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• Passing python's file like object to ffmpeg via subprocess

  3 juillet 2012, par tejinderss

  I have a django FileField, which i use to store wav files on the Amazon s3 server. I have set up the celery task to read that file and convert it to mp3 and store it to another FileField. Problem i am facing is that i am unable to pass the input file to ffmpeg as the file is not the physical file on the hard disk drive. To circumvent that, i used stdin to feed the input stream of the file with the django's filefield. Here is the example :

  output_file = NamedTemporaryFile(suffix='.mp3')
  
  subprocess.call(['ffmpeg', '-y', '-i', '-', output_file.name], stdin=recording_wav)

  where recording_wav file is : , which is actually stored on the amazon s3 server.
  The error for the above subprocess call is :

  AttributeError: 'cStringIO.StringO' object has no attribute 'fileno'

  How can i do this ? Thanks in advance for the help.

  Edit :

  Full traceback :

  [2012-07-03 04:09:50,336: ERROR/MainProcess] Task api.tasks.convert_audio[b7ab4192-2bff-4ea4-9421-b664c8d6ae2e] raised exception: AttributeError("'cStringIO.StringO' object has no attribute 'fileno'",)
  
  Traceback (most recent call last):
  
    File "/home/tejinder/envs/tmai/local/lib/python2.7/site-packages/celery/execute/trace.py", line 181, in trace_task
  
      R = retval = fun(*args, **kwargs)
  
    File "/home/tejinder/projects/tmai/../tmai/apps/api/tasks.py", line 56, in convert_audio
  
      subprocess.Popen(['ffmpeg', '-y', '-i', '-', output_file.name], stdin=recording_wav)
  
    File "/usr/lib/python2.7/subprocess.py", line 672, in __init__
  
      errread, errwrite) = self._get_handles(stdin, stdout, stderr)
  
    File "/usr/lib/python2.7/subprocess.py", line 1043, in _get_handles
  
      p2cread = stdin.fileno()
  
    File "/home/tejinder/envs/tmai/local/lib/python2.7/site-packages/django/core/files/utils.py", line 12, in <lambda>
  
      fileno = property(lambda self: self.file.fileno)
  
    File "/home/tejinder/envs/tmai/local/lib/python2.7/site-packages/django/core/files/utils.py", line 12, in <lambda>
  
      fileno = property(lambda self: self.file.fileno)
  
  AttributeError: &#39;cStringIO.StringO&#39; object has no attribute &#39;fileno&#39;
  
  </lambda></lambda>

• ffmpeg h.264 invalid cutting

  1er mai 2012, par E.Ar

  I have an s3 bucket with several hundreds video files.
  Those files were created by cutting parts of larger video files using ffmpeg.
  I wrote a script for this, which downloads the original video file from another bucket, runs ffmpeg to cut the file, and uploads the new file to it's bucket.
  For downloading and uploading from/to s3 i used this php library.
  The ffmpeg syntax I used :

  ffmpeg -y -vsync 2 -async 1 -ss [time-in] -t [duration] -i [large-input-video.mp4] -vcodec copy -acodec copy [short-output-video.mp4]

  Which should just cut the original file between the specified times, without any changes to the a/v codecs.
  All the original video files are encoded in h.264, and this is also the required encoding for the new files (which will be streamed through a CDN to the clients' flash players).

  My problem is that only a small part of the new files are coming out as encoded in h.264, but most of them aren't (h.264 is a must, otherwise the files wont play on the clients' side).
  I can't trace the problem to the original videos, since when i use the same ffmpeg command manually, with the same parameters and on the same files, the output files come out just fine. It seems arbitrary.

  I use ffprobe to get information about the files' codecs.
  For example :
  ffprobe of one of the large (original) video files :

  ...
  Stream #0.0(und) : Video : h264, yuv420p, 640x352, 499 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc
  ...

  ffprobe of the corresponding new cut file :

  ...
  Stream #0.0(und) : Video : mpeg4, yuv420p, 640x352 [PAR 1:1 DAR 20:11], 227 kb/s, 25 fps, 25 tbr, 25 tbn, 25 tbc
  ...

  As can be seen, the difference is in 'mpeg4' vs. 'h264'.

  Any insights on what can cause the new files to come out in the wrong encoding would be greatly appreciated.

  Thanks !

  Edit : Problem Resolved
  After analyzing all the files, I noticed that about two thirds of them are coming out in the wrong codec.
  Since I used three machines for the cutting process (three separate EC2 servers), it occurred to me that on two of them there is a bad installation of ffmpeg (as @LordNeckbeard suggested in his answer).
  I ran the process again, only on the invalid files, on the third machine alone - which produced the desired result.

• iOS Recorded Video Playback on Android

  1er mars 2015, par Nirav

  I am trying to record video from iPhone device using UIImagePickerController and able to store it in MP4 format. The same video is uploaded on the Amazon S3 cloud.

  When I try to play the same video on Android devices, it fails to play with an error, cannot play.

  I searched forums/google and found that ffmpeg should be used to compress the video before uploading. I want to do the compression on the phone itself rather than on the server. Which is the best way to achieve this ?

  Regards,

  Nirav