Beiträge von Dan Miller

  • Having all kinds of problems with gamma.


    My thinking was that I only have 300 horizontal right now, and I am beginning with 3840 in the source. It has to get scaled somewhere, right? If so, my I9-9990 / GTX2080 can probably do it better than the RPi. Anyway, I changed it to 1.


    I got the best results with the gamma set to 1 for all three colors. I will explain in more detail below.


    I am using the SK9822 protocol. It adds two more configuration settings over the APA102... Do you know what they are?

    • Max Current - Defaults to 31
    • Adaptive Current Threshold - Defaults to 255


    I would love an explanation somewhere to these...


    Zitat von jeroen warmerdam

    thats weird, are you sure you set everything correct in LED layout and saved your setup?


    did you use the hyperion free app to test with different effects and colours? > you can download it from the Playstore and then connect to localIP:19444


    It isn't that weird. The gradient in PPT only has full black for a very thin vertical strip. When you see what I discovered (again, I will detail it below) it will make more sense.


    I have the Hyperion app. I am going to email myself the same PPT file and test it from my phone.


    Zitat von jeroen warmerdam

    as last, did you connect the GND to your whole setup? use more GND pins to your PSU on the RPI, don't forget the ledstrip and levelshifter


    That's the one thing my background in AV (been in the industry since 1974) has taught me. A good ground can save the day. The Mean Well supply is providing the 5V and Ground for the whole system. I will add as many more to the Pi as there are pins for. According to the pinouts on the level shifter IC (74HCT245N - The Philips Semiconductor version) I tie the ground to two pins, 10 and 19.


    Here is a question about the level shifter. It is an eight channel device. I am only using two, data and clock. I read somewhere that best practices suggests that the unused channels should also be tied to ground. But I couldn't find details. Do I tie both in and out sides of the unused channels?


    Anyway, I did some more testing and here is what I found:


    The system has extremely high bit resolution as it approaches black. I made a slide that was full black and a strip in the middle that had an RGB value of 16.16,16. No problem. I then started to reduce the value of the strip. It disappeared at 1,1,1, but it was visible at 2,2,2. Against a background of 0,0,0. Hell, unless my room is pitch black, I can't even see that in my monitor. This was using a gamma value of 1.0 for all colors.


    BUT (you knew there had to be one, right?)


    When I did the inverse (background of full white [255,255,255]), I had to bring the stripe in the middle down to 16,16,16 before I could detect a slight difference in brightness. Putting this in terms of video, it is clipping whites BIG TIME. If I made the middle stripe 192,192,192 I could barely detect a slight difference in level of those pixels at a gamma of 7 (!) for all colors.


    So how do I fix this? If I use the brightness setting it drops the whole strip of pixels. The same goes for the max current.


    Do I need to do the color calibration for intensity as well as the hue? I am fine with the colors, so I didn't do the calibration. If I set white for 16,16,16 (or wherever it tops out in luminance) will that solve things? And then should I do all of the other colors? Or will the brightness compensation handle that. AND, if I take the time to do the luminance for all 7 colors, then can I turn brightness compensation off altogether?


    I am attaching the powerpoint in case anyone wants to play.

  • Having all kinds of problems with gamma.

    I finally got things built and I am testing and attempting to do a rough calibration with the pixels on the floor. Here is the problem:


    I am simply trying to get a good greyscale. I have made a PowerPoint slide that is a gradient from white on the left to black in the center and white on the right.


    What I am seeing is little to no grey. The entire strip is bright white until the middle where about 20 pixels are off. Bordering the black pixels it is very slightly less than full white.


    If I increase the gamma the amount of black pixels goes up, but there is still no gradient. These pixels supposedly have 24 bit color capability, so I should have 256 shades of grey available. I have played with as many setting as I can find to no avail.


    Here is my setup:


    • 300 Pixels (SK9822) when installed it will be about 475, but testing with 300.

      • Settings - all 300 at the top of the image, 0 on the sides and bottom. I just want to capture and show the top of my PowerPoint slide.


    • 60A MeanWell Power supply - Inserting power at the beginning and the end of the strip
    • RPi4b - slightly overclocked, 8GB version
    • Logic level conversion using 74HCT245
    • Video capture from Hyperion Windows capture

      • Settings: Scaling factor - 16



    Thoughts?

