The submitted tgvoiprate app got a score of 1228 which means it is less precise than the solution that always returned 3.0 as the result. Unfortunately, this is not good enough to compete for the prize.

This is not a good idea for encoding and writing data to an ogg file inside a blocking callback in a single thread - avcodec_encode_audio2 and av_interleaved_write_frame can take a lot of time, especially in the case of variable data rates .
The receive cycle is locked until the page is written - so it increases the temporal latency and you loose some data. You must exit this handler as soon as it possible to not affect receiving process - save data to the buffer(pipe) which is being processed by asynchronous task.

Maybe not an issue, but in compare to other submissions very high CPU usage

Can't manage to make tgvoipcall work on Buster. Every time ends with

error connecting with params:
caller> tag_hex = 'ba7201826967456c4c090d70a4ae365b'
caller> encryption_key_hex = '2297537d8196e1c9008fff319eeaa2d461be76fa591b2b66bb6318efef53abc801ef3d82d16c51ae29c0ba8760268551c86f8f189de7f6deae54ce6ca06c8d648cf7fa....redacted
caller> sound_in = '/home/user/voip/samples/file.ogg'
caller> sound_out = 'out.ogg'
caller> config = '/home/user/voip/tests/config.json'
caller> role = 'caller'

Same for callee. Tcpdump shows traffic both to and from reflector.
Is libtgvoip linked statically? Any way to enable libtgvoip debug output?

The ogg file was sample15_4a30a6c03e108b963d0afe692558e3ec.ogg from provided samples, both ways. Tried other files as well.

Here is the config:
https://pastebin.com/raw/29fQSfGF

VPN is not used, because the relector is on the same network, so blockings etc can't affect.