Hi, I'm experiencing exactly the same issue on MacOS 10.13.6.
What's interesting is that if I use "open file with MPV" menu, it works fine.

UPDATE
I figured out that running mpv with --input-ipc-server=/tmp/mpvsocket from shell works fine. That means that mpv is not picking up that parameter from conf file for some reason.

Any news on this?

I made a upgrade on homebrew today. Now again same issue as in first post described.

svp says: (Playback [64f9ee6b]: VS - Could not initialize VapourSynth scripting.)

Also, like @vasek discribed: "if I use "open file with MPV" menu, it works fine."  Same for me....

Edit:

I uninstalled mpv with brew force command and reinstalled with: brew install mpv  --with-libbluray --with-vapoursynth  --with-bundle
Now everything works as it should..!!!!

Greetings
sv

UPDATE
I figured out that running mpv with --input-ipc-server=/tmp/mpvsocket from shell works fine. That means that mpv is not picking up that parameter from conf file for some reason.

thanks for quick response..!!
I only have one mpv on my system.. I tried different ways to fix it without luck..
So, i restored mpv from my ccc backup.
Now, everything is running just fine.

Anyway, thanks again.

After today's "brew upgrade" on my mac, when i start mpv, svp no longer working.

Error: Playback [4904d4db]: VS - libavfilter filter 'vapoursynth' not found!

i tried to switch vapoursynth version from latest back to previous but made no difference..
also tried with uninstalling mpv and reinstall.. still same issue/error.....

Here the svp log:

Main: starting up SVP 4 Mac [4.2.0.137]...
Main: args: none
Main: working dir is /Applications/SVP 4 Mac.app/Contents/Resources/
Main: data dir set to /Users/stephan/Library/Application Support/SVP4/
Settings: loading main.cfg OK
Settings: loading ui.cfg OK
Settings: loading frc.cfg OK
Settings: loading profiles.cfg OK
Settings: loading custom.cfg OK
Settings: loading lights.cfg OK
Main: using Qt 5.7.1 (x86_64-little_endian-lp64 shared (dynamic) release build; by Clang 7.0.2 (clang-700.1.81) (Apple))
Main: device scale is 1, user defined scale is 0
Main: system locale is [en-de]
Main: preferred language is [de-de]
Main: setting language file to en.qm...
Main: module 'plugins/libsvpflow1_vs64.dylib': 4.2.0.133
Main: module 'plugins/libsvpflow2_vs64.dylib': 4.2.0.145
Main: VLC filter (64 bit): 0.9.0.114
Main: running OpenCL info...
Main: collecting system information...
macOS 10.13.6 High Sierra
CPU: Intel Core i7-6700K [base frequency 3823 MHz, 8 threads]
Video: reading OpenCL info...
Video: 2 GPU OpenCL device(s) on Apple [OpenCL 1.2 (May 24 2018 20:07:03)] (Apple)
Video 1: device name 'SKL Graphics' (Intel Inc., ver.1.2(Jun 25 2018 19:28:17)) [gpuID=11]: OK
Video 2: device name 'GeForce GTX 980 Ti' (NVIDIA, ver.10.33.0 387.10.10.10.40.105) [gpuID=12]: OK
Memory:  32768  MB total,  15305 MB free
System: finding network settings...
Power: AC is ON [1]
Screens: updating information, 1 screen(s) found
Screens: screen 0 (HDTV) - 1920x1080 @60.000 Hz, x1.0 [47 DPI]
Screens: primary screen is 0
Main: preparing video profiles...
Main: preparing performance graphs...
Main: preparing mpv...
Main: preparing remote control...
RemoteControl: started
Main: preparing main menu...
Main: loading extensions...
Extensions: found svpcast 0.9.5.137 ...
Extensions: found svpcode 1.0.0.137 ...
Extensions: found svplight 2.0.0.116 ...
Extensions: found svptube 2.1.0.136 ...
Main: initialization completed in 2978 ms
Updates: checking now...
Performance: quick estimation = 909 (previous value was 907)
VideoPlayer: mpv connected, waiting for the video info...
VideoPlayer: mpv 0.28.2
Media: video 640x480 [PAR 1.000] at 25.000 fps [constant]
Media: codec type is xvid
Playback: starting up...
Playback [4904d4db]: resulting video frame 640x480
Playback [4904d4db]: 23 acceptible profiles, best is '720x544-@-25' [292]
Playback [4904d4db]: enabled while video is playing
Playback [4904d4db]: playing at 175 [25 *7/1]
Playback [4904d4db]: VS - libavfilter filter 'vapoursynth' not found!
Playback [4904d4db]: full screen mode deactivated
Playback [4904d4db]: deleted

