diff --git a/src/file_dv.c b/src/file_dv.c
index 24bc27b8..1a356719 100644
--- a/src/file_dv.c
+++ b/src/file_dv.c
@@ -34,7 +34,7 @@
 #include "__fc_builtin.h"
 #endif
 
-/*@ requires \valid(file_stat); */
+/*@ requires valid_register_header_check(file_stat); */
 static void register_header_check_dv(file_stat_t *file_stat);
 
 const file_hint_t file_hint_dv= {
@@ -47,14 +47,9 @@ const file_hint_t file_hint_dv= {
 };
 
 /*@
-  @ requires buffer_size > 0;
-  @ requires (buffer_size&1)==0;
-  @ requires \valid_read(buffer+(0..buffer_size-1));
-  @ requires \valid(file_recovery);
   @ requires file_recovery->data_check==&data_check_NTSC;
-  @ requires file_recovery->calculated_file_size <= PHOTOREC_MAX_FILE_SIZE;
-  @ requires \separated(buffer, file_recovery);
-  @ ensures \result == DC_CONTINUE || \result == DC_STOP;
+  @ requires valid_data_check_param(buffer, buffer_size, file_recovery);
+  @ ensures  valid_data_check_result(\result, file_recovery);
   @ assigns file_recovery->calculated_file_size;
   @*/
 static data_check_t data_check_NTSC(const unsigned char *buffer, const unsigned int buffer_size, file_recovery_t *file_recovery)
@@ -77,22 +72,20 @@ static data_check_t data_check_NTSC(const unsigned char *buffer, const unsigned
 }
 
 /*@
-  @ requires \valid(fr);
   @ requires fr->file_check == &file_check_dv_NTSC;
-  @ requires valid_file_recovery(fr);
-  @ ensures  valid_file_recovery(fr);
+  @ requires valid_file_check_param(fr);
+  @ ensures  valid_file_check_result(fr);
   @ assigns *fr->handle, errno, Frama_C_entropy_source, fr->file_size;
   @*/
 static void file_check_dv_NTSC(file_recovery_t *fr)
 {
-  unsigned char buffer_header[512];
-  unsigned char buffer[120000];
+  char buffer_header[512];
   uint64_t fs=fr->file_size/120000*120000;
   if(my_fseek(fr->handle, 0, SEEK_SET) < 0 ||
       fread(&buffer_header, sizeof(buffer_header), 1, fr->handle) != 1)
     return ;
 #if defined(__FRAMAC__)
-  Frama_C_make_unknown((char *)&buffer_header, sizeof(buffer_header));
+  Frama_C_make_unknown(&buffer_header, sizeof(buffer_header));
 #endif
   if(fs > 0)
     fs-=120000;
@@ -100,12 +93,17 @@ static void file_check_dv_NTSC(file_recovery_t *fr)
     fs-=120000;
   /*@ loop assigns fs, *fr->handle, errno, Frama_C_entropy_source, fr->file_size; */
   while(fs < fr->file_size &&
-      my_fseek(fr->handle, fs, SEEK_SET) >= 0 &&
-      fread(&buffer, sizeof(buffer), 1, fr->handle) == 1)
+      my_fseek(fr->handle, fs, SEEK_SET) >= 0)
   {
+    char buffer[120000];
     unsigned int i;
+    if(fread(&buffer, sizeof(buffer), 1, fr->handle) != 1)
+    {
+      fr->file_size=fs;
+      return;
+    }
 #if defined(__FRAMAC__)
-    Frama_C_make_unknown((char *)&buffer, sizeof(buffer));
+    Frama_C_make_unknown(&buffer, sizeof(buffer));
 #endif
     /*@ loop assigns i, fr->file_size; */
     for(i=1; i<sizeof(buffer); i+=0x50)
@@ -120,14 +118,9 @@ static void file_check_dv_NTSC(file_recovery_t *fr)
 }
 
