what it gives you with 24 bits.

-------------------------------------------

Until you have time to experiment -- i.e., to find out if your display has any such quirks -- the best default Color Space choice is YCbCr 4:4:4 with Deep Color OFF. That's the default format for video on HDMI and thus the one most likely to have been well tested when your display was engineered.

-------------------------------------------

"Dithering" is a process of adding small, random variations to the low order video bits of the pixels. This eliminates artifacts due to "digital quantization".

Dithering is necessary for all modern digital displays. But it is ALMOST ALWAYS the case that the display does that ITELF. However there are some displays out there which do not Dither -- sometimes dependent on the particular video setting choices you've made in the display. So the OPPO players offer the ability to do Dithering in the player for such cases.

Dithering should not be done twice. So if you turn on Dithering in the OPPO and don't notice an improvement in your video, the odds are your display is already doing its own Dithering, and thus you should turn Dithering off in the output from the OPPO so it isn't happening twice.
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post #27157 of 27161 Old Yesterday, 06:53 PM
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Originally Posted by wmcclain View Post
"Why" is fading into the mists of time. It had to do with conserving bandwidth in the mid-20th century.

Here is a background article: http://en.wikipedia.org/wiki/Chroma_subsampling

The BDP-83 FAQ had this old entry which may still be applicable: What if I want to set the color space manually?

-Bill

Bill, sorry to go off topic, but I did a thread search for Oppo 93 Audio Dropouts and couldn't find anything.
Can you please help?


Expendables 3 BluRay, Dolby Atmos, random sudden Audio Dropouts
My other Atmos Transformers 4 plays fine. I don't think the Bluray Disc is the problem.
It played fine on my Sony BDP-S6200
Oppo93 shows 1/3 English Dolby TrueHD 7.1 48K AVC BDMV 23.976Hz 16:9
Oppo Firmware: BPx-82-1009
Denon AVR-X4100W Info shows:
Source: Oppo 93
Sound: Dolby Atmos
Signal: Dolby Atmos
But Audio dropouts occur.

Others have reported same problem (including Oppo 93) at:
http://forum.blu-ray.com/showthread.php?p=10074528


Thanks for any help,
sgibson

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post #27158 of 27161 Old Yesterday, 07:22 PM
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Bill, sorry to go off topic, but I did a thread search for Oppo 93 Audio Dropouts and couldn't find anything.
Can you please help?


Expendables 3 BluRay, Dolby Atmos, random sudden Audio Dropouts
My other Atmos Transformers 4 plays fine. I don't think the Bluray Disc is the problem.
It played fine on my Sony BDP-S6200
Oppo93 shows 1/3 English Dolby TrueHD 7.1 48K AVC BDMV 23.976Hz 16:9
Oppo Firmware: BPx-82-1009
Denon AVR-X4100W Info shows:
Source: Oppo 93
Sound: Dolby Atmos
Signal: Dolby Atmos
But Audio dropouts occur.

Others have reported same problem (including Oppo 93) at:
http://forum.blu-ray.com/showthread.php?p=10074528


Thanks for any help,
sgibson
The dropouts are not reproducible at the same points? I would suspect some sort of seamless branching (so-called) on the disc if it was replicable.

-Bill
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post #27159 of 27161 Old Yesterday, 07:39 PM
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Originally Posted by sgibson View Post
Bill, sorry to go off topic, but I did a thread search for Oppo 93 Audio Dropouts and couldn't find anything.
Can you please help?


Expendables 3 BluRay, Dolby Atmos, random sudden Audio Dropouts
My other Atmos Transformers 4 plays fine. I don't think the Bluray Disc is the problem.
It played fine on my Sony BDP-S6200
Oppo93 shows 1/3 English Dolby TrueHD 7.1 48K AVC BDMV 23.976Hz 16:9
Oppo Firmware: BPx-82-1009
Denon AVR-X4100W Info shows:
Source: Oppo 93
Sound: Dolby Atmos
Signal: Dolby Atmos
But Audio dropouts occur.

Others have reported same problem (including Oppo 93) at:
http://forum.blu-ray.com/showthread.php?p=10074528


Thanks for any help,
sgibson
I'm pretty sure it is bad coding on the disc. If you do some more searching of "Expendables 3 audio dropouts",
you will find many other players (including Sony players and the Denon you reported in another thread )
are having the same issues.

~Dave

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JVC DLA-RS40-U... Oppo BDP-105D... Toshiba HD-XA2... Uverse VIP-2250... Roku Streaming Stick... Emotiva XPA-3... Onkyo TX-SR805
JBL LC2 (x3) ... JBL L820 (x6) ... SVS PB10-ISD (x2) ... SVS 20-39-PCI
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post #27160 of 27161 Old Yesterday, 08:15 PM
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Originally Posted by sgibson View Post
Bill, sorry to go off topic, but I did a thread search for Oppo 93 Audio Dropouts and couldn't find anything.
Can you please help?


Expendables 3 BluRay, Dolby Atmos, random sudden Audio Dropouts
My other Atmos Transformers 4 plays fine. I don't think the Bluray Disc is the problem.
It played fine on my Sony BDP-S6200
Oppo93 shows 1/3 English Dolby TrueHD 7.1 48K AVC BDMV 23.976Hz 16:9
Oppo Firmware: BPx-82-1009
Denon AVR-X4100W Info shows:
Source: Oppo 93
Sound: Dolby Atmos
Signal: Dolby Atmos
But Audio dropouts occur.

Others have reported same problem (including Oppo 93) at:
http://forum.blu-ray.com/showthread.php?p=10074528


Thanks for any help,
sgibson
Not Bill, but you can almost certainly cure the dropouts by using HDMI Audio LPCM instead of Bitstream in the OPPO. That will get you LPCM output of the TrueHD 7.1 track (which is what an Atmos track is underneath), and if you don't actually have an Atmos speaker setup you are good to go.

If you have an Atmos speaker setup and want to use it, you'll need to use Bitstream output from the OPPO, and that risks the dropouts. Get in touch with OPPO Tech Support to see if they have any other suggestions.
--Bob

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post #27161 of 27161 Old Today, 05:45 AM
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RGB has a Red, Green, and Blue value for each and every pixel. Equal values of R, G, and B give you a shade of gray between Black and White. YCbCr has a gray scale, luminance value (confusingly labeled Y) and two color difference values telling how much Blue and Red respectively to add to, or subtract from, that gray scale to get the desired color. For example, subtract ALL the Blue and Red from the specified gray scale and you get Green of the desired brightness.

<munch>

Dithering should not be done twice. So if you turn on Dithering in the OPPO and don't notice an improvement in your video, the odds are your display is already doing its own Dithering, and thus you should turn Dithering off in the output from the OPPO so it isn't happening twice.
--Bob
Bob - that is fabulous information and written in a way that non-techies can easily understand. I thank you for the time spent on this and really appreciate it. I have copied it to a Word document for future reference.
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