stream-lavf-o-append is an mpv "action" that only works as an init option, not a runtime property — all calls returned -3. Using stream-lavf-o as a single property set works correctly.
stream-lavf-o-append is an mpv "action" that only works as an init option, not a runtime property — all calls returned -3. Using stream-lavf-o as a single property set works correctly.