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• Erros in compiling and running FFmpeg C example code

  11 juillet 2019, par Tina J

  I’ve been trying to change an FFmpeg’s example code HERE to call other filters using its C APIs. Say the filter be freezedetect=n=-60dB:d=8 which normally runs like this :

  ffmpeg -i small.mp4 -vf "freezedetect=n=-60dB:d=8" -map 0:v:0 -f null -

  And prints outputs like this :

  [freezedetect @ 0x25b91c0] lavfi.freezedetect.freeze_start: 5.005
  
  [freezedetect @ 0x25b91c0] lavfi.freezedetect.freeze_duration: 2.03537
  
  [freezedetect @ 0x25b91c0] lavfi.freezedetect.freeze_end: 7.04037

  However, the original example displays frames, not these metadata information. How can I change the code to print this metadata information (and not the frames) ?

  I’ve been trying to change the display_frame function below into a display_metadata function. Looks like the frame variable has a metadata dictionary which looks promising, but my attempts failed to use it. I’m also new to C language.

  Original display_frame function :

  static void display_frame(const AVFrame *frame, AVRational time_base)
  
  {
  
      int x, y;
  
      uint8_t *p0, *p;
  
      int64_t delay;
  
  
  
      if (frame->pts != AV_NOPTS_VALUE) {
  
          if (last_pts != AV_NOPTS_VALUE) {
  
              /* sleep roughly the right amount of time;
  
               * usleep is in microseconds, just like AV_TIME_BASE. */
  
              delay = av_rescale_q(frame->pts - last_pts,
  
                                   time_base, AV_TIME_BASE_Q);
  
              if (delay > 0 && delay < 1000000)
  
                  usleep(delay);
  
          }
  
          last_pts = frame->pts;
  
      }
  
  
  
      /* Trivial ASCII grayscale display. */
  
      p0 = frame->data[0];
  
      puts("\033c");
  
      for (y = 0; y < frame->height; y++) {
  
          p = p0;
  
          for (x = 0; x < frame->width; x++)
  
              putchar(" .-+#"[*(p++) / 52]);
  
          putchar('\n');
  
          p0 += frame->linesize[0];
  
      }
  
      fflush(stdout);
  
  }

  My new display_metadata function that needs to be completed :

  static void display_metadata(const AVFrame *frame)
  
  {
  
  
  
  //    printf("%d\n",frame->height);
  
  
  
      AVDictionary* dic = frame->metadata;
  
  
  
      printf("%d\n",*(dic->count));
  
  
  
  //    fflush(stdout);
  
  } 

• KeyError : 1 on Python when the code points to a value that exists [closed]

  10 décembre 2020, par oo92

  I am using the following code to traverse a list JSON output. There are about 100 streamers I want to take screens from but the code fails after the first one where I call the ffmpeg. I put a code after the ffmpeg to see if Python is running it at all and it does :

  


  Traceback (most recent call last):&#xA;  File "/home/onur/Desktop/pythonProject/main.py", line 12, in <module>&#xA;    username = streams_now[i][&#x27;channel&#x27;][&#x27;display_name&#x27;]&#xA;KeyError: 1&#xA;auronplay it is &#xA;</module>

  


  This is my code :

  


  import streamlink, os
from twitch import TwitchClient

client = TwitchClient(client_id='frl3dqgn21bbpp6tajjvg5pdevczac')

streams_now = client.streams.get_live_streams(limit=100)

print(streams_now[2]['channel']['display_name'])

for i in range(0, 99):
  username = streams_now[i]['channel']['display_name']
  streams_now = streamlink.streams('http://twitch.tv/' + username)
  stream = streams_now["best"].url
  dir_path = os.getcwd() + '/' + username
  os.mkdir(dir_path)
  os.system('ffmpeg -i ' + stream + f' -ss 20 -vframes 10 -r 0.2 -f image2 {dir_path}/' + username + '_output_%09d.jpg')
  print(username + ' it is ')


  


  The line that throws the error is username = streams_now[i]['channel']['display_name']. However, this line cannot throw an error because I am testing it before the for loop :

  


  print(streams_now[2]['channel']['display_name'])

  


  and I get this : shroud

  


• how to explain this C language code from ffmpeg remuxing

  20 avril 2017, par Fidona

  can someone help me what the meaning of this code ? this is a code from ffmpeg remuxing code.

  static void log_packet(const AVFormatContext *fmt_ctx, const AVPacket *pkt, const char *tag, int hours, int mins, int secs, int us, int *time )
  
  {
  
      AVRational *time_base = &fmt_ctx->streams[pkt->stream_index]->time_base;
  
      total = total + pkt->duration;
  
    //  printf( "%d:%d:%d.%d \n", hours,  mins,  secs, us );
  
      *time = av_q2d(*time_base) * pkt->pts ;
  
  }

  I’m kind of new to C language. thank you !