Recherche avancée

Sur d’autres sites (6578)

• checkasm : Serialize read_time() calls on x86

  8 octobre 2014, par Henrik Gramner

  checkasm : Serialize read_time() calls on x86
  Improves the accuracy of benchmarks, especially in short functions.
  To quote the Intel 64 and IA-32 Architectures Software Developer’s Manual :
  
  "The RDTSC instruction is not a serializing instruction. It does not necessarily
  
  wait until all previous instructions have been executed before reading the counter.
  
  Similarly, subsequent instructions may begin execution before the read operation
  
  is performed. If software requires RDTSC to be executed only after all previous
  
  instructions have completed locally, it can either use RDTSCP (if the processor
  
  supports that instruction) or execute the sequence LFENCE ;RDTSC."
  RDTSCP would accomplish the same task, but it’s only available since Nehalem.
  This change makes SSE2 a requirement to run checkasm.
  

  • [DH] tools/checkasm.c

• avcodec/ffv1 : Fix segfaults on allocation error

  14 septembre 2020, par Andreas Rheinhardt

  avcodec/ffv1 : Fix segfaults on allocation error
  When allocating FFV1 slice contexts fails, ff_ffv1_init_slice_contexts()
  
  frees everything that it has allocated, yet it does not reset the
  
  counter for the number of allocated slice contexts. This inconsistent
  
  state leads to segfaults lateron in ff_ffv1_close(), because said
  
  function presumes that the slice contexts have been allocated.
  
  Fix this by making sure that the number of slice contexts on error is
  
  consistent (namely zero).
  (This issue only affected the FFV1 decoder, because the encoder does not
  
  clean up after itself on init failure.)
  Reviewed-by : Michael Niedermayer <michael@niedermayer.cc>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavcodec/ffv1.c

• fftools/ffmpeg : stop using AVStream.nb_frames in do_video_stats()

  16 décembre 2021, par Anton Khirnov

  fftools/ffmpeg : stop using AVStream.nb_frames in do_video_stats()
  Its use for muxing is not documented, in practice it is incremented per
  
  each packet successfully passed to the muxer's write_packet(). Since
  
  there is a lot of indirection between ffmpeg receiving a packet from the
  
  encoder and it actually being written (e.g. bitstream filters, the
  
  interleaving queue), using nb_frames here is incorrect.
  Add a new counter for packets received from encoder instead.
  

  • [DH] fftools/ffmpeg.c
  • [DH] fftools/ffmpeg.h