There are two parts to this change:

The function get_playback_filename() declared in platform.h, which returns the file name of the currently viewed item.
The memory search program which looks for the address of the playback file name. You trigger this by the new menu item "Debug parameters -> Memory browser", and it loops through the memory, searching for a hard coded string.

Index: include/gui.h
===================================================================
--- include/gui.h	(revision 459)
+++ include/gui.h	(working copy)
@@ -18,6 +18,7 @@
                 GUI_MODE_READ,
                 GUI_MODE_OSD,
                 GUI_MODE_CALENDAR,
+                GUI_MODE_MEMSEARCH,
                 GUI_MODE_BENCH,
                 GUI_MODE_MPOPUP };
 
Index: include/platform.h
===================================================================
--- include/platform.h	(revision 459)
+++ include/platform.h	(working copy)
@@ -265,6 +265,10 @@
 long get_target_dir_num();
 long get_target_file_num();
 
+// Copy the string at POINTER_PLAYBACK_FILENAME. Return NULL on failure.
+// Caller owns the memory for the returned char pointer.
+char *get_playback_filename();
+
 /******************************************************************/
 
 void kbd_key_press(long key);
Index: platform/ixus860_sd870/shooting.c
===================================================================
--- platform/ixus860_sd870/shooting.c	(revision 459)
+++ platform/ixus860_sd870/shooting.c	(working copy)
@@ -1,4 +1,6 @@
 #define PARAM_FILE_COUNTER      0x38
+#define POINTER_PLAYBACK_FILENAME   0x590a8
+#define POINTER_PLAYBACK_THUMBNAIL  0x5980c
 
 // DRYOS-Notes:
 // propertycase
Index: platform/generic/shooting.c
===================================================================
--- platform/generic/shooting.c	(revision 459)
+++ platform/generic/shooting.c	(working copy)
@@ -840,6 +840,16 @@
     return v;
 }
 
+char *get_playback_filename() {
+#ifdef POINTER_PLAYBACK_FILENAME
+	char *path = umalloc(32);
+	strncpy(path, (char *) POINTER_PLAYBACK_FILENAME, 32);
+	return path;
+#else
+	return NULL;
+#endif
+}
+
 int shooting_get_zoom() {
     return lens_get_zoom_point();
 }
Index: core/gui_lang.c
===================================================================
--- core/gui_lang.c	(revision 459)
+++ core/gui_lang.c	(working copy)
@@ -427,6 +427,8 @@
 "339 \"RAWconv\"\n"
 
 "340 \"AF key\"\n"
+
+"341 \"Memory search\"\n"
 ;
 
 //-------------------------------------------------------------------
Index: core/gui_lang.h
===================================================================
--- core/gui_lang.h	(revision 459)
+++ core/gui_lang.h	(working copy)
@@ -438,9 +438,11 @@
 #define LANG_MENU_BAD_PIXEL_RAW_CONVERTER 339
 
 #define LANG_MENU_VIDEO_AF_KEY  340
+
+#define LANG_MENU_DEBUG_MEMORY_SEARCH   341
 //-------------------------------------------------------------------
 
-#define GUI_LANG_ITEMS                  340
+#define GUI_LANG_ITEMS                  341
 
 //-------------------------------------------------------------------
 extern void gui_lang_init();
Index: core/Makefile
===================================================================
--- core/Makefile	(revision 459)
+++ core/Makefile	(working copy)
@@ -13,7 +13,8 @@
 
 OBJS=entry.o nothumb.o main.o gui_draw.o gui_menu.o gui_palette.o gui_mbox.o \
      gui_reversi.o gui_debug.o gui_fselect.o gui_read.o gui.o kbd.o conf.o \
-     histogram.o gui_batt.o gui_space.o gui_osd.o script.o raw.o gui_sokoban.o gui_calendar.o \
+     histogram.o gui_batt.o gui_space.o gui_osd.o script.o raw.o gui_sokoban.o \
+     gui_calendar.o gui_memsearch.o \
      gui_lang.o gui_bench.o gui_mpopup.o gui_grid.o motion_detector.o raw_merge.o
 
