Hdmi signal drop on volume change

1st Official Post

    Hi fellow members,

    I have a question regarding my pi4 setup. My pi4 is connect to a sony av receiver which is connected to a LG tv. So far so good. But when i change the audio volume the hdmi signal is dropping for 10 seconds. This is not only happening during playback. Changing the volume in the libreelec menu is also dropping the signal. Is there any setting in the config.txt which will prevent this behaviour? Many thanks,, kind regards ,,


    libreelec version 9.2.1

    Edited once, last by A1RFORCE1 (May 5, 2020 at 7:35 PM).

    Hi DA Flex, thanxz . I have tried this setup and it’s working ok. But now i don”t have the audio over my receiver, cause the pi4 does not have another audio out 😔. before the pi4 I had a popcorn hour a-400 connected on exactly the same way without any problems so I think somehow the pi4 reacts on the av receiver putting the volume level on the tv screen which i can’t turn off

    • Official Post

    If it has been working before, better HDMI cables might help. Maybe volume change increases data rate, and one or both of your HDMI cables can't handle that data rate. HDMI 2.0 or 2.1 standard cables work fine for RPi 4.

    At config.txt you can try hdmi_safe=1 for maximum compatibility among devices.

    Just replaced all cables with HDMI 2.0b. The problem still persists .. Reinstalled the popcorn hour a-400 with the same setup which doesn't give any problems.

    Also the flag hdmi_safe=1 doesn't work.

    Is there an option to get the audio to the second hdmi output. So i can connect the PI4 directly to the tv on the first hdmi out and the audio to the receiver on the second hdmi out ?

    • Official Post

    Sorry to hear that. At least your cables are now conform to 4K.

    Probably your former A-400 had a lower data rate, because it wasn't a 4K device. I think we now have isolated the AVR as the trouble maker when using higher data rates.

    The only advice I can give is to order even more stuff. /shrug

    The second HDMI port (HDMI-1) for audio doesn't work. Get an HDMI audio extractor to connect your AVR separately.

    Little update:

    I tried the kodi nightly build, and switched the dtoverlay from vc4-fkms-3d to vc4-kms-3d-pi4 and the volume problem is solved. So problably the error is in the vc4-fkms-3d driver or it's missing some parameters for this setup to work.

    Leaving the new pi4 kms driver is not an option at this moment, because the picture is constantly freezing . And I see a lot of alsa audio errors in the log. 1 problem solved, 1 new problem created :)

    Will do, but it doesn’t look like a data rate problem to me. when i am just in the kodi main menu without playing anything and change the volume the hdmi also drops just presenting a main screen. that looks like pretty basic data 🧐. But if all fails i keep the extractor in mind 😀

    Tested with the resolution 640 * 480p problem

    still persists

    second test with audio passthrough turned off (and 640 * 480) problem still remains.
    maybe there is a difference in how the drivers actually address the gpu hardware

    • Official Post

    OK, here is my next and final theory. People often believe that HDMI pass-through is a simple in-and-out process, but that's not right. Your AVR has to analyze incoming HDMI data to find relevant commands. My theory now is that RPi's volume change data are challenging for your AVR's processor. Probably so challenging that pass-through of video HDMI data will be dropped for the period of volume change.

    However, my advice stays the same: get the extractor. Then your AVR just has to deal with audio data.

    Fixed.

    Used the nightly build 22-05 noobs (Index of /) (LibreELEC-RPi4.arm-9.80-nightly-20200522-76f70e9-noobs.tar)

    replaced rpi4 folder in official noobs release (Download NOOBS for Raspberry Pi)

    On command:

    mount -o remount,rw /flash

    changed dtoverlay to dtoverlay=vc4-kms-v3d-pi4 in /flash/distroconfig.txt

    On libreelec interface:
    Changed audio output device in libreelec system config to : ALSA: vc4-hdmi,MAI PCM vc4-hdmi-hifi-0 S/PDIF

    enabled audio Passthrough for all

    No freezing, no hdmi signal drop by the avr...

    Hopefully Libreelec 10 will use this by design :)

    Edited once, last by A1RFORCE1 (May 22, 2020 at 2:23 PM).