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i found out what caused it.
tmpgenc settings use their own parameter for the buffer (for whatever reason). so when i put in 1120 as i used in ffmpeg it just calculated something completely different in the background. and when i matched the tmpgenc settings to match the ffmpeg buffer it started to look like the ffmpeg output in the screenshot.
after playing around with the settings some more it turns out the way i am calculating the bufsize creates a too high value to keep the spikes below the maxrate. it also has to do with the combination between the bframes and the bufsize. the bframes need to be at 2 (always) and the bufsize around 420 (in this specific case).
i always thought the bufsize is calculated the following way: bitrate*8/framerate
i'll now be using: bitrate*3/framerate
is there something like a correct math for the bufsize?
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