Presets have effect at 1st pass also even with fast 1st pass (at least part of the options that influence slice type decision). You should use same preset (same options) for 1st and 2nd pass.
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Is this how to use multipass:
Render using 1st pass, then render using nth pass and OVERWRITE the previosly created avi file?
Yes. 1st pass is only needed for generation of stats and mbtree files and avi itself is usually 0-byte frames i.e. not playable (may be only audio).
What about the preset setting? Does that have an effect on the first pass or only the second?
Presets have effect at 1st pass also even with fast 1st pass (at least part of the options that influence slice type decision). You should use same preset (same options) for 1st and 2nd pass.
Ok thank you for the help.