libavfilter changed the way a format list is passed to vf_format. Now
you have to separate formats with "|" instead of ":". If you use "|",
it prints an annoying message on every reinit:
[format @ 0x8bbaaa0]This syntax is deprecated. Use '|' to separate the list items.
...and it will probably stop working without warning at some point in
the future.
We need some very annoying ifdeffery to detect this case, because
libavfilter version numbers are just plain incompatible between Libav
and ffmpeg. There is no other way to detect this.
(Sometimes I wonder whether ffmpeg and especially Libav actually like
causing unnecessary pain for their users, and intentionally break stuff
in the most annoying way possible. Sigh...)
Resetting the filter graph helps dealing with filters which save state
between frames. This is important especially if they modify frame timing
or emit additional frames.
Unfortunately the libavfilter API doesn't have a way to do this
directly, so we have to use a dirty trick: we recreate the whole graph,
including format negotiation down and filter string parsing. ffplay does
this too. If libavfilter somehow decides to change output format or size
from what the first run in config() returned, mpv will explode. The same
applies to vf_next_query_format() return values (although this could be
mitigated, should it really happen).
Requires recent FFmpeg/Libav git versions. Earlier versions will not
be supported, as the API is different. (A libavfilter version that
uses AVFrame instead of AVFilterBuffer is needed.)
Note that this is sort of useless, because the option parser prevents
you from making use of the full libavfilter graph syntax. This has to be
fixed later.
Most of the filter creation code (half of the config() function) has
been taken from avplay.c.
This code is not based on MPlayer's vf_lavfi. The MPlayer code doesn't
compile as it hasn't been updated through multiple libavfilter API
changes, making it completely useless as a starting point.
wm4