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• configure : Enable -fno-common for Darwin targets, avoid linker warnings

  29 avril, par Martin Storsjö

  configure : Enable -fno-common for Darwin targets, avoid linker warnings
  Since GCC 10 and llvm.org Clang 11, -fno-common is the default.
  
  However Apple's Xcode Clang hasn't followed suit yet, and still
  
  defaults to -fcommon.
  Compiling with -fcommon causes uninitialized global variables to
  
  be treated as "common" (which allows multiple object files to have
  
  similar definitions).
  Common variables seem to have the issue that their intended alignment
  
  isn't signaled, so the linker assumes that they may need alignment
  
  according to their full size.
  With large global tables, this can lead to linker warnings like
  
  this, with Xcode 16.3 :
      ld : warning : reducing alignment of section __DATA,__common from 0x8000 to 0x4000 because it exceeds segment maximum alignment
  This can be reproduced with a small snippet like this :
      char table[16385] ;
  
      int main(int argc, char* argv[])  return 0 ; 
  Compiling with -fno-common avoids this issue and warning, and
  
  matches the default behaviour of other compilers. (Compiling with
  
   fno-common also avoids the risk of accidentally accepting
  
  duplicate definitions of global variables, as long as they are
  
  uninitialized.)
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] configure

• rtpdec_hevc : Drop a duplicated, nonstandard entry

  17 septembre 2014, par Vittorio Giovara

  rtpdec_hevc : Drop a duplicated, nonstandard entry
  The RFC spec draft only specifies the "H265" name - there is no
  
  specification saying how to interpret "HEVC" (if such a packet
  
  format is specified it could be an entirely different format).
  Since this is a very new standard (still a draft), there is little
  
  need for compatibility with existing, broken implementations. Therefore
  
  remove the extra alias, to avoid the risk of encouraging incorrect
  
  usage.
  Intentionally keeping the ff_hevc_dynamic_handler name for the
  
  handler, to use "hevc" consistently as name for the codec instead
  
  of "h265" within the library internals as long as there only is one
  
  single variant in actual use.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] libavformat/rtpdec.c
  • [DH] libavformat/rtpdec_formats.h
  • [DH] libavformat/rtpdec_hevc.c

• movenc : Add a flag for indicating a discontinuous fragment

  20 novembre 2014, par Martin Storsjö

  movenc : Add a flag for indicating a discontinuous fragment
  This allows creating a later mp4 fragment without sequentially
  
  writing the earlier ones before (when called from a segmenter).
  Normally when writing a fragmented mp4 file sequentially, the
  
  first timestamps of a fragment are adjusted to match the
  
  end of the previous fragment, to make sure the timestamp is the
  
  same, even if it is calculated as the sum of previous fragment
  
  durations. (And for the first packet in a file, the offset of
  
  the first packet is written using an edit list.)
  When writing an individual mp4 fragment discontinuously like this
  
  (with potentially writing the earlier fragments separately later),
  
  there’s a risk of getting a gap in the timeline if the duration
  
  field of the last packet in the previous fragment doesn’t match up
  
  with the start time of the next fragment.
  Using this requires setting -avoid_negative_ts make_non_negative
  
  (or -avoid_negative_ts 0).
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavformat/movenc.c
  • [DBH] libavformat/movenc.h