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On some DVDs, I think I'm seeing the ICP as red edges are very jagged. Is the CUE filter also for that? It doesn't seem to do anything.
Anyone? The Oppo filters this on the same content but the Lumagen doesn't.
 

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If you put the max/min pattern used in the Chroma Burst through an FFT, you will see there are harmonics above Nyquist. You cannot perfectly sample an analog signal near Nyquist and that the Chroma Burst works in this case is due to the special case that you are digitally generating coincident samples.

There are no actual harmonics above the Nyquist limit. Frequencies above Nyquist are aliased frequencies, which are inherently spurious. Sure, they come out of the math, but part of signal reconstruction is filtering out the aliased frequencies, because they are not actually part of the original signal.


However, actual video will not have any significant energy near Nyquist, and so the result of the Chroma Burst pattern does not necessarily represent how actual video will be processed.

Real video does have some energy near Nyquist, and rolling it off can affect the image in a visible way. There is actually more high frequency energy in modern video than there was in the past, now that we have lots of content generated and mastered entirely digitally. We believe it is useful to preserve as much of those high frequencies as one can reasonably preserve, given the limitations of real-world resampling filters. Thus we believe the test is useful. As to how important it is relative to other tests, that's a judgment call. For the most part, the chroma bursts test is more intended as a relative test to see if different color modes are getting you a cleaner signal with less processing, or for use to make sure nothing is being lost inadvertently because some extra processing is turned on that shouldn't be.


Most of the time most people won't notice moderate (or heck, severe) rolloff of the chroma channel. But that's kind of a low bar to get over. Most people don't notice the difference between SD and HD. Home video enthusiasts are generally trying to push the envelope and get the absolute best picture possible.


The clamping amplitude loss on conversion to RGB does affect the output of a Nyquist filter after the amplitude loss. The signal amplitude will be reduced in YCbCr. I can't say whether it is a visible aspect of the loss in this case of not.
I don't even know if you're disagreeing with me on this. My point is that the clamping is applied to all of the signal, not just the high frequencies. RGB clipping is not a reason why you would see differential amplitude of the high frequencies.


Don
 

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Discussion Starter #283
The very last two chroma bursts on the menu are the RGB legal bursts. We have a Cb and Cr version. These won't work very well visually because you have to manipulate the opposing channels to keep the channel you care about within the RGB limits. e.g. The Cr burst will ramp Cb and Y so that Cr stays legal. I hope that makes sense.
Stacey:
Yes this makes sense.

Thanks for the information.
 

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Discussion Starter #284
On some DVDs, I think I'm seeing the ICP as red edges are very jagged. Is the CUE filter also for that? It doesn't seem to do anything.
The ICP bug is when the Chroma Macroblocks (only, and does not affect Luma) are interpreted with the wrong vertical scanline order by the MPEG decoder. This can cause a ragged Chroma edge. I don't think products manufactured in the past six years, and maybe more, would still have this bug, but it is possible.

The CUE filter should mitigate ICP to some degree since it is a vertical Chroma (only) blur filter. It will also blur Chroma vertical for products that do not have ICP, and so the CUE filter should be left off in this case. For players without ICP, the softening of the Chroma vertical edges might be hard to see given the the MEPG Chroma resolution is 1/4 that of Luma and the filter does not have a strong effect except the ICP.

You say the CUE filter has no effect. Since we have not looked at the CUE filter for some time there is a chance a bug crept in and it is not getting enabled when you turn it on. If we get some time we can look at this, but it is not going to be a high priority for us as it should not be needed for any recent products.
 

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Discussion Starter #285
1) There are no actual harmonics above the Nyquist limit. Frequencies above Nyquist are aliased frequencies, which are inherently spurious. Sure, they come out of the math, but part of signal reconstruction is filtering out the aliased frequencies, because they are not actually part of the original signal.

2) Real video does have some energy near Nyquist, and rolling it off can affect the image in a visible way. There is actually more high frequency energy in modern video than there was in the past, now that we have lots of content generated and mastered entirely digitally. We believe it is useful to preserve as much of those high frequencies as one can reasonably preserve, given the limitations of real-world re-sampling filters. Thus we believe the test is useful. As to how important it is relative to other tests, that's a judgment call. For the most part, the chroma bursts test is more intended as a relative test to see if different color modes are getting you a cleaner signal with less processing, or for use to make sure nothing is being lost inadvertently because some extra processing is turned on that shouldn't be.

3) Most of the time most people won't notice moderate (or heck, severe) rolloff of the Chroma channel. But that's kind of a low bar to get over. Most people don't notice the difference between SD and HD. Home video enthusiasts are generally trying to push the envelope and get the absolute best picture possible.

