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• avcodec/wmaprodec : Make decoders init-threadsafe

  5 mai 2021, par Andreas Rheinhardt

  avcodec/wmaprodec : Make decoders init-threadsafe
  In this case this actually fixes a potential data race : The static VLC
  
  tables were reinitialized every time an AVCodecContext has been
  
  initialized ; while the mutex in avcodec_open2() ensured that the VLCs
  
  could not be initialized concurrently by multiple threads, nothing
  
  guaranteed that these VLCs are not read concurrently (when decoding a
  
  packet with an already initialized AVCodecContext) while another thread
  
  initializes them. This is undefined behaviour despite the values being
  
  written coinciding with the earlier values.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/wmaprodec.c

• avcodec/jpeg2000dec : Make decoder init-threadsafe

  7 mai 2021, par Andreas Rheinhardt

  avcodec/jpeg2000dec : Make decoder init-threadsafe
  The JPEG-2000 decoder and encoder share common luts ; the decoder
  
  initializes them once, guarded by a dedicated AVOnce, whereas
  
  the encoder initializes them always during init. This means that
  
  the decoder is not init-threadsafe ; in fact there is a potential
  
  data race because these luts can be initialized while an active
  
  decoder/encoder is using them.
  Fix this and make the decoder init-threadsafe by making the
  
  initialization function guard initialization itself with a dedicated
  
  AVOnce.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/jpeg2000.c
  • [DH] libavcodec/jpeg2000dec.c

• Why SIGSEGV appears when trying to decode audio using libavcodec.57 and libopus-1.2 alpha2-1 ?

  10 août 2021, par Greg Joy

  I'm decoding audio using FFMPEG libavcodec's function avcodec_decode_audio4(). Everything works perfect on Windows and Ubuntu 18.04, but I receive segmentation fault when trying to run the same app on Debian 9. I've debugged my code with gdb, and it showed this result :

  


  Thread 24 "SDLAudioDev2" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7ffff7fea700 (LWP 1657)]
0x00007fffecdd6eff in ?? () from /usr/lib/x86_64-linux-gnu/libopus.so.0
(gdb) bt
#0  0x00007fffecdd6eff in ?? ()
   from /usr/lib/x86_64-linux-gnu/libopus.so.0
#1  0x00007fffecde0b18 in ?? ()
   from /usr/lib/x86_64-linux-gnu/libopus.so.0
#2  0x00007fffece04ac1 in ?? ()
   from /usr/lib/x86_64-linux-gnu/libopus.so.0
#3  0x00007fffece05b5b in ?? ()
   from /usr/lib/x86_64-linux-gnu/libopus.so.0
#4  0x00007fffece0e87e in ?? ()
   from /usr/lib/x86_64-linux-gnu/libopus.so.0
#5  0x00007fffece0eba7 in opus_multistream_decode ()
   from /usr/lib/x86_64-linux-gnu/libopus.so.0
#6  0x00007ffff4f8a235 in ?? ()
   from /usr/lib/x86_64-linux-gnu/libavcodec.so.57
#7  0x00007ffff51893fd in avcodec_decode_audio4 ()
   from /usr/lib/x86_64-linux-gnu/libavcodec.so.57
#8  0x00007ffff5189e78 in ?? ()
   from /usr/lib/x86_64-linux-gnu/libavcodec.so.57
#9  0x00007ffff518f098 in avcodec_send_packet ()


  


  Seems that data race appears somewhere. I've tried to remove avcodec_decode_audio4() and use avcodec_send_packet() and avcodec_receive_frame() functions, however in libavcodec.57 of FFMPEG ver.3.2.10 function avcodec_send_packet() invokes avcodec_decode_audio4() and the problem occurs again.

  


  Could someone help me with what do I need to change to make it all be compatible with Debian 9 packages' versions, please ?

  


  On Windows I have libavcodec.58, on Ubuntu 18.04 libavcodec.57 ver.3.4.8

  


  On Debian 9 I have libavcodec.57 ver.3.2.15