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• Slowing down audio of a video using FFMPEG

  8 mars 2015, par jhodzzz

  Good day. Before anything else, I would like to say that I am a newbie with regards to video filters on FFMPEG. So please bear with me, :) Thanks in advance..

  Anyways, I am trying to slow down a video clip that will be embedded and played within my delphi project. So far, slowing the video works fine by using the setpts filter. here’s my partial code :

  FFPlayer.VideoFilters := Format('setpts=(1/' + FloatToStr(FSpeed) + ')*PTS, nativeeq=%d:%d:%d:%d, nativehue=%d:%d:%d:%d',
  
    [0, 0, 0, 0, 0, 0, 0, 0]);

  where FSpeed is a changing value that ranges 0.5 - 2.5. With this code, the video capture speeds up or slows down, but the audio doesn’t. So as I was searching for the code to slow down the audio, I came across this link that provides the filter codes for speeding up or slowing down the video capture and audio. A line there mentioned that the filter code to slow down the audio and video capture at the same time is :

  ffmpeg -i input.mkv -filter_complex "[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]" -map "[v]" -map "[a]" output.mkv

  I tried adding "atempo=2.0" to my partial code making it :

  FFPlayer.VideoFilters := Format('setpts=(1/' + FloatToStr(FSpeed) + ')*PTS, atempo=2.0, nativeeq=%d:%d:%d:%d, nativehue=%d:%d:%d:%d',
  
    [0, 0, 0, 0, 0, 0, 0, 0]);

  but video didn’t show up at all.

  I am hoping you could enlighten me with this one. Thanks.

• Losing video when splitting mpg from middle [migrated]

  12 avril 2014, par ARip1979

  Very new to ffmpeg so bear with me.

  I'm trying to split an mpg in two pieces. It's a 4m 36s video. I want the first piece to be 170s and the second to be the rest. I have tried a bunch of different methods.

  ffmpeg -i input.mpg -vcodec copy -acodec copy -ss 00:00:00 -t 00:2:50 output1.mpg
  
  ffmpeg -i input.mpg -vcodec copy -acodec copy -ss 00:02:50 output2.mpg
  
  
  
  ffmpeg -i input.mpg -t 170 -c copy output1.mpg -ss 170 -c copy output2.mpg

  And a bunch of others. Every thing I've tried gives me a great first output1.mpg but output2.mpg is always missing the video. The file is saved as .mpg but it is only audio.

  I found one option that said to try this for the 2nd piece.

  ffmpeg -ss 170 -i input.mpg -t 176 -c copy output2.mpg

  and that sometimes there are errors so to try :

  ffmpeg -ss 170 -i input.mpg -t 176 output2.mpg

  With the possibility that omitting '-c copy' might result in a good output.
  So the first one above with '-c copy' gave me the same result, no video. The second option resulted in video and audio but the video was severely degraded in quality.

  Can anyone help me ? Why do I keep losing the video on the 2nd piece. I'm a newb but this seems pretty straight forward.

  Thanks in advance !

• how to resize an image stream from mongo gridfs

  13 septembre 2014, par CurlyFro

  i’m still new to node so bear with me.

  i have images stored in mongo gridfs. how do i resize the image stream ? i’m trying to use ffmpeg. here’s my method :

  exports.read = function (req, res) {
  
  var db = mongoose.connection.db;
  
  var id = new ObjectID(req.params.imageId);
  
  var store = new GridStore(db, id, 'r', {root: 'fs'});
  
  
  
  store.open(function (err, store) {
  
      if (err) return err;
  
  
  
      res.header("Content-Type", store.metadata['Content Type']);
  
      res.header("Content-Disposition", "attachment; filename='" + store.filename + "'");
  
  
  
      new ffmpeg()
  
          .input(store.stream(true))
  
          .size('650x365')
  
          .output('/temp/screenshot.png')
  
          .run();
  
  
  
      store.stream(true).pipe(res)
  
  });
  
  };

  but i’m getting an error :

  Error : ffmpeg exited with code 1 : pipe:0 : Invalid data found when processing input.

  what am i doing wrong ?