jbuf: fix possible division by zero

[sreimers]

No description provided.

[juha-h]

I tested the PR and now I was able to hear audio with this config:

05-19 07:30:44.184 15260 15260 I Baresip : audio_buffer_mode adaptive
05-19 07:30:44.184 15260 15260 I Baresip : audio_buffer 20-300
05-19 07:30:44.184 15260 15260 I Baresip : audio_jitter_buffer_type adaptive
05-19 07:30:44.184 15260 15260 I Baresip : audio_jitter_buffer_delay 0-20
05-19 07:30:44.184 15260 15260 I Baresip : video_jitter_buffer_type adaptive
05-19 07:30:44.184 15260 15260 I Baresip : video_jitter_buffer_delay 0-50

But when looking at it, I started to wonder why there doesn't exist video_buffer_mode and video_buffer config variables?

[sreimers]

But when looking at it, I started to wonder why there doesn't exist video_buffer_mode and video_buffer config variables?

Only audio has a separate aubuf (controlled by audio_buffer options), to handle thread safety and realtime requirements:

auplay <-- aubuf <-- aufilt <-- decode <--- jbuf <--- RTP

Video pipeline looks like this:

 vidisp <-- vidfilt <-- decoder <--- jbuf <---  RTP