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• avcodec/smvjpegdec : Make decoder init-threadsafe

  27 novembre 2020, par Andreas Rheinhardt

  avcodec/smvjpegdec : Make decoder init-threadsafe
  The only thing that stands in the way of adding the
  
  FF_CODEC_CAP_INIT_THREADSAFE flag to the SMV JPEG decoder is its usage
  
  of ff_codec_open2_recursive() : This function requires its caller to hold
  
  the lock for the mutex that guards initialization of AVCodecContexts
  
  whose codecs have a non-threadsafe init function and only callers whose
  
  codec does not have the FF_CODEC_CAP_INIT_THREADSAFE flag set hold said
  
  lock (the others don't need to care about said lock). But one can set
  
  the flag if one switches to avcodec_open2() at the same time.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavcodec/smvjpegdec.c

• avcodec/cri : Make decoder init-threadsafe

  26 novembre 2020, par Andreas Rheinhardt

  avcodec/cri : Make decoder init-threadsafe
  The only thing that stands in the way of adding the
  
  FF_CODEC_CAP_INIT_THREADSAFE flag to the Cintel RAW decoder is its usage
  
  of ff_codec_open2_recursive() : This function requires its caller to hold
  
  the lock for the mutex that guards initialization of AVCodecContexts
  
  whose codecs have a non-threadsafe init function and only callers whose
  
  codec does not have the FF_CODEC_CAP_INIT_THREADSAFE flag set hold said
  
  lock (the others don't need to care about said lock). But one can set
  
  the flag if one switches to avcodec_open2() at the same time.
  Reviewed-by : Anton Khirnov <anton@khirnov.net>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavcodec/cri.c

• avcodec : Fix invalid uses of ff_codec_open2_recursive()

  26 novembre 2020, par Andreas Rheinhardt

  avcodec : Fix invalid uses of ff_codec_open2_recursive()
  Normally no two codecs with FF_CODEC_CAP_INIT_THREADSAFE unset
  
  can be initialized at the same time : a mutex in avcodec_open2()
  
  ensures this. This implies that one cannot simply open a codec
  
  with a non-threadsafe init-function from the init function of
  
  a codec whose own init function is not threadsafe either as the child
  
  codec couldn't acquire the lock.
  ff_codec_open2_recursive() exists to get around this limitation :
  
  If the init function of the child codec to be initialized is not
  
  thread-safe, the mutex is unlocked, the child is initialized and
  
  the mutex is locked again. This of course has as a prerequisite that
  
  the parent AVCodecContext actually holds the lock, i.e. that the
  
  parent codec's init function is not thread-safe. If it is, then one
  
  can (and has to) just use avcodec_open2() directly (if the child's
  
  init function is not thread-safe, then avcodec_open2() will have to
  
  acquire the mutex itself (and potentially wait for it), so that it is
  
  perfectly fine for an otherwise thread-safe init function to open
  
  a codec with a potentially non-thread-safe init function via
  
  avcodec_open2()).
  Yet several of the users of ff_codec_open2_recursive() have the
  
  FF_CODEC_CAP_INIT_THREADSAFE flag set ; this only worked because
  
  all the child codecs' init functions were thread-safe themselves
  
  so that ff_codec_open2_recursive() didn't touch the mutex at all.
  
  But of course the real solution to this is to directly use
  
  avcodec_open2().
  Reviewed-by : Anton Khirnov <anton@khirnov.net>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavcodec/avrndec.c
  • [DH] libavcodec/imm5.c
  • [DH] libavcodec/tdsc.c