On Wed, Mar 13, 2024 at 01:24:25PM +0100, Niklas Haas wrote: > From: Niklas Haas <g...@haasn.dev> > > This filter's existing design has a number of issues: > > - There is no guarantee whatsoever about the order in which frames are > pushed onto the main and ref link, due to this being entirely > dependent on the order in which downstream filters decide to request > frames from their various inputs. As such, there is absolutely no > synchronization for ref streams with dynamically changing resolutions > (see e.g. fate/h264/reinit-*). > > - For some (likely historical) reason, this filter outputs its ref > stream as a second ref output, which is in principle completely > unnecessary (complex filter graph users can just duplicate the input > pin), but in practice only required to allow this filter to > "eventually" see changes to the ref stream (see first point). In > particular, this means that if the user uses the "wrong" pin, this > filter may break completely. > > - The default filter activation function is fundamentally incapable of > handling filters with multiple inputs cleanly, because doing so > requires both knowledge of how these inputs should be internally > ordered, but also how to handle EOF conditions on either input (or > downstream). Both of these are best left to the filter specific > options. (See #10795 for the consequences of using the default > activate with multiple inputs). > > Switching this filter to framesync fixes all three points: > > - ff_framesync_activate() correctly handles multiple inputs and EOF > conditions (and is configurable with the framesync-specific options) > - framesync only supports a single output, so we can (indeed must) drop > the redundant ref output stream > > Update documentation, changelog and tests to correspond to the new usage > pattern. > > Fixes: https://trac.ffmpeg.org/ticket/10795 > --- > Changelog | 2 + > doc/filters.texi | 10 +- > libavfilter/vf_scale.c | 130 ++++++++++++----------- > tests/filtergraphs/scale2ref_keep_aspect | 3 +- > 4 files changed, 76 insertions(+), 69 deletions(-)
this causes ./ffplay --help to segfault [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB It is dangerous to be right in matters on which the established authorities are wrong. -- Voltaire
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