 /*@
-  @ requires buffer_size > 0;
-  @ requires (buffer_size&1)==0;
-  @ requires \valid_read(buffer+(0..buffer_size-1));
-  @ requires \valid(file_recovery);
   @ requires file_recovery->data_check==&data_check_PAL;
-  @ requires file_recovery->calculated_file_size <= PHOTOREC_MAX_FILE_SIZE;
-  @ requires \separated(buffer, file_recovery);
-  @ ensures \result == DC_CONTINUE || \result == DC_STOP;
+  @ requires valid_data_check_param(buffer, buffer_size, file_recovery);
+  @ ensures  valid_data_check_result(\result, file_recovery);
   @ assigns file_recovery->calculated_file_size;
   @*/
 static data_check_t data_check_PAL(const unsigned char *buffer, const unsigned int buffer_size, file_recovery_t *file_recovery)
@@ -150,22 +143,20 @@ static data_check_t data_check_PAL(const unsigned char *buffer, const unsigned i
 }
 
 /*@
-  @ requires \valid(fr);
   @ requires fr->file_check == &file_check_dv_PAL;
-  @ requires valid_file_recovery(fr);
-  @ ensures  valid_file_recovery(fr);
+  @ requires valid_file_check_param(fr);
+  @ ensures  valid_file_check_result(fr);
   @ assigns *fr->handle, errno, Frama_C_entropy_source, fr->file_size;
   @*/
 static void file_check_dv_PAL(file_recovery_t *fr)
 {
-  unsigned char buffer_header[512];
-  unsigned char buffer[144000];
+  char buffer_header[512];
   uint64_t fs=fr->file_size/144000*144000;
   if(my_fseek(fr->handle, 0, SEEK_SET) < 0 ||
       fread(&buffer_header, sizeof(buffer_header), 1, fr->handle) != 1)
     return ;
 #if defined(__FRAMAC__)
-  Frama_C_make_unknown((char *)&buffer_header, sizeof(buffer_header));
+  Frama_C_make_unknown(&buffer_header, sizeof(buffer_header));
 #endif
   if(fs > 0)
     fs-=144000;
@@ -173,12 +164,17 @@ static void file_check_dv_PAL(file_recovery_t *fr)
     fs-=144000;
   /*@ loop assigns fs, *fr->handle, errno, Frama_C_entropy_source, fr->file_size; */
   while(fs < fr->file_size &&
-      my_fseek(fr->handle, fs, SEEK_SET) >= 0 &&
-      fread(&buffer, sizeof(buffer), 1, fr->handle) == 1)
+      my_fseek(fr->handle, fs, SEEK_SET) >= 0)
   {
     unsigned int i;
+    char buffer[144000];
+    if(fread(&buffer, sizeof(buffer), 1, fr->handle) != 1)
+    {
+      fr->file_size=fs;
+      return;
+    }
 #if defined(__FRAMAC__)
-    Frama_C_make_unknown((char *)&buffer, sizeof(buffer));
+    Frama_C_make_unknown(&buffer, sizeof(buffer));
 #endif
     /*@ loop assigns i, fr->file_size; */
     for(i=1; i<sizeof(buffer); i+=0x50)
@@ -195,13 +191,9 @@ static void file_check_dv_PAL(file_recovery_t *fr)
 
 /*@
   @ requires buffer_size >= 8;
-  @ requires \valid_read(buffer+(0..buffer_size-1));
-  @ requires valid_file_recovery(file_recovery);
-  @ requires \valid(file_recovery_new);
-  @ requires file_recovery_new->blocksize > 0;
   @ requires separation: \separated(&file_hint_dv, buffer+(..), file_recovery, file_recovery_new);
-  @ ensures \result == 0 || \result == 1;
-  @ ensures  \result!=0 ==> valid_file_recovery(file_recovery_new);
+  @ requires valid_header_check_param(buffer, buffer_size, safe_header_only, file_recovery, file_recovery_new);
+  @ ensures  valid_header_check_result(\result, file_recovery_new);
   @*/
 static int header_check_dv(const unsigned char *buffer, const unsigned int buffer_size, const unsigned int safe_header_only, const file_recovery_t *file_recovery, file_recovery_t *file_recovery_new)
 {