diff --git a/validate/gst/validate/Makefile.am b/validate/gst/validate/Makefile.am
index cb49af17a9..269d626e3b 100644
--- a/validate/gst/validate/Makefile.am
+++ b/validate/gst/validate/Makefile.am
@@ -9,6 +9,7 @@ libgstvalidate_@GST_API_VERSION@_la_SOURCES = \
 	gst-validate-report.c \
 	gst-validate-scenario.c \
 	gst-validate-override.c \
+	gst-validate-utils.c \
 	gst-validate-override-registry.c \
 	gst-validate-media-info.c \
         validate.c
@@ -28,6 +29,7 @@ noinst_HEADERS = \
 	gst-validate-report.h \
 	gst-validate-runner.h \
 	gst-validate-scenario.h \
+	gst-validate-utils.h \
 	gst-validate-media-info.h
 
 lib_LTLIBRARIES = \
diff --git a/validate/gst/validate/gst-validate-scenario.c b/validate/gst/validate/gst-validate-scenario.c
index 51279d3542..d556f2847c 100644
--- a/validate/gst/validate/gst-validate-scenario.c
+++ b/validate/gst/validate/gst-validate-scenario.c
@@ -33,6 +33,7 @@
 #include "gst-validate-scenario.h"
 #include "gst-validate-reporter.h"
 #include "gst-validate-report.h"
+#include "gst-validate-utils.h"
 
 #define GST_VALIDATE_SCENARIO_GET_PRIVATE(o) \
   (G_TYPE_INSTANCE_GET_PRIVATE ((o), GST_TYPE_VALIDATE_SCENARIO, GstValidateScenarioPrivate))
@@ -81,7 +82,6 @@ struct _GstValidateScenarioPrivate
 };
 
 
-/* Some helper method that are missing iin Json itscenario */
 static guint
 get_flags_from_string (GType type, const gchar * str_flags)
 {
@@ -124,11 +124,43 @@ _free_scenario_action (GstValidateAction * act)
   g_slice_free (GstValidateAction, act);
 }
 
+static gboolean
+_set_variable_func (const gchar *name, double *value, gpointer user_data)
+{
+  GstValidateScenario *scenario = GST_VALIDATE_SCENARIO (user_data);
+
+  if (!g_strcmp0 (name, "duration")) {
+    gint64 duration;
+
+    if (!gst_element_query_duration (scenario->priv->pipeline,
+        GST_FORMAT_TIME, &duration)) {
+      GST_WARNING_OBJECT (scenario, "Could not query duration");
+      return FALSE;
+    }
+    *value = duration / GST_SECOND;
+
+    return TRUE;
+  } else if (!g_strcmp0 (name, "position")) {
+    gint64 position;
+
+    if (!gst_element_query_position (scenario->priv->pipeline,
+        GST_FORMAT_TIME, &position)) {
+      GST_WARNING_OBJECT (scenario, "Could not query position");
+      return FALSE;
+    }
+    *value = ((double) position / GST_SECOND);
+
+    return TRUE;
+  }
+
+  return FALSE;
+}
+
 static gboolean
 _execute_seek (GstValidateScenario * scenario, GstValidateAction * action)
 {
   GstValidateScenarioPrivate *priv = scenario->priv;
-  const char *str_format, *str_flags, *str_start_type, *str_stop_type;
+  const char *str_format, *str_flags, *str_start_type, *str_stop_type, *str_start;
   gboolean ret = TRUE;
 
   gdouble rate = 1.0, dstart, dstop;
@@ -141,9 +173,16 @@ _execute_seek (GstValidateScenario * scenario, GstValidateAction * action)
   GstEvent *seek;
 
   if (!gst_structure_get_double (action->structure, "start", &dstart)) {
-    GST_WARNING_OBJECT (scenario, "Could not find start for a seek, FAILED");
-    return FALSE;
+    gchar *error = NULL;
+
+    if (!(str_start = gst_structure_get_string(action->structure, "start"))) {
+      GST_WARNING_OBJECT (scenario, "Could not find start for a seek, FAILED");
+      return FALSE;
+    }
+    dstart = parse_expression (str_start, _set_variable_func,
+        scenario, &error);
   }
+
   if (dstart == -1.0)
     start = GST_CLOCK_TIME_NONE;
   else
diff --git a/validate/gst/validate/gst-validate-utils.c b/validate/gst/validate/gst-validate-utils.c
new file mode 100644
index 0000000000..d25cd6b07c
--- /dev/null
+++ b/validate/gst/validate/gst-validate-utils.c
