ext/spc/: Add support for some essential features like seeking, reading song duration and extended tags. Fixes bug #4...

Original commit message from CVS:
Patch by: Brian Koropoff <brianhk at cs dot washington dot edu>
* ext/spc/Makefile.am:
* ext/spc/gstspc.c: (gst_spc_dec_class_init),
(gst_spc_dec_src_query_type), (gst_spc_dec_init),
(gst_spc_dec_dispose), (gst_spc_dec_sink_event),
(gst_spc_duration), (gst_spc_fadeout), (gst_spc_dec_src_event),
(gst_spc_dec_src_query), (spc_play), (spc_setup):
* ext/spc/gstspc.h:
* ext/spc/tag.c: (spc_tag_is_extended), (spc_tag_is_text_format),
(spc_tag_is_present), (spc_tag_unpack_date), (spc_tag_clear),
(spc_tag_get_info), (spc_tag_free):
* ext/spc/tag.h:
Add support for some essential features like seeking, reading song
duration and extended tags. Fixes bug #454151.

5 files changed, 679 insertions, 35 deletions

diff --git a/ext/spc/Makefile.am b/ext/spc/Makefile.am
index 18a878b2..656421bc 100644
--- a/ext/spc/Makefile.am
+++ b/ext/spc/Makefile.am
@@ -1,6 +1,6 @@
 plugin_LTLIBRARIES = libgstspc.la
 
-libgstspc_la_SOURCES = gstspc.c
+libgstspc_la_SOURCES = gstspc.c tag.c
 
 libgstspc_la_CFLAGS = $(GST_CFLAGS) $(SPC_CFLAGS)
 libgstspc_la_LIBADD = $(GST_LIBS) $(SPC_LIBS)
diff --git a/ext/spc/gstspc.c b/ext/spc/gstspc.c
index 8c24c650..3eee98f0 100644
--- a/ext/spc/gstspc.c
+++ b/ext/spc/gstspc.c
@@ -1,5 +1,6 @@
 /* Copyright (C) 2004-2005 Michael Pyne <michael dot pyne at kdemail net>
  * Copyright (C) 2004-2006 Chris Lee <clee at kde org>
+ * Copyright (C) 2007 Brian Koropoff <bkoropoff at gmail com>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ -24,12 +25,14 @@
 #include "gstspc.h"
 
 #include <string.h>
+#include <glib/gprintf.h>
+#include <glib.h>
 
 static const GstElementDetails gst_spc_dec_details =
 GST_ELEMENT_DETAILS ("OpenSPC SPC decoder",
     "Codec/Audio/Decoder",
     "Uses OpenSPC to emulate an SPC processor",
-    "Chris Lee <clee@kde.org>");
+    "Chris Lee <clee@kde.org>, Brian Koropoff <bkoropoff@gmail.com>");
 
 static GstStaticPadTemplate sink_factory =
 GST_STATIC_PAD_TEMPLATE ("sink", GST_PAD_SINK, GST_PAD_ALWAYS,
@@ -52,6 +55,7 @@ static gboolean gst_spc_dec_src_query (GstPad * pad, GstQuery * query);
 static GstStateChangeReturn gst_spc_dec_change_state (GstElement * element,
     GstStateChange transition);
 static void spc_play (GstPad * pad);
+static void gst_spc_dec_dispose (GObject * object);
 static gboolean spc_setup (GstSpcDec * spc);
 
 static gboolean
@@ -117,15 +121,30 @@ static void
 gst_spc_dec_class_init (GstSpcDecClass * klass)
 {
   GstElementClass *element_class = (GstElementClass *) klass;
+  GObjectClass *gobject_class = (GObjectClass *) klass;
 
   element_class->change_state = GST_DEBUG_FUNCPTR (gst_spc_dec_change_state);
+  gobject_class->dispose = gst_spc_dec_dispose;
 }
 
+static const GstQueryType *
+gst_spc_dec_src_query_type (GstPad * pad)
+{
+  static const GstQueryType query_types[] = {
+    GST_QUERY_DURATION,
+    GST_QUERY_POSITION,
+    (GstQueryType) 0
+  };
+
+  return query_types;
+}
+
+
 static void
 gst_spc_dec_init (GstSpcDec * spc, GstSpcDecClass * klass)
 {
   spc->sinkpad = gst_pad_new_from_static_template (&sink_factory, "sink");
-  gst_pad_set_query_function (spc->sinkpad, NULL);
+  /* gst_pad_set_query_function (spc->sinkpad, NULL); */
   gst_pad_set_event_function (spc->sinkpad, gst_spc_dec_sink_event);
   gst_pad_set_chain_function (spc->sinkpad, gst_spc_dec_chain);
   gst_element_add_pad (GST_ELEMENT (spc), spc->sinkpad);
@@ -133,11 +152,26 @@ gst_spc_dec_init (GstSpcDec * spc, GstSpcDecClass * klass)
   spc->srcpad = gst_pad_new_from_static_template (&src_factory, "src");
   gst_pad_set_event_function (spc->srcpad, gst_spc_dec_src_event);
   gst_pad_set_query_function (spc->srcpad, gst_spc_dec_src_query);
+  gst_pad_set_query_type_function (spc->srcpad, gst_spc_dec_src_query_type);
   gst_pad_use_fixed_caps (spc->srcpad);
   gst_element_add_pad (GST_ELEMENT (spc), spc->srcpad);
 
