Allow setting the environment variable FFMPEG_DATADIR to locate preset files.

Patch by Robert Krüger <krueger signal7 de>.

Originally committed as revision 22923 to svn://svn.ffmpeg.org/ffmpeg/trunk

doc/ffmpeg-doc.texi

@@ -806,9 +806,9 @@ preset options identifies the preset file to use according to the
 following rules:
 
 First ffmpeg searches for a file named @var{arg}.ffpreset in the
-directories @file{$HOME/.ffmpeg}, and in the datadir defined at
-configuration time (usually @file{PREFIX/share/ffmpeg}) in that
-order. For example, if the argument is @code{libx264-max}, it will
+directories @file{$FFMPEG_DATADIR} (if set), and @file{$HOME/.ffmpeg}, and in
+the datadir defined at configuration time (usually @file{PREFIX/share/ffmpeg})
+in that order. For example, if the argument is @code{libx264-max}, it will
 search for the file @file{libx264-max.ffpreset}.
 
 If no such file is found, then ffmpeg will search for a file named

ffmpeg.c

@@ -3890,19 +3890,22 @@ static int opt_preset(const char *opt, const char *arg)
     FILE *f=NULL;
     char filename[1000], tmp[1000], tmp2[1000], line[1000];
     int i;
-    const char *base[2]= { getenv("HOME"),
+    const char *base[3]= { getenv("FFMPEG_DATADIR"),
+                           getenv("HOME"),
                            FFMPEG_DATADIR,
                          };
 
     if (*opt != 'f') {
-        for(i=!base[0]; i<2 && !f; i++){
-            snprintf(filename, sizeof(filename), "%s%s/%s.ffpreset", base[i], i ? "" : "/.ffmpeg", arg);
+        for(i=0; i<3 && !f; i++){
+            if(!base[i])
+                continue;
+            snprintf(filename, sizeof(filename), "%s%s/%s.ffpreset", base[i], i != 1 ? "" : "/.ffmpeg", arg);
             f= fopen(filename, "r");
             if(!f){
                 char *codec_name= *opt == 'v' ? video_codec_name :
                                   *opt == 'a' ? audio_codec_name :
                                                 subtitle_codec_name;
-                snprintf(filename, sizeof(filename), "%s%s/%s-%s.ffpreset", base[i],  i ? "" : "/.ffmpeg", codec_name, arg);
+                snprintf(filename, sizeof(filename), "%s%s/%s-%s.ffpreset", base[i],  i != 1 ? "" : "/.ffmpeg", codec_name, arg);
                 f= fopen(filename, "r");
             }
         }