MadelineProto can now make phone calls!
It does that thanks to the \danog\MadelineProto\VoIP class, which is a wrapper for grishka's awesome library.
See https://daniil.it/MadelineProto/#calls for installation instructions.

The VoIP class has methods for:
* playing audio files in calls
* playing files on hold (when there are no files left to play)
* setting the audio output file
accepting incoming calls
* discarding calls
* setting a rating for completed calls
* getting the emoji visualization of the encryption key
* fetching the configuration needed to encode/decose audio files (usually it's always 16 bit signed linear PCM with a sample rate of 48 kHz and one channel)
* and much more! See https://daniil.it/MadelineProto/API_docs/types/PhoneCall.html

Input/output audio can be converted from/to any audio/video file using ffmpeg (just don’t forget to provide the correct number of channels, sample rate and bit depth, 

ffmpeg -i anyaudioorvideo -f s"$bitnumber"le -ac $channelNumber -ar $bitRate -acodec pcm_s"$bitnumber"le output.raw

).

You can also stream the audio track of video streams (even from youtube), or audio streams. Just stream the data to a FIFO, and use ffmpeg to output the converted audio to another FIFO that will be used as input file.

To make a call, use the request_call method: it accepts one parameter with the ID of the person to call, and returns a VoIP object.

Accepting calls is just as easy: you will receive an updatePhoneCall (https://daniil.it/MadelineProto/API_docs/constructors/updatePhoneCall.html) object from your update source (see update handling), and you will simply have to call accept() to accept the call.

See https://daniil.it/MadelineProto/#calls for more info.