4) I don't even know if you're disagreeing with me on this. My point is that the clamping is applied to all of the signal, not just the high frequencies. RGB clipping is not a reason why you would see differential amplitude of the high frequencies.

Don
1) You mention that the points are a "Sine wave" and I agree. The issue I am pointing out is that a Nyquist filter will treat them as a Sine Wave, when actually they are representing a Square Wave. That is: Max one end of the range, then max the other, without intervening values. If a TV/Projector were able to reproduce these perfectly they are showing two, and only two colors, which is a square wave.

Since the values are treated as a Sine Wave by the Nyquist filter this can create the issue I have been mentioning. The simplest example I can think of is a burst with two equal values at max value and two at minimum value. Then if a Nyquist filter is applied too these to create samples between each pair of samples, the created values will try to represent a Sine Wave, but this is actually the problem. The resulting sample between the two max samples will be significantly higher than the maximum value and significantly overflow, and be clamped. Then the output of the clamped Nyquist filter has three max value samples, one mid-range value, and then three minimum values. This ends up as a trapezoidal Wave but the Nyquist filter did try to make it a Sine Wave. For example if the values had not been at max/min the filter would have converted what should look like a Square Wave into an approximation of a Sine Wave, since the mid-point between the two upper values would remain clamped at max while the originals values are decreased (to a certain point). Because of this the resulting waveform shape changes. That said, I am still agreeing the patterns have value. My concern is the interpretation of the results.

2) I agree there can be some energy near Nyquist, but, especially with compression, I believe for actual "real world" video it is not significant. The Chroma Burst pattern has 100% energy at Nyquist, which is not possible with a actual source (especially with a filter at the front of the video pipeline so the video can be efficiently and effectively compressed). This can lead to misinterpretation of the results of test patterns like the Chroma Burst, which is really the only thing I am trying to point out. However, once again, agree the Chroma Burst pattern is useful.

3) I actually think we are agreeing on the essential points. Specifically we agree that we want to provide absolutely best possible performance. We do need to temper actual video verses test patterns in our trade-offs as we architect the Radiance. We certainly do not want to make test patterns look better to the determent of actual video. Fortunately this is generally not an issue. The Chroma Burst is a good example. We used it to evaluate our pipeline and were able to improve the pattern, and improve actual video when this highlighted a couple places were we could increase precision in the Verilog code.

4) I agree that clamping will affect all frequencies. My point was this can "look like" roll-off on a high frequency pattern.

So I am agreeing the patterns have value and am only trying to help people interpret the results. Also, I agree that you, Stacey, and we are doing our best to provide and support the very best in video. Finally, I believe these discussion help enthusiasts see "under the hood" about the level of detail needed for quality video, which by itself is a great goal.
 

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Discussion Starter #286
Anyone? The Oppo filters this on the same content but the Lumagen doesn't.
I highly doubt the Oppo has the ICP issue. So it is not filtering this, it doesn't exist in the first place because they do MPEG decode of interlaced source correctly.

Also the Radiance CUE filter must receive the source with ICP at the original resolution. If you have the DVD player set to scale video that has ICP that makes it a totally different problem.

So, comparing the Oppo output verses the Radiance filtering the output from a DVD player with the ICP issue is not a valid comparison.
 

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I highly doubt the Oppo has the ICP issue. So it is not filtering this, it doesn't exist in the first place because they do MPEG decode of interlaced source correctly.

Also the Radiance CUE filter must receive the source with ICP at the original resolution. If you have the DVD player set to scale video that has ICP that makes it a totally different problem.

So, comparing the Oppo output verses the Radiance filtering the output from a DVD player with the ICP issue is not a valid comparison.
I think there's some confusion in what I was saying. I only use an Oppo 103 for DVDs. This is an example of what I'm seeing.

When playing DVDs on the Oppo set to Source Direct which means the 2020 is upscaling 480i to 1080p60, you can see in the picture on the edge of red along the the gray there is jagged streaking. I see this whenever there's solid red. The CUE filter makes no difference on or off. This doesn't show in the picture that well so it's a lot more apparent in person.

http://i.imgur.com/jMVWyao.jpg

For comparison's sake, this is how it looks when the Oppo is set to 1080p so it's handling the upscaling. It doesn't have any jagged streaking.

http://i.imgur.com/ByffQ8N.jpg

Both the 2020 and Oppo have their latest firmware.
 

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Discussion Starter #288 (Edited)
chronoclast:
Okay. I thought from your description you were talking about an ICP issue.

Is the Oppo output and the Radiance output set to 4:2:2? If not, please try 4:2:2 for output from both. Make sure all Radiance enhancements, including Darbee DVP (which is on by default) are turned off in the Radiance. Enhancements can cause issues, and the issue like this and would be increased if the Radiance receives and SD sourcea and scales it, rather than an HD source.

