Passing python's file like object to ffmpeg via subprocess

Question

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: Attribut…

Accepted Answer

Use `subprocess.Popen.communicate` to pass the input to your subprocess:

```
command = ['ffmpeg', '-y', '-i', '-', output_file.name]
process = subprocess.Popen(command, stdin=subprocess.PIPE)
process.communicate(recording_wav)
```

For extra fun, you could use the ffmpeg's output to avoid your NamedTemporaryFile:

```
command = ['ffmpeg', '-y', '-i', '-', '-f', 'mp3', '-']
process = subprocess.Popen(command, stdin=subprocess.PIPE)
recording_mp3, errordata = process.communicate(recording_wav)
```

Passing python's file like object to ffmpeg via subprocess

Solution

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