diff --git a/xorriso/xorriso.1 b/xorriso/xorriso.1
index 41a3b9bf..99b98a6d 100644
--- a/xorriso/xorriso.1
+++ b/xorriso/xorriso.1
@@ -2,7 +2,7 @@
 .\" First parameter, NAME, should be all caps
 .\" Second parameter, SECTION, should be 1-8, maybe w/ subsection
 .\" other parameters are allowed: see man(7), man(1)
-.TH XORRISO 1 "Apr 11, 2009"
+.TH XORRISO 1 "Apr 13, 2009"
 .\" Please adjust this date whenever revising the manpage.
 .\"
 .\" Some roff macros, for reference:
@@ -1808,7 +1808,11 @@ Parameters are:
 .br
  "block_size="32k|64k|128k size of compression blocks
 .br
- "default" same as "level=6:block_size=32k"
+ "by_magic=on" enables an expensive test at image generation time which checks
+files from disk whether they already are zisofs compressed, e.g. by program
+mkzftree.
+.br
+ "default" same as "level=6:block_size=32k:by_magic=off"
 .TP
 \fB\-speed\fR number[k|m|c|d|b]
 Set the burn speed. Default is 0 = maximum speed.
@@ -2692,7 +2696,7 @@ Personality "\fBmkisofs\fR" accepts the options listed with:
   -as mkisofs -help --
 .br
 Among them: -R (always on), -J, -o, -M, -C, -path-list, -m, -exclude-list,
--f, -print-size, -pad, -no-pad, -V, -v, -version, -graft-points,
+-f, -print-size, -pad, -no-pad, -V, -v, -version, -graft-points, -z,
 -no-emul-boot, -b, -c, -boot-info-table, -boot-load-size, -input-charset,
 -output-charset, pathspecs as with xorriso -add.
 A lot of options are not supported and lead to failure of the mkisofs
diff --git a/xorriso/xorriso.c b/xorriso/xorriso.c
index 0a2407ad..cd4e0bea 100644
--- a/xorriso/xorriso.c
+++ b/xorriso/xorriso.c
@@ -4124,6 +4124,7 @@ int Xorriso_new(struct XorrisO ** xorriso,char *progname, int flag)
  m->filter_list_closed= 0;
  m->zlib_level_default= m->zlib_level= 6;
  m->zisofs_block_size= m->zisofs_block_size_default= (1 << 15);
+ m->zisofs_by_magic= 0;
  m->do_overwrite= 2;
  m->do_reassure= 0;
  m->drive_blacklist= NULL;
@@ -9946,6 +9947,8 @@ int Xorriso_genisofs(struct XorrisO *xorriso, char *whom,
 "  -no-emul-boot               Boot image is 'no emulation' image",
 "  -boot-info-table            Patch boot image with info table",
 "  isolinux_mbr=on|auto|off    Control eventual isohybrid MBR generation",
+"  -z, -transparent-compression",
+"                              Enable transparent compression of files",
 "  -v, -verbose                Verbose",
 "  -version                    Print the current version",
 "@End_of_helptexT@"
@@ -10094,6 +10097,9 @@ int Xorriso_genisofs(struct XorrisO *xorriso, char *whom,
      Xorriso_option_acl(xorriso, "on", 0);
    } else if(strcmp(argv[i], "--xattr")==0) {
      Xorriso_option_xattr(xorriso, "on", 0);
+   } else if(strcmp(argv[i], "-z")==0 ||
+             strcmp(argv[i], "-transparent-compression")==0) {
+     Xorriso_option_zisofs(xorriso, "by_magic=on", 0);
    } else
      was_other_option= 1;
 
