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• Change bitrate of USB camera

  12 décembre 2018, par Nick Saw

  I use ELP USB camera with h264-codec output.

  Ffmpeg-command to take the video stream :

  ffmpeg -i /dev/video1 -c:v copy output.ts

  As result I have a video with 4Mb bitrate - this value is too high for my task.

  There is the same situation when I use GSTreamer :

  gst-launch-1.0 v4l2src device=/dev/video1 ! video/x-h264,width=1280,height=720,framerate=30/1 ! mpegtsmux ! filesink location=output.ts

  I know that it’s possible to change the bitrate if we decode h264 the stream firstly and then encode it to h264 again. This operation requires too much CPU-power of my NanoPI device.

  The main question is :
  Is it possible to change a USB-camera’s bitrate without decoding ?

  Thanks in advance !

• Android video encoding with fr and resolution manipulation

  24 février 2017, par apSTRK

  I want to be able to take a video recorded with an Android device and encode it to a new Resolution and Frame Rate using my app. The purpose is to upload a much smaller version of the original video (in size), since this will be videos 30 min long or more.

  So far, I’ve read of people saying FFmpeg is they way to go. However, the documentation seems to be lacking.

  I have also considered using http opencv http://opencv.org/platforms/android.html

  Considering I need to manipulate the video resolution and frame rate, which tool do you think can do such things better ? Are there any other technologies to consider ?

  An important question is, since this will be long videos, is it reasonable to do the encoding in an android device (Consider power resources, time, etc.)

  Thanks in advance !

• Is async.js needed to process multiple ffmpeg conversions at the same time ?

  15 février 2019, par jurelik

  I’m trying to convert youtube videos to mp3 via my Node.js server, using ’ytdl-core’ and ’fluent-ffmpeg’. Since the server is intended to process multiple requests at the same time, it got me thinking whether or not async.js is needed to convert videos in a time efficient manner.

  The interesting thing however, is that upon testing the handling of multiple requests with and without using async.js, the result seems to be the same both ways - the time it takes to convert 3 videos is the same.

  Here is the code I’m using without async.js :

  server.get('/download/:id', (req, res) => {
  
  
  
    const id = req.params.id;
  
    let stream = ytdl(`https://www.youtube.com/watch?v=${id}`);
  
  
  
    ffmpeg(stream)
  
      .audioCodec('libmp3lame')
  
      .audioBitrate(128)
  
      .toFormat('mp3')
  
      .save(`public/downloads/${id}.mp3`)
  
      .on('error', err => {
  
        console.log(err);
  
      })
  
      .on('end', () => {
  
        console.log('file downloaded');
  
        send(req, `public/downloads/${id}.mp3`).pipe(res);
  
      });
  
  });

  And this is the code using async.js :

  let queue = async.queue((task, callback) => {
  
    let stream = ytdl(`https://www.youtube.com/watch?v=${task.id}`);
  
  
  
    ffmpeg(stream)
  
    .audioCodec('libmp3lame')
  
    .audioBitrate(128)
  
    .toFormat('mp3')
  
    .save(`public/downloads/${task.id}.mp3`)
  
    .on('error', err => {
  
      console.log(err);
  
      callback(err)
  
    })
  
    .on('end', () => {
  
      send(task.req, `public/downloads/${task.id}.mp3`).pipe(task.res);
  
      callback('file sucessfully downloaded');
  
    });
  
  }, 5);
  
  
  
  queue.drain = function() {
  
    console.log('all items downloaded');
  
  }
  
  
  
  server.get('/download/:id', (req, res) => {
  
    queue.push({req: req, id: req.params.id, res: res}, err => {
  
      console.log(err);
  
    });
  
  });

  Does anyone have any ideas why both methods seem to finish conversion at roughly the same time ? I would imagine using async.js should finish converting the videos faster due to processing in parallel, but that isn’t the case.

  Any thoughts would be much appreciated !