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• Revision 2b426969c3 : Simplify RDMULT and RDDIV derivation Don't divide RDMULT and RDDIV by 100 when

  26 septembre 2013, par Guillaume Martres

  Changed Paths :
   Modify /vp9/encoder/vp9_rdopt.c

  
  
  Simplify RDMULT and RDDIV derivation

  Don't divide RDMULT and RDDIV by 100 when RDMULT > 1000. This was
  probably done to avoid overflow when the rd cost was stored in a 32 bits
  integer but this is not the case anymore. This change will make it easier
  to support multiple quantizers per frame.

  derf compression gain at speed 0 : 0.037%

  Change-Id : Ibeeb9b7cfa1a132a7af41bc90fc07a3bba0857f6

• FFmpeg with PHP causes Internal Server Error

  19 novembre 2015, par Scott Heath

  I have a PHP script that calls exec() to convert video files using ffmpeg. The script works fine with smaller files, but larger files, usually around 20MB, produce a 500 Internal Server Error after the conversion has run for about 45 seconds.

  The max_execution_time is set to 600 seconds (10 minutes) and the max post and upload sizes are set to 1000 MB. The server is Unix based and is not running in safe mode.

  Although the issue only happens with larger sizes, I’m not even sure it’s a file size issue. The script will pass with a 12.6MB MOV file but will fail with an 11MB MP4 file.

  Below is the exec() line from my script :

  exec('ffmpeg -y -i '.escapeshellarg($uploadFile).' -vcodec libx264 -ab 128k -ac 2 -b 640k -g 300 -keyint_min 25 -sc_threshold 40 -i_qfactor 0.71 -maxrate 10M -bufsize 10M -qcomp 0.6 -qmin 10 -qmax 51 -qdiff 4 -level 30 '.$convertFile);

  Thanks !

• How to capture camera devices on Windows using Libav ?

  22 septembre 2011, par Occulta

  Is there any way to capture frames from as many camera types as DirectShow do on Windows platform using Libav ? I need to capture a camera output without using DirectShow filters and I want my application to work with many camera devices types.

  I have searched the Internet about this capability of libav and found that it can be done via libav using special input format "vfwcap". Something like that (don't sure about code correctness - I wrote it by myself) :

  AVFormatParameters formatParams = NULL;
  
  AVInputFormat* pInfmt = NULL;
  
  pInFormatCtx*  pInFormatCtx = NULL;
  
  
  
  av_register_all();
  
  
  
  //formatParams.device = NULL; //this was probably deprecated and then removed
  
  formatParams.channel = 0;
  
  formatParams.standard = "ntsc"; //deprecated too but still available
  
  formatParams.width = 640;
  
  formatParams.height = 480;
  
  formatParams.time_base.num = 1000;
  
  formatParams.time_base.den = 30000; //so we want 30000/1000 = 30 frames per second
  
  formatParams.prealloced_context = 0;
  
  
  
  
  
  pInfmt = av_find_input_format("vfwcap");
  
  if( !pInfmt )
  
  {
  
    fprintf(stderr,"Unknown input format\n");
  
    return -1;
  
  }
  
  
  
  // Open video file (formatParams can be NULL for autodetecting probably)
  
  if (av_open_input_file(&pInFormatCtx, 0, pInfmt, 0, formatParams) < 0)
  
     return -1; // Couldn't open device
  
  
  
  /* Same as video4linux code*/

  So another question is : how many devices are supported by Libav ? All I have found about capture cameras output with libav on windows is advice to use DirectShow for this purpose because libav supports too few devices. Maybe situation has already changed now and it does support enough devices to use it in production applications ?

  If this isn't possible.. Well I hope my question won't be useless and this composed from different sources piece of code will help someone interested in this theme 'coz there are really too few information about it in the whole internet.