[FFmpeg-devel] libavformat/avisynth: AvxSynth deprecation and switch to AviSynth+

[Stephen Hutchinson]

With the release of version 3.5 earlier this evening, AviSynth+ can now 
be built and used natively on the same platforms AvxSynth could, making 
AvxSynth completely obsolete.

Due to that, is there a preference for how we should handle this?  I 
have two different patchsets ready to send.

The first simply adds a warning message that AvxSynth is deprecated and 
urges the user to upgrade to AviSynth+ 3.5 or higher.  The actual switch 
would then probably occur after the message has been visible for one or 
two releases of FFmpeg.

The second just up and removes the AvxSynth-specific branching and 
streamlines the demuxer so that it assumes only AviSynth(+) is being 
used at all times, with the USING_AVISYNTH checks reverted back to 
simple _WIN32 at the spots it's still necessary to compensate for 
platform differences.

On the one hand, it would be kind of rude to apply the second patchset 
with no advance warning to users that AvxSynth will suddenly cease to work.

But on the other hand, AvxSynth itself is such a dead project at this 
point that the demuxer was always lopsided in favor of Windows and the 
vast majority of users probably aren't/weren't even aware AvxSynth 
existed, let alone that FFmpeg could use it (I still see people calling 
the ability to open AviSynth scripts a Windows-only feature, even though 
it's been possible on Linux, et al., with AvxSynth for the last 7-7.5 
years, with FFmpeg and x264 both gaining the ability to use it in 
February/March 2013).