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Green lines on screen when using Wi-Fi

By David @david2025-03-13 15:25:03.759Zassigned to
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    Ather @ather
      2025-03-13 11:07:10.987Z

      I have the green lines issue when using the C790 HDMI board over WiFi.

      When I connect it using ethernet cable it works perfectly.

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      1. David @david2025-03-13 15:28:04.897Z

        Hi @ather, I'm sorry you're running into this display issue when using Wi-Fi.

        I've moved your comment to its own post so we can discuss it as a standalone issue.

        Are you seeing this issue on a device you built yourself? And can I confirm that you're referring to this HDMI capture device?

        Please let me know if you have any questions.

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        1. AAther @ather
            2025-03-13 20:46:38.600Z

            Yes, I did build one using RPi 4 and Geekworm C790.

            I also have Geekworm X630 with the X1300 A2 I2S board and didn't face any issue with that board.

            I don't understand, could it be due to Wi-Fi interference ?

            Reply
            1. David @david2025-03-17 12:50:44.260Z

              Thanks for confirming, @ather.

              I don't understand, could it be due to Wi-Fi interference ?

              I'm not sure - nobody has reported this behavior before. But I can't think of any other possible explanations right now.

              Can you reproduce the green line behavior and then share the output of a few commands to see if there's any information that might help with troubleshooting here?

              SSH into your device and then run the following command:

              iw wlan0 info

              The output from the command should look something like this (feel free to remove the addr and ssid values):

              Interface wlan0
    ifindex 3
    wdev 0x1
    addr [removed]
    ssid [removed]
    type managed
    wiphy 0
    channel 52 (5260 MHz), width: 80 MHz, center1: 5290 MHz
    txpower 31.00 dBm

              Then could you run the following command:

              iwlist wlan0 channel

              The output should look something like this:

              wlan0     32 channels in total; available frequencies :
          Channel 01 : 2.412 GHz
          Channel 02 : 2.417 GHz
          Channel 03 : 2.422 GHz
          Channel 04 : 2.427 GHz
          Channel 05 : 2.432 GHz
          Channel 06 : 2.437 GHz
          Channel 07 : 2.442 GHz
          Channel 08 : 2.447 GHz
          Channel 09 : 2.452 GHz
          Channel 10 : 2.457 GHz
          Channel 11 : 2.462 GHz
          Channel 12 : 2.467 GHz
          Channel 13 : 2.472 GHz
          Channel 34 : 5.17 GHz
          Channel 36 : 5.18 GHz
          Channel 38 : 5.19 GHz
          Channel 40 : 5.2 GHz
          Channel 42 : 5.21 GHz
          Channel 44 : 5.22 GHz
          Channel 46 : 5.23 GHz
          Channel 48 : 5.24 GHz
          Channel 52 : 5.26 GHz
          Channel 56 : 5.28 GHz
          Channel 60 : 5.3 GHz
          Channel 64 : 5.32 GHz
          Channel 100 : 5.5 GHz
          Channel 104 : 5.52 GHz
          Channel 108 : 5.54 GHz
          Channel 112 : 5.56 GHz
          Channel 116 : 5.58 GHz
          Channel 120 : 5.6 GHz
          Channel 124 : 5.62 GHz
          Current Frequency=5.26 GHz (Channel 52)

              That information should help me understand a little more about the Wi-Fi configuration here and may help with troubleshooting. Perhaps we'll need to change the frequency your TinyPilot's Wi-Fi uses.

              Please let me know if you have any questions.

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              1. D@Drew
                  2025-04-11 21:58:28.255Z

                  Hello David,
                  I am having the same issue where I see green lines when connected to WiFi but no issues when connected to LAN.

                  I think you are right by changing the frequency, so I want to try changing mine. Can you paste the SSH command for changing the frequency please?

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                  1. AAther @ather
                      2025-04-11 22:13:15.272Z

                      Hi Drew,

                      Which capture card are you using, assuming you have DIY device.

                      Reply
                      1. D@Drew
                          2025-04-14 18:47:10.356Z

                          Hi Ather,

                          Thanks for the reply. I am using a Tinypilot Voyager 2a. I ended up figuring out the root of my problem—my device was too far away from my router. The onboard WiFi was not strong enough to pick up the signal, so I solved this by using a WiFi repeater and plugged into the device via Ethernet from the repeater. Thanks for the help though.

                          Reply
                        • In reply toDrew⬆:
                          David @david2025-04-14 11:26:35.298Z

                          Hi @Drew, I'm sorry you're also running into this issue.

                          Can I confirm which device you're running (e.g., a TinyPilot Voyager 2a)?

                          Could you share a screenshot showing what the screen looks like when you see this behavior?

                          After looking into this some more, I'm not sure it's possible to select specific frequencies. You may be able guide your TinyPilot to a frequency band by editing /etc/wpa_supplicant/wpa_supplicant.conf on your TinyPilot (via SSH), but I'm not sure how reliable this is.

                          Open the file using nano:

                          sudo nano /etc/wpa_supplicant/wpa_supplicant.conf

                          Then edit the file with a new freq_list= value, where the value is the frequency in megahertz. So for 5.18 GHz (Channel 36), you would use freq_list=5180:

                          network={
    ssid="Your_SSID"
    psk="Your_Password"
    freq_list=5180
}

                          Save the file (ctrl + o then ctrl + x). Then run the following command to propagate the changes:

                          sudo wpa_cli -i wlan0 reconfigure

                          This doesn't force your device to use the frequency, but it will guide it. If you use iw wlan0 info, you can see which frequency your device is using. If you run sudo wpa_cli -i wlan0 reconfigure again, the frequency may change.

                          Please let me know if this changes the behavior at all.

                          Reply
                          1. D@Drew
                              2025-04-14 18:46:46.291Z

                              Hi David,

                              Thanks for the reply. I am using a Tinypilot Voyager 2a. I ended up figuring out the root of my problem—my device was too far away from my router. The onboard WiFi was not strong enough to pick up the signal, so I solved this by using a WiFi repeater and plugged into the device via Ethernet from the repeater. Thanks for the help though.

                              Reply
                              1. David @david2025-04-15 10:49:16.907Z

                                Thanks for the update and those details, @Drew!

                                I'm glad to hear connecting via Ethernet made the lines go away. I'm not confident that the issue is related to a weak Wi-Fi signal though - the primary symptom of a weak Wi-Fi signal would be greater latency and latency spikes if the Wi-Fi signal drops. A broken screen image would point to something else.

                                It would be interesting to see whether you have the same green lines when using Wi-Fi with the device close to the Wi-Fi access point to confirm you have the same behavior with a stronger connection. You don't have to test this if you're happy with your current setup, however.

                                Feel free to reach out again if you have any questions.

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