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• How to open a remote radio stream with ffmpeg's `avformat_open_input` without segfault ?

  19 août 2020, par Keyboard embossed forhead

  I'm at the beginning stage of writing a small app to stream internet radio stations. For the moment I'm just trying to get the detected info of the input stream. Whilst I am successful in getting all the stream's details via the the command line tool (ffmpeg -i ${URL}), calling the library's avformat_open_input(...) method call results in a SEGFAULT (a stack overflow to be precise when checked in valgrind).

  


  Passing a local file url works fine though in both the command line utility and the library call.

  


  Here's a minimal example :

  


  int test() {
    const char      * station_url = "http://stream.srg-ssr.ch/m/rsc_de/aacp_96";
    const char      * test_file   = "test.mp3"; //works
    AVFormatContext * av_ctx      = avformat_alloc_context();
    int               ret         = 0;

    avformat_network_init();

    if( ( ret = avformat_open_input( &av_ctx, station_url, NULL, NULL ) ) < 0 ) { //SEGFAULT   
        printf( "Could not open file '%s': %i", station_url, ret );
        return -1;
    }

    printf( "Format %s, duration %ld us", av_ctx->iformat->long_name, av_ctx->duration );

    avformat_network_deinit();
    return 0;
}


  


  If anyone with experience in dealing with acquiring remote streams using ffmpeg libraries in C has some insights I'd be grateful. Thanks in advance.

  


  I'm using ffmpeg v4.3.1 on Linux.

  


• ppc : reduce overreads when loading 8 pixels in altivec dsp functions

  13 février 2014, par Janne Grunau

  ppc : reduce overreads when loading 8 pixels in altivec dsp functions
  Altivec can only load naturally aligned vectors. To handle possibly
  
  unaligned data a second vector is loaded from an offset of the original
  
  location and the data is recovered through a vector permutation.
  
  Overreads are minimal if the offset for second load points to the last
  
  element of data. This is 7 for loading eight 8-bit pixels and overreads
  
  are reduced from 16 bytes to 8 bytes if the pixels are 64-bit aligned.
  
  For unaligned pixels the overread is reduced from 23 bytes to 15 bytes
  
  in the worst case.
  

  • [DBH] libavcodec/ppc/dsputil_altivec.c

• Streaming a webcam to a web server to be streamed on web

  19 octobre 2012, par gazzwi86

  I intend on streaming a web cam from a Raspberry Pi to a server, which can then serve the stream up to users over the web. I would ideally like the stream to work across all browsers with minimal complication, so the current mjpeg format I presume would not be ideal.

  Firstly, I would like to know if ffmpeg is the right tool for the job as its what I'm experimenting with at the moment ? I also looked at using ffmpeg and motion but didnt see the need for motion as I don't need motion detection. My config for ffmpeg is listed below :

  I installed via apt-get :

  apt-get install ffmpeg

  I have create a config file /etc/ffserver.conf containing the following :

  Port 80
  
  BindAddress 0.0.0.0
  
  MaxClients 10
  
  MaxBandwidth 50000
  
  NoDaemon
  
  
  
  <feed>
  
      file /tmp/webcam.ffm
  
      FileMaxSize 10M
  
  </feed>
  
  
  
  <stream>
  
      Feed webcam.ffm
  
      Format mpjpeg
  
      VideoSize 640x480
  
      VideoFrameRate 15
  
      VideoBitRate 2000
  
      VideoQMin 1
  
      VideoQMax 10
  
      strict -1
  
  </stream>

  I have created a file in the sbin called webcam.sh containing the following :

  ffserver -f /etc/ffserver.conf & ffmpeg -v verbose -r 5 -s 640x480 -f video4linux2 -i /dev/video0 http://localhost/webcam.ffm

  Running the above starts the stream but at the moment viewing http://webcam.mjpeg starts a file downloading which seems not to start in chrome and doing the same with and html file with the stream in a img tag doesnt work.