fix: refactor stream variants

Proposed changes

Completes #86 bullet point 4

This change refactors how we store the stream variants and also sets up the transcoder for unit tests and cleans up the way transcoder invokes ffmpeg.

Previously we did some jank way of having variants and then variants that reference other variants which was really messy. Now we have variants and transcode states. Variants can either reference 1 or more transcode states. The HLS manifest is then created to comprise these changes

#EXTM3U
#EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="595eaf20-9b81-4e6a-8767-5e48d620d9e1",NAME="595eaf20-9b81-4e6a-8767-5e48d620d9e1",AUTOSELECT=YES,DEFAULT=YES,URI="595eaf20-9b81-4e6a-8767-5e48d620d9e1/index.m3u8"
#EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="adf09098-38ec-4447-a2b6-ff3735df4ac0",NAME="adf09098-38ec-4447-a2b6-ff3735df4ac0",AUTOSELECT=YES,DEFAULT=YES,URI="adf09098-38ec-4447-a2b6-ff3735df4ac0/index.m3u8"
#EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="d3c355b1-02b5-4ce7-b866-27c520c5c92e",NAME="d3c355b1-02b5-4ce7-b866-27c520c5c92e",AUTOSELECT=YES,DEFAULT=YES,URI="d3c355b1-02b5-4ce7-b866-27c520c5c92e/index.m3u8"
#EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="0f3bd47a-5a29-4dc6-af88-62ad3f1df7c0",NAME="0f3bd47a-5a29-4dc6-af88-62ad3f1df7c0",AUTOSELECT=YES,DEFAULT=YES,URI="0f3bd47a-5a29-4dc6-af88-62ad3f1df7c0/index.m3u8"
#EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="3a20175f-5bfb-400c-9aa2-358df5501052",NAME="3a20175f-5bfb-400c-9aa2-358df5501052",AUTOSELECT=YES,DEFAULT=YES,URI="3a20175f-5bfb-400c-9aa2-358df5501052/index.m3u8"
#EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="d08827ef-6aea-45c9-97b1-1608e3198b95",NAME="d08827ef-6aea-45c9-97b1-1608e3198b95",AUTOSELECT=YES,DEFAULT=YES,URI="d08827ef-6aea-45c9-97b1-1608e3198b95/index.m3u8"
#EXT-X-STREAM-INF:GROUP="opus",NAME="audio-only",BANDWIDTH=98304,CODECS="opus",AUDIO="595eaf20-9b81-4e6a-8767-5e48d620d9e1"
595eaf20-9b81-4e6a-8767-5e48d620d9e1/index.m3u8
#EXT-X-STREAM-INF:GROUP="aac",NAME="audio-only",BANDWIDTH=131072,CODECS="mp4a.40.2",AUDIO="adf09098-38ec-4447-a2b6-ff3735df4ac0"
adf09098-38ec-4447-a2b6-ff3735df4ac0/index.m3u8
#EXT-X-STREAM-INF:GROUP="opus",NAME="source",BANDWIDTH=8290304,CODECS="av01.0.13M.08.0.110.01.01.01.0,opus",RESOLUTION=3840x2160,FRAME-RATE=60,VIDEO="d3c355b1-02b5-4ce7-b866-27c520c5c92e",AUDIO="595eaf20-9b81-4e6a-8767-5e48d620d9e1"
d3c355b1-02b5-4ce7-b866-27c520c5c92e/index.m3u8
#EXT-X-STREAM-INF:GROUP="aac",NAME="source",BANDWIDTH=8323072,CODECS="av01.0.13M.08.0.110.01.01.01.0,mp4a.40.2",RESOLUTION=3840x2160,FRAME-RATE=60,VIDEO="d3c355b1-02b5-4ce7-b866-27c520c5c92e",AUDIO="adf09098-38ec-4447-a2b6-ff3735df4ac0"
d3c355b1-02b5-4ce7-b866-27c520c5c92e/index.m3u8
#EXT-X-STREAM-INF:GROUP="opus",NAME="720p",BANDWIDTH=4194304,CODECS="avc1.640033,opus",RESOLUTION=1280x720,FRAME-RATE=60,VIDEO="0f3bd47a-5a29-4dc6-af88-62ad3f1df7c0",AUDIO="595eaf20-9b81-4e6a-8767-5e48d620d9e1"
0f3bd47a-5a29-4dc6-af88-62ad3f1df7c0/index.m3u8
#EXT-X-STREAM-INF:GROUP="aac",NAME="720p",BANDWIDTH=4227072,CODECS="avc1.640033,mp4a.40.2",RESOLUTION=1280x720,FRAME-RATE=60,VIDEO="0f3bd47a-5a29-4dc6-af88-62ad3f1df7c0",AUDIO="adf09098-38ec-4447-a2b6-ff3735df4ac0"
0f3bd47a-5a29-4dc6-af88-62ad3f1df7c0/index.m3u8
#EXT-X-STREAM-INF:GROUP="opus",NAME="480p",BANDWIDTH=2146304,CODECS="avc1.640033,opus",RESOLUTION=853x480,FRAME-RATE=30,VIDEO="3a20175f-5bfb-400c-9aa2-358df5501052",AUDIO="595eaf20-9b81-4e6a-8767-5e48d620d9e1"
3a20175f-5bfb-400c-9aa2-358df5501052/index.m3u8
#EXT-X-STREAM-INF:GROUP="aac",NAME="480p",BANDWIDTH=2179072,CODECS="avc1.640033,mp4a.40.2",RESOLUTION=853x480,FRAME-RATE=30,VIDEO="3a20175f-5bfb-400c-9aa2-358df5501052",AUDIO="adf09098-38ec-4447-a2b6-ff3735df4ac0"
3a20175f-5bfb-400c-9aa2-358df5501052/index.m3u8
#EXT-X-STREAM-INF:GROUP="opus",NAME="360p",BANDWIDTH=1122304,CODECS="avc1.640033,opus",RESOLUTION=640x360,FRAME-RATE=30,VIDEO="d08827ef-6aea-45c9-97b1-1608e3198b95",AUDIO="595eaf20-9b81-4e6a-8767-5e48d620d9e1"
d08827ef-6aea-45c9-97b1-1608e3198b95/index.m3u8
#EXT-X-STREAM-INF:GROUP="aac",NAME="360p",BANDWIDTH=1155072,CODECS="avc1.640033,mp4a.40.2",RESOLUTION=640x360,FRAME-RATE=30,VIDEO="d08827ef-6aea-45c9-97b1-1608e3198b95",AUDIO="adf09098-38ec-4447-a2b6-ff3735df4ac0"
d08827ef-6aea-45c9-97b1-1608e3198b95/index.m3u8

In this manifest we transcode both AAC audio and OPUS audio, Opus is smaller and better quality than AAC so it should be preferred if the client supports Opus.

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ScuffleTV / scuffle