I’ve moved this thread into its own topic as it’s unrelated to the original post. The issue here is that the setup used adds playback for 7 HEVC streams on a Pi4. It turns out, this is around the maximum of what’s possible, as each decoder will use up CMA memory.
This type of memory is shared with the decoder hardware and is usually limited to 512MB. Adding a Pi variant with more memory won’t change that. Each decoder uses parts of that memory to place decoded video frames into and with a lot of decoders it fills up pretty quickly.
On a Pi5 this is less of an issue as the 512MB limit has been mostly lifted due to how the decoder hardware accesses available memory. So a Pi5 would probably help in this case.