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• FFMPEG concat leaves audio gapes between clips

  14 novembre 2022, par GotCubes

  I'm writing a python script that uses subprocess to invoke FFMPEG, not using pyffmpeg.

  



  My script generates a variable number of MP4 files using the AAC audio codec, and concatenates them together using FFMPEG. Here is how I'm constructing each clip :

  



  ffmpeg -loop 1 -i image.jpg -i recording.mp3 -tune stillimage -c:a aac -b:a 256k -shortest clip.mp4


  



  The command I'm using to concatenate them is :

  



  ffmpeg -f concat -i clip_names.txt -c copy video_raw.mp4


  



  I then take that resulting video, and mix a looping audio track over it, and adjust the volume. (Sorry for the awful formatting)

  



  ffmpeg -i video_raw -filter_complex
                 "amovie=Tracks/Breaktime.mp3:loop=0,
                  volume=0.1,
                  asetpts=N/SR/TB[aud];
                  [0:a][aud]amix[a]"
-map 0:v -map [a] -b:a 256k -shortest final_video.mp4


  



  These commands seem to work as I intend them to. When I play the resulting MP4 from my local machine, everything plays without issue.

  



  However, I uploaded the video to YouTube, and ran into issues. When the video is played from YouTube, there is about a second of silence at every timestamp where two clips were concatenated, before the next clip begins. I've tried this from Chrome, IE, and Firefox, all with the same issues.

  



  Based on what I've looked into so far, I think it could be an issue with how the priming samples of each individual clip are handled. I'm not obligated to keep using MP4 or AAC, so if using a different audio/video codec would work better, feel free to suggest !

  



  Is there some type of manipulation I can do in FFMPEG to get rid of the priming samples, or somehow process them differently ? In the end, I'm looking for each clip to play back to back without the delay that the concat operation seems to insert. Thank you !

  


• Want to convert WebM files to Mp4, AVI, MOV etc

  17 janvier 2015, par shilpi_agrawal

  I converted Mp4, AVI, MOV files to WebM using ffmpeg with good quality. Now I need my original files with same size and quality. Will it be possible to get it back ?

• How to have multiple websocket RTSP streams ?

  6 octobre 2020, par kinx

  After spending some time reading various open-source projects on how to develop RTSP and WebSocket streams, I've almost built a simple project that allows me to display multiple streams on the page.

  


  I have a working example of just one stream working with the code below. A single URL in an array is sent to the client via WebSocket and with JSMPeg, it displays it with some success.

  


  However, I'm not sure how to build this where I have multiple sockets with an RTSP stream in each one and how to give each socket url it's own id. The idea is to encrypt the URL and when the client requests the list of streams, send back that as a socket id, and with JSMPeg, request that data.

  


  Server :

  


  class Stream extends EventEmitter {
  constructor() {
    super();
    this.urls = ["rtsp://someIPAddress:554/1"];
    this.urls.map((url) => {
      this.start(url);
    });
  }
  start(url) {
    this.startStream(url);
  }
  setOptions(url) {
    const options = {
      "-rtsp_transport": "tcp",
      "-i": url,
      "-f": "mpegts",
      "-codec:v": "mpeg1video",
      "-codec:a": "mp2",
      "-stats": "",
      "-b:v": "1500k",
      "-ar": "44100",
      "-r": 30,
    };
    let params = [];
    for (let key in options) {
      params.push(key);
      if (String(options[key]) !== "") {
        params.push(String(options[key]));
      }
    }
    params.push("-");
    return params;
  }
  startStream(url) {
    const wss = new WebSocket.Server({ port: 8080 });
    this.child = child_process.spawn("ffmpeg", this.setOptions(url));
    this.child.stdout.on("data", (data) => {
      wss.clients.forEach((client) => {
        client.send(data);
      });
      return this.emit("data", data);
    });
  }
}

const s = new Stream();
s.on("data", (data) => {
  console.log(data);
});


  


  In the constructor, there's an array of URLs, while I only have one here, i'd like to add multiple. I create a websocket and send that back. What I'd like to do is encrypt that URL with Crypto.createHash('md5').update(url).digest('hex') to give it it's own ID and create a websocket based on that id, send the data to that websocket and send that with a list of other id's to the client.

  


  client :

  


    <canvas style="width: 100%"></canvas>&#xA;  <code class="echappe-js">&lt;script type=&quot;text/javascript&quot;&gt;&amp;#xA;    var player = new JSMpeg.Player(&quot;ws://localhost:8080&quot;, {&amp;#xA;      loop: true,&amp;#xA;      autoplay: true,&amp;#xA;      canvas: document.getElementById(&quot;video&quot;),&amp;#xA;    });&amp;#xA;  &lt;/script&gt;&#xA;

  


  What I'd like to do here is request from /api/streams and get back an array of streams/socket id's and request them from the array.

  


  But how do I open up multiple sockets with multiple URLs ?