[libav-bugs] [Bug 645] New: Too many slices, increase MAX_SLICES and recompile

bugzilla at libav.org bugzilla at libav.org
Fri Feb 28 17:18:46 CET 2014


           Summary: Too many slices, increase MAX_SLICES and recompile
           Product: Libav
           Version: 9
          Platform: All
        OS/Version: Mac OS
            Status: NEW
          Severity: normal
          Priority: Normal
         Component: libavcodec
        AssignedTo: bugzilla at libav.org
        ReportedBy: tgreenwood at cafex.com

Created attachment 466
  --> http://bugzilla.libav.org/attachment.cgi?id=466
H264 stream which triggers error

H264 streams from CounterPath Bria and some Cisco phones routinely trigger this
message.  I attach a file extracted from an RTP stream.

I have changed this value and it appears to significantly reduce occasional
artefacts.  Unfortunately the artefacts happen very infrequently and generally
on long running streams - hence I don't have an actual capture of one with
actual artefacts.

I have been using libav via gstreamer - in order to reproduce you can use the
following command with gstreamer 1.2.1:

export GST_DEBUG=*:3
gst-launch-1.0 filesrc location=bria-h264.mka ! matroskademux ! avdec_h264 !
videoconvert ! videoscale ! 'video/x-raw, width=640, height=480' ! ximagesink

I have recompiled with MAX_SLICES set to 32 which resolves the issue with this
stream and in our testing has reduced a number of artefacts associated with
long running streams.

I have seen cases where increasing to 64 was required to avoid the error
message, but I haven't yet captured any stream where MAX_SLICES passes 32 - so
think that values over 32 were somehow caused by corruption of the RTP stream. 
Also I have not seen a reduction in artefacts when MAX_SLICES was increased to
64 - so I suspect artefacts that setting MAX_SLICES to 32 would be the best
choice to resolve these issues.

The issue has been seen on Mac OSX and Centos Linux.

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