audio sync error for some TV channels

maco · January 2, 2021 at 5:22 PM

First of all thanks for your great work. I’m running LibreELEC-RPi4.arm-9.2.6 on a Raspberry Pi 4 with 2 GB and almost everything is working great.

Just when watching live TV I am having problems. On some of the channels the video judders and the audio is stuttering (like described here: LibreELEC 9.2.X video judder and stuttering [renamed]). Usually this is not happening the whole time but after switching to another channel it happens always for roughly the first minute. In the log I see then the following warning: ActiveAE - large audio sync error (see attached logfile).

Aditionally I see in all live TV channels that the aq and the vq (ctrl+shift+o) is much worse then watching a film.

I am using the latest nightly build of the tvheadend server (the problem also occurred with the default tvheadend server). But I do not think that there is a problem because on my laptop I can watch the stream without a problem (with the VLC player).

If I do a recording and play the recording the stuttering is gone even though it was there while watching it live.

I already tried different settings regarding whitelisting, deinterlacing and player settings but nothing helped.

**Da Flex** · January 2, 2021 at 6:02 PM Official Post

Read this thread: Click!

PS: If you are using custom settings at config.txt, go back to default.

maco · January 2, 2021 at 11:20 PM

Thanks for your fast answer.

I removed my custom changes from the config.txt (some devicetree overlays) and tried all four different settings:

- de-interlacing off, sync-to-display off

- de-interlacing off, sync-to-display on

- de-interlacing on, sync-to-display on

- de-interlacing on, sync-to-display off

Unfortunately I got the same audio sync errors in all cases.

**Da Flex** · January 3, 2021 at 2:00 AM Official Post

Thanks for testing! Do you use a DVB-T tuner on USB? If yes, then you probably know about the case of harry_fine , which appears at your first link. On that thread we spoke about nearly every potential bottleneck. I don't think I can add new ideas to that topic. I'm just waiting for feedback from harry_fine ...

harry_fine · January 3, 2021 at 5:24 PM

Made no difference. Thanks for watching for my response, I was so frustrated I sort of dropped it.

I've ordered a new tuner, I still think mine has a problem. It should be here tomorrow. I will let you know.

maco · January 3, 2021 at 9:26 PM

Yes I use an USB DVB-T tuner (PCTV DVB-S2 461e) and I already tried most of what was mentioned for harry_fine. I just wanted to be sure that I did not overlook anything (especially inside the logs) as I am new to libreelec.

I do not think that my tuner is broken because if I watch the same live TV stream on my Laptop (with the VLC player) it is working. Additionally if I record the live TV stream I can watch it without problems afterwards (even though the scenes where stuttering during the recording).

So I think there is some difference in between the recorded video and audio and the live one.

I will have a look if I can find out what the difference in between a recorded and a live stream is.

maco · January 4, 2021 at 11:09 AM

I could not see any difference in between the recorded and the live stream regarding the codec information (checked with the VLC player, CTRL+J).

What I could see is that frames where skipped when the studdering occurred (ctrl+shift+o in kodi).

This is gone if I deactivate the hardware acceleration (Settings/Player/Videos - Official Kodi Wiki). This is MMAL in my case (I am using a raspberry pi 4). The only thing I see then is sometimes a dropped frame but this does not influence the viewing experience for me.

The same behavior is also described here: Audio Problems with Raspberry Pi 4 and MMAL (Full logs and demofile included)

I will have a more detailed look at this the next days because the above mentioned forum entry mentions that this problem could be related to the audio configuration (I am using a hifiberry digi+ connected to a AV receiver as audio device). But to deactivate hardware acceleration is a good workaround for me at the moment.

maco · January 4, 2021 at 10:16 PM

Changing the audio configuration like described here Audio Problems with Raspberry Pi 4 and MMAL (Full logs and demofile included) (audio_pwm_mode=1) did not change anything for me so I will keep MMAL disabled.

Thanks for your help!