Her the brew info vapoursynth:

vapoursynth: stable 43 (bottled), HEAD
Video processing framework with simplicity in mind
http://www.vapoursynth.com
/usr/local/Cellar/vapoursynth/40 (22 files, 3.1MB) *
  Poured from bottle on 2017-12-06 at 21:37:01
/usr/local/Cellar/vapoursynth/42.1 (22 files, 3.1MB)
  Poured from bottle on 2018-01-18 at 15:26:25
/usr/local/Cellar/vapoursynth/43 (22 files, 3.1MB)
  Poured from bottle on 2018-02-01 at 21:54:59
/usr/local/Cellar/vapoursynth/43_1 (22 files, 3.1MB)
  Poured from bottle on 2018-03-03 at 00:27:18
/usr/local/Cellar/vapoursynth/43_2 (22 files, 3MB)
  Poured from bottle on 2018-07-12 at 16:27:08
From: https://github.com/Homebrew/homebrew-co … ursynth.rb
==> Dependencies
Build: autoconf ✘, automake ✘, libtool ✘, pkg-config ✔, nasm ✔
Required: libass ✔, python ✔, tesseract ✔, zimg ✔
==> Requirements
Required: macOS >= 10.11 ✔
==> Options
--HEAD
    Install HEAD version

Her the brew info mpv:

mpv: stable 0.28.2 (bottled), HEAD
Media player based on MPlayer and mplayer2
https://mpv.io
/usr/local/Cellar/mpv/0.28.2 (63 files, 53.8MB) *
  Built from source on 2018-07-12 at 17:03:07 with: --with-bundle --with-libbluray --with-vapoursynth
From: https://github.com/Homebrew/homebrew-co … ula/mpv.rb
==> Dependencies
Build: pkg-config ✔, python@2 ✔
Required: libass ✔, ffmpeg ✔, lua@5.1 ✔
Recommended: jpeg ✔, little-cms2 ✔, mujs ✔, youtube-dl ✔
Optional: jack ✘, libaacs ✘, libarchive ✘, libbluray ✔, libcaca ✘, libdvdnav ✘, libdvdread ✔, pulseaudio ✘, rubberband ✘, uchardet ✔, vapoursynth ✔
==> Requirements
Required: macOS >= 10.8 ✔
Optional: x11 ✘
==> Options
--with-bundle
    Enable compilation of the .app bundle.
--with-jack
    Build with jack support
--with-lgpl
    Build with LGPLv2.1 or later license
--with-libaacs
    Build with libaacs support
--with-libarchive
    Build with libarchive support
--with-libbluray
    Build with libbluray support
--with-libcaca
    Build with libcaca support
--with-libdvdnav
    Build with libdvdnav support
--with-libdvdread
    Build with libdvdread support
--with-pulseaudio
    Build with pulseaudio support
--with-rubberband
    Build with rubberband support
--with-uchardet
    Build with uchardet support
--with-vapoursynth
    Build with vapoursynth support
--with-x11
    Build with x11 support
--without-jpeg
    Build without jpeg support
--without-little-cms2
    Build without little-cms2 support
--without-mujs
    Build without mujs support
--without-youtube-dl
    Build without youtube-dl support
--HEAD
    Install HEAD version
==> Caveats
zsh completions have been installed to:
  /usr/local/share/zsh/site-functions

Thanks in advance!!!!