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• Live streaming : node-media-server + Dash.js configured for real-time low latency

  7 juillet 2021, par Maoration

  We're working on an app that enables live monitoring of your back yard.
Each client has a camera connected to the internet, streaming to our public node.js server.

  



  I'm trying to use node-media-server to publish an MPEG-DASH (or HLS) stream to be available for our app clients, on different networks, bandwidths and resolutions around the world.

  



  Our goal is to get as close as possible to live "real-time" so you can monitor what happens in your backyard instantly.

  



  The technical flow already accomplished is :

  



  


  1. ffmpeg process on our server processes the incoming camera stream (separate child process for each camera) and publishes the stream via RTSP on the local machine for node-media-server to use as an 'input' (we are also saving segmented files, generating thumbnails, etc.). the ffmpeg command responsible for that is :

     



     -c:v libx264 -preset ultrafast -tune zerolatency -b:v 900k -f flv rtmp://127.0.0.1:1935/live/office

  


  2. node-media-server is running with what I found as the default configuration for 'live-streaming'

     



     private NMS_CONFIG = {
server: {
  secret: 'thisisnotmyrealsecret',
},
rtmp_server: {
  rtmp: {
    port: 1935,
    chunk_size: 60000,
    gop_cache: false,
    ping: 60,
    ping_timeout: 30,
  },
  http: {
    port: 8888,
    mediaroot: './server/media',
    allow_origin: '*',
  },
  trans: {
    ffmpeg: '/usr/bin/ffmpeg',
    tasks: [
      {
        app: 'live',
        hls: true,
        hlsFlags: '[hls_time=2:hls_list_size=3:hls_flags=delete_segments]',
        dash: true,
        dashFlags: '[f=dash:window_size=3:extra_window_size=5]',
      },
    ],
  },
},


     



     } ;

  


  3. As I understand it, out of the box NMS (node-media-server) publishes the input stream it gets in multiple output formats : flv, mpeg-dash, hls.
with all sorts of online players for these formats I'm able to access and the stream using the url on localhost. with mpeg-dash and hls I'm getting anything between 10-15 seconds of delay, and more.

  


  



  ---

  



  My goal now is to implement a local client-side mpeg-dash player, using dash.js and configure it to be as close as possible to live.

  



  my code for that is :

  



  


  


  &#xD;&#xA;&#xD;&#xA;    &#xD;&#xA;        &#xD;&#xA;        &#xD;&#xA;    &#xD;&#xA;    &#xD;&#xA;        <div>&#xD;&#xA;            <video autoplay="" controls=""></video>&#xD;&#xA;        </div>&#xD;&#xA;        <code class="echappe-js">&lt;script src=&quot;https://cdnjs.cloudflare.com/ajax/libs/dashjs/3.0.2/dash.all.min.js&quot;&gt;&lt;/script&gt;&#xD;&#xA;&#xD;&#xA;        &lt;script&gt;&amp;#xD;&amp;#xA;            (function(){&amp;#xD;&amp;#xA;                // var url = &quot;https://dash.akamaized.net/envivio/EnvivioDash3/manifest.mpd&quot;;&amp;#xD;&amp;#xA;                var url = &quot;http://localhost:8888/live/office/index.mpd&quot;;&amp;#xD;&amp;#xA;                var player = dashjs.MediaPlayer().create();&amp;#xD;&amp;#xA;                &amp;#xD;&amp;#xA;                &amp;#xD;&amp;#xA;&amp;#xD;&amp;#xA;                // config&amp;#xD;&amp;#xA;                targetLatency = 2.0;        // Lowering this value will lower latency but may decrease the player&amp;#x27;s ability to build a stable buffer.&amp;#xD;&amp;#xA;                minDrift = 0.05;            // Minimum latency deviation allowed before activating catch-up mechanism.&amp;#xD;&amp;#xA;                catchupPlaybackRate = 0.5;  // Maximum catch-up rate, as a percentage, for low latency live streams.&amp;#xD;&amp;#xA;                stableBuffer = 2;           // The time that the internal buffer target will be set to post startup/seeks (NOT top quality).&amp;#xD;&amp;#xA;                bufferAtTopQuality = 2;     // The time that the internal buffer target will be set to once playing the top quality.&amp;#xD;&amp;#xA;&amp;#xD;&amp;#xA;&amp;#xD;&amp;#xA;                player.updateSettings({&amp;#xD;&amp;#xA;                    &amp;#x27;streaming&amp;#x27;: {&amp;#xD;&amp;#xA;                        &amp;#x27;liveDelay&amp;#x27;: 2,&amp;#xD;&amp;#xA;                        &amp;#x27;liveCatchUpMinDrift&amp;#x27;: 0.05,&amp;#xD;&amp;#xA;                        &amp;#x27;liveCatchUpPlaybackRate&amp;#x27;: 0.5,&amp;#xD;&amp;#xA;                        &amp;#x27;stableBufferTime&amp;#x27;: 2,&amp;#xD;&amp;#xA;                        &amp;#x27;bufferTimeAtTopQuality&amp;#x27;: 2,&amp;#xD;&amp;#xA;                        &amp;#x27;bufferTimeAtTopQualityLongForm&amp;#x27;: 2,&amp;#xD;&amp;#xA;                        &amp;#x27;bufferToKeep&amp;#x27;: 2,&amp;#xD;&amp;#xA;                        &amp;#x27;bufferAheadToKeep&amp;#x27;: 2,&amp;#xD;&amp;#xA;                        &amp;#x27;lowLatencyEnabled&amp;#x27;: true,&amp;#xD;&amp;#xA;                        &amp;#x27;fastSwitchEnabled&amp;#x27;: true,&amp;#xD;&amp;#xA;                        &amp;#x27;abr&amp;#x27;: {&amp;#xD;&amp;#xA;                            &amp;#x27;limitBitrateByPortal&amp;#x27;: true&amp;#xD;&amp;#xA;                        },&amp;#xD;&amp;#xA;                    }&amp;#xD;&amp;#xA;                });&amp;#xD;&amp;#xA;&amp;#xD;&amp;#xA;                console.log(player.getSettings());&amp;#xD;&amp;#xA;&amp;#xD;&amp;#xA;                setInterval(() =&gt; {&amp;#xD;&amp;#xA;                  console.log(&amp;#x27;Live latency= &amp;#x27;, player.getCurrentLiveLatency());&amp;#xD;&amp;#xA;                  console.log(&amp;#x27;Buffer length= &amp;#x27;, player.getBufferLength(&amp;#x27;video&amp;#x27;));&amp;#xD;&amp;#xA;                }, 3000);&amp;#xD;&amp;#xA;&amp;#xD;&amp;#xA;                player.initialize(document.querySelector(&quot;#videoPlayer&quot;), url, true);&amp;#xD;&amp;#xA;&amp;#xD;&amp;#xA;            })();&amp;#xD;&amp;#xA;&amp;#xD;&amp;#xA;        &lt;/script&gt;&#xD;&#xA;    &#xD;&#xA;

