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• Convert audio blob to mp3 on expressjs server

  27 septembre 2020, par islalobo

  I have a little app that captures sound and stores the audio as an audio blob encoded as base64 on an expressjs server. I would like to convert these audio files into .mp3 or .wav - any binary usable format. My understanding of audio files is very basic and I'm looking to gain a better understanding. Any guidance is appreciated. I've read through several posts and issues, but I'm just a bit lost right now.

  


  Here is my client-side capture of the audio, encoding and then posting to expressjs server.

  


  const saveMessage = async function(base64AudioMessage) {
    await fetch('/messages', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ message: base64AudioMessage })
      }).then(res => {
        if (res.status === 201) {
          const response = res.json()
          .then(response => {
            console.log(response);
            populateAudioMessages(response.id); // shows the recording that was just saved
          });
        }
        console.log('Invalid status saving audio message: ' + res.status);
      });
      return true;
  }

  sendButton.addEventListener('click', () => {
    const reader = new FileReader();
    reader.readAsDataURL(audio.audioBlob);
    reader.onload = async () => {
      const base64AudioMessage = reader.result.split(',')[1];
      
      await saveMessage(base64AudioMessage);
    };
  });


  


  Here is the post method on my expressjs server. It's very messy as I have been trying to use ffmpeg to convert the posted files to .mp3 format.

  


  app.post('/messages', (req, res) => {
  if (!req.body.message) {
    return res.status(400).json({ error: 'No req.body.message' });
  }
  const messageId = v4();
  writeFile(messageFolder + messageId, req.body.message, 'base64')
  .then(() => {
      console.log('messages was saved!');
      try {
        console.log('attempting to make an mp3 ', audioFolder + messageId);
        const process = new ffmpeg(`${messageFolder}${messageId}`);
        process.then((audio) => {
          console.log('audio is ready to be processed ', audio);
          audio.fnExtractSoundToMP3(`${audioFolder}${messageId}.mp3`, (error, file) => {
            console.log('There is an error ', error);
            console.log('There is a file ', file);
            if (!error) {
              console.log('Audio File ', file);
              const file = file;
              console.log('what a success! ', messageId && messageId, file && file);
              res.status(201).json({
                message: 'Saved message',
              });
            }
          })
        }, (err) => {
          console.log('An error occurred, ', err);
        });
      } catch(e) {
        console.log('error code ', e.code);
        console.log('error message ', e.msg);
      }
  })
  .catch(err => {
    console.log('Error writing message to file', err);
    res.sendStatus(500);
  });
});


  


• ffmpeg error : "at least one output file must be specified" only live server

  3 avril 2017, par Tarun Bhardwaj

  ffmpeg -i background.jpg -i with-logo.mp4 -filter_complex [1:v]colorkey=0x3BBD1E:0.3:0.2[ckout];[0:v][ckout]overlay[out] -map [out] with-bg1.mp4

  I am using ffmpeg command for create video, when i am using it on my local sever its working fine, but when goes live server it shows error

  At least one output file must be specified

  sh : [0:v][ckout]overlay[out] : command not found

  Please help me whats problem with this code.

• Is there any way in ffmpeg to cut a video with embedded subtitles and multiple audio tracks accordingly ? [closed]

  21 février 2024, par Harsh

  I have a video which had multiple audio tracks and embedded subtitles. I tried using ffmpeg to cut it, but I could not get the subtitles with it, nor the audio tracks. Here's the command I tried :

  


  ffmpeg -i input.mkv -ss 00:01:16 -to 00:02:46 -map "[0:0]:v" -map "[0:3]:a" -map "[0:4]:s" -c copy output.mkv 


  


  I tried using this command -

  


  ffprobe -v info input.mkv


  


  to collect information about the streams and substituted the streams, but for some reason it gave an error which read something along the lines of - Output with label 0:0 does not exist. Is there an alternative to achieve the result I wish ?

  


  Edit - I tried this command :

  


  ffmpeg -i input.mkv -ss 00:01:16 -to 00:02:46 -map 0 -c:a copy -c:s copy output.mkv


  


  It does the task BUT I have trouble seeing the video on my pc, it just shows a black screen (VLC) but on my mobile when I watch it using PLAYit, it works fine but I can't see the first 8 seconds for some reason. Anyways fix for this ?