drawtext causes a muted video output

[abubelinha]

I am using both CLI ffmpeg and python-ffmpeg in the same environment, which is Termux app installed in a Samsung GS8+ Android phone.

When I run this command I get the expected output (text overlayed on the input video).

$ ffmpeg -i input.mp4 -vf "drawtext=text='© Leóñardo da Vinci':x=(1100-text_w):y=(600-text_h):fontsize=32:fontcolor=black:box=1:boxcolor=white@0.5: boxborderw=5" -c:a copy ffmpeg_drawtext-output.mp4

When I run it in Python, the output video is muted (no audio):

ffmpeg \
        .input("input.mp4") \
        .drawtext(text='© Leónardo da Vinci', x='(1100-text_w)', y='(600-text_h)', fontsize=32, fontcolor='black', box=1, boxcolor='white@0.5',  boxborderw=5) \
        .output("pyffmpeg_out.mp4") \
        .run()

Perhaps both commands are not equivalent?
What is the exact python-ffmpeg implementation of the above ffmpeg command?

[abubelinha]

I have just seen #229, which was closed because the problem is explained in FAQs.

In the FAQs I found this:

Why did my audio stream get dropped?
Some ffmpeg filters drop audio streams, and care must be taken to preserve the audio in the final output. The .audio and .video operators can be used to reference the audio/video portions of a stream so that they can be processed separately and then re-combined later in the pipeline.
This dilemma is intrinsic to ffmpeg, and ffmpeg-python tries to stay out of the way while users may refer to the official ffmpeg documentation as to why certain filters drop audio.
As usual, take a look at the examples (Audio/video pipeline in particular).

If this is a frequent question it would be worth showing an example (in the FAQs) of such audio-video separation & recombination.

But in my example above the problem is not in ffmpeg, which does not drop audio when I add text to my file.
This only happens when I try to do the same in Python.