Allow user to force audio codec to be used instead of relying the default one

Overview

Regarding this issue of mine earlier. Would it be possible to expose field AvFormatContext::audio_codec_id for user to force specific audio codec?

Documentation of the field here.

Maybe add this to av.open() to be optional argument.

Example:

av.open('alsa-device', format='alsa', audio_codec='pcm_s32le')

I could also take this one and make contribution to this awesome library if this is considered something needed in general. Any thoughts?