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• Converting AAC stream to DASH MP4 with high fragment length precision

  5 mars 2017, par vdudouyt

  For my HTML5 project I need to create a fragmented MP4 file with a single audio stream (no video), each fragment of which has a duration of exactly 0.1 second.

  Accordingly to ffmpeg docs, you can accomplish that by passing a value in microseconds with ’-frag_duration’ - which I found to be working and playable with HTML5 MediaSource API :

  $ ffmpeg -y -i input.aac -c:a libfdk_aac -b:a 64k -level:v 13 -r 25 -strict experimental -movflags empty_moov+default_base_moof -frag_duration 100000 output.mp4

  As we have a 210 second audio split up by 0.1s fragments, I expect that in output.mp4 we’d have 2100 fragments, hence 2100 moof atoms. But, upon inspecting it I’ve figured out that we only have 1811 moof atoms - which means that some (or maybe even all) fragments are bigger than expected :

  $ python ~/git/mp4viewer/src/showboxes.py output.mp4 |grep moof|wc -l
  
  1811

  Could anybody tell me what’s wrong, and how could I accomplish what I want ?

  Right now my assumption is that during an encoding I have AAC frame length which is not a multiple of 0.1s, hence ffmpeg has no chance to produce the fragments that are strictly equal to 0.1s but I’m not sure. If somebody can confirm that - and let me know a way to explicitly set AAC frame_size in FFMPEG (I couldn’t find anything like that in the docs), or completely disprove this - it would be also highly appreciated.

• ffmpeg processing the live screen streaming has high latency

  27 février 2020, par Ant's

  I’m trying to do live screen sharing using ffmpeg using the following command :

  ffmpeg -f avfoundation -i "1:1" -c:v libx264 -threads 4 -preset ultrafast -c:a aac -ar 44100 -f flv rtmp://localhost/live/test

  Now I have a rtmp server, which receives the data and using flv.js, I’m showing the live stream video on the browser. The integration works perfectly fine, but the problem was the stream is getting delayed very much. There is a delay for say atleast 10s ; I’m not sure, whether we can make it less delay (more like instant screen share).

  Note : I’m using the Node RTMP server using https://github.com/illuspas/Node-Media-Server. The code for that is over here :

  const NodeMediaServer = require('node-media-server');
  
  
  
  const config = {
  
    rtmp: {
  
      port: 1935,
  
      chunk_size: 6000,
  
      gop_cache: true,
  
      ping: 30,
  
      ping_timeout: 60
  
    },
  
    http: {
  
      port: 8000,
  
      allow_origin: '*'
  
    }
  
  };
  
  
  
  var nms = new NodeMediaServer(config)
  
  nms.run();

  Any suggestions ? I’m on MacOS

• ffmpeg processing a live screen streaming has high latency

  27 février 2020, par Ant's

  I’m trying to do live screen sharing using ffmpeg using the following command :

  ffmpeg -f avfoundation -i "1:1" -c:v libx264 -threads 4 -preset ultrafast -c:a aac -ar 44100 -f flv rtmp://localhost/live/test

  Now I have a rtmp server, which receives the data and using flv.js, I’m showing the live stream video on the browser. The integration works perfectly fine, but the problem was the stream is getting delayed very much. There is a delay for say atleast 10s ; I’m not sure, whether we can make it less delay (more like instant screen share).

  Note : I’m using the Node RTMP server using https://github.com/illuspas/Node-Media-Server. The code for that is over here :

  const NodeMediaServer = require('node-media-server');
  
  
  
  const config = {
  
    rtmp: {
  
      port: 1935,
  
      chunk_size: 6000,
  
      gop_cache: true,
  
      ping: 30,
  
      ping_timeout: 60
  
    },
  
    http: {
  
      port: 8000,
  
      allow_origin: '*'
  
    }
  
  };
  
  
  
  var nms = new NodeMediaServer(config)
  
  nms.run();

  Any suggestions ? I’m on MacOS