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• Merge mp3 files at specific duration in Android

  18 mai 2017, par Gio Vanno

  First I’m new in Android.

  I’m trying to make an app that can combine a lot of music(mp3 files im using) at specific duration with the selected music via seekbar.

  My main plan is to merge multiple audio files at specific time.

  example :
  when i pressed the drum button at 5 sec(via seekbar), and then guitar button at 6 sec.

  when i clicked the merge button, it will merged the selected mp3 file with those 2 mp3 files at their respective time.

  from what i’m searching so far, the possible way is by using ffmpeg from this :

  -How to overlay two audio files using ffmpeg

  -Merge mp3 files using FFmpeg on Android

  but i don’t see them merged at specified time.

  maybe there’s another way besides ffmpeg,or i’ve missed something ?

  thank you

• Firebase Functions : completing long processes without touching maximum timeout

  10 juin 2017, par Scott Ewing

  I have to transcode videos from webm to mp4 when they’re uploaded to firebase storage. I have a code demo here that works, but if the uploaded video is too large, firebase functions will time out on me before the conversion is finished. I know it’s possible to increase the timeout limit for the function, but that seems messy, since I can’t ever confirm the process will take less time than the timeout limit.

  Is there some way to stop firebase from timing out without just increasing the maximum timeout limit ?

  If not, is there a way to complete time consuming processes (like video conversion) while still having each process start using firebase function triggers ?

  If even completing time consuming processes using firebase functions isn’t something that really exists, is there some way to speed up the conversion of fluent-ffmpeg without touching the quality that much ? (I realize this part is a lot to ask. I plan on lowering the quality if I absolutely have to, as the reason webms are being converted to mp4 is for IOS devices)

  For reference, here’s the main portion of the demo I mentioned. As I said before, the full code can be seen here, but this section of the code copied over is the part that creates the Promise that makes sure the transcoding finishes. The full code is only 70 something lines, so it should be relatively easy to go through if needed.

  const functions = require('firebase-functions');
  
  const mkdirp = require('mkdirp-promise');
  
  const gcs = require('@google-cloud/storage')();
  
  const Promise = require('bluebird');
  
  const ffmpeg = require('fluent-ffmpeg');
  
  const ffmpeg_static = require('ffmpeg-static');

  (There’s a bunch of text parsing code here, followed by this next chunk of code inside an onChange event)

  function promisifyCommand (command) {
  
      return new Promise( (cb) => {
  
          command
  
          .on( 'end',   ()      => { cb(null)  } )
  
          .on( 'error', (error) => { cb(error) } )
  
          .run();
  
      })
  
  }
  
  return mkdirp(tempLocalDir).then(() => {
  
      console.log('Directory Created')
  
      //Download item from bucket
  
      const bucket = gcs.bucket(object.bucket);
  
      return bucket.file(filePath).download({destination: tempLocalFile}).then(() => {
  
        console.log('file downloaded to convert. Location:', tempLocalFile)
  
        cmd = ffmpeg({source:tempLocalFile})
  
                 .setFfmpegPath(ffmpeg_static.path)
  
                 .inputFormat(fileExtension)
  
                 .output(tempLocalMP4File)
  
        cmd = promisifyCommand(cmd)
  
        return cmd.then(() => {
  
          //Getting here takes forever, because video transcoding takes forever!
  
          console.log('mp4 created at ', tempLocalMP4File)
  
          return bucket.upload(tempLocalMP4File, {
  
              destination: MP4FilePath
  
          }).then(() => {
  
            console.log('mp4 uploaded at', filePath);
  
          });
  
        })
  
      });
  
    });

• Bash - Not able to replace the variable in ffmpeg subtitle

  20 juin 2017, par Steven Foong

  I have 175 mp4 video files and subtitle file with extension ass. Unfortunately my smart TV not able to read the subtitle title. I plan to burn (hardcode) the subtitle into the video.

  I use this command

  ffmpeg -i orgvideo.mp4 -vf subtitles="subtitle.ass" newvideo.mp4

  it work. So I plan to use bash shell script to automate the process.

  Everything is the script is working , but the ffmpeg command line wouldn’t able to retrieve the subtitle variable.

  After google around, I found that my file name has special character and space, that cause my script not working. If the video file name and the subtitle file is simple, then the script should be no problem.

  This is my script.

  for f in *.mp4
  
  do
  
  new="${f%%.mp4} (CHT).mp4"
  
  subtitle="${f%%.mp4}.chi.ass"
  
  < /dev/null ffmpeg -i "$f" -vf subtitles="$subtitle" "$new"
  
  done

  The ffmpeg having problem reading the subtitle file variable. Anyone can help ?