Add support for multi-output filters; implement split filter

[kkroening]

The split operator now does the right thing:

import ffmpeg

overlay_file = ffmpeg.input('overlay.png')
split = (ffmpeg
    .input('input.mp4')
    .hflip()
    .split()
)
(ffmpeg
    .concat(
        split[0].vflip(),
        split[1]
    )
    .output('out.mp4')
)

This paves the way to having both multi-input and multi-output components. To access particular outputs of a multi-output node, use either the .stream function or bracket shorthand:

split = in.split()
split0 = split.stream(0)
split1 = split[1]

I decided to forego the automatic split stuff for now. It was probably more work to add multi-output support right away, but I think it's more correct in the long run. The automatic splitting will eventually happen as a pre-processing step and produce the same kind of graph as though the split were inserted manually.

[depau]

Great! I'll test it on Saturday and let you know.

[depau]

This doesn't seem to work with merge_output. I tried to adjust the code but ended up messing up everything, so I just quit trying

import ffmpeg

i = ffmpeg.input("test.ogg")
s = i.split()
l = [s[i].output("out"+str(i)) for i in range(5)]

print(l)

[output(filename='out0')[None] <165772f6fba8>,
 output(filename='out1')[None] <1fb1f5f0ca46>,
 output(filename='out2')[None] <1f417509efbd>,
 output(filename='out3')[None] <1451115eaeca>,
 output(filename='out4')[None] <2e7c02df8060>]

o = ffmpeg.merge_outputs(*l)

---------------------------------------------------------------------------

TypeError                                 Traceback (most recent call last)

<ipython-input-8-7629009c961a> in <module>()
----> 1 o = ffmpeg.merge_outputs(*l)


[removed]/ffmpeg-python/ffmpeg/_ffmpeg.py in merge_outputs(*streams)
     38     """Include all given outputs in one ffmpeg command line
     39     """
---> 40     return MergeOutputsNode(streams, merge_outputs.__name__).stream()
     41 
     42 


[removed]/ffmpeg-python/ffmpeg/nodes.py in __init__(self, stream, name)
    176             outgoing_stream_type=OutputStream,
    177             min_inputs=1,
--> 178             max_inputs=None
    179         )
    180 


TypeError: __init__() missing 2 required positional arguments: 'args' and 'kwargs'

[kkroening]

Ooooooh looks like there aren't any tests for merge_outputs! Regression alert.

I'll make a fix.

[kkroening]

Ok should be fixed.

Also note that I made it so that merge_outputs is not required. If desired, you can instead do this:

in_ = ffmpeg.input('in.mp4').hflip()
out1 = ffmpeg.output('out1.mp4')
out2 = ffmpeg.output('out1.mp4')
ffmpeg.run([out1, out2], overwrite_output=True)

The merge_outputs + .overwrite_output style is still available as well.

And you can do the same thing with get_args or view:

ffmpeg.view([out1, out2])

Basically anything that takes a stream_spec can take a single stream, list of streams, or stream dict.

[kkroening]

This probably won't affect you, but I also uncovered this edgecase-ish bug: #23

[kkroening]

Let me know if this fixes it for you. Thanks for testing

[depau]

Okay it seems to work now with merge_outputs.

It gives out this which looks quit good to me:

ffmpeg -i test.ogg \
-filter_complex [0]split[s0][s1][s2][s3][s4];[s0]hflip[s5];[s5]vflip[s6] \
-map [s6] out0wfilters \
-map [s1] out1 \
-map [s2] out2 \
-map [s3] out3 \
-map [s4] out4

[depau]

Nope. See split documentation. It needs the number of splits.
https://ffmpeg.org/ffmpeg-filters.html#split_002c-asplit

I added it manually to the command line and now works. Let me see what I can do with the code.

[kkroening]

Should be fixed now. I'm gonna merge this. Let me know if there are any issues.