I use a RP 4 with raspbian as a basic media center. It is running a mopidy music server using alsamixer. The sound via the HDMI is has no dropping. But with mp4s, large or small, the issue is the same. Using VLC, the video is fluid but the sound is dropping intermittently for the first 15 mins and then the sound stops dropping and as long I don't stop the video, the sound does ot drop. With MPlayer, the sound drops a lot less , but the video is dropping images and can start to drop sync. Watching a video stream from a website in Chromium has the same issues than VLC. Firefox ESR drops too.
The CPU does not peak above 40% and the SD card virtually empty. The services are virtually at 0% so the PI is not being pushed.
I cannot see any reason why the sound is intermittent at the beginning and that it stabilises. Does anyone have an idea? Thank you