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• FFMPEG get_buffer2 multi-thread random crash

  4 November 2015, by arnaud

  I’m doing a multi-thread FFMPEG video player. Basically it decodes and display 16 MP4 video files ( using h264 codec ) at the same time, using my own threads / jobs subsystem.
  For future extension I want to provide my own memory buffer for AVFrame decoding. To do this, I simply used get_buffer2 hook method. My get_buffer2 handles currently only use av_malloc & av_free (to validate everything is working ). Here is my handler:

  void our_buffer_default_free(void *opaque, uint8_t *data)
  
  {
  
      av_free(data);
  
  }
  
  
  
  int our_get_buffer(struct AVCodecContext *c, AVFrame *pic, int flags)
  
  {
  
      assert(c->codec_type == AVMEDIA_TYPE_VIDEO);
  
  
  
      pic->linesize[0] = pic->width;
  
      pic->linesize[1] = pic->width/2;
  
      pic->linesize[2] = pic->width/2;
  
  
  
      void* pYBuffer = av_malloc(pic->linesize[0] * pic->height);
  
      void* pUBuffer = av_malloc(pic->linesize[1] * pic->height / 2);
  
      void* pVBuffer = av_malloc(pic->linesize[2] * pic->height / 2);
  
      assert(pYBuffer);
  
      assert(pUBuffer);
  
      assert(pVBuffer);
  
  
  
      pic->data[0] = (uint8_t*)pYBuffer;
  
      pic->data[1] = (uint8_t*)pUBuffer;
  
      pic->data[2] = (uint8_t*)pVBuffer;
  
      pic->buf[0] = av_buffer_create(pic->data[0], pic->linesize[0] * pic->height, our_buffer_default_free, NULL, 0);
  
      pic->buf[1] = av_buffer_create(pic->data[1], pic->linesize[1] * pic->height / 2, our_buffer_default_free, NULL, 0);
  
      pic->buf[2] = av_buffer_create(pic->data[2], pic->linesize[2] * pic->height / 2, our_buffer_default_free, NULL, 0);
  
      return 0;
  
  }

  • If I don’t hook get_buffer2 (keep ffmpeg use its own AVFrame memory allocation) and activate my multithread job system, everything is running ok ( no crash)
  • If I hook get_buffer2 with the code provided and multi-thread activated, I get some random crashs ( after few seconds or minutes, random )
  • If I hook get_buffer2 without multi-thread activated, everything is running ok (no crash)

  So it seems the way I hook "get_buffer2" is not thread safe, but I just don’t see why. ( I guess av_malloc & av_free are threadsafe on windows platform)

  Any idea?

  PS: I don’t have many details on the crash because I’m using a pre-compiled FFMPEG. It often crash in avcodec57.dll. I’m using windows 64bits system, my app & FMMPEG binaries are both 32bits. Details about FFMPEG version used:

  Zeranoe's FFmpeg Builds Home Page: /ffmpeg.zeranoe.com/builds/>
  
  
  
  FFmpeg version: 20151103-git-6df2c94
  
    libavutil      54. 30.100 / 54. 30.100
  
    libavcodec     56. 57.100 / 56. 57.100
  
    libavformat    56. 40.101 / 56. 40.101
  
    libavdevice    56.  4.100 / 56.  4.100
  
    libavfilter     5. 32.100 /  5. 32.100
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  2.101 /  1.  2.101
  
    libpostproc    53.  3.100 / 53.  3.100

• avfilter/af_astats: fix possible crash because of undefined float to integer rounding

  11 January 2021, by Marton Balint

  avfilter/af_astats: fix possible crash because of undefined float to integer rounding
  Fixes ticket #9049.
  Signed-off-by: Marton Balint <cus@passwd.hu>
  

  • [DH] libavfilter/af_astats.c

• FFMPEG avformat_open_input() function causes program to crash

  22 December 2019, by helong jin

  carsh code VS2019 windows7.ffmpeg4.2.