diff --git a/doc/general.texi b/doc/general.texi
index 5f27bac5e5..9db065fb44 100644
--- a/doc/general.texi
+++ b/doc/general.texi
@@ -218,7 +218,7 @@ following image formats are supported:
     @tab fourcc: CLJR
 @item Creative YUV           @tab     @tab  X
     @tab fourcc: CYUV
-@item Dirac                  @tab  X  @tab  X
+@item Dirac                  @tab  E  @tab  E
     @tab supported through external libdirac/libschroedinger libraries
 @item Duck TrueMotion v1     @tab     @tab  X
     @tab fourcc: DUCK
@@ -241,7 +241,7 @@ following image formats are supported:
 @item H.261                  @tab  X  @tab  X
 @item H.263(+)               @tab  X  @tab  X
     @tab also known as RealVideo 1.0
-@item H.264                  @tab     @tab  X
+@item H.264                  @tab  E  @tab  X
     @tab encoding supported through external library libx264
 @item HuffYUV                @tab  X  @tab  X
 @item IBM Ultimotion         @tab     @tab  X
@@ -304,7 +304,7 @@ following image formats are supported:
     @tab fourcc: SP5X
 @item TechSmith Camtasia     @tab     @tab  X
     @tab fourcc: TSCC
-@item Theora                 @tab  X  @tab  X
+@item Theora                 @tab  E  @tab  X
     @tab encoding supported through external library libtheora
 @item THP                    @tab     @tab  X
     @tab Used on the Nintendo GameCube.
@@ -331,18 +331,20 @@ following image formats are supported:
 
 @code{X} means that encoding (resp. decoding) is supported.
 
+@code{E} means that support is provided through an external library.
+
 @section Audio Codecs
 
 @multitable @columnfractions .4 .1 .1 .1 .7
 @item Name @tab Encoding @tab Decoding @tab Comments
 @item 4X IMA ADPCM           @tab     @tab  X
 @item 8SVX audio             @tab     @tab  X
-@item AAC                    @tab  X  @tab  X
+@item AAC                    @tab  E  @tab  X
     @tab encoding supported through external library libfaac
 @item AC-3                   @tab IX  @tab IX
-@item AMR-NB                 @tab  X  @tab  X
+@item AMR-NB                 @tab  E  @tab  E
     @tab supported through external library libamrnb
-@item AMR-WB                 @tab  X  @tab  X
+@item AMR-WB                 @tab  E  @tab  E
     @tab supported through external library libamrwb
 @item AMV IMA ADPCM          @tab     @tab  X
     @tab Used in AMV files
@@ -370,9 +372,9 @@ following image formats are supported:
 @item Enhanced AC-3          @tab     @tab  X
 @item FLAC lossless audio    @tab IX  @tab  X
 @item G.726  ADPCM           @tab  X  @tab  X
-@item GSM                    @tab  X  @tab  X
+@item GSM                    @tab  E  @tab  E
     @tab supported through external library libgsm
-@item GSM_MS                 @tab  X  @tab  X
+@item GSM_MS                 @tab  E  @tab  E
     @tab supported through external library libgsm
 @item id RoQ DPCM            @tab  X  @tab  X
     @tab Used in Quake III, Jedi Knight 2, other computer games.
@@ -386,7 +388,7 @@ following image formats are supported:
     @tab Used in DVD-Audio and Blu-Ray discs.
 @item Monkey's Audio         @tab     @tab  X
     @tab Only versions 3.97-3.99 are supported.
-@item MPEG audio layer 1/3   @tab  X  @tab IX
+@item MPEG audio layer 1/3   @tab  E  @tab IX
     @tab MP3 encoding supported through external library LAME
 @item MPEG audio layer 2     @tab IX  @tab IX
 @item MS IMA ADPCM           @tab  X  @tab  X
@@ -414,7 +416,7 @@ following image formats are supported:
     @tab experimental codec
 @item Sonic lossless         @tab  X  @tab  X
     @tab experimental codec
-@item Speex                  @tab     @tab  X
+@item Speex                  @tab     @tab  E
     @tab supported through external library libspeex
 @item THP ADPCM              @tab     @tab  X
     @tab Used on the Nintendo GameCube.
@@ -430,6 +432,8 @@ following image formats are supported:
 
 @code{X} means that encoding (resp. decoding) is supported.
 
+@code{E} means that support is provided through an external library.
+
 @code{I} means that an integer-only version is available, too (ensures high
 performance on systems without hardware floating point support).