@@ -0,0 +1,467 @@
+/* GStreamer
+ *
+ * Copyright (C) 2013 Thibault Saunier <thibault.saunier@collabora.com>
+ *
+ * gst-validate-utils.c - Some utility functions
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#include<math.h>
+#include<ctype.h>
+#include<stdio.h>
+#include<string.h>
+#include<stdlib.h>
+
+#include "gst-validate-utils.h"
+
+#define PARSER_BOOLEAN_EQUALITY_THRESHOLD (1e-10)
+#define PARSER_MAX_TOKEN_SIZE 256
+#define PARSER_MAX_ARGUMENT_COUNT 10
+
+typedef struct
+{
+  const gchar *str;
+  gint len;
+  gint pos;
+  jmp_buf err_jmp_buf;
+  const gchar *error;
+  void *user_data;
+  ParseVariableFunc variable_func;
+} MathParser;
+
+static gdouble _read_power (MathParser * parser);
+
+static void
+_error (MathParser * parser, const gchar * err)
+{
+  parser->error = err;
+  longjmp (parser->err_jmp_buf, 1);
+}
+
+static gchar
+_peek (MathParser * parser)
+{
+  if (parser->pos < parser->len)
+    return parser->str[parser->pos];
+  _error (parser, "Tried to read past end of string!");
+  return '\0';
+}
+
+static gchar
+_peek_n (MathParser * parser, gint n)
+{
+  if (parser->pos + n < parser->len)
+    return parser->str[parser->pos + n];
+  _error (parser, "Tried to read past end of string!");
+  return '\0';
+}
+
+static gchar
+_next (MathParser * parser)
+{
+  if (parser->pos < parser->len)
+    return parser->str[parser->pos++];
+  _error (parser, "Tried to read past end of string!");
+  return '\0';
+}
+
+static gdouble
+_read_double (MathParser * parser)
+{
+  gchar c, token[PARSER_MAX_TOKEN_SIZE];
+  gint pos = 0;
+  gdouble val = 0.0;
+
+  c = _peek (parser);
+  if (c == '+' || c == '-')
+    token[pos++] = _next (parser);
+
+  while (isdigit (_peek (parser)))
+    token[pos++] = _next (parser);
+
+  c = _peek (parser);
+  if (c == '.')
+    token[pos++] = _next (parser);
+
+  while (isdigit (_peek (parser)))
+    token[pos++] = _next (parser);
+
+  c = _peek (parser);
+  if (c == 'e' || c == 'E') {
+    token[pos++] = _next (parser);
+
+    c = _peek (parser);
+    if (c == '+' || c == '-') {
+      token[pos++] = _next (parser);
+    }
+  }
+
+  while (isdigit (_peek (parser)))
+    token[pos++] = _next (parser);
+
+  token[pos] = '\0';
+
+  if (pos == 0 || sscanf (token, "%lf", &val) != 1)
+    _error (parser, "Failed to read real number");
+
+  return val;
+}
+
+static gdouble
+_read_term (MathParser * parser)
+{
+  gdouble v0;
+  gchar c;
+
+  v0 = _read_power (parser);
+  c = _peek (parser);
+
+  while (c == '*' || c == '/') {
+    _next (parser);
+    if (c == '*') {
+      v0 *= _read_power (parser);
+    } else if (c == '/') {
+      v0 /= _read_power (parser);
+    }
+    c = _peek (parser);
+  }
+  return v0;
+}
+
+static gdouble
+_read_expr (MathParser * parser)
+{
+  gdouble v0 = 0.0;
+  gchar c;
+
+  c = _peek (parser);
+  if (c == '+' || c == '-') {
+    _next (parser);
+    if (c == '+')
+      v0 += _read_term (parser);
+    else if (c == '-')
+      v0 -= _read_term (parser);
+  } else {
+    v0 = _read_term (parser);
+  }
+
+  c = _peek (parser);
+  while (c == '+' || c == '-') {
+    _next (parser);
+    if (c == '+') {
+      v0 += _read_term (parser);
+    } else if (c == '-') {
+      v0 -= _read_term (parser);
+    }
+
+    c = _peek (parser);
+  }
+
+  return v0;
+}
+
+static gdouble
+_read_boolean_comparison (MathParser * parser)
+{
+  gchar c, oper[] = { '\0', '\0', '\0' };
+  gdouble v0, v1;
+
+
+  v0 = _read_expr (parser);
+  c = _peek (parser);
+  if (c == '>' || c == '<') {
+    oper[0] = _next (parser);
+    c = _peek (parser);
+    if (c == '=')
+      oper[1] = _next (parser);
