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• Chrome "stalling" when streaming mp3 file from nodejs windows only

  8 octobre 2015, par Alan Hollis

  We’ve got a really annoying bug when trying to send mp3 data. We’ve got the following set up.

  Web cam producing aac -> ffmpeg convert to adts -> send to nodejs server -> ffmpeg on server converts adts to mp3 -> mp3 then streamed to browser.

  This works *perfectly" on Linux ( chrome with HTML5 and flash, firefox flash only )

  However on windows the sound just "stalls", no matter what combination we use ( browser/html5/flash ). If however we shutdown the server the sound then immediately starts to play as we expect.

  For some reason on windows based machines it’s as if the sound is being buffered "waiting" for something but we don’t know what that is.

  Any help would be greatly appreciated.

  Relevant code in node

      res.setHeader('Connection', 'Transfer-Encoding');
  
      res.setHeader('Content-Type', 'audio/mpeg');
  
      res.setHeader('Transfer-Encoding', 'chunked');
  
      res.writeHeader('206');
  
  
  
      that.eventEmitter.on('soundData', function (data) {
  
          debug("Got sound data" + data.cameraId + " " + req.params.camera_id);
  
          if (req.params.camera_id == data.cameraId) {
  
              debug("Sending data direct to browser");
  
              res.write(data.sound);
  
          }
  
      });

  Code on browser

         soundManager.setup({
  
                              url: 'http://dashboard.agricamera.co.uk/themes/agricamv2/swf/soundmanager2.swf',
  
                              useHTML5Audio: false,
  
                              onready: function () {
  
                                  that.log("Sound manager is now ready")
  
                                  var mySound = soundManager.createSound({
  
                                      url: src,
  
                                      autoLoad: true,
  
                                      autoPlay: true,
  
                                      stream: true,
  
                                  });
  
                              }
  
                          });

• Strange "pause" in video after concatenation of two mp4 videos

  3 octobre 2016, par user606521

  I am concatenating two mp4 videos. The problem is that first video (intro.mp4) lasts 5 seconds, second video (output.mp4) lasts 2 seconds and video created by concatenating them lasts 9 seconds (and should last 5+2 = 7 seconds). In final.mp4 video the last frame from first video (intro.mp4) i shown for additional 2 seconds before second video (output.mp4) is played. It looks like a lag when watching video. What I am doing wrong ?

  list.txt :

  file 'data/intro.mp4'
  
  file 'output.mp4'

  command :

  ./bin/ffmpeg -f concat -i list.txt -c copy final.mp4

  output :

  ffmpeg version 2.7.2 Copyright (c) 2000-2015 the FFmpeg developers
  
    built with llvm-gcc 4.2.1 (LLVM build 2336.11.00)
  
    configuration: --prefix=/Volumes/Ramdisk/sw --enable-gpl --enable-pthreads --enable-version3 --enable-libspeex --enable-libvpx --disable-decoder=libvpx --enable-libmp3lame --enable-libtheora --enable-libvorbis --enable-libx264 --enable-avfilter --enable-libopencore_amrwb --enable-libopencore_amrnb --enable-filters --enable-libgsm --enable-libvidstab --enable-libx265 --disable-doc --arch=x86_64 --enable-runtime-cpudetect
  
    libavutil      54. 27.100 / 54. 27.100
  
    libavcodec     56. 41.100 / 56. 41.100
  
    libavformat    56. 36.100 / 56. 36.100
  
    libavdevice    56.  4.100 / 56.  4.100
  
    libavfilter     5. 16.101 /  5. 16.101
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  2.100 /  1.  2.100
  
    libpostproc    53.  3.100 / 53.  3.100
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7f8a6a80e600] Auto-inserting h264_mp4toannexb bitstream filter
  
  Input #0, concat, from 'list.txt':
  
    Duration: N/A, start: 0.000000, bitrate: 1296 kb/s
  
      Stream #0:0: Video: h264 (High) (avc1 / 0x31637661), yuv420p, 960x540, 1163 kb/s, 23.98 fps, 23.98 tbr, 11988 tbn, 47.95 tbc
  
      Stream #0:1: Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 133 kb/s
  
  [mp4 @ 0x7f8a6c006a00] Codec for stream 0 does not use global headers but container format requires global headers
  
  [mp4 @ 0x7f8a6c006a00] Codec for stream 1 does not use global headers but container format requires global headers
  
  Output #0, mp4, to 'final.mp4':
  
    Metadata:
  
      encoder         : Lavf56.36.100
  
      Stream #0:0: Video: h264 ([33][0][0][0] / 0x0021), yuv420p, 960x540, q=2-31, 1163 kb/s, 23.98 fps, 23.98 tbr, 11988 tbn, 11988 tbc
  
      Stream #0:1: Audio: aac ([64][0][0][0] / 0x0040), 48000 Hz, stereo, 133 kb/s
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (copy)
  
    Stream #0:1 -> #0:1 (copy)
  
  Press [q] to stop, [?] for help
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7f8a6a80e600] Auto-inserting h264_mp4toannexb bitstream filter
  
  frame=  258 fps=0.0 q=-1.0 Lsize=     997kB time=00:00:09.84 bitrate= 829.5kbits/s    
  
  video:897kB audio:93kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.634306%

• Faster way of getting number of key frames than "show_frames" in ffprobe ?

  19 novembre 2016, par Will Tower

  I’m making a little in-house utility using ffmpg and ffprobe. Works fine and does what is needed : give a count of the number of key frames in a video file plus some other details.

  Alas, with the large video files this will be used on it can take many seconds for show_frames to return – and I then have to parse the JSON dump of frame data and keep a running count of the total key frames.

  Is there a faster way ? Perhaps it is listed in the "stream" or "format" data dumps and I am not recognizing what it is being called ? I’ve been through the ffmpg and ffprobe docs and didn’t find anything else.