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• Get ffmpeg information in friendly way

  17 septembre 2012, par JBernardo

  Every time I try to get some information about my video files with ffmpeg, it pukes a lot of useless information mixed with good things.

  I'm using ffmpeg -i name_of_the_video.mpg.

  There are any possibilities to get that in a friendly way ? I mean JSON would be great (and even ugly XML is fine).

  By now, I made my application parse the data with regex but there are lots of nasty corners that appear on some specific video files. I fixed all that I encountered, but there may be more.

  I wanted something like :

  {
  
    "Stream 0": {
  
       "type": "Video",
  
       "codec": "h264",
  
       "resolution": "720x480"
  
    },
  
    "Stream 1": {
  
       "type": "Audio",
  
       "bitrate": "128 kbps",
  
       "channels": 2
  
    }
  
  }

• ffmpeg +libx264 iPhone -> 'avcodec_encode_video' return always 0 . please advice

  2 janvier 2014, par isaiah

                   av_register_all();

          AVCodec *codec ;
          AVCodecContext *c= NULL ;
          int  out_size, size, outbuf_size ;
          //FILE *f ;
          uint8_t *outbuf ;
          printf("Video encoding\n") ;
          /* find the mpeg video encoder */
  
          codec =avcodec_find_encoder(CODEC_ID_H264) ;//avcodec_find_encoder_by_name("libx264") ; //avcodec_find_encoder(CODEC_ID_H264) ;//CODEC_ID_H264) ;
  
          NSLog(@"codec = %i",codec) ;
  
          if (!codec) 
  
              fprintf(stderr, "codec not found\n") ;
  
              exit(1) ;
  
             
  
  c= avcodec_alloc_context() ;
          /* put sample parameters */
  
          c->bit_rate = 400000 ;
  
          c->bit_rate_tolerance = 10 ;
  
          c->me_method = 2 ;
  
          /* resolution must be a multiple of two */
  
          c->width = 352 ;//width ;//352 ;
  
          c->height = 288 ;//height ;//288 ;
  
          /* frames per second */
  
          c->time_base= (AVRational)1,25 ;
  
          c->gop_size = 10 ; /* emit one intra frame every ten frames */
  
          //c->max_b_frames=1 ;
  
          c->pix_fmt = PIX_FMT_YUV420P ;
          c ->me_range = 16 ;
  
          c ->max_qdiff = 4 ;
  
          c ->qmin = 10 ;
  
          c ->qmax = 51 ;
  
          c ->qcompress = 0.6f ;
  

  'avcodec_encode_video' is always 0 .

  I guess that because 'non-strictly-monotonic PTS' warning, do you konw same situation ?

• X264 encoding using Opencv

  29 novembre 2011, par user573193

  I am working with a high resolution camera : 4008x2672. I a writing a simple program which grabs frame from the camera and sends the frame to a avi file. For working with such a high resolution, I found only x264 codec that could do the trick (Suggestions welcome). I am using opencv for most of the image handling stuff. As mentioned in this post http://doom10.org/index.php?topic=1019.0 , I modified the AVCodecContext members as per ffmpeg presets for libx264 (Had to do this to avoid broken ffmpeg defaults settings error). This is output I am getting when I try to run the program

  libx264 @ 0x992d040]non-strictly-monotonic PTS 
  
  1294846981.526675 1 0 //Timestamp camera_no frame_no
  
  1294846981.621101 1 1
  
  1294846981.715521 1 2
  
  1294846981.809939 1 3
  
  1294846981.904360 1 4
  
  1294846981.998782 1 5
  
  1294846982.093203 1 6
  
      Last message repeated 7 times
  
  [avi @ 0x992beb0]st:0 error, non monotone timestamps 
  
  -614891469123651720 >= -614891469123651720
  
  
  
   OpenCV Error: Unspecified error (Error while writing video frame) in
  
   icv_av_write_frame_FFMPEG, file 
  
  /home/ajoshi/ext/OpenCV-2.2.0/modules/highgui/src/cap_ffmpeg.cpp, line 1034
  
  terminate called after throwing an instance of 'cv::Exception'
  
   what():  /home/ajoshi/ext/OpenCV-2.2.0/modules/highgui/src/cap_ffmpeg.cpp:1034:
  
  error: (-2) Error while writing video frame in function icv_av_write_frame_FFMPEG

  Aborted

  Modifications to the AVCodecContext are :

  if(codec_id == CODEC_ID_H264)
  
  {
  
      //fprintf(stderr, "Trying to parse a preset file for libx264\n");
  
      //Setting Values manually from medium preset
  
      c->me_method = 7;
  
      c->qcompress=0.6;
  
      c->qmin = 10;
  
      c->qmax = 51;
  
      c->max_qdiff = 4;
  
      c->i_quant_factor=0.71;
  
      c->max_b_frames=3;
  
      c->b_frame_strategy = 1;
  
      c->me_range = 16;<br />
  
      c->me_subpel_quality=7;
  
      c->coder_type = 1;
  
      c->scenechange_threshold=40;
  
      c->partitions = X264_PART_I8X8 | X264_PART_I4X4 | X264_PART_P8X8 | X264_PART_B8X8;
  
      c->flags = CODEC_FLAG_LOOP_FILTER;
  
      c->flags2 = CODEC_FLAG2_BPYRAMID | CODEC_FLAG2_MIXED_REFS | CODEC_FLAG2_WPRED | CODEC_FLAG2_8X8DCT | CODEC_FLAG2_FASTPSKIP;
  
      c->keyint_min = 25;
  
      c->refs = 3;
  
      c->trellis=1;
  
      c->directpred = 1;
  
      c->weighted_p_pred=2;
  
  }

  I am probably not setting the dts and pts values which I believed ffmpeg should be setting it for me.

  Any sugggestions welcome.
  Thanks in advance