   spc->buf = NULL;
   spc->initialized = FALSE;
+  spc_tag_clear (&spc->tag_info);
+}
+
+static void
+gst_spc_dec_dispose (GObject * object)
+{
+  GstSpcDec *spc = GST_SPC_DEC (object);
+
+  if (spc->buf) {
+    gst_buffer_unref (spc->buf);
+    spc->buf = NULL;
+  }
+
+  spc_tag_free (&spc->tag_info);
 }
 
 static GstFlowReturn
@@ -160,7 +194,7 @@ static gboolean
 gst_spc_dec_sink_event (GstPad * pad, GstEvent * event)
 {
   GstSpcDec *spc = GST_SPC_DEC (gst_pad_get_parent (pad));
-  gboolean result;
+  gboolean result = TRUE;
 
   switch (GST_EVENT_TYPE (event)) {
     case GST_EVENT_EOS:
@@ -180,6 +214,38 @@ gst_spc_dec_sink_event (GstPad * pad, GstEvent * event)
   return result;
 }
 
+static gint64
+gst_spc_duration (GstSpcDec * spc)
+{
+  gint64 total_ticks =
+      spc->tag_info.time_intro +
+      spc->tag_info.time_loop * spc->tag_info.loop_count +
+      spc->tag_info.time_end;
+  if (total_ticks) {
+    return (gint64) gst_util_uint64_scale (total_ticks, GST_SECOND, 64000);
+  } else if (spc->tag_info.time_seconds) {
+    gint64 time = (gint64) spc->tag_info.time_seconds * GST_SECOND;
+
+    return time;
+  } else {
+    return (gint64) (3 * 60) * GST_SECOND;
+  }
+}
+
+static gint64
+gst_spc_fadeout (GstSpcDec * spc)
+{
+  if (spc->tag_info.time_fade) {
+    return (gint64) gst_util_uint64_scale ((guint64) spc->tag_info.time_fade,
+        GST_SECOND, 64000);
+  } else if (spc->tag_info.time_fade_milliseconds) {
+    return (gint64) (spc->tag_info.time_fade_milliseconds * GST_MSECOND);
+  } else {
+    return 10 * GST_SECOND;
+  }
+}
+
+
 static gboolean
 gst_spc_dec_src_event (GstPad * pad, GstEvent * event)
 {
@@ -187,6 +253,79 @@ gst_spc_dec_src_event (GstPad * pad, GstEvent * event)
   gboolean result = FALSE;
 
   switch (GST_EVENT_TYPE (event)) {
+    case GST_EVENT_SEEK:
+    {
+      gdouble rate;
+      GstFormat format;
+      GstSeekFlags flags;
+      GstSeekType start_type, stop_type;
+      gint64 start, stop;
+      gboolean flush;
+
+      gst_event_parse_seek (event, &rate, &format, &flags, &start_type, &start,
+          &stop_type, &stop);
+
+      if (format != GST_FORMAT_TIME) {
+        GST_DEBUG_OBJECT (spc, "seeking is only supported in TIME format");
+        break;
+      }
+
+      if (start_type != GST_SEEK_TYPE_SET || stop_type != GST_SEEK_TYPE_NONE) {
+        GST_DEBUG_OBJECT (spc, "unsupported seek type");
+        break;
+      }
+
+      if (stop_type == GST_SEEK_TYPE_NONE)
+        stop = GST_CLOCK_TIME_NONE;
+
+      if (start_type == GST_SEEK_TYPE_SET) {
+        guint64 cur =
+            gst_util_uint64_scale (spc->byte_pos, GST_SECOND, 32000 * 2 * 2);
+        guint64 dest = (guint64) start;
+
+        dest = CLAMP (dest, 0, gst_spc_duration (spc) + gst_spc_fadeout (spc));
+
+        if (dest == cur)
+          break;
+
+        flush = (flags & GST_SEEK_FLAG_FLUSH) == GST_SEEK_FLAG_FLUSH;
+
+        if (flush) {
+          gst_pad_push_event (spc->srcpad, gst_event_new_flush_start ());
+        } else {
+          gst_pad_stop_task (spc->srcpad);
+        }
+
+        GST_PAD_STREAM_LOCK (spc->srcpad);
+
+        if (flags & GST_SEEK_FLAG_SEGMENT) {
+          gst_element_post_message (GST_ELEMENT (spc),
+              gst_message_new_segment_start (GST_OBJECT (spc), format, cur));
+        }
+
+        if (flush) {
+          gst_pad_push_event (spc->srcpad, gst_event_new_flush_stop ());
+        }
+
+        if (stop == GST_CLOCK_TIME_NONE)
+          stop = (guint64) (gst_spc_duration (spc) + gst_spc_fadeout (spc));
+
+        gst_pad_push_event (spc->srcpad, gst_event_new_new_segment (FALSE, rate,
+                GST_FORMAT_TIME, dest, stop, dest));
+
+        /* spc->byte_pos += OSPC_Run(-1, NULL, (unsigned int) (gst_util_uint64_scale(dest - cur, 32000*2*2, GST_SECOND))); */
+        spc->seekpoint =
+            gst_util_uint64_scale (dest, 32000 * 2 * 2, GST_SECOND);
+        spc->seeking = TRUE;
+
+        gst_pad_start_task (spc->srcpad, (GstTaskFunction) spc_play,
+            spc->srcpad);
+
+        GST_PAD_STREAM_UNLOCK (spc->srcpad);
+        result = TRUE;
+      }
+      break;
+    }
     default:
       break;
   }
@@ -204,6 +343,33 @@ gst_spc_dec_src_query (GstPad * pad, GstQuery * query)
   gboolean result = TRUE;
 
