Develop a SIP client to play back pre-recorded information to callers

Basically, we need to build a service that will play back pre-recorded messages on a variety of topics to end users. This is for a non-profit/charitable organization and the budget is limited, but am open to negotiation on that front. These could range in length from 1 minute to 30 minutes long in more extreme cases. Callers will be directed to this service from an existing IVR. Recordings will be made manually (or otherwise generated in some fashion) prior to being inserted into this system. What it must do: - load (and reload upon change) configuration from a text file (to allow easy generation and updating by external tools) - log each call session (who called, how long they were on, what they listened to) for statistics reporting - allow blocking of calls for specific caller ID pattern (do not answer or answer and disconnect with a message) - register with a SIP provider - answer incoming calls - disconnect user (with a message) after X minutes total time on system (configurable) - present the user with (potentially nested) menus of options, as configured - repeat menu options 3 times before disconnecting a user for non-response - menus and content will be available as pre-recorded audio files (.WAV or as required) - allow assignment to each content item a "content identifier" for stats gathering (since menu options might change over time) - during playback, must permit: * backing out of the current item or menu (DTMF *), * skipping forward by (configurable) % of audio length (DTMF 6), * skipping back by (configurable) % of audio length, * skipping to next file in the current menu, if any (DTMF 9), * skipping to previous file in the current menu, if any (DTMF 6) What it must work with: - needs to run on a Ubuntu 14 Linux-based server (can install additional libraries or tools if needed) - will be used with [login to view URL] as a SIP provider but I do not believe there is anything particularly special about them How it must be written: - use C/C++ (open to negotiation if you have a better idea -- could be convinced to use Python for example, notwithstanding that I don't know it) - you will need to develop locally and send my way for testing - needs to be fault tolerant, but this is not a mission critical application that requires enterprise-level engineering - all source code must be managed through a BitBucket team account git) - would prefer to ultimately release this as an open-source project (GPL or otherwise) if possible I played around a little with PJSIP ([login to view URL]) and it would seem this is a relatively straightforward ask, but I simply do not have the time to figure out the details, SIP calls, etc. Example configuration file (syntax negotiable - but to give you an idea of where this is going): [options] max_call_time = 3600s fwd_skip_size = 15 bwd_skip_size = 15 too_many_calls_msg = [login to view URL] no_response_msg = [login to view URL] welcome_msg = [login to view URL] goodbye_msg = [login to view URL] [blocks] 5555551212 5555551414 [root] 1=menu:news 2=menu:tech 3=menu:bb #=hangup [news] 1=news/[login to view URL],News-May15-Rec 2=news/[login to view URL],News-May23-Rec 3=news/[login to view URL],News-May30-Rec *=menu:root #=hangup [tech] 1=tech/[login to view URL],Help-Signup 2=tech/[login to view URL],Help-Members *=menu:root #=hangup ... and so on ...