[J_E_F_F]

I upgraded from #0922 to #1010 and watching a HEVC concert today, saw the overheat icon for the first time in a long time. It only lasted a minute, but it is not something I have seen recently with these beta builds and not on that specific file in a long time.

ffmpeg normally achieves multi-core parallelism by decoding multiple frames in parallel.
But sometimes due to dependencies this is not possible (e.g. frames depending on an I frame that is currently being decoded).
In this case you may see kodi dropping frames even though cpu is much less than 400% (4 cores maxed).

The last update added some within-frame parallelism for files encoded with tiles or wpp (wavefront parallel processing) which can help this situation.
But it may make the 4 arm cores busier for short periods which may increase temperature.

Really the only solution is to improve cooling. The Flirc/Kodi case is highly recommended.
You may also find that decreasing arm_freq / over_voltage will keep temperatures down (and with the continued performance improvements that may be feasible).

Keep the sdram and core/v3d overclock as they don't affect heat as much as the arm and do provide a useful performance benefit.

Thanks, I've commented out arm_freq=1300 and over_voltage=4, and I do already have gpu_mem_1024=320
My Pi's are mounted vertically in open air with heart sinks installed.

What were the ssh commands to show how many times the heat/governor has kicked in, and also to show how many dropped frames?