   switch (GST_QUERY_TYPE (query)) {
+    case GST_QUERY_DURATION:
+    {
+      GstFormat format;
+
+      gst_query_parse_duration (query, &format, NULL);
+      if (!spc->initialized || format != GST_FORMAT_TIME) {
+        result = FALSE;
+        break;
+      }
+      gst_query_set_duration (query, GST_FORMAT_TIME,
+          gst_spc_duration (spc) + gst_spc_fadeout (spc));
+      break;
+    }
+    case GST_QUERY_POSITION:
+    {
+      GstFormat format;
+
+      gst_query_parse_position (query, &format, NULL);
+      if (!spc->initialized || format != GST_FORMAT_TIME) {
+        result = FALSE;
+        break;
+      }
+      gst_query_set_position (query, GST_FORMAT_TIME,
+          (gint64) gst_util_uint64_scale (spc->byte_pos, GST_SECOND,
+              32000 * 2 * 2));
+      break;
+    }
     default:
       result = gst_pad_query_default (pad, query);
       break;
@@ -220,11 +386,48 @@ spc_play (GstPad * pad)
   GstSpcDec *spc = GST_SPC_DEC (gst_pad_get_parent (pad));
   GstFlowReturn flow_return;
   GstBuffer *out;
+  gboolean seeking = spc->seeking;
+  gint64 duration, fade, end, position;
+
+  if (!seeking) {
+    out = gst_buffer_new_and_alloc (1600 * 4);
+    gst_buffer_set_caps (out, GST_PAD_CAPS (pad));
+    GST_BUFFER_TIMESTAMP (out) =
+        (gint64) gst_util_uint64_scale ((guint64) spc->byte_pos, GST_SECOND,
+        32000 * 2 * 2);
+    spc->byte_pos += OSPC_Run (-1, (short *) GST_BUFFER_DATA (out), 1600 * 4);
+  } else {
+    if (spc->seekpoint < spc->byte_pos) {
+      OSPC_Init (GST_BUFFER_DATA (spc->buf), GST_BUFFER_SIZE (spc->buf));
+      spc->byte_pos = 0;
+    }
+    spc->byte_pos += OSPC_Run (-1, NULL, 1600 * 4);
+    if (spc->byte_pos >= spc->seekpoint) {
+      spc->seeking = FALSE;
+    }
+    out = gst_buffer_new ();
+    gst_buffer_set_caps (out, GST_PAD_CAPS (pad));
+  }
+
+  duration = gst_spc_duration (spc);
+  fade = gst_spc_fadeout (spc);
+  end = duration + fade;
+  position =
+      (gint64) gst_util_uint64_scale ((guint64) spc->byte_pos, GST_SECOND,
+      32000 * 2 * 2);
+
+  if (position >= duration) {
+    gint16 *data = (gint16 *) GST_BUFFER_DATA (out);
+    guint32 size = GST_BUFFER_SIZE (out) / sizeof (gint16);
+    unsigned int i;
 
-  out = gst_buffer_new_and_alloc (1600 * 4);
-  gst_buffer_set_caps (out, GST_PAD_CAPS (pad));
+    gint64 num = (fade - (position - duration));
 
-  OSPC_Run (-1, (short *) GST_BUFFER_DATA (out), 1600 * 4);
+    for (i = 0; i < size; i++) {
+      /* Apply a parabolic volume envelope */
+      data[i] = (gint16) (data[i] * num / fade * num / fade);
+    }
