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• 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 ?

• Is there a way to prevent black frames from appearing at the start of a video when using -c:v copy ?

  11 juillet 2023, par MethanE

  My task seems simple. Using ffmpeg in terminal, I'm trying to pass through the exact video settings minus the audio, and i've been successful, except for the fact that the videos start with a frame of black before the actual video plays.

  


  currently using this :

  


  for i in *.*;do ffmpeg -i "$i" -an -c:v copy "${i%.*}_noaudio.mp4";done


  


  My current thought is it may be related to the error I'm getting (the vid still exports), but I'm not certain :
Missing key frame while searching for timestamp : 1001

  


  Input video metadata :

  


  Metadata :
major_brand : XAVC
minor_version : 16785407
compatible_brands : XAVCmp42iso2
creation_time : 2021-09-12T20:13:46.000000Z
Duration : 00:00:17.52, start : 0.000000, bitrate : 107315 kb/s
Stream #0:0(und) : Video : h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 3840x2160 [SAR 1:1 DAR 16:9], 96798 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc (default)

  


  Googling led me to try not using -c:v copy as there might be a glitch related to h264 keyframes and instead using -c:v libx264 but i really don't want to have to re-encode as I don't want to lose any quality. The file I tried this on went from 135 mb down to 6.

  


  Thanks for your help. Kind of a newb at this.

  


• ffmpeg output the time with scan the black screen in the vdeo file

  23 décembre 2023, par jack

  I use the below command to detect the black screen in the video, but it can't output the time field with detected. May I know does have any command can let ffmpeg output the time in the detected ?

  


  ffmpeg -i "inputfile.mkv" -vf "blackdetect=d=2:pix_th=0.00" -an -f null -


  


  Output :

  


  [blackdetect @ 0000024d543c41c0] black_start:876.009 black_end:878.011 black_duration:2.002

[blackdetect @ 0000024d543c41c0] black_start:893.026 black_end:895.028 black_duration:2.002


  


  I checked the below of ffmpeg website

  


  https://ffmpeg.org/ffmpeg-filters.html


  


  but I still can't understand it and I need your help.