[FFmpeg-trac] #2526(undetermined:open): ffmpeg on windows crashes when using Avisynth 2.5.8

FFmpeg trac at avcodec.org
Wed Aug 7 06:18:00 CEST 2013

#2526: ffmpeg on windows crashes when using Avisynth 2.5.8
             Reporter:  Zarxrax      |                    Owner:
                 Type:  defect       |                   Status:  open
             Priority:  important    |                Component:
              Version:  unspecified  |  undetermined
             Keywords:  regression   |               Resolution:
             Blocking:               |               Blocked By:
Analyzed by developer:  0            |  Reproduced by developer:  0

Comment (by qyot27):

 After some more backtracing with a build of ffmpeg that had asm and
 compiler optimizations disabled, I was able to zero in on what I believe
 is the issue: accessing avs_bit_blt under AviSynth 2.5.8 is what causes
 the crash, possibly due to problems further up the chain, but I wasn't
 able to smoke out that part.  Unfortunately, due to what that function
 does, I'm not sure it can be fixed without changing the method in which
 the data is copied to the output (x264 doesn't use avs_bit_blt, opting for
 some other method of doing this).

 The version check ended up not being based on what x264 does, so the
 license issue isn't a problem with the patch I've submitted to the mailing

 The side effect of this is that one of the working cases, that of using
 Version(), will no longer work with 2.5.8.  But since most (or all) other
 video inputs wouldn't work with 2.5.8 as it stands, and the check
 basically tells you that you're using a pre-2.6 version of AviSynth and
 that's the reason it won't work, I view that as sort of a necessary evil
 just to get it to stop crashing.  It wouldn't be very useful for just
 Version() to work while virtually nothing else does.

 @Trigunflame: I don't think that problem is related to this.  For
 starters, I don't believe LAV Filters touches AviSynth at all (it's not
 one of the formats listed in LAV Splitter's selection dialog, at any
 rate), not to mention Video for Windows, so if it's the only thing you're
 relying on there I don't think it'd work (which would explain the problem
 with VirtualDub, but if the VfW dependency isn't resolved, then AVISource
 won't work anywhere).  You'd need to use ffdshow's VFW interface and the
 right ACM codecs to resolve that...and keep it to all 32-bit versions so
 there isn't a bittage conflict.

Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2526#comment:14>
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