We will need to look at the source and see for ourselves since you say the pictures don't show it as well as in person. What DVD is this from? If it is available we will buy it to evaluate.
 

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chronoclast:
Okay. I thought from your description you were talking about an ICP issue.

Is the Oppo output and the Radiance output set to 4:2:2? If not, please try 4:2:2 for output from both. Make sure all Radiance enhancements, including Darbee DVP (which is on by default) are turned off in the Radiance. Enhancements can cause issues, and the issue would be increased if the Radiance receives and SD sourcea and scales it, rather than an HD source.

We will need to look at the source and see for ourselves since you say the pictures don't show it as well as in person. What DVD is this from? If it is available we will buy it to evaluate.
Oppo and Radiance were both set to 4:2:2 output and the Darbee and all enhancements were turned off when I took the pictures.

The example pictures are from Sherlock Hound. Another easy way to see this issue is on any DVD that has a piracy warning at the start with the letters in red against a black background, like Mulholland Drive.

Any DVDs of the show Futurama exhibit this issue well too. The main character wears a red jacket and it's digital animation so things are often not moving.
 

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Discussion Starter #290
Oppo and Radiance were both set to 4:2:2 output and the Darbee and all enhancements were turned off when I took the pictures.

The example pictures are from Sherlock Hound. Another easy way to see this issue is on any DVD that has a piracy warning at the start with the letters in red against a black background, like Mulholland Drive.

Any DVDs of the show Futurama exhibit this issue well too. The main character wears a red jacket and it's digital animation so things are often not moving.
Thanks for the information.

One concern I have has to due to players trying to "enhance" SD material. The reason SDI options were popular in the DVD era is that these enhancements could not be defeated, and were actuality damaging the video. The SDI option bypassed these "enhancements" and so provided a much better picture.

Given the legacy of Bluray players also having DVD decoder, and potentially those "enhancements," the issue you see could actually be the Oppo MPEG decoder enabling some "enhancement" that may not be able to be defeated while outputting SD. I don't know if this is the case or not.

If you have different DVD player, or some similar material on a DVR that can output both SD and HD for SD source, you might want to check them out. The problem is there is no way to know if they also have such an issue, and for cable/satellite, the higher compression may this SD output issue worse.
 

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Thanks for the information.

One concern I have has to due to players trying to "enhance" SD material. The reason SDI options were popular in the DVD era is that these enhancements could not be defeated, and were actuality damaging the video. The SDI option bypassed these "enhancements" and so provided a much better picture.

Given the legacy of Bluray players also having DVD decoder, and potentially those "enhancements," the issue you see could actually be the Oppo MPEG decoder enabling some "enhancement" that may not be able to be defeated while outputting SD. I don't know if this is the case or not.

If you have different DVD player, or some similar material on a DVR that can output both SD and HD for SD source, you might want to check them out. The problem is there is no way to know if they also have such an issue, and for cable/satellite, the higher compression may this SD output issue worse.
I haven't seen any reports that the Oppo enhances anything when outputting source direct other than the NR issue from the QDEO. The jaggedness differs in appearance some on the discs I've seen it on. Could this be in the discs' encodes and I'm only seeing it now because the Radiance's scaler is retaining more detail than the Oppo's scaler? If that's the case I'll live with it as the PQ from the Radiance's upscaling is better than the Oppo's otherwise.
 

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Discussion Starter #292
I haven't seen any reports that the Oppo enhances anything when outputting source direct other than the NR issue from the QDEO. The jaggedness differs in appearance some on the discs I've seen it on. Could this be in the discs' encodes and I'm only seeing it now because the Radiance's scaler is retaining more detail than the Oppo's scaler? If that's the case I'll live with it as the PQ from the Radiance's upscaling is better than the Oppo's otherwise.
I am glad you agree the Radiance NoRing(TM) scaling is superior.

I do not know if the issue you see is specific to the disc or not. You could try a similarly saturated disc from another source and see if you get similar results. One thing you can look at is the bit-rate at that section of the disc. Many players have a feature to enable showing the bit rate on the screen, but I am not sure if the Oppo does.

A lower bit rate would tend to imply there are going to be issues with the encoding itself, especially with sharp-edged highly-saturated colors. This is because high compression throws out high frequencies and much more so for Chroma than Luma. So if a higher bit rate eliminate the issue, it is disc specific. If not, it is harder to determine the source.
 

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I am glad you agree the Radiance NoRing(TM) scaling is superior.