@@ -10302,6 +10308,9 @@ not_enough_args:;
      /* was already handled in first argument scan */;
    } else if(strcmp(argv[i], "--xattr")==0) {
      /* was already handled in first argument scan */;
+   } else if(strcmp(argv[i], "-z")==0 ||
+             strcmp(argv[i], "-transparent-compression")==0) {
+     /* was already handled in first argument scan */;
    } else if(argv[i][0]=='-' && argv[i][1]!=0) {
      sprintf(xorriso->info_text, "-as %s: Unknown option %s",
              whom, Text_shellsafe(argv[i], sfe, 0));
@@ -14321,7 +14330,7 @@ int Xorriso_option_help(struct XorrisO *xorriso, int flag)
 "compressed content is detected with a file in the ISO image.",
 "  -zisofs option[:options]",
 "                 Set global zisofs parameters:",
-"                   level=0|...|9 , block_size=32k|64k|128k",
+"                   level=0|...|9 , block_size=32k|64k|128k , by_magic=on|off",
 "",
 "Write-to-media options:",
 "  -rollback      Discard the manipulated ISO image and reload it.",
@@ -14464,13 +14473,14 @@ int Xorriso_option_help(struct XorrisO *xorriso, int flag)
 "",
 "Compatibility emulation (argument list may be ended by list delimiter --):",
 "  -as mkisofs  [-help|-version|-o|-R|-J|-V|-P|-f|-m|-exclude-list|-no-pad|",
-"                -M|-C|-graft-points|-path-list|pathspecs|",
+"                -M|-C|-graft-points|-path-list|pathspecs|-z|",
 "                -no-emul-boot|-b|-c|-boot-info-table|-boot-load-size]",
 "              Perform some mkisofs gestures, understand pathspecs as mkisofs",
 "              does. Commit happens outside emulation at usual occasions.",
-"  -as cdrecord [-help|-v|dev=|speed=|blank=|fs=|-eject|-atip|padsize=|path|-]",
+"  -as cdrecord [-help|-v|dev=|speed=|blank=|fs=|-eject|-atip|padsize=|-multi]",
+"               path|-",
 "              Perform some cdrecord gestures, eventually write at most one",
-"              data track to blank or overwriteable media.",
+"              data track to blank, appendable or overwriteable media.",
 "  -pacifier \"xorriso\"|\"cdrecord\"|\"mkisofs\"",
 "              Choose format of UPDATE pacifier during write operations.",
 "",
@@ -17094,9 +17104,16 @@ int Xorriso_option_zisofs(struct XorrisO *xorriso, char *mode, int flag)
      }
      xorriso->zisofs_block_size= num;
 
+   } else if(strncmp(cpt, "by_magic=", 8)==0) {
+     if(strncmp(cpt + 9, "on", l - 9) == 0)
+       xorriso->zisofs_by_magic= 1;
+     else
+       xorriso->zisofs_by_magic= 0;
+
    } else if(strncmp(cpt, "default", l)==0) {
      xorriso->zlib_level= xorriso->zlib_level_default;
      xorriso->zisofs_block_size= xorriso->zisofs_block_size_default;
+     xorriso->zisofs_by_magic= 0;
 
    } else {
 unknown_mode:;
diff --git a/xorriso/xorriso_private.h b/xorriso/xorriso_private.h
index edcd4978..39a270f8 100644
--- a/xorriso/xorriso_private.h
+++ b/xorriso/xorriso_private.h
@@ -134,6 +134,7 @@ struct XorrisO { /* the global context of xorriso */
  int zlib_level_default;
  int zisofs_block_size;
  int zisofs_block_size_default;
+ int zisofs_by_magic;
 
