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• Moving .wav files from S3 to /tmp folder in AWS Lambda

  1er août 2019, par sleepyrobot

  I am currently trying to overlay two .wav files from S3 in AWS Lambda using FFMPEG. I am using node.js to do this. Here’s my process :

  1. Retrieve the files from S3, and save it to the Lambda /tmp folder
  2. Merge the two audio files, and save the output to the /tmp folder
  3. Upload the output from /tmp folder to S3.

  However, I am encountering errors on the first part, since the .wav files being downloaded are corrupted and distorted.

  I have tried using streams for this. However, I am still grasping its concept. I would appreciate any help. For my first try, I tried to retrieve an object from S3 and reupload the same

  I have tried using function for getting the audio file from S3 :

  async function readIn(bucketName, inputFilename, transfer, local) {
  
      console.log('reading in locally?', local);
  
      console.log(`reading from ${inputFilename} to ${transfer}`);
  
  
  
  // inputFilename is the key name (object name)
  
  // transfer is the filepath to where the obj will be transferred to (example: /tmp/audio1.wav)
  
  
  
      const writeStream = fs.createWriteStream(transfer);
  
      var file;
  
  
  
      local? await new Promise((resolve, revoke) => {
  
          file = fs.createReadStream(inputFilename);
  
          writeStream.on('finish', () => {
  
              console.log('file finished reading');
  
              resolve();
  
          });
  
          writeStream.on('error', (err) => {
  
              console.log('things messed up');
  
              revoke();
  
          });
  
          file.pipe(writeStream);
  
      }) : await new Promise((resolve, revoke) => {
  
          writeStream.on('finish', () => {
  
              console.log('file finished reading');
  
              resolve();
  
          });
  
          writeStream.on('error', (err) => {
  
              console.log('things messed up');
  
              revoke();
  
          });
  
          s3.getObject({
  
              Bucket : bucketName,
  
              Key    : inputFilename
  
          }, function(err, data) {
  
              if (err) {
  
                  console.log(err, err.stack);
  
              } else {
  
                  console.log('data got!');
  
              }
  
          }).createReadStream().pipe(writeStream);
  
      });
  
      console.log('returning to main from reading');
  
      return;
  
  }

  For uploading the file to S3 :

  async function writeOut(bucketName, outFile, transfer, contentType) {
  
  
  
          console.log('uploading', bucketName, outFile, transfer);
  
          return s3.upload({
  
              Bucket: bucketName,
  
              Key: outFile,
  
              Body: fs.createReadStream(transfer),
  
              //ACL: 'private',
  
              ContentType: contentType
  
          }).promise();
  
  }

  For merging the files (I haven’t tried this yet) :

  async function mergeFile(transfer1, transfer2, output) {
  
      await new Promise((resolve, revoke) => {
  
          console.log('beginning merge');
  
          var outStream = fs.createWriteStream('/tmp/output.wav');
  
  
  
          childProcess.exec('cp /var/task/ffmpeg /tmp/.; chmod 755 /tmp/ffmpeg;',
  
          function (error, stdout, stderr) {
  
              if (error) {
  
                  console.log('[ERROR]: An error occured in altering FFMPEG permission: ', error);
  
              } else {
  
                 console.log("[SUCCESS]: Successfully altered FFMPEG permission!");
  
                 // merge audio files
  
                  ffmpeg('/tmp/audio1.wav')
  
                  .input('/tmp/audio2.wav')
  
                  .on('error', function(err) {
  
                  console.log('An error occurred with merging: ' + err.message);
  
                  })
  
                  .complexFilter(
  
                  {
  
                  filter: 'amix',
  
                  inputs: ['0:a','1:a']
  
                  })
  
                  .on('end', function() {
  
                  console.log('Merging finished!');
  
                  })
  
                  .pipe(outStream, { end: true });
  
                  //.save('/tmp/output.wav');
  
                  //////  
  
              }
  
          })
  
      });}

  However, the resulting file is corrupted. Is there any error in the functions ? Please help. Thanks !

• Multiframe Dicom file not readable by some viewers

  12 mai 2023, par PizzaPasNette

  I have developed a program in C++ that works in 2 major steps :

  


  


  • extract frames from a video with ffmpeg and convert them to jpeg
ffmpeg -i videofile.mp4 -q:v 1 -r desired_framerate tmp_04%d.jpeg

    


  


  • create a multiframe Dicom file from those jpeg images via DCMTK

    


    //Example for one image&#xA;&#xA;// Get the n-th image&#xA;QFile* imageFile = new QFile("Path/To/Image");&#xA;&#xA;// Read the image inside a byte array&#xA;QByteArray * ba = new QByteArray();&#xA;imageFile->open(QIODevice::ReadOnly);&#xA;*ba = imageFile->readAll();&#xA;&#xA;// Insert the byte array in the Dicom file&#xA;cond = jpegPixelItem->putUint8Array(reinterpret_cast<uint8>(ba->data()), ba->size());&#xA;&#xA;// Rinse and repeat&#xA;</uint8>

    


  


  


  It works well and can be displayed on most viewers but some complain about the Transfer Syntax being wrong.
As of now, I'm using the "JPEGLossless:Non-hierarchical-1stOrderPrediction" but It seems some viewers can't read my Dicom file unless I change the Transfer Syntax to "JPEG Baseline (Process 1)" which is a lossy Transfer Syntax.

  


  I assume the problem comes from the first step of the program with ffmpeg that might be creating lossy JPEG images but I'm not sure because I'm using the "best" q:v scale as I've seen in other posts on the subject.

  


  Therefore, my 2 main questions are :

  


  

  • why do some viewers have no problems displaying the dicom file whereas some others can't ?

  


  • is there any way to obtain lossless JPEG images from a ffmpeg command ?

  


  


• ffmpeg to encode MKV or MP4 with segmented Parts in one file

  28 juillet 2014, par Phil

  Is it Possible to create an MP4 or MKV file where the Video, Meta and Audio Data is segmented and placed alternated in a single File ? (By segmented I don’t mean different Video or Audio Tracks.)

  So that it looks like something like this :
  [meta][video][audio][meta][video][audio]…

  I searched for "segmenting", "clustering", and other buzz words. But the most searches ended up in an HTTP-Livestreaming where One File is segmented in single files.
  That Segmenting Technology is okay (so you can stream it). But I don’t want these segments in single Files, i want them to be in one single MKV or MP4 File.

  Maybe someone has any clue.