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• When is the callback function of avio_alloc_context() triggered as the official ffmpeg documents ?

  2 septembre 2021, par user14767109

  According to the official FFmpeg documents (such as the two links below), the fifth parameter of avio_alloc_context() function is the callback function. How can this callback function be triggered ?

  


  I don't understand the official documents very well.

  


  AVIOContext* avio_alloc_context(unsigned char * buffer,
    int     buffer_size,
    int     write_flag,
    void *  opaque,
    int(*)(void *opaque, uint8_t *buf, int buf_size)     read_packet,
    int(*)(void *opaque, uint8_t *buf, int buf_size)     write_packet,
    int64_t(*)(void *opaque, int64_t offset, int whence) seek
)


  


  Function link : function link

  


  Code link：code link

  


• ffmpeg rtsp_transport to rtmp issues

  16 mars 2015, par RandomCouch

  I’m working on a project that requires taking rtsp links from youtube, and using ffmpeg to stream those videos to an rtmp server. My solution works, however it is having some issues.

  I’m using these settings :

   -max_delay 0 -initial_pause 0 -rtsp_transport udp -i " + inputLink + " -vcodec libx264 -acodec mp3 -ab 48k -bit_rate 450 -r 25 -s 640x480 -f flv "  + stream

  inputLink is replaced with the rtsp link, and stream is replaced with the rtmp server link

  So this works but here are the issues I’m having :

  • At the beginning of each video, there is a big lag spike/lots of frames dropped, and then the video resyncs and plays normally

  • Some videos would crash ffmpeg, with a "Conversion failed" message and many frames dropped during the conversion/stream.

  • At the end of each video it would start lagging/ dropping frame, right near the end of the video, in other words it doesn’t end normally, every video ends by lagging out / dropping frames

  I’ve been struggling for a long time just to get this working, and now I finally did, I just need to perfect it by taking care of those two issues, if anyone has useful information about the rtsp_transport protocol and how to make it stream with no issues, I would greatly appreciate it. Thanks !

• ‘_snprintf’ was not declared in this scope

  3 avril 2015, par Yoohoo

  I am working on a ffmepg c++ project which links a hpp file, in the hpp file :

  #define snprintf _snprintf
  
  #include 
  
  #include <cstdio>
  
  #include 
  
  include 
  
  
  
  #if defined _MSC_VER &amp;&amp; _MSC_VER >= 1200
  
  #pragma warning( disable: 4244 4510 4512 4610 4146 4996 4005)
  
  
  
  #define sprintf sprintf_s
  
  #define _sprintf _sprintf_s
  
  #define _snprintf _snprintf_s
  
  
  
  #endif  
  
  
  
  
  
  snprintf (oc->filename, sizeof(oc->filename), "%s", filename);
  
  </cstdio>

  it gives the error :

  ‘_snprintf’ was not declared in this scope

  It is quite weird the error shows ‘_snprintf’ while what I use is ’snprint’. This code is wrote by others, I did not understand these #define he used. If i remove the line #define sprintf sprintf_s, it gives error :

  segmentation fault(core dumped)

  Due to ffmpeg is incompatible with C++, I have include the stdio.h and cstdio both within extern C and out of extern C, but the error continue show out. What is the problem ? How to fix it ?