RPi4 analogue sound output not working usably

1st Official Post

    RPi4 with LE 9.2.4 which I just installed. When I connect analogue cable out to cinch inputs on my amp, sound is useless. I can hear it somewhat but it is stuttering, words can not be understood at all. So, it is not that there is no sound, something can be heard but is unrecognizable - like a robot distorted voice.

    Furthermore, at the same time, the picture h.265 1024p is skipping over like it is being read off from a slow source (it is being received from a DVB-T2 USB tuner local on this same RPi using TVh).

    But, the sound is the same if I play something from the network, the same TV programs but SD and from a different source. In all instances, sound is useless: mpeg2audio or aac sound can not be heard normally. I can not hear GUI sounds, too.

    When I select (using the menus) audio output HDMI only, I can still hear some very muted sounds from the analogue out! When I put sound output to Analogue only, words are somewhat more recognizable but again not normal. Combined HDMI and analogue out is somewhere middle bad in between. All three settings give out some mostly unrecognizable, slow motion and distorted low volume sound to the analog out and all three are different.

    When I try the second RPi4 with LE 9.2.4 connecting it to the analogue audio, the same problem. When I use this second RPi4 to watch the live TV DVB-T2 FullHD stream from the first RPi4 USB tuner, sound is normal on this second RPi4 as it is connected over HDMI.

    Analogue AV cable is OK since I just pulled it from the RPi2 with LE7 where everything works perfectly over analogue output. Amp is not the problem. Picture signal from RPi4 over the same analogue cable is also normal.

    Edited once, last by pila (August 24, 2020 at 11:39 AM).

    If RPi4 is connected to TV with HDMI, than it has normal sound on analogue output. If I unplug HDMI cable, I still have normal sound on analogue output.

    But, as soon as I activate analogue composite video out and reboot, sound it is broken (possibly the video too, as I have observed skipping in h265 FullHD):

    > mount -o remount,rw /flash

    > nano /flash/config.txt

    sdtv_mode=2

    enable_tvout=1

    > mount -o remount,ro /flash

    > reboot

    So, the problem is with enable_tvout and how it changes clocks at RPi4. Now, the big issue is: is this a hardware bug in RPi4 related to composite video or can LE fix this issue?

    • Official Post

    I'm pretty sure it's a software bug. LE updates the RPi firmware, but you can install different firmware for testing. If you have audio pass-through enabled, disable it for another test.

    After you did both tests, write a complete bug report.

    PS: I was just reading that RPi 4 users get an LE 9.2.5 hot fix, which contains new firmware: click. So try this first.

    I have tried LE 9.2.5 but no change. Passtrough is off entire time.

    But, an RPi forum recommended adding audio_pwm_mode=1 which enabled analogue sound to work. Now, my parents would likely not even notice anything is wrong.

    There are some small hicups with the sound every 10 or 15 seconds or so and the sound is bit out of sync. DVB-T2 FullHD h265 stream - it seems picture is not skipping any more! But, sound had no hicups and the sync problem was smaller when a DVB-T2 tuner was on another RPi4.

    I think this means we can rule hardware problem out. I guess I should file an LE bug report.