First N sec not played from pulseaudio over HDMI on Android TV
Found the cause:

check this question:
https://askubuntu.com/questions/218444/sound-output-starts-delayed

so I commented out this line:

 load-module module-suspend-on-idle


in file /etc/pulse/default.pa, and issued pulseaudio -k waited for restart and now it works without any delay. Hurray!