Buster is obsolete, so I won't make any claims as to what can or can't be achieved with the kernel shipped with it.
The current Pi kernel can drive both HDMIs and VEC (analogue TV block) at the same time, but has some limitations. The main thing is that the VEC requires very specific PLL configuration, and that can compromise other blocks in the SoC - that is why enabling composite disables all other display outputs.
You can tweak the vc4-kms-v3d-pi4 overlay such that it doesn't disable the HDMI outputs (just look at the fragments that the "composite" override disables), but I can't guarantee that there won't be limitations (eg 4k60 may not be possible from the HDMI).
The current Pi kernel can drive both HDMIs and VEC (analogue TV block) at the same time, but has some limitations. The main thing is that the VEC requires very specific PLL configuration, and that can compromise other blocks in the SoC - that is why enabling composite disables all other display outputs.
You can tweak the vc4-kms-v3d-pi4 overlay such that it doesn't disable the HDMI outputs (just look at the fragments that the "composite" override disables), but I can't guarantee that there won't be limitations (eg 4k60 may not be possible from the HDMI).
Statistics: Posted by 6by9 — Sun Feb 11, 2024 3:51 pm