I do not know if the issue you see is specific to the disc or not. You could try a similarly saturated disc from another source and see if you get similar results. One thing you can look at is the bit-rate at that section of the disc. Many players have a feature to enable showing the bit rate on the screen, but I am not sure if the Oppo does.

A lower bit rate would tend to imply there are going to be issues with the encoding itself, especially with sharp-edged highly-saturated colors. This is because high compression throws out high frequencies and much more so for Chroma than Luma. So if a higher bit rate eliminate the issue, it is disc specific. If not, it is harder to determine the source.
I didn't think of testing the Oppo set to 480i output. When set to that the jaggies disappear completely. The lines are all smooth. The image quality degrades slightly since the Oppo's processor isn't being bypassed but the Radiance is still handling upscaling/deinterlacing to 1080p. Whether set to Source Direct or 480i, it's a 480i signal from the Oppo either way so the Radiance handles it the same right? I suspect it's an issue with the Oppo's Source Direct output.
 

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doesn't this look like a chroma delay problem ? Have you tried adjusting the delay for the Cr channel on the Radiance ? Should be worth a try. I could imagine that the delay is generally present, you're just noticing it much more on animated content.
 

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doesn't this look like a chroma delay problem ? Have you tried adjusting the delay for the Cr channel on the Radiance ? Should be worth a try. I could imagine that the delay is generally present, you're just noticing it much more on animated content.
This sorta helps. It clears up the jaggies on lower red saturations but higher saturations are still being a problem. When I adjust it some levels of higher saturation gets better while others get worse and vice versa. I can't seem to find a sweet spot that smooths it all out.
 

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Discussion Starter #296
I didn't think of testing the Oppo set to 480i output. When set to that the jaggies disappear completely. The lines are all smooth. The image quality degrades slightly since the Oppo's processor isn't being bypassed but the Radiance is still handling upscaling/deinterlacing to 1080p. Whether set to Source Direct or 480i, it's a 480i signal from the Oppo either way so the Radiance handles it the same right? I suspect it's an issue with the Oppo's Source Direct output.
A 480i signal will be handled the same by the Radiance, independent of the Oppo "Source Direct," or "480i" output settong. Since they look different the Oppo is handling them differently. You can confirm both as 480i by pressing the OK button on the Lumagen remote and the input mode will show on the status screen.

Fudoh is correct to have you try the Chroma offsets. As you noticed it is difficult to get Chroma and Luma timing perfect due to the lower resolution of the Chroma. So best bet is to find a selection that balances the various Chroma saturation levels.
 

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I've got it now. I was too close to the TV when I was first adjusting it. Setting the Cr channel's delay to -0.5625 clears it all up. Thank you both for helping.
 

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I have only ever come across a couple of problems where heat may have been an issue with a mini installation. In those cases the unit was located in a non optimal location and was not installed vertically as it is designed to be used. In such an installation the use of an additional heatsink would likely solve any issue...and in any case, it is extremely rare.
Okay, but why does it have the LED and IR sensor installed along the edge of the unit? With the Mini on the wall, I can't see the green LED from my seat and the remote barely works, because the sensor is pointed at the ceiling.


With regard to the Chroma Burst Pattern, is this something directly related to the 2020, or do all Lumagen processors share this high frequency roll off of the video signal, which I understand is undetectable with normal video images.
 

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Okay, but why does it have the LED and IR sensor installed along the edge of the unit? With the Mini on the wall, I can't see the green LED from my seat and the remote barely works, because the sensor is pointed at the ceiling.


With regard to the Chroma Burst Pattern, is this something directly related to the 2020, or do all Lumagen processors share this high frequency roll off of the video signal, which I understand is undetectable with normal video images.
Pres: Speak to Lumagen about the design..nothing to do with me...as for the other question, as all Radiance units share the same base architecture i would expect they all behave in the same way.
 

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Discussion Starter #300
...With regard to the Chroma Burst Pattern, is this something directly related to the 2020, or do all Lumagen processors share this high frequency roll off of the video signal, which I understand is undetectable with normal video images.
Please reread my above posts on Chroma bandwidth. The Chroma Burst test pattern is not a good indicator of Chroma bandwidth for real video for anything that is actually processing the video as it has out-of-bound frequency components. It cannot be used to imply there is some "undetectable with normal video images" roll off of Chroma. The Chroma Burst pattern is useful, but not for this.

It is true that no filter is perfect, but the Chroma bandwidth of the Radiance with real world video is simply excellent. The Radiance - since it is processing the video and converting 4:2:2 to 4:4:4 and back - behaves exactly as it should with the Chroma Burst pattern.

That said, all current Radiance units have the same architecture and perform essentially the same. The 2XXX units do have improved precision compared to the RadianceMini/XS/XD/XE.
 
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