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• Moov atom in android MeidaRecorder recorded data

  11 mars 2013, par mmmaaak

  I have a problem :

  I record data from camera using MediaRecorder in my Android app. I save it in socket, not in file. This data's length may be different. At the other side of socket connection, I save it in file. Connection may be interrupted at any unexpected moment. So after android socket disconnection I try to decode received data using ffmpeg. But as I understood, it cant find moov atom in this file. I've read some info about moov, so I think that MediaRecorder puts moov atom in the end of file. But if recording was interrupted, writing moov atom was skipped.

  I also have read that for data with unknown length (progressive loading, streaming) it is possible to write moov atom at the begining of the file.

  How to write my own moov data into the stream ? May I use MediaRecorder for this ? Or it is neccessary to do it manualy ? How to generate valid moov data ? If anybody has already solved this problem, please give me advice..

• Save a partial video file locally using NodeJS

  25 octobre 2017, par Sami

  I have a serverless web application that is deployed on AWS and I have to take a screenshot from an uploaded video to S3. I am using ffmpeg to extract the screenshot but the only drawback is that I have to download the video file first in order to let ffmpeg work with it.
  Knowing the fact I am using AWS Lambda and I don’t have limits for video length users might upload large files which makes AWS Lambda to hit the storage limit.
  To overcome this I thought of downloading a small chunk of the video and use it with ffmpeg to extract the thumbnail so using the S3.getOjbect method with range params I was able to download a chunk of the file but ffmpeg couldn’t understand it.
  Here is my code :

  s3.getObject({
  
    Bucket: bucketName,
  
    Key: key,
  
    Range: 'bytes=0-1048576'
  
  }, (err, data) => {
  
    fs.writeFile(fileName, data.Body, error => {
  
      if (error)
  
        console.log(error)
  
      else
  
        console.log('File saved');
  
    })
  
  })

  And the code to extract the thumbnail :

  const ffmpeg = require('fluent-ffmpeg');
  
  new ffmpeg(fileName).screenshots({
  
    timestamps: [0],
  
    filename: 'thumb.png',
  
    folder: '.'
  
  })

  And I am getting this error from ffmpeg

  Error: ffmpeg exited with code 1: ./test.mp4: Invalid data found when processing input

  I know there is a problem in saving the file like this but I couldn’t find any solution that solves my problem. If anybody has one that would be much appreciated.

  UPDATE :
  It turns out that ffmpeg does this for me, I just gave it the url and it downloaded what it needs to render the screenshot without the need to download the file locally and the code looks like this :

  const ffmpeg = require('fluent-ffmpeg');
  
  new ffmpeg(url).screenshots({
  
    timestamps: [0],
  
    filename: 'thumb.png',
  
    folder: '.'
  
  })

• avcodec/mpeg4videodec : Use union to save space

  21 mai, par Andreas Rheinhardt

  avcodec/mpeg4videodec : Use union to save space
  At most one of block32 and dpcm_macroblock is used at any given time.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/mpeg4videodec.h