+
+
+    v1 = _read_expr (parser);
+
+    if (g_strcmp0 (oper, "<") == 0) {
+      v0 = (v0 < v1) ? 1.0 : 0.0;
+    } else if (g_strcmp0 (oper, ">") == 0) {
+      v0 = (v0 > v1) ? 1.0 : 0.0;
+    } else if (g_strcmp0 (oper, "<=") == 0) {
+      v0 = (v0 <= v1) ? 1.0 : 0.0;
+    } else if (g_strcmp0 (oper, ">=") == 0) {
+      v0 = (v0 >= v1) ? 1.0 : 0.0;
+    } else {
+      _error (parser, "Unknown operation!");
+    }
+  }
+  return v0;
+}
+
+static gdouble
+_read_boolean_equality (MathParser * parser)
+{
+  gchar c, oper[] = { '\0', '\0', '\0' };
+  gdouble v0, v1;
+
+  v0 = _read_boolean_comparison (parser);
+  c = _peek (parser);
+  if (c == '=' || c == '!') {
+    if (c == '!') {
+      if (_peek_n (parser, 1) == '=') {
+        oper[0] = _next (parser);
+        oper[1] = _next (parser);
+      } else {
+        return v0;
+      }
+    } else {
+      oper[0] = _next (parser);
+      c = _peek (parser);
+      if (c != '=')
+        _error (parser, "Expected a '=' for boolean '==' operator!");
+      oper[1] = _next (parser);
+    }
+    v1 = _read_boolean_comparison (parser);
+    if (g_strcmp0 (oper, "==") == 0) {
+      v0 = (fabs (v0 - v1) < PARSER_BOOLEAN_EQUALITY_THRESHOLD) ? 1.0 : 0.0;
+    } else if (g_strcmp0 (oper, "!=") == 0) {
+      v0 = (fabs (v0 - v1) > PARSER_BOOLEAN_EQUALITY_THRESHOLD) ? 1.0 : 0.0;
+    } else {
+      _error (parser, "Unknown operation!");
+    }
+  }
+  return v0;
+}
+
+static gdouble
+_read_boolean_and (MathParser * parser)
+{
+  gchar c;
+  gdouble v0, v1;
+
+  v0 = _read_boolean_equality (parser);
+
+  c = _peek (parser);
+  while (c == '&') {
+    _next (parser);
+
+    c = _peek (parser);
+    if (c != '&')
+      _error (parser, "Expected '&' to follow '&' in logical and operation!");
+    _next (parser);
+
+    v1 = _read_boolean_equality (parser);
+    v0 = (fabs (v0) >= PARSER_BOOLEAN_EQUALITY_THRESHOLD
+        && fabs (v1) >= PARSER_BOOLEAN_EQUALITY_THRESHOLD) ? 1.0 : 0.0;
+
+    c = _peek (parser);
+  }
+
+  return v0;
+}
+
+static gdouble
+_read_boolean_or (MathParser * parser)
+{
+  gchar c;
+  gdouble v0, v1;
+
+  v0 = _read_boolean_and (parser);
+
+  c = _peek (parser);
+  while (c == '|') {
+    _next (parser);
+    c = _peek (parser);
+    if (c != '|')
+      _error (parser, "Expected '|' to follow '|' in logical or operation!");
+    _next (parser);
+    v1 = _read_boolean_and (parser);
+    v0 = (fabs (v0) >= PARSER_BOOLEAN_EQUALITY_THRESHOLD
+        || fabs (v1) >= PARSER_BOOLEAN_EQUALITY_THRESHOLD) ? 1.0 : 0.0;
+    c = _peek (parser);
+  }
+
+  return v0;
+}
+
+static gboolean
+_init (MathParser * parser, const gchar * str,
+    ParseVariableFunc variable_func, void *user_data)
+{
+  parser->str = str;
+  parser->len = strlen (str) + 1;
+  parser->pos = 0;
+  parser->error = NULL;
+  parser->user_data = user_data;
+  parser->variable_func = variable_func;
+
+  return TRUE;
+}
+
+static gdouble
+_parse (MathParser * parser)
+{
+  gdouble result = 0.0;
+
+  if (!setjmp (parser->err_jmp_buf)) {
+    result = _read_expr (parser);
+    if (parser->pos < parser->len - 1) {
+      _error (parser,
+          "Failed to reach end of input expression, likely malformed input");
+    } else
+      return result;
+  } else {
+    return sqrt (-1.0);
+  }
+  return sqrt (-1.0);
+}
+
+static gdouble
+_read_argument (MathParser * parser)
+{
+  gchar c;
+  gdouble val;
+
+  val = _read_expr (parser);
+  c = _peek (parser);
+  if (c == ',')
+    _next (parser);
+
+  return val;
+}
+
+static gdouble
+_read_builtin (MathParser * parser)
+{
+  gdouble v0 = 0.0, v1 = 0.0;
+  gchar c, token[PARSER_MAX_TOKEN_SIZE];
