1 files changed, 25 insertions, 9 deletions
diff --git a/DOCS/tech-overview.txt b/DOCS/tech-overview.txt
index 9582caaea4..e242df1325 100644
--- a/DOCS/tech-overview.txt
+++ b/DOCS/tech-overview.txt
@@ -186,15 +186,31 @@ audio/out/:
     why buggy audio drivers can have a bad influence on playback quality.
 
 sub/:
-    A big mess. Contains subtitle rendering (parts of it), OSD rendering,
-    subtitle loading.
-
-    There are about 3 types of subtitles: image subs, ASS subs, text subs. Also,
-    there are 3 rendering methods: image subs, libass, internal subtitle
-    renderer. Also, subtitles can come from demuxers or external files. All the
-    possible combinations create weird special cases, e.g. taking a text
-    subtitle event from the demuxer and converting it to ass for display is
-    different from loading a text subtitle and converting it to ass.
+    Contains subtitle and OSD rendering.
+
+    sub.c/.h is actually the OSD code. It queries dec_sub.c to retrieve
+    decoded/rendered subtitles. osd_libass.c is the actual implementation of
+    the OSD text renderer (which uses libass, and takes care of all the tricky
+    fontconfig/freetype API usage and text layouting).
+
+    Subtitle loading is now in demux/ instead. demux_libass.c wraps loading
+    .ass subtitles via libass. demux_lavf.c loads most subtitle types via
+    FFmpeg. demux_subreader.c is the old MPlayer code. It's used as last
+    fallback, or to handle some text subtitle types on Libav. (It also can
+    load UTF-16 encoded subtitles without requiring the use of -subcp.)
+    demux_subreader.c should eventually go away (maybe).
+
+    The subtitles are passed to dec_sub.c and the subtitle decoders in sd_*.c
+    as they are demuxed. All text subtitles are rendered by sd_ass.c. If text
+    subtitles are not in the ASS format, subtitle converters are inserted, for
+    example sd_srt.c, which is used to convert SRT->ASS. sd_srt.c is also used
+    as general converter for text->ASS (to prevent interpretation of text as
+    ASS tags).
+
+    Text subtitles can be preloaded, in which case they are read fully as soon
+    as the subtitle is selected, and then effectively stored in an ASS_Track.
+    It's used for external text subtitles, and required to make codepage
+    detection as well as timing postprocessing work.
 
 core/timeline/:
     A timeline is the abstraction used by mplayer.c to combine several files