I managed to enable inline header on the OMX H.264 hardware encoder. inline header(SPS/PPS) are mandatory to play an already launched stream.
Yes but there is a problem : the latency grow over the time. There is a strange time calculation problem inside the muxer? I get a lot of traces "application provided invalid, non monotonically increasing dts to muxer in stream X/0" and the ffmpeg process always freeze at 3335/0 (with no trace).
Without inline header : no latency (about 0.2s on raspberry pi 4 / 720x576 25FPS) No "... increasing dts to muxer" error. disadvantage: I can't resume the already launched stream.
With software x264 encoder : no latency (about 0.2s on raspberry pi 4 / 720x576 25FPS) No "... increasing dts to muxer" error. disadvantage: It consume a lot of CPU power...
How to fix the timestamp(?) calculation inside ffmpeg muxer code to take into account the addition of SPS / PPS NALUs ?