Add a note about ffmpeg

INSTALL

@@ -25,7 +25,7 @@ Libraries:
  - libantlr3c (ANTLR3 C runtime, version 3.2 for tarball builds)
  - Avahi client libraries, 0.6.24 minimum
  - sqlite3 3.5.0+ with update notify API enabled
- - ffmpeg
+ - ffmpeg 0.5+
  - confuse
  - libevent 1.4+
  - libavl
@@ -46,6 +46,19 @@ always the case, so you may need to rebuild sqlite3 to enable the update
 notify API. See the sqlite3 doc and look for SQLITE_ENABLE_UPDATE_NOTIFY.
 
 
+Note about ffmpeg
+-----------------
+
+ffmpeg is a central piece of forked-daapd and most other FLOSS multimedia
+applications. The version of ffmpeg you use will potentially have a great
+influence on your experience with forked-daapd.
+
+The following versions of ffmpeg are supported and known to work:
+ - ffmpeg 0.5.x: has issues with metadata (tags) extraction, notably with
+   MP3 files and ID3 tags in general;
+ - ffmpeg 0.6.x: known to work better with regard to metadata extraction
+
+
 Building from the git tree
 --------------------------