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• fluent-ffmpeg sometimes crashes entire amazon ec2 instance

  24 octobre 2020, par Mick Marsden

  I have a nodejs application where I'm using fluent-ffmpeg to convert captured video files via the html <input file="file" /> tag to mp4 format. I'm also using ffmpeg-static to provide static binaries for fluent-ffmpeg's file path. But in order for the conversion to happen, I upload the captured video file via multer, and when that completes, multer passes the video url to fluent-ffmpeg. The code looks like this :

  


  app.post("/upload-and-convert", async function(req, res) {

   var filepath;
   var path;

    try {

        const upload = util.promisify(uploadVideo());

        await upload(req, res);

        console.log(req.file);
        console.log("Success");
        filepath = req.file.filename;
        console.log(filepath);
        path = './public/uploads/' + filepath;
        console.log(path);

    } catch (e) {
       let response_json = {
                success: false,
        };
        res.setHeader("content-type", "application/json");
        res.send(response_json);
    }

    if(path != undefined)
    {

        console.log("Path not undefined, going to start FFMPEG");
        ffmpeg(path)
        .format('mp4')
        .size('720x720').autopad()
        .on('end', function() {
            console.log('file has been converted successfully');
        })
        .on('error', function(err) {
            console.log('an error happened: ' + err.message);
            let response_json = {
                success: false,
            };
            res.setHeader("content-type", "application/json");
            res.send(response_json);
        })
        .save('./public/uploads/video.mp4')
        .on('end', function() {
            console.log('file has been saved successfully');
            let response_json = {
                success: true,
                fileURL: 'https://websiteurl/uploads/video.mp4'
            };
            res.setHeader("content-type", "application/json");
            res.send(response_json);
        })

    } else
    {
        let response_json = {
            success: false,
        };
        res.setHeader("content-type", "application/json");
        res.send(response_json);
    }
});


  


  Most times, the code runs fine and returns the fileURL as intended. Sometimes however, it completely crashes the amazon ec2 instance, and requires the instance be rebooted before it works again. I've checked the logs, and the server-error logs output no issues. The server-out logs when it crashes outputs the final console log before ffmpeg starts :

  


          console.log("Path not undefined, going to start FFMPEG");


  


  The moment it reaches the ffmpeg(path), it goes down. It doesn't log any error, even though I have included error handling on the operation.

  


  This has stumped me for days. I cannot figure out the commonality to explain why sometimes it crashes, and sometimes it does not. Note that this even happened before I started using the ffmpeg-static package. My node version is 12.19.0, and ffmpeg-static currently installs ffmpeg at version 4.3.1 if I recall correctly.

  


  If anyone could help that would be great.

  


• how can i insert an empty subtitle

  22 avril 2020, par Ginso

  i have a bunch of mp4 files and i would like to convert them to mkv, so that the automatic selection auf audio and subtitle track of vlc works.
the thing is some of them have 4 subtitles (first german and english only for foreign languages and then german and english for all) and some of them only 2 (because in those episodes there are no foreign languages). Can i insert 2 empty subtitle tracks before them so that i can set my vlc to select the first or second subtitle when i watch them ?

  



  i convert the episodes with 4 subtitles like this :

  



  ffmpeg -i in.mp4 -map 0:0 -map 0:1 -map 0:2 -map 0:3 -map 0:4 -map 0:5 -map 0:6 out.mkv

  



  0:0 is of course the video

  



  0:1 and 0:2 are audio tracks

  



  the rest are the subtitles

  



  BTW : is there a language code for forced subtitles ? -metadata:s:s:1 language=?

  


• use of ffmpeg select filter

  3 avril 2019, par user651177

  I am stuck with the use of ffmpeg select filter as I want to pick up only the ending frame of a input video but I cannot figure out the selection expression for the filter to get the work done,
  my code looks like this :

  ffmpeg -i in.mp4  -filter_complex  "select=expr_selecting_lastest_frame, overlay=overlay_expr"  out.jpg

  now how do I coding the expr_selecting_lastest_frame ?
  do you guys have ideas ?
  is there any other way to get the work done ? please help, thank you !