  


  


  




  with the online test video (https://dash.akamaized.net/envivio/EnvivioDash3/manifest.mpd) I see that the live latency value is close to 2 secs (but I have no way to actually confirm it. it's a video file streamed. in my office I have a camera so I can actually compare latency between real-life and the stream I get).
however when working locally with my NMS, it seems this value does not want to go below 20-25 seconds.

  



  Am I doing something wrong ? any configuration on the player (client-side html) I'm forgetting ?
or is there a missing configuration I should add on the server side (NMS) ?

  


• why cmd just print command and dosen't work ?

  11 octobre 2019, par 杨士弘

  I tried create a website that could upload mp4 then my server would transcode it to ts and create a m3u8 playlist。
  I wanted to use cmd to control ffmpeg to do this，and I use visual basic to do this.

  Here is my code：

    Dim fileName As String = "borderoflife"
  
    Dim file As String = "borderoflife.mp4"
  
    Dim appPath As String = "C:\allen0916\"
  
    Dim saveDir As String = "test2\"
  
  
  
    Dim savePath As String = appPath & saveDir
  
    Dim saveResult As String = savePath & file
  
  
  
    Dim Content_Type_A As String = "video/mp4"
  
  
  
    Dim m3u8Path As String = Path.Combine(savePath, fileName + ".m3u8")
  
    Dim para As String = String.Format("/C ffmpeg -i {0} -profile:v baseline -level 3.0 -s 640x360 -start_number 0 -hls_time 10 -hls_list_size 0 -f hls {1} ", saveResult, m3u8Path)
  
  
  
    Dim output As String = "none" 
  
    Dim p As Process = New Process()
  
  
  
    p.StartInfo.FileName = "cmd.exe"
  
    p.StartInfo.UseShellExecute = False 
  
    p.StartInfo.RedirectStandardInput = True 
  
    p.StartInfo.RedirectStandardOutput = True 
  
    p.StartInfo.RedirectStandardError = True 
  
    p.StartInfo.CreateNoWindow = True 
  
    p.Start()
  
    p.StandardInput.WriteLine(para) 
  
    p.StandardInput.WriteLine("exit")
  
    p.StandardInput.AutoFlush = True
  
    p.StandardInput.Close() 
  
    output = p.StandardOutput.ReadToEnd() 
  
    p.WaitForExit()
  
    p.Close()
  
  
  
   If System.IO.File.Exists(m3u8Path) <> True Then
  
        context.Response.Write(output)
  
    Else
  
        context.Response.Write("Success")
  
    End If  

  and every time output just returns ：

  Microsoft Windows [version 10.0.17763.737]
  
  (c) 2018 Microsoft Corporation. 
  
  
  
  c:\windows\system32\inetsrv>/C ffmpeg -i C:\allen0916\test2\borderoflife.mp4 -profile:v baseline -level 3.0 -s 640x360 -start_number 0 -hls_time 10 -hls_list_size 0 -f hls C:\allen0916\test2\borderoflife.m3u8 
  
  
  
  c:\windows\system32\inetsrv>exit

  it seems cmd.exe just print my command and not working，
  Dose somebody know why？

• images->video->web canvas : RGB/YUV issues

  5 février 2016, par nrob

  We’ve written an web app which :

  1. takes 3D, time dependent weather data
  2. tiles each 3D time point to make a 2D frame (written out as a png image)
  3. stitches these frames together into a video (using ffmpeg/avconv)
  4. streams this video into a web app
  5. polls the canvas for frames
  6. sends the frames to the GPU where they are converted back to 3D and ray traced

  You can see the app here, code here and you can see the data video here

  Currently the pngs are written as RGB images, the video codec is in YUV and getting frames from the canvas returns RGB. As such there is a significant loss of information due to the conversion between image spaces.

  Does anyone have suggestions what is the best way round this ?

  I’ve tried a bunch of RGB video codecs, but I can’t get any to work, and I don’t know if the web browser will support it anyway. Can anyone suggest a good RGB codec (both lossy and lossless would be great)

  Also, is it possible to write to YUV images/read them from a video canvas in HTML5 ?

  Ultimately, I don’t even want anything to do with images/videos, I’m just hacking the codecs to stream/compress large animated 3D data volumes