Recherche avancée

Sur d’autres sites (11471)

• Thread safety of FFmpeg when using av_lockmgr_register

  12 août 2013, par Stocastico

  My application uses FFmpeg to read video streams. So far, I ensured thread safety by defining my own global lock and looking for all the methods inside FFmpeg libraries which are not thread safe.
  This makes the code a bit messy, so while looking for better ideas I found this answer, but apparently I couldn't make use of the suggestions.
  I tried testing it in my own environment, but I always get critical heap error. Here's the test code

  class TestReader
  
  {
  
  public:
  
   TestReader( std::string sVid )
  
   {
  
     m_sVid = sVid;
  
     m_cVidPtr.reset( new VideoReader() );
  
   }
  
  
  
   ~TestReader()
  
   {}
  
  
  
   void operator() ()
  
   {
  
      readVideoThread();
  
   }
  
  
  
   private:
  
   int readVideoThread()
  
   {
  
     m_cVidPtr->init( m_sVid.c_str() );
  
     MPEGFrame::pointer cFramePtr;
  
  
  
     for ( int i=0; i< 500; i++ )
  
     {
  
       cFramePtr = m_cVidPtr->getNextFrame();
  
     }
  
  
  
     return 0;
  
   }
  
   boost::shared_ptr<videoreader> m_cVidPtr;
  
   std::string m_sVid;
  
  };
  
  
  
  /*****************************************************************************/
  
  int lockMgrCallback(void** cMutex, enum AVLockOp op)
  
  {
  
   if (nullptr == cMutex)
  
     return -1;
  
  
  
   switch(op)
  
   {
  
   case AV_LOCK_CREATE:
  
     {
  
       *cMutex = nullptr;
  
       boost::mutex* m = new boost::mutex();
  
       *cMutex = static_cast(m);
  
       break;
  
     }
  
   case AV_LOCK_OBTAIN:
  
     {
  
       boost::mutex* m =  static_cast(*cMutex);
  
       m->lock();
  
       break;
  
     }
  
   case AV_LOCK_RELEASE:
  
     {
  
       boost::mutex * m = static_cast(*cMutex);
  
       m->unlock();
  
       break;
  
     }
  
   case AV_LOCK_DESTROY:
  
     {
  
       boost::mutex * m = static_cast(*cMutex);
  
       delete m;
  
       break;
  
     }
  
   default:
  
     break;
  
   }
  
   return 0;
  
  }
  
  
  
  int testFFmpegMultiThread( std::string sVideo )
  
  {
  
   if ( ::av_lockmgr_register( &amp;lockMgrCallback ) )
  
   {
  
     std::cout &lt;&lt; "Could not initialize lock manager!" &lt;&lt; std::endl;
  
     return -1;
  
   }
  
   TestReader c1(sVideo);
  
   TestReader c2(sVideo);
  
   boost::thread t1( c1 );
  
   boost::thread t2( c2 );
  
  
  
   t1.join();
  
   t2.join();
  
  
  
   return 0;
  
  }
  
  </videoreader>

  The classes VideoReader and MPEGFrame are just wrappers and have always worked perfectly in single threaded scenarios, or in multi-threaded scenario managed using my own global lock.
  Am I missing something obvious ? Can anybody point me to some working code ? Thanks in advance

• HEVC/H.265 interlaced format support in ffmpeg or VLC

  30 décembre 2020, par Ernestas Gruodis

  "Music Box Russia" channel over satellite transmits in HEVC 1920x1080 25fps interlaced - and after recording VLC recognizes file as 50 fps, and resolution 1920x540 - half a height. But on satellite tuner the player works fine - it plays a file as 1920x1080 25fps... When we can expect support for HEVC/H.265 interlaced ? Here is recorded file (Garry Grey & Eva Miller - wtf). Also - a lot of lost frames in VLC player statistics..

  


  EDIT :

  


  I found some interesting info how in HEVC the interlace video content can be indicated here :

  


  


  Unlike to H.264/AVC, interlace-dedicated coding in HEVC is not exist :

  


  

  • No mixed frame-field interaction (like PAFF in H.264/AVC)

  


  • No interlace scanning of transform coefficients

  


  • No correction MVX[1] (or y-component of MV) if current and reference pictures are in different polarity (top-bottom or
bottom-top).

  


  


  However, in HEVC the interlace video content can be indicated
(signaled in VPS/SPS and pic_timing SEI messages the latter are
transmitted for every picture in the sequence). Interlace-related
setting :

  


  


  • in VPS/SPS set general_interlaced_source_flag=1 and general_progressive_source_flag=0. Indeed, the HEVC standard says :

    


    if general_progressive_source_flag is equal to 0 and
general_interlaced_source_flag is equal to 1, the source scan type of
the pictures in the CVS should be interpreted as interlaced only.

    


  


  • in VPS/SPS set general_frame_only_constraint_flag=0

    


  


  • in SPS VUI set field_seq_flag=1 and frame_field_info_present_flag=1. Notice that if these flags are ON
then picture timing SEIs shall be present for each picture.

    


  


  • transmission of Picture Timing SEI per picture with the following parameters :

    


    source_scan_type = 0 to indicate interlace mode
for top field picture signal pict_struct=1 and for bottom field picture pict_struct=2

    


  


  


  


  Perhaps it is possible to pass these parameters to ffmpeg/vlc before playing a file ?

  


• avformat/utils : Use static mutexes instead of ff_lock_avformat()

  17 mai 2024, par Andreas Rheinhardt

  avformat/utils : Use static mutexes instead of ff_lock_avformat()
  Its existence is a remnant of (libavcodec's) lock-manager API
  
  which has been removed in a04c2c707de2ce850f79870e84ac9d7ec7aa9143.
  
  There is no need to use the same lock for avisynth, chromaprint
  
  or tls, so switch to ordinary static mutexes instead.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavformat/avisynth.c
  • [DH] libavformat/chromaprint.c
  • [DH] libavformat/internal.h
  • [DH] libavformat/tls_gnutls.c
  • [DH] libavformat/tls_openssl.c
  • [DH] libavformat/utils.c