Impossible to write linear chains of filter in ffmpeg, only distinct chains

[MarcBresson]

Hello,

I know this project has stalled, but for anyone wondering the same thing as me, it is currently impossible in ffmpeg to write linear chains of filters (https://ffmpeg.org/ffmpeg-filters.html#Filtering-Introduction)

I needed to merge multiple audio file onto the same track/channel. For this, I had to use the chain of filters amerge=inputs=2,pan=mono|c0<c1+c2[a]. Unfortunately, these two filters must be in the same chain.

The way I patched my issue was messy, but I compiled my ffmpeg command and "manually" replaced the semi-colon using the good old .replace method. I then run the command using subprocess.Popen