[FFmpeg-devel] libx264 (no-)mbtree parameter

Erik Slagter erik
Fri Dec 4 18:37:24 CET 2009

> > - enabling b-pyramid disables mbtree automatically (and vv) (dodgy but
> > quick)
> > - an extra bit in one of the flags
> > - "mis"-use one of the existing avcontext fields that aren't used by
> > libx264, e.g. prediction_order_method (I really don't know the semantics
> > of this field in other codecs, just a wild guess)
> > - ignore the issue completely and wait for libx264 to implement
> > b-pyramid-compatible mbtree semantics and guess that would obsolete
> > no-mbtree.
> It's still useful in general, as the faster speed presets in x264 use
> --no-mbtree.  Make it a flag.


BTW: I did some benchmarks this afternoon with the latest x264, highest
quality settings suitable for "main" profile, and it appears mb_tree is
actually faster than the old code, in this context (which obviously
surprised me). The question is whether this remains relevant if it holds
over the whole range of settings. Anyone experience? Also it seems to be
more efficient (I am very carefully here ;-)) even though it doesn't
implement b-pyramid.

Maybe one of the x264 devels can comment on this?

> > i_slice_max_size;    /* Max size per slice in bytes; includes estimated
> This is probably the one that I've seen the most requests for.

If I only knew what it does ;-) Would there by any chance be comparable
functionality in other codecs so a field in avcodec can be reused?

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