[FFmpeg-trac] #25(avfilter:new): "Access violation reading location 0x00000000" using yadif/libavfilter on MSVC++

FFmpeg trac at avcodec.org
Mon Mar 28 16:07:49 CEST 2011


#25: "Access violation reading location 0x00000000" using yadif/libavfilter on
MSVC++
--------------------+-----------------------
Reporter:  fpretto  |       Owner:  michael
    Type:  defect   |      Status:  new
Priority:  normal   |   Component:  avfilter
 Version:  git      |  Resolution:
Keywords:           |  Blocked By:
Blocking:           |  Reproduced:  0
Analyzed:  0        |
--------------------+-----------------------

Comment (by fpretto):

 Really seems alignment problems. Here is the disassembly were libavfilter
 crashes:

 6D783C61  punpcklbw   xmm0,xmm7
 6D783C65  movq        xmm1,mmword ptr [esi+eax]
 6D783C6A  punpcklbw   xmm1,xmm7
 6D783C6E  movq        xmm2,mmword ptr [ebx]
 6D783C72  punpcklbw   xmm2,xmm7
 6D783C76  movq        xmm3,mmword ptr [esi]
 6D783C7A  punpcklbw   xmm3,xmm7
 6D783C7E  movdqa      xmm4,xmm3
 6D783C82  paddw       xmm3,xmm2
 6D783C86  psraw       xmm3,1
 6D783C8B  movdqa      xmmword ptr [esp+30h],xmm0
 <----------------------------
 6D783C91  movdqa      xmmword ptr [esp+20h],xmm3
 6D783C97  movdqa      xmmword ptr [esp+10h],xmm1
 6D783C9D  psubw       xmm2,xmm4
 6D783CA1  pabsw       xmm2,xmm2
 6D783CA6  movq        xmm3,mmword ptr [ebx+edx]
 6D783CAB  punpcklbw   xmm3,xmm7
 6D783CAF  movq        xmm4,mmword ptr [ebx+eax]
 6D783CB4  punpcklbw   xmm4,xmm7

 Maybe libavfilter is not aligning aware like other parts of ffmpeg
 (looking around I saw ffmpeg must use its allocation functions
 internally)? Just decoding seems ok here. Sorry but can't debug more if
 not teached how to do so.

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/25#comment:4>
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