Rewrite RTSP server #372
Rewrite RTSP server #372
Commits on Feb 13, 2024
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step 0: make room for the rebuilt implementation
- so that code can be established upon existing example in Live555. - Result will look simmilar to this, but will be rebuild as series of logical steps
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step 1: import example from Live555 library
- that will be base of rtsp server - file originaly located in Live555 library source code at testProgs/testOnDemandRTSPServer.cpp
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step 1: rename file and add UG copyright
copyright notice was added from original file BasicRTSPOnlyServer.cpp
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step 1: remove http(s) tunneling and TLS
these features are not used needed by UltraGrid
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step 1: drop unused media formats, keep MPEG-4
MPEG-4 video is not deleted because it can serve as example of handling subsessions
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step 2: add rtsp server class, typedef to og name
- basic structure for UltragridRTSPServer class - make copying not possible because server can't be copied - add typedef reference to name used in previous implementation
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step 2: move initialization logic to constructor
move inicialization logic from main() to constructor of new class
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step 2: import announceURL function from Live555
- copied announceURL function from Live555 library at testProgs/announceURL.cpp - copied becase is functional and searchable for future modifications - function handles displaying url, that server listens on, to comandline
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step 2: add announceURL to class
move announceURL function to class so funcitonality is more clear
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step 3: create base for media subsessions
they will serve as container for various media transmitted by UG
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step 3: repsesent UG rtp payload as subsession
- add basic structure for UltragridRTSPSubsessionCommon class - add typedef reference to name used in previous implementation
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step 3: inherit Live555 subsession functionality
- add definitions for all needed functions - ServerMediaSubsession is chosen because it is common ancestor in Live555's subsessions
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step 3: provide a mechanism to direct media stream
function redirectStream changes destination adress and port in UG module sender
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step 3: implement RTSP playback control
- starts stream by changing destination adress and port to the ones got in function getStreamParameters - deletes stream by changing destination address and port to localhost
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step 4: instantiate subsession for audio and video
- inherits from UltragridRTSPSubsessionCommon because implementation of needed functions (by ServerMediaSubsession) is the same - exept for SDP Lines which are added later - Factory method (createNew) is used because Live555 library needs pointer to structure and all subsessions in Live555 library are created this way
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step 4: specify modules for directing media stream
- Tell UG what modules shoud be notified when changing direction of media stream - MODULE_CLASS_SENDER - controls video stream - MODULE_CLASS_AUDIO - controls audio stream - MODULE_CLASS_NONE - only used as stop (like \0 in string)
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step 4: generate SDP description of media stream
Generate description of provided media according to SDP protocol defined in RFC 8866 with modifications for RTSP protocol defined in RFC 2326
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step 5: add way to specify port for rtsp server
- if user don't specify port number default 8554 will be used - Live555 does not have mechanism to tell if port is already in use so user must specify available port
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step 5: add supported media types, rename refs
in previous version of rtsp_utils.h file the struct was named differently so all references have to be renamed
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step 5: instantiate subsessions for rtsp server
replace MPEG-4 example with new subsessions made for UG
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step 5: extract starting server from constructor
- serverStopFlag if set to 0 server is running when set to 1 it stops - serverRunner built so it can be launched from pthread_create - destructor cleans memory
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step 6: add files to host rtsp server management
they will be used by UG to interface with rtsp server
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step 6: class to manage rtsp server
- basic structure of ultragrid_rtsp class - it provides control of rtsp server
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step 6: start and stop server thread
- new thread is created for rtsp server because control flow needs to be given to Live555 - server stops by setting server_stop_flag to 1 - char is used because it is needed by Live555 library - because rtsp server does not need to know about threads two 'runner' functions are used to separate server and threads
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step 7: remove Live555 library version check
new implementation is built on version 2023.11.30 of Live555
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step 7: override number of channels for OPUS
- OPUS does not support mono - RFC 7587 specifies that in SDP number of channels must be 2
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step 7: remove unused parameter
- in previous implementation parameter audio_bps was used in initialization of rtsp server but was not used internally - it is kept in the process of creating new implementaion (git commits) for reference with previous implementaion