  • Newbie with weird setup - a few questions...


    I actually returned the WS2812B strips and am getting 2 rolls of SK9822s - still from BTF (according to a couple of the Amazon reviews they are actually legit APA102s - we'll see. But they're the next best thing). From what I read the Pi can control them much better because of the separate clock channel.


    The hardest part for me is that this is my living room and my home office - what I am typing this on right now. So I need this to be as bulletproof as possible before I do this install, because taking the screen down and putting it back up is not easy.


    What advantages are there to using a separate controller? Are there some that are more liked for this than others?


    And my biggest concern is HDCP. Working from the PC I don't really care, but this PC is also a server for ~24 TB of ripped Blu-rays, all of them either FHD or UHD. And HDCP is a nightmare. I know because I am a field engineer for Panasonic and can't tell you how many unexplained problems eventually got explained by HDCP issues. If it was as simple as "it either plays or it doesn't" that wouldn't be a problem because it is easy to identify. But it's more like: image shuts off after 45 minutes into a show or movie, shifting between a digital snow picture and normal, AV sync getting horribly messed up - like seconds instead of ms.


    Another question: I see some people - like you for example - have a converter for HDMI to composite and then a separate grabber. Others are using (and what I am trying first) a single unit capture device - in with HDMI and out the back with USB3. The one that I am using is this:



    Obviously I know that I won't be using a 4K stream to the Pi, but I figured if it was powerful enough to stream 4k, then it should do 1080 with little to no latency. Or do I want to feed an even lower resolution into the Pi?


    I should have all the gear in place by tomorrow. Then I have to cut and solder strips, power insertion, etc... Hoping Thursday will be the go day.


    Thanks for everything so far...

  • Newbie with weird setup - a few questions...

    So I am taking the plunge here - as much about learning how to do pixels effectively as it is about having a really cool home theater. What makes this a little different is that I am using a projector, so there is going to be a LOT of pixels. So here are my questions...

    • Amount of pixels. I am using WS2812B strips from BTF. They are the 5050 variety with 300 LEDs/M. The outside dimensions of the screen frame are 51" tall by 86" wide and due to the way the screen attaches to the wall the only place I can attach the pixels is the back of the frame right at the perimeter. which calculates to 128 pixels across v 76 pixels high for a total of 408 pixels. When I did the calculations yesterday I started thinking about processing power and scaling. I am using a Pi4 with 8gB of ram which I have a big cooler attached to so I can overclock it a little if necessary, but will it be necessary? How many pixels can be processed?



    • Distance to the wall. Currently I have the screen attached to the wall using 1x2, which moves it out from the wall by 0.75". I plan on adding another 2x2 to this which will move it out to 2.25", but compared to a flat panel, it is still really close. What distance from the wall do you guys find works best for you?



    • Pi alone or use a controller and why. I have seen some videos where people say to run the pixels directly from the Pi, and others that let the pi feed data to a controller. If the Pi can do it, wouldn't that potentially be lower in latency than adding another device? Do I need a separate controller and what are the pros / cons specific to Hyperion NG?



    • Power supply... Ii have a Mean Well 60A 5V supply and have no problem injecting power to the strips wherever it's necessary, but I don't want to run that much current through the Pi, so I would think to feed the strips their DC directly. But the Pi would at least need to share the ground in order for the data feed to mean anything correct? So should I use the same supply to power the Pi?



    • HDCP. My projector is 4K and all of the sources are either 4K native or upscaling (My Roku will deliver 4K all of the time, regardless of the source native). There will NOT be HDR All of my sources are connected to a Marantz preamp with two separate HDMI outputs and can also internally direct the secondary monitor output to analog video (either composite or Y/Pb/Pr component). I have an HDMI to RSB 3 gaming adapter that can stream 4K/60 to the USB, but I'm sure it would clog up the front end of the Pi. But the bigger concern is HDCP. I am using a TV tuner, a Roku Ultra and a UHD Blu-Ray player along with a PC all feeding to the Marantz Preamp. I am a video product engineer and have had enough bad experiences over the last 20 years with HDCP to know that it is bound to be a problem. So here is my question: How do you guys deal with HDCP?


    I know this is a lot of questions, but I could not find any FAQ or setup docs here. If anyone can direct me to where they might be, that would be great too.


    Thanks in advance.


    Best,


    Dan