[mythtv-commits] Ticket #12888: Memory Alignment Bug when calling swscale

[MythTV]

#12888: Memory Alignment Bug when calling swscale
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     Reporter:  Robert Allan <rallan@…>  |      Owner:
         Type:  Bug Report - Crash       |     Status:  new
     Priority:  minor                    |  Milestone:  unknown
    Component:  MythTV - General         |    Version:  0.28.0
     Severity:  medium                   |   Keywords:
Ticket locked:  0                        |
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 There is a memory misalignment bug when calling swscale.cpp from
 mythavutil.cpp. This shows itself a ‘Bus Error’ when run on an Arm based
 Raspberry Pi3. Mythpreviewgen currently causes this failure and previews
 cannot be generated.

 Whilst memory misalignment appears to be a well known fault with swscale
 due to the packed format, I cannot work out what needs to be changed in
 the calling routine to wrap the buffers to get the correct alignment.

 The offending line is (as found by putting diagnostic output above and
 below):

 sws_scale(d->swsctx, src->data, src->linesize, 0, height, dst->data,
 dst->linesize);

 in function

 int MythAVCopy::Copy(AVPicture *dst, AVPixelFormat dst_pix_fmt, const
 AVPicture *src, AVPixelFormat pix_fmt, int width, int height)

 Web searching appears to indicate that the function
 avcodec_align_dimensions2 should be called but this requires a
 AVCodecContext object in the call and where to find this is not readily
 apparent to me.

 MythTV is version 0.28 with many of the subsequent fixes indicated by Trac
 implemented. My compiler is gcc v4.9.2, being the latest readily available
 on the Raspberry Pi.

 Any help would be much appreciated.

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Ticket URL: <https://code.mythtv.org/trac/ticket/12888>
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