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• How can I get start time of rtsp-sesson via ffmpeg (C++) ? start_time_realtime always equal -9223372036854775808

  5 août 2019, par chuchuchu

  I’m trying to get a frame by rtsp and calculate its real-world timestamp. I previously used Live555 for this (presentationTime).

  As far as I understand, ffmpeg does not provide such functionality, but provides the ability to read the relative time of each frame and the start time of the stream. In my case, the frame timestamps (pts) works correctly, but the stream start time (start_time_realtime) is always -9223372036854775808.

  I’m trying to use simple example from this Q : https://stackoverflow.com/a/11054652/5355846

  Value does not change. regardless of the position in the code

  int main(int argc, char** argv) {
  
      // Open the initial context variables that are needed
  
      SwsContext *img_convert_ctx;
  
      AVFormatContext* format_ctx = avformat_alloc_context();
  
      AVCodecContext* codec_ctx = NULL;
  
      int video_stream_index;
  
  
  
      // Register everything
  
      av_register_all();
  
      avformat_network_init();
  
  
  
      //open RTSP
  
      if (avformat_open_input(&format_ctx, "path_to_rtsp_stream",
  
                              NULL, NULL) != 0) {
  
          return EXIT_FAILURE;
  
      }
  
      ...
  
  }

  while (av_read_frame(format_ctx, &packet) >= 0 && cnt < 1000) { //read ~ 1000 frames
  
  
  
          //// here!
  
          std::cout<< " ***** "
  
          << std::to_string(format_ctx->start_time_realtime) 
  
          << " | "<start_time
  
          << " | "<best_effort_timestamp;
  
  
  
  ...
  
  }

  ***** -9223372036854775808 | 0 | 4120 | 40801 Frame : 103

  What am I doing wrong ?

• ffmpeg : drawtext fade in/out with zmq

  11 novembre 2019, par jb_alvarado

  There are several ways to fade in and out text in ffmpeg. But I only found solutions where the actual time is known.

  But what can I do, when I don’t know the current running time and I would like to fade in and out a text ?

  Let’s say I have an endless stream and I want to fade in a text with zmqsend. And the fade should start immediately. For that my understanding is, that I need to store some time information in a variable and calculate with that. But storing variables is not possible in ffmpeg expressions - right ?

  For testing purposes here are a playing instance :

  ffplay -dumpgraph 1 -f lavfi "color=s=512x288:c=black,zmq,drawtext=text=''"

  For adding some text with zmq I can run now :

  echo Parsed_drawtext_2 reinit text="Hello\ World,\ what’s\ up?" | zmqsend

  Or if I know the running time and after 10 seconds I want the text fade in :

  "text='Hello\ World':fontsize=:fontcolor=ffffff:alpha='if(lt(t,10),0,if(lt(t,11),(t-10)/1,if(lt(t,16),1,if(lt(t,17),(1-(t-16))/1,0))))'"

  My goal is now to have an expression what I can send, so that ffmpeg starts fading in the text and out after a certain time.

  Something like :

  now=t,if(lt(t,now+10),0,if(lt(t,now+11),(t-(now+10))/1,if(lt(t,now+16),1,if(lt(t,now+17),(1-(t-(now+16)))/1,0))))

  Is there a way to store variables in expression, or is there any other way to realize this ?

• FFmpeg from Python has Corrupted Output

  14 juillet 2019, par Mazyod

  In a python script, I have :

  os.system(ff_cmd)
  
  # also tried Popen(ff_cmd, shell=True).wait()

  Then, I ran that same ff_cmd from terminal directly. Here are the results :

  # ff_cmd
  
  ffmpeg -i "114006.mp3" -acodec pcm_s16le -ar 16000 -ac 1 "114-006-a4dec52a.wav"
  
  
  
  # after running from python
  
  % file 114-006-a4dec52a.wav
  
  114-006-a4dec52a.wav: Audio file with ID3 version 2.4.0, contains:MPEG ADTS, layer III, v2,  40 kbps, 16 kHz, Monaural
  
  
  
  # after running from terminal
  
  % file 114-006-a4dec52a.wav
  
  114-006-a4dec52a.wav: RIFF (little-endian) data, WAVE audio, Microsoft PCM, 16 bit, mono 16000 Hz

  Can anyone please explain why in the world would they result in different outputs ?

  ---

  Output from Python :

  ffmpeg version 4.1.4 Copyright (c) 2000-2019 the FFmpeg developers
  
    built with Apple LLVM version 10.0.1 (clang-1001.0.46.4)
  
    configuration: --prefix=/usr/local/Cellar/ffmpeg/4.1.4 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags='-I/Library/Java/JavaVirtualMachines/adoptopenjdk-12.0.1.jdk/Contents/Home/include -I/Library/Java/JavaVirtualMachines/adoptopenjdk-12.0.1.jdk/Contents/Home/include/darwin' --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libmp3lame --enable-libopus --enable-librubberband --enable-libsnappy --enable-libtesseract --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-videotoolbox --disable-libjack --disable-indev=jack --enable-libaom --enable-libsoxr
  
    libavutil      56. 22.100 / 56. 22.100
  
    libavcodec     58. 35.100 / 58. 35.100
  
    libavformat    58. 20.100 / 58. 20.100
  
    libavdevice    58.  5.100 / 58.  5.100
  
    libavfilter     7. 40.101 /  7. 40.101
  
    libavresample   4.  0.  0 /  4.  0.  0
  
    libswscale      5.  3.100 /  5.  3.100
  
    libswresample   3.  3.100 /  3.  3.100
  
    libpostproc    55.  3.100 / 55.  3.100
  
  [mp3 @ 0x7ffa34001800] Estimating duration from bitrate, this may be inaccurate
  
  Input #0, mp3, from '/.../114006.mp3':
  
    Duration: 00:00:09.53, start: 0.000000, bitrate: 64 kb/s
  
      Stream #0:0: Audio: mp3, 22050 Hz, stereo, fltp, 64 kb/s
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (mp3 (mp3float) -> pcm_s16le (native))
  
  Press [q] to stop, [?] for help
  
  Output #0, wav, to '/.../114-006-a4dec52a.wav':
  
    Metadata:
  
      ISFT            : Lavf58.20.100
  
      Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 16000 Hz, mono, s16, 256 kb/s
  
      Metadata:
  
        encoder         : Lavc58.35.100 pcm_s16le
  
  size=     298kB time=00:00:09.53 bitrate= 256.1kbits/s speed= 166x    
  
  video:0kB audio:298kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.025564%

  Output from terminal :

  ffmpeg version 4.1.4 Copyright (c) 2000-2019 the FFmpeg developers
  
    built with Apple LLVM version 10.0.1 (clang-1001.0.46.4)
  
    configuration: --prefix=/usr/local/Cellar/ffmpeg/4.1.4 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags='-I/Library/Java/JavaVirtualMachines/adoptopenjdk-12.0.1.jdk/Contents/Home/include -I/Library/Java/JavaVirtualMachines/adoptopenjdk-12.0.1.jdk/Contents/Home/include/darwin' --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libmp3lame --enable-libopus --enable-librubberband --enable-libsnappy --enable-libtesseract --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-videotoolbox --disable-libjack --disable-indev=jack --enable-libaom --enable-libsoxr
  
    libavutil      56. 22.100 / 56. 22.100
  
    libavcodec     58. 35.100 / 58. 35.100
  
    libavformat    58. 20.100 / 58. 20.100
  
    libavdevice    58.  5.100 / 58.  5.100
  
    libavfilter     7. 40.101 /  7. 40.101
  
    libavresample   4.  0.  0 /  4.  0.  0
  
    libswscale      5.  3.100 /  5.  3.100
  
    libswresample   3.  3.100 /  3.  3.100
  
    libpostproc    55.  3.100 / 55.  3.100
  
  [mp3 @ 0x7f98ed005800] Estimating duration from bitrate, this may be inaccurate
  
  Input #0, mp3, from '/.../114006.mp3':
  
    Duration: 00:00:09.53, start: 0.000000, bitrate: 64 kb/s
  
      Stream #0:0: Audio: mp3, 22050 Hz, stereo, fltp, 64 kb/s
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (mp3 (mp3float) -> pcm_s16le (native))
  
  Press [q] to stop, [?] for help
  
  Output #0, wav, to '/.../114-006-a4dec52a.wav':
  
    Metadata:
  
      ISFT            : Lavf58.20.100
  
      Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 16000 Hz, mono, s16, 256 kb/s
  
      Metadata:
  
        encoder         : Lavc58.35.100 pcm_s16le
  
  size=     298kB time=00:00:09.53 bitrate= 256.1kbits/s speed= 469x    
  
  video:0kB audio:298kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.025564%