readme notes on other applciations

README.md

@@ -2,12 +2,40 @@
 `sync-mpv` synchronizes video playback between `mpv` clients running
 on multiple computers.
 
+Rationale: If multiple computers are playing the same stream at the same time,
+and are not synchronized, the audio will sound like an echo (or worse).
+
+Use case: Live streaming OBS Studio output to multiple computers across a LAN.
+
 
 # Upstream
+## sync-mpv
 This present repo is an updated fork of this repo:
 
 * https://github.com/mdnghtman/sync-mpv
 
+See `README-upstream.md` for upstream's README.
+
+## mpv
+* Ideally this would be in `mpv`, but they haven't implement it yet, afaict:
+https://github.com/mpv-player/mpv/issues/1272
+
+## mplayer
+* "Older" `mplayer` has this ability with options like `-udp-master`, but it
+doesn't support SRT and recent codecs.
+
+# Similar Projects
+There are many different similar projects, namely have two+ machines
+play the same video at the same time. I tried many of them, but they
+didn't work for my use case. For instance:
+
+* The application was for file playback, not "realtime" streaming.
+* Used for synchronization "far" across the Internet, so acceptable
+delays are in the 1-5 second range. That is far too much latency,
+it is ideally 20ms or below.
+* Not maintained.
+* Too much overhead (e.g. QT).
+* Audio only. Something like JACK doing streaming video would be ideal.
 
 # Copyright
 Unofficial project, not related to mdnghtman or mpv.