Note on Raspberry Pi Camera Module bitrate

With this kind of configuration:

[Service]
ExecStartPre = v4l2-ctl --set-ctrl video_bitrate_mode=1,video_bitrate=3000000
ExecStart = ffmpeg \
    -nostdin \
    -f lavfi \
    -i anullsrc=channel_layout=mono:sample_rate=44100 \
    -f video4linux2 \
    -input_format h264 \
    -video_size 1280x720 \
    -framerate 30 \
    -re \
    -thread_queue_size 32 \
    -use_wallclock_as_timestamps 1 \
    -i /dev/video0 \
    -vcodec copy \
    -acodec aac \
    -b:a 128k \
    -f flv \
    -shortest \
    "rtmp://a.rtmp.youtube.com/live2/aaaa-bbbb-cccc-dddd"

CPU load heavily depends on video_bitrate. With the value of 3000000 the load is around 50-55%, while on 4500000 it's already 60-65%.

With video_bitrate_mode=0 it's truly variable yet unpredictable. Depending on an actual scene I observed values of 0.2-10 Mbit/s, and the highest bitrate caused the load of 100% with unstable communication and freezes on YouTube.