Capacity of broadcast channels

It is given in the book by El Gamal that

The capacity region of the DM-BC depends on the channel conditional pmf $ p(y_1 , y _2 |x)$ only through the conditional marginal pmfs $ p(y_1 |x)$ and $ p(y_ 2 |x)$

The statement made is about the entire capacity region. Every point in the capacity region means that there exists a sequence of $ (2^{nR_1},2^{nR_2},n)$ (considering only private messages) codes with 0 error. I am wondering about the converse.

For a given sequence of codes, would broadcast channels with identical marginals have the same achievability, ie, if it is achievable in the first channel, would it be achievable in the second channel and vice versa?

What are various mechanisms for establishing secure channels [closed]

By Wikipedia definition of secure channel is one that protects from overhearing and tampering.

I know we can use certificates to establish a secure channel via TLS/SSL. This is possible if there is access to a CA.

If I don’t have access to a CA what other mechanisms are possible for establishing a secure channel?


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Handling metallic roughness maps colour channels

I’m trying to use a metalness/roughness workflow and I’m not sure how to translate the colour channels into the different metalness and roughness attributes. I’m not sure if there’s a standard on how to encode that information and I can’t find any online resources on how to treat the colour channels so I’m guessing that there is no standard.

I have had materials which have used only the R and B channels and having the B channel set as 0 and I have had materials that somehow use all the RGB channels and I’m confused as to why they would need a third channel to determine metallness and roughness.

My question is, how should I determine the format that the map is in and which channel corresponds to which attribute?

Update: I’ve already come to terms that I’ll probably have to compile new shaders for different materials but I’m trying to figure out a way of identifying the format that a map is in. It would appear that for one of the models I’m using, it stores its bump map in the R channel. I didn’t even know that was an option

Update 2: I imagine I’ll have to just delegate this to the asset pipeline and have the user select which channels to sample from. That or have a hardcoded format and make sure that any PBR materials imported follow that format

speaker-test returns all 6 channels to front speakers

OS: KUBUNTU 19.04 Soundcard: Creative Soundblaster ZxR Sound Setup: front (left/right), center, bass, rear (left/right)

My problem is, that all speaker outputs are played at the front speakers.

I did the following:

  • Set speaker setup at Plasma sound settings to “Analog Surround 5.1-Output + Analog Stereo-Input”
  • If I click on any rear speaker there, to test audio output, they are played on front speakers. The setup seems very faulty:
    • rear right: output on front left and right at the same time
    • rear left: output on front left and right at the same time
    • center: output on front left and right at the same time
    • front left: output on front left (one of two correct speakers)
    • front right: output on front right (one of two correct speakers)
  • I then executed alsamixer and noticed that my NVIDIA Graphics card was initially selected. I switched with F6 to my ZxR and set it up like this: enter image description here
  • I ran speaker-test -Dplug:surround51 -c6 -twav. An error message appeared and I was unable to perform the command: Error when opening the device: -2
  • I googled how to set the default device and so I did cat /proc/asound/cards:
 0 [NVidia         ]: HDA-Intel - HDA NVidia                       HDA NVidia at 0xdf080000 irq 17  1 [Creative       ]: HDA-Intel - HDA Creative                       HDA Creative at 0xdf204000 irq 19 

with kate ~/.asoundrc I set my default device:

defaults.pcm.card 1 defaults.ctl.card 1 defaults.timer.card 1 
  • after a restart speaker-test -Dplug:surround51 -c6 -twav was working: Unfortunately rear left output is on front left, rear right output is on front right, center appears to be on both front (left/right) speakers

Does anyone have any idea how I can fix this?