stream_lavf: add support for data URIs

Only FFmpeg supports them and they need to be in the format data://
like other protocols or prefixed with ffmpeg:// or lavf://.

Closes #4058

DOCS/man/mpv.rst

@@ -673,6 +673,10 @@ PROTOCOLS
     either aliases to documented protocols, or are just redirections to
     protocols implemented and documented in FFmpeg.
 
+    ``data:`` is supported in FFmpeg (not in Libav), but needs to be in the
+    format ``data://``. This is done to avoid ambiguity with filenames. You
+    can also prefix it with ``lavf://`` or ``ffmpeg://``.
+
 ``ytdl://...``
     By default, the youtube-dl hook script (enabled by default for mpv CLI)
     only looks at http URLs. Prefixing an URL with ``ytdl://`` forces it to

player/lua/ytdl_hook.lua

@@ -295,7 +295,7 @@ mp.add_hook("on_load", 10, function ()
 
             msg.debug("streamurl: " .. streamurl)
 
-            mp.set_property("stream-open-filename", streamurl)
+            mp.set_property("stream-open-filename", streamurl:gsub("^data:", "data://", 1))
 
             mp.set_property("file-local-options/force-media-title", json.title)
 

stream/stream_lavf.c

@@ -416,6 +416,7 @@ const stream_info_t stream_info_ffmpeg = {
   .protocols = (const char *const[]){
      "rtmp", "rtsp", "http", "https", "mms", "mmst", "mmsh", "mmshttp", "rtp",
      "httpproxy", "hls", "rtmpe", "rtmps", "rtmpt", "rtmpte", "rtmpts", "srtp",
+     "data",
      NULL },
   .can_write = true,
   .is_safe = true,