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I have a technical question which relates to a Blu-ray player, a projector, HDMI cables, and a characteristic green/purple flashing/banding phenomenon. I'm not getting much headway in the projector forum, but I thought someone could provide me background info here in this forum.


There is a common phenomenon with one projector (Panasonic PT-AX200U) which exhibits itself as green or purple flashes. It's a split-second horizontal band of colour that might appear a few times during a movie. Some people watching movies with me don't seem to notice it, but it's painfully obvious to me.


I've theorized that this is due to HDMI cable quality and length, but what threw me for a loop is that a few people now have stated that their green/purple flashing issue was eliminated simply by getting a firmware update of the projector. They did not change their cables. So, I am getting that firmware update, but have no idea what it does. One possibility is that the update corrects hardware incompatibilities. Another possibility is that the update somehow changes the behaviour to iffy signals. Nonetheless I'm still suspicious that this could represent a bandwidth/HDMI cable quality issue. I'm just trying to figure out how a firmware update could correct it.


This issue has been reported several times with Sony's BDP-S350 Blu-ray player as the source for example. People report it is more common with 1080p than with 1080i and uncommon with 720p. Presumably they mean 1080p60, but I have noticed it with 1080p24 (and 1080i). (In contrast, I have not noticed it with 1080i from another video source.)


Interestingly the Sony setting for HDMI is factory set at 'Auto', which asks the display device what to use out of the following:

YCbCr (4:2:2) - Outputs YCbCr 4:2:2 video signals.
YCbCr (4:4:4) - Outputs YCbCr 4:4:4 video signals.
RGB (16-235) - Select this when connecting to a device with an HDCP- compliant DVI jack.
RGB (0-255) - Select this when connecting to an RGB (0-255) device. HDMI Outputs audio signals from the HDMI OUT jack.


What makes me think this could be a bandwidth issue are two things:


1) One person reported the projector's flashing issue disappeared when he added a signal repeater.

2) One person reported the projector's flashing issue disappeared when he changed the BR player's HDMI setting from 'Auto' to 'RGB (16-235)'.


I'm thinking a bandwidth issue could be "corrected" in a firmware update if the machine is sending back identifier information that prioritizes a lower colour depth, thus requiring lower video bandwidth. What are the comparative video bandwidths required for these settings? Does any of this make sense to you, or am I completely out to lunch?


In my case, cable quality does make some sense too. I have a 25' Monoprice 26 gauge cable, running from a receiver. I chose 26 gauge only because of bendability and size, but will try Blue Jeans' 24 gauge Series 2 cable. I will do this even if the firmware update corrects the problem. I understand the diameter of the cable is 9.5 mm. It turns out my wire conduit's internal width is 9.5 mm so it should fit. (When I was originally looking at 24 gauge cable, some was spec'd at 10 mm or perhaps larger with a net jacket, which is why I went with 26 gauge.)
 

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I'm thinking a bandwidth issue could be "corrected" in a firmware update if the machine is sending back identifier information that prioritizes a lower colour depth, thus requiring lower video bandwidth. What are the comparative video bandwidths required for these settings? Does any of this make sense to you, or am I completely out to lunch?

It's possible, but I feel unlikely. This doesn't sound like an HDMI problem in terms of signaling exactly, which is usually the sparklies. It may be HDCP related though, which COULD be exacerbated by cabling. If it is an HDCP issue, the bandwidth of the signal you send shouldn't really be relevant. If it's related to cabling bandwidth, lowering the source resolution should make the problem go away.

Quote:
People report it is more common with 1080p than with 1080i and uncommon with 720p.

Note that 1080i60 bandwidth is much lower than 720p.

Quote:
What are the comparative video bandwidths required for these settings?

The RGB range has no bearing on bandwidth whatsoever. However, choosing RGB output is the same as choosing 4:4:4 component, so in that sense they do have an impact but no difference between the two of them.. However, the component subsampling choices should, 4:2:2 will have 2/3rds the bandwidth of 4:4:4. In other words the only one that will be lower is 4:2:2 component. Everything else is 4:4:4, which is all the same.

Quote:
I understand the diameter of the cable is 9.5 mm. It turns out my wire conduit's internal width is 9.5 mm so it should fit.

There is also the connector though...
 
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