Index: libvo/vo_jpeg.c
===================================================================
--- libvo/vo_jpeg.c (revision 43149)
+++ libvo/vo_jpeg.c (working copy)
@@ -78,6 +78,7 @@
 int jpeg_dpi = 72; /** Screen resolution = 72 dpi */
 char *jpeg_outdir = NULL;
 char *jpeg_subdirs = NULL;
+char *jpeg_prefix = NULL;
 int jpeg_maxfiles = 1000;

 static int framenum = 0;
@@ -259,8 +260,8 @@
     framenum++;

     /* snprintf the full pathname of the outputfile */
-    snprintf(buf, BUFLENGTH, "%s/%s/%08d.jpg", jpeg_outdir, subdirname,
-                                                                    framenum);
+    snprintf(buf, BUFLENGTH, "%s/%s/%s%08d.jpg", jpeg_outdir, subdirname,
+                                                        jpeg_prefix, framenum);

     framecounter++;

@@ -344,6 +345,7 @@
         {"dpi",         OPT_ARG_INT,    &jpeg_dpi,              NULL, 0},
         {"outdir",      OPT_ARG_MSTRZ,  &jpeg_outdir,           NULL, 0},
         {"subdirs",     OPT_ARG_MSTRZ,  &jpeg_subdirs,          NULL, 0},
+        {"prefix",      OPT_ARG_MSTRZ,  &jpeg_prefix,           NULL, 0},
         {"maxfiles",    OPT_ARG_INT,    &jpeg_maxfiles, (opt_test_f)int_pos, 0},
         {NULL, 0, NULL, NULL, 0}
     };
@@ -360,6 +362,7 @@
     jpeg_maxfiles = 1000;
     jpeg_outdir = strdup(".");
     jpeg_subdirs = NULL;
+    jpeg_prefix = strdup(""); /* default to no prefix */

     if (subopt_parse(arg, subopts) != 0) {
         return -1;
@@ -389,6 +392,10 @@
         mp_msg(MSGT_VO, MSGL_V, "%s: maxfiles --> %d\n", info.short_name,
                                                                 jpeg_maxfiles);
     }
+    if (jpeg_prefix) {
+        mp_msg(MSGT_VO, MSGL_V, "%s: prefix --> %s\n", info.short_name,
+                                                                jpeg_prefix);
+    }

     mp_msg(MSGT_VO, MSGL_INFO, "%s: %s\n", info.short_name,
                                             MSGTR_VO_SuboptionsParsedOK);