+  gint pos = 0;
+
+  c = _peek (parser);
+  if (isalpha (c) || c == '_') {
+    while (isalpha (c) || isdigit (c) || c == '_') {
+      token[pos++] = _next (parser);
+      c = _peek (parser);
+    }
+    token[pos] = '\0';
+
+    if (_peek (parser) == '(') {
+      _next (parser);
+      if (g_strcmp0 (token, "min") == 0) {
+        v0 = _read_argument (parser);
+        v1 = _read_argument (parser);
+        v0 = MIN (v0, v1);
+      } else if (g_strcmp0 (token, "max") == 0) {
+        v0 = _read_argument (parser);
+        v1 = _read_argument (parser);
+        v0 = MAX (v0, v1);
+      } else {
+        _error (parser, "Tried to call unknown built-in function!");
+      }
+
+      if (_next (parser) != ')')
+        _error (parser, "Expected ')' in built-in call!");
+    } else {
+      if (parser->variable_func != NULL
+          && parser->variable_func (token, &v1, parser->user_data)) {
+        v0 = v1;
+      } else {
+        _error (parser, "Could not look up value for variable %s!");
+      }
+    }
+  } else {
+    v0 = _read_double (parser);
+  }
+
+  return v0;
+}
+
+static gdouble
+_read_parenthesis (MathParser * parser)
+{
+  gdouble val;
+
+  if (_peek (parser) == '(') {
+    _next (parser);
+    val = _read_boolean_or (parser);
+    if (_peek (parser) != ')')
+      _error (parser, "Expected ')'!");
+    _next (parser);
+  } else {
+    val = _read_builtin (parser);
+  }
+
+  return val;
+}
+
+static gdouble
+_read_unary (MathParser * parser)
+{
+  gchar c;
+  gdouble v0;
+  c = _peek (parser);
+  if (c == '!') {
+    _error (parser, "Expected '+' or '-' for unary expression, got '!'");
+  } else if (c == '-') {
+    _next (parser);
+    v0 = -_read_parenthesis (parser);
+  } else if (c == '+') {
+    _next (parser);
+    v0 = _read_parenthesis (parser);
+  } else {
+    v0 = _read_parenthesis (parser);
+  }
+  return v0;
+}
+
+static gdouble
+_read_power (MathParser * parser)
+{
+  gdouble v0, v1 = 1.0, s = 1.0;
+
+  v0 = _read_unary (parser);
+
+  while (_peek (parser) == '^') {
+    _next (parser);
+    if (_peek (parser) == '-') {
+      _next (parser);
+      s = -1.0;
+    }
+    v1 = s * _read_power (parser);
+    v0 = pow (v0, v1);
+  }
+
+  return v0;
+}
+
+gdouble
+parse_expression (const gchar * expr, ParseVariableFunc variable_func,
+    gpointer user_data, gchar ** error)
+{
+  gdouble val;
+  MathParser parser;
+  gchar **spl = g_strsplit (expr, " ", -1);
+  gchar *expr_nospace = g_strjoinv ("", spl);
+
+  _init (&parser, expr_nospace, variable_func, user_data);
+  val = _parse (&parser);
+  g_strfreev (spl);
+  g_free (expr_nospace);
+
+  if (error) {
+    if (parser.error)
+      *error = g_strdup (parser.error);
+    else
+      *error = NULL;
+  }
+  return val;
+}
diff --git a/validate/gst/validate/gst-validate-utils.h b/validate/gst/validate/gst-validate-utils.h
new file mode 100644
index 0000000000..510a211108
--- /dev/null
+++ b/validate/gst/validate/gst-validate-utils.h
@@ -0,0 +1,37 @@
+/* GStreamer
+ *
+ * Copyright (C) 2013 Thibault Saunier <thibault.saunier@collabora.com>
+ *
+ * gst-validate-utils.h - Some utility functions
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#ifndef EXPRESSION_PARSER_H
+#define EXPRESSION_PARSER_H
+
+#include<setjmp.h>
+#include<stdlib.h>
+#include<glib.h>
+
+typedef int (*ParseVariableFunc) (const gchar *name,
+    double *value, gpointer user_data);
+
+gdouble parse_expression (const gchar *expr,
+                          ParseVariableFunc variable_func,
+                          gpointer user_data,
+                          gchar **error);
+#endif