 gui.o: FORCE
Index: core/gui_memsearch.c
===================================================================
--- core/gui_memsearch.c	(revision 0)
+++ core/gui_memsearch.c	(revision 0)
@@ -0,0 +1,47 @@
+#include "stdlib.h"
+#include "gui.h"
+#include "gui_draw.h"
+#include "gui_memsearch.h"
+
+//-------------------------------------------------------------------
+// Search parameters
+#define SEARCH_STRING  "A/DCIM/100CANON/MVI_2519.AVI"
+#define START_ADDRESS (void*) 0x0
+#define END_ADDRESS (void*) 0x100000
+
+//-------------------------------------------------------------------
+// Display parameters
+#define OUTPUT_COLOR   (MAKE_COLOR(COLOR_WHITE, COLOR_BLACK))
+#define ERROR_COLOR    (MAKE_COLOR(COLOR_WHITE, COLOR_RED))
+#define X_POSITION     2
+#define Y_POSITION     1
+#define DONE_MSG       "Done"
+#define NOT_FOUND_MSG  "Not found"
+
+//-------------------------------------------------------------------
+void gui_memsearch_init() {
+    void* addr;
+    int found = 0;
+	char buf[32];
+    int y = Y_POSITION;
+
+	draw_clear();
+
+	const char* search_string = SEARCH_STRING;
+	int len = strlen(search_string);
+
+    for (addr = START_ADDRESS; addr < END_ADDRESS; addr += 0x4) {
+    	if (memcmp(search_string, addr, len) == 0) {
+    		sprintf(buf, "0x%08X", addr);
+    		draw_txt_string(X_POSITION, y, buf, OUTPUT_COLOR);
+    		found = 1;
+    		y = y + 1;
+    	}
+    }
+
+    if (found) {
+    	draw_txt_string(X_POSITION, y+1, DONE_MSG, OUTPUT_COLOR);
+    } else {
+       draw_txt_string(X_POSITION, y, NOT_FOUND_MSG, ERROR_COLOR);
+    }
+}
Index: core/gui_memsearch.h
===================================================================
--- core/gui_memsearch.h	(revision 0)
+++ core/gui_memsearch.h	(revision 0)
@@ -0,0 +1,9 @@
+#ifndef GUI_MEMSEARCH_H
+#define GUI_MEMSEARCH_H
+
+//-------------------------------------------------------------------
+extern void gui_memsearch_init();
+
+//-------------------------------------------------------------------
+
+#endif
Index: core/gui.c
===================================================================
--- core/gui.c	(revision 459)
+++ core/gui.c	(working copy)
@@ -23,6 +23,7 @@
 #include "gui_osd.h"
 #include "gui_read.h"
 #include "gui_calendar.h"
+#include "gui_memsearch.h"
 #include "gui_bench.h"
 #include "gui_grid.h"
 #include "histogram.h"
@@ -105,6 +106,7 @@
 static void gui_draw_load_menu_rbf(int arg);
 static void gui_draw_load_rbf(int arg);
 static void gui_draw_calendar(int arg);
+static void gui_draw_memsearch(int arg);
 static void gui_draw_load_lang(int arg);
 static void gui_menuproc_mkbootdisk(int arg);
 #ifndef OPTIONS_AUTOSAVE
@@ -273,6 +275,7 @@
     {LANG_MENU_DEBUG_PROPCASE_PAGE,     MENUITEM_INT|MENUITEM_F_UNSIGNED|MENUITEM_F_MINMAX,   &debug_propcase_page, MENU_MINMAX(0, 12😎 },
     {LANG_MENU_DEBUG_SHOW_MISC_VALS,    MENUITEM_BOOL,          &debug_vals_show },
     {LANG_MENU_DEBUG_MEMORY_BROWSER,    MENUITEM_PROC,          (int*)gui_draw_debug },
+    {LANG_MENU_DEBUG_MEMORY_SEARCH,     MENUITEM_PROC,          (int*)gui_draw_memsearch },
     {LANG_MENU_DEBUG_BENCHMARK,         MENUITEM_PROC,          (int*)gui_draw_bench },
     {LANG_MENU_DEBUG_DUMP_RAM,          MENUITEM_BOOL,          &conf.ns_enable_memdump },
     {LANG_MENU_DEBUG_MAKE_BOOTABLE,     MENUITEM_PROC, 	    	(int*)gui_menuproc_mkbootdisk },
@@ -1569,6 +1572,7 @@
             case GUI_MODE_DEBUG:
             case GUI_MODE_OSD:
             case GUI_MODE_CALENDAR:
+            case GUI_MODE_MEMSEARCH:
             case GUI_MODE_BENCH:
                 draw_restore();
                 gui_mode = GUI_MODE_MENU;
@@ -2272,6 +2276,12 @@
 }
 
 //-------------------------------------------------------------------
+void gui_draw_memsearch(int arg) {
+    gui_mode = GUI_MODE_MEMSEARCH;
+    gui_memsearch_init();
+}
+
+//-------------------------------------------------------------------
 static void gui_draw_rbf_selected(const char *fn) {
     if (fn) {
         strcpy(conf.reader_rbf_file, fn);

One potential improvement is to store the search string in a file instead of hard code it. That way if you don't need to recompile if you want to look for a different string. But I figured that if you are looking for memory addresses, you are very likely to be a programmer, so recompiling shouldn't be a big deal.

Using the memory search program, I found two useful addresses: one for the playback filename, one for the corresponding thumbnail. I only added get_playback_filename(), and I can add one for the thumbnail as well, if there is interest.

Please let me know what you think. Thanks!