  int do_overwrite; /* 0=off, 1=on, 2=nondir */
  int do_reassure;  /* 0=off, 1=on, 2=tree */
diff --git a/xorriso/xorriso_timestamp.h b/xorriso/xorriso_timestamp.h
index f987b9f9..c3bc5c21 100644
--- a/xorriso/xorriso_timestamp.h
+++ b/xorriso/xorriso_timestamp.h
@@ -1 +1 @@
-#define Xorriso_timestamP "2009.04.11.172644"
+#define Xorriso_timestamP "2009.04.14.092306"
diff --git a/xorriso/xorrisoburn.c b/xorriso/xorrisoburn.c
index 25d43204..67a13f8e 100644
--- a/xorriso/xorrisoburn.c
+++ b/xorriso/xorrisoburn.c
@@ -1140,7 +1140,7 @@ int Xorriso_write_session(struct XorrisO *xorriso, int flag)
  struct burn_track **tracks;
  enum burn_disc_status s;
  IsoImage *image= NULL;
- IsoNode *node;
+ IsoNode *node, *root_node;
  ElToritoBootImage *bootimg;
  enum eltorito_boot_media_type emul_type= ELTORITO_NO_EMUL;
  int profile_number;
@@ -1403,11 +1403,36 @@ int Xorriso_write_session(struct XorrisO *xorriso, int flag)
  if(ret<0)
    {ret= 0; goto ex;}
 
+ if(xorriso->zisofs_by_magic) {
+   sprintf(xorriso->info_text,
+           "Checking disk file content for zisofs compression headers.");
+   Xorriso_msgs_submit(xorriso, 0, xorriso->info_text, 0, "UPDATE", 0);
+   root_node= (IsoNode *) iso_image_get_root(image);
+   ret= iso_node_zf_by_magic(root_node,
+             (xorriso->out_drive_handle == xorriso->in_drive_handle) | 2 | 16);
+   if(ret<0) {
+     Xorriso_report_iso_error(xorriso, "", ret,
+              "Error when examining file content for zisofs headers",
+              0, "FAILURE", 1);
+   }
+   ret= Xorriso_eval_problem_status(xorriso, 1, 0);
+   if(ret<0)
+     {ret= 0; goto ex;}
+   sprintf(xorriso->info_text,
+           "Check for zisofs compression headers done.");
+   Xorriso_msgs_submit(xorriso, 0, xorriso->info_text, 0, "UPDATE", 0);
+ }
+
  /* >>> omit iso_image_update_sizes if the image was filled up very quickly */;
 
  ret= iso_image_update_sizes(image);
  if(ret < 0) {
    Xorriso_process_msg_queues(xorriso, 0);
+   if(ret<0) {
+     Xorriso_report_iso_error(xorriso, "", ret,
+              "Error when updating file sizes",
+              0, "FAILURE", 1);
+   }
    ret= Xorriso_eval_problem_status(xorriso, 1, 0);
    if(ret<0)
      {ret= 0; goto ex;}
@@ -10364,6 +10389,7 @@ int Xorriso_set_zisofs_params(struct XorrisO *xorriso, int flag)
 int Xorriso_status_zisofs(struct XorrisO *xorriso, char *filter, FILE *fp,
                           int flag)
 /*
+ bit0= do only report non-default settings
  bit1= do only report to fp
 */ 
 {
@@ -10372,12 +10398,16 @@ int Xorriso_status_zisofs(struct XorrisO *xorriso, char *filter, FILE *fp,
  iso_zisofs_get_refcounts(&ziso_count, &osiz_count, 0);
  if((flag & 1) && xorriso->zlib_level == xorriso->zlib_level_default &&
     xorriso->zisofs_block_size == xorriso->zisofs_block_size_default &&
-    ziso_count == 0 && osiz_count == 0)
+    xorriso->zisofs_by_magic == 0 &&
+    ziso_count == 0 && osiz_count == 0 &&
+    filter[0] == 0)
    return 2;
  sprintf(xorriso->result_line,
-         "-zisofs level=%d:block_size=%dk:ziso_used=%.f:osiz_used=%.f\n",
-         xorriso->zlib_level, xorriso->zisofs_block_size / 1024,
-         (double) ziso_count, (double) osiz_count);
+   "-zisofs level=%d:block_size=%dk:by_magic=%s:ziso_used=%.f:osiz_used=%.f\n",
+   xorriso->zlib_level, xorriso->zisofs_block_size / 1024,
+   xorriso->zisofs_by_magic ? "on" : "off",
+   (double) ziso_count, (double) osiz_count);
+
  Xorriso_status_result(xorriso, filter, fp, flag&2);
  return(1);
 }