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• Reduce RTMP buffer while decoding using ffmpeg

  15 janvier 2019, par Alberto Padilla

  I’m setting up a new server using nginx and nginx-rtmp-module. I installed a DeckLink Duo2 card to output SDI signals comming from the RTMP stream.

  Everything works really great using this simple nginx.conf configuration :

  rtmp {
  
      server {
  
              listen 1935;
  
              chunk_size 4096;
  
  
  
              wait_video on;
  
              wait_key on;
  
  
  
              sync 10ms;
  
  
  
              application live {
  
                  live on;
  
                  record off;
  
  
  
                  exec_push /home/myuser/bin/ffmpeg -i rtmp://127.0.0.1/live/mystreamname -f decklink -format_code pal -pix_fmt uyvy422 'DeckLink Duo (1)';
  
              }  
  
     }
  
  }

  My goal is to achieve the absolute minimum delay between the received stream and the SDI output.

  I can achieve 3 seconds "waving hand" delay using the configuration that I mentioned. However, using ffplay I observe 1.5s delay using the -fflags nobuffer option.

  As ffplay cannot output to a decklink device, I want ffmpeg to reduce the buffer to the minimum, but I can’t find the way to do it. All the -rtmp_buffer or -fflag nobuffer or any other options have no impact on the delay.

  The stream is being received in the same machine ffmpeg is running, that is why it makes sense to reduce the ffmpeg buffering to the minimum if I want to achieve low delay.

  Any tips ?

• How to chose a stream from all stream in ffmpeg

  27 février 2016, par combo_ci

  I try to convert a UDP stream (that genrated from DVB signal) to HLS m3u8 file with this code :

  ffmpeg -i udp://239.1.2.1:60001 -acodec aac -strict -2 -vcodec libx264 -hls_wrap 100 -f hls /var/www/html/ts/1.m3u8 

  UDP stream contain 1 channel (in this case IRIB-TV1).

  When i run this code ffmpeg detect all of service and channel that streamed from DVB card with this message :

  Input #0, mpegts, from 'udp://239.1.2.1:60001':
  
  Duration: N/A, start: 77906.812644, bitrate: N/A
  
  Program 101 
  
  Metadata:
  
    service_name    : IRIB-TV1
  
    service_provider: IRIB
  
  Stream #0:0[0x3f2]: Video: h264 (Main) ([27][0][0][0] / 0x001B), yuv420p(tv, bt470bg), 720x576 [SAR 12:11 DAR 15:11], 25 fps, 50 tbr, 90k tbn, 50 tbc
  
  Stream #0:1[0x3f3](per): Audio: aac_latm ([17][0][0][0] / 0x0011), 48000 Hz, stereo, fltp
  
  Program 102 
  
  Metadata:
  
    service_name    : IRIB-TV2
  
    service_provider: IRIB
  
  Program 103 
  
  Metadata:
  
    service_name    : IRIB-TV3
  
    service_provider: IRIB
  
  Program 104 
  
  Metadata:
  
    service_name    : IRIB-TV4
  
    service_provider: IRIB

  As you see ffmpeg finf 4 channel in UDP stream, But VLC play only channel 1(IRIB-TV1).

  Now i have have 2 question :

  1-Can I get all channel and service via this ffmpeg code ?

  2-Can i choose a spesial stream from this ffmpeg code ?(i know that ffmpeg can choose a stream with -map otion but i want to choose other service_name that in output log)

• After compressing the video, it's quality getting dull in Android

  9 septembre 2015, par Parth Bhayani

  I have done with the video compressing using ffmpeg in Android and I am having some problem in it.

  I have captured one video of exactly one minute and it has 123 MB of size on my nexus 5. I did video compressing of the same video from 123 MB to 1.30 MB approx and it will take 2 minutes near about and that was successfully done.

  But the question is that I have the compressed video in my SD Card and when I’ll play it, the quality of the video is totally dull, below is my code using ffmpeg.

  String[] complexCommand = {"ffmpeg", "-i", videoPath, "-strict","experimental","-s", "160x120","-r","25", "-vcodec", "mpeg4", "-b", "150k", "-ab","48000", "-ac", "2", "-ar", "22050", demoVideoFolder + "Compressed_Video.mp4"};
  
  
  
  LoadJNI vk = new LoadJNI();
  
              try {
  
                   vk.run(complexCommand, workFolder, getApplicationContext(),
  
                   false);
  
                  GeneralUtils.copyFileToFolder(vkLogPath, demoVideoFolder);
  
              } catch (Throwable e) {
  
                  Log.e(Prefs.TAG, "vk run exeption.", e);
  
              } finally {
  
                  if (wakeLock.isHeld())
  
                      wakeLock.release();
  
                  else {
  
                      Log.i(Prefs.TAG,
  
                              "Wake lock is already released, doing nothing");
  
                  }
  
              }
  
              Log.i(Prefs.TAG, "doInBackground finished");

  Here videopath is my filepath and demofolder is my output folder. I have attached the snapshot, just have a look into it.

  

  Please, tell me what I should do, so just in advance your efforts will be highly appreciated and thanks for that.