Pi4 A/V sync issues with passthrough

    Hi,

    my former setup included the Pi4 and a TV that were connected by HDMI and audio passthrough was disabled. I've never experienced any A/V sync issues with that setup.

    I've recently acquired a soundbar and my setup is now Pi4 -> HDMI -> TV -> HDMI (eARC) -> soundbar.

    When I play a 1080p video with audio passthrough on LibreELEC 10.0.3 I experience a significant audio delay of approx. 750ms for all H264 encoded videos that I tried. Once I pause the video and then continue playing it the delay decreases to approx. 400ms. Any iteration of pausing and continuing to play the video then leaves that audio delay unchanged by approx. 400ms.

    I read about a variety of things I can do for general A/V sync issues (add force_turbo=1 or core_freq_min=500 to config.txt, make sure HW decoding is enabled, Sync Playback to Display is set to off), but none of those alleviated my issue with A/V sync.

    Any help is much appreciated.

    Thanks,

    hangy