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A simple Python wrapper around ffmpeg

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ffmpy is the simplest ffmpeg wrapper one can imagine. Under the hood it uses Python’s subprocess module to run ffmpeg exeutable. In other words it’s a (bit) more user-friendly interface to compiling a command line to be passed to subprocess. Input can be specified as a file path as well as sent to STDIN via ffmpeg’s pipe protocol. Same for output - it can be written to a file or sent to STDOUT.


You guessed it:

~$ pip install ffmpy


ffmpy resembles the command line approach ffmpeg uses. It can read from an arbitrary number of input “files” (regular files, pipes, network streams, grabbing devices, etc.) and write into arbitrary number of output “files”. See ffmpeg documentation for further details about how ffmpeg command line options and arguments work.

The simplest example of usage is converting media from one format to another (in this case from MPEG transport stream to MP4) preserving all other attributes:

In [1]: ff = FFmpeg(inputs={'/tmp/input.ts': None}, outputs={'/tmp/output.mp4': None})
In [2]: ff.cmd_str
Out[2]: 'ffmpeg -i /tmp/input.ts /tmp/output.mp4'
In [3]

If at the same time we wanted to re-encode video and audio using different codecs we’d have to specify additional output options:

In [1]: ff = FFmpeg(inputs={'/tmp/input.ts': None}, outputs={'/tmp/output.mp4': '-c:a mp2 -c:v mpeg2video'})
In [2]: ff.cmd_str
Out[2]: 'ffmpeg -i /tmp/input.ts -c:a mp2 -c:v mpeg2video /tmp/output.mp4'
In [3]

A more complex usage example would be demultiplexing an MPEG transport stream into separate elementary (audio and video) streams and save them in MP4 containers preserving the codecs:

In [1]: ff = FFmpeg(inputs={'/tmp/input.ts': None}, outputs={'/tmp/video.mp4': '-map 0:0 -c:a copy -f mp4', '/tmp/audio.mp4': '-map 0:1 -c:a copy -f mp4'})
In [2]: ff.cmd_str
Out[2]: 'ffmpeg -i /tmp/input.ts -map 0:1 -c:a copy -f mp4 /tmp/audio.mp4 -map 0:0 -c:a copy -f mp4 /tmp/video.mp4'
In [3]

To multiplex video and audio back into an MPEG transport stream with re-encoding:

In [1]: ff = FFmpeg(inputs={'/tmp/video.mp4': None, '/tmp/audio.mp4': None}, outputs={'/tmp/output.ts': '-c:v h264 -c:a ac3'})
In [2]: ff.cmd_str
Out[2]: 'ffmpeg -i /tmp/audio.mp4 -i /tmp/video.mp4 -c:v h264 -c:a ac3 /tmp/output.ts'
In [3]

There are cases where the order of inputs and outputs must be preserved (e.g. when using ffmpeg’s -map option). In these cases the use of regular Python dictionary will not work because it does not preserve order. Instead, use OrderedDict. For example we want to multiplex one video and two audio streams into an MPEG transport streams re-encoding both audio streams using different codecs. Here we use an OrderedDict to preserve the order of inputs so they match the order of streams in output options:

In [1]: from collections import OrderedDict
In [2]: inputs = OrderedDict([('/tmp/video', None), ('/tmp/audio_1', None), ('/tmp/audio_2', None)])
In [3]: outputs = {'/tmp/output.ts', '-map 0 -c:v h264 -map 1 -c:a:0 ac3 -map 2 -c:a:1 mp2'}
In [4]: ff = FFmpeg(inputs=inputs, outputs=outputs)
In [5]: ff.cmd_str
Out[5]: 'ffmpeg -i /tmp/video -i /tmp/audio_1 -i /tmp/audio_2 -map 0 -c:v h264 -map 1 -c:a:0 ac3 -map 2 -c:a:1 mp2 /tmp/output.ts'
In [6]:

ffmpy can read input from STDIN and write output to STDOUT. This can be achieved by using ffmpeg’s pipe protocol. The following example reads data from a file containing raw video frames in RGB format and passes it to ffmpy on STDIN; ffmpy in its turn will encode raw frame data with H.264 and pack it in an MP4 container passing the output to STDOUT:

In [1]: ff = FFmpeg(inputs={'pipe:0': '-f rawvideo -pix_fmt rgb24 -s:v 640x480'}, outputs={'pipe:1': '-c:v h264 -f mp4'})
In [2]: ff.cmd_str
Out[2]: 'ffmpeg -f rawvideo -pix_fmt rgb24 -s:v 640x480 -i pipe:0 -c:v h264 -f mp4 pipe:1'
In [3]:'/tmp/rawvideo', 'rb').read())

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