8 Replies Latest reply on Jul 29, 2016 11:37 AM by khbuchner

    rx 480 hdmi to dvi 2560x1600 flickers

    khbuchner

      Hi,

      I have a rx 480 and a lg 3000h 30" monitor with a native resolution of 2560x1600. The problem is that the monitor has only dvi, the card only dp and hdmi.

      So I tried several cables with passive connections:

      - dp to dvi: without virtual super resolution only resolution up to 1280x800, with vsr 2560x1600 is selectable, but the picture is very blurred

      - hdmi to dvi: with vsr 2560x1600 possible and sharp picture, but flickers, mostly when the picture is dark

      I searched in the internet, but the articles are very confusing: Some say, these connections would be only possible with active adapters, but obviously, hdmi to dvi is working, but with filckering.

      Why is hdmi to dvi working at all in this resolution 2560x1600? Is there anything I can try to get a working configuration without an expensive active adapter?

       

      MfG Karl-Heinz

        • Re: rx 480 hdmi to dvi 2560x1600 flickers
          amdpete

          You need an active adaptor for that resolution.

            • Re: rx 480 hdmi to dvi 2560x1600 flickers
              khbuchner

              Hi amdpete,

              thanks for your reply, I feared that, then there is no other option than to send back the rx 480 and to use my old card again.

              But still I wonder why it is partly working with hdmi to dvi. Are monitor and card out of spec here?

              MfG Karl-Heinz

                • Re: rx 480 hdmi to dvi 2560x1600 flickers
                  speeder

                  Your monitor is not out of spec.

                   

                  It is that DVI has a data limit higher than HDMI, thus the monitor is flickering because it is attempting to display all the data it receives (ie: enough to display something, but not enough to display all frames correctly).

                   

                  DP has enough data limit, but DP works too different from full-limit DVI, thus it requires a special converter (instead of just an adapter that re-route wires).

                    • Re: rx 480 hdmi to dvi 2560x1600 flickers
                      khbuchner

                      Hdmi and dvi seems to me the same, so why is dvi working up to this resolution and hdmi not? Is this artificially or are there e.g. emi issues with the cable? Finally, is it possible to accelerate the hdmi communication by driver settings?

                      Regards,

                      Karl-Heinz

                        • Re: rx 480 hdmi to dvi 2560x1600 flickers
                          speeder

                          DVI was invented to be a way to transport data for computer monitors, the first version of DVI, invented in 1999, supported monitors up to 2560x1600, 60fps, red, blue, and green channels, 8-bit each. Didn't supported audio.

                           

                          HDMI was invented to be a way to transport video from a DVD player to a television, it supports tranfer of encrypted (to avoid piracy) video data, and encrypted audio, the video data resolution is related to the maximum resolution of the DVD, in 2003 (when the first HDMI came out), this was 1920x1200, 60fps, using TV signals (it is not R, G, B 8-bit each, it is something else).

                           

                          They are fundamentally different, made for different purposes, the reason why HDMI ended being on computers is partly political and too long to explain.

                           

                          But in short, HDMI and DVI have nothing to do with each other, beside that both are digital. The proper port for a computer monitor, is DVI, or DisplayPort, HDMI on a computer monitor is a "hack" of sorts, and you should use the HDMI port on your computer only to output to actual TVs, not to monitors.

                           

                          That said, the RX480 supports the newest HDMI, that does have sufficient data speed for your monitor, but it requires a special converter, because the rest of what I said is still true (HDMI is for TVs, not monitors, and works differently than DVI and DP), and you would need to buy a converter that supports new HDMI too (I didn't saw any, all converters use older HDMI format, that is slower, intended to be used with 1080p and 1080i and 720p TVs only)

                            • Re: rx 480 hdmi to dvi 2560x1600 flickers
                              khbuchner

                              Hi speeder,

                              thanks for your answer, but this does not explain for me, why hdmi to dvi is partly working in this resolution here. Right at the moment I'm sitting in front of my monitor with hdmi to dvi and 2560x1600, and no flickering. It seems that it is because the screen has to display white and other brighter colors, flickering seems to be worse when it shows darker colors.

                              Regards,

                              Karl-Heinz

                                • Re: rx 480 hdmi to dvi 2560x1600 flickers
                                  speeder

                                  LCD panels work by "holding" the image for a while, this is why they are blurry compared to CRTs too (and why to make screens for virtual reality googles was hard, it required some modifications to normal LCD tech, and requires very high framerate).

                                   

                                  The brighter the image, the longer it "stays" on the screen.

                                   

                                  So, if you are rendering only half of the frames, and display for example 100% blue screen, you would see something like 70% blue, as the screen alternates 100% blue, and black, faster than you can notice, because of how LCD works.

                                   

                                  But now you want a 20% blue screen, now you are alternating almost-black with actual black, this time you end seeing actual flickering.

                                   

                                  If you lower your refresh rate (and if your montior actually accepts low refresh rate), then you might get better results, but only if you can lower it enough to send all frames through the converter (this might mean even slow as 40fps, depending on the resolution).

                                   

                                  Also, if you are reading black text on white background, you won't see the black text flicker, since one frame is intentionally black, and the other "accidentaly" black, but "black to black" is still black.

                                   

                                  Now, playing Dark Souls on your current setup probably would be funky.

                                    • Re: rx 480 hdmi to dvi 2560x1600 flickers
                                      khbuchner

                                      Hi speeder,

                                      thanks for your answer, you are right, when I play e.g. crysis 3, the flicker from the monitor is mostly not distinguishable from the hectic gameplay, so I think I can live with it. But in my amateurish view: if only the actual communication speed between pc and monitor would be 5% faster, anything would be ok. I will try your suggestion with lowering the refresh rate, perhaps it helps.

                                      Regards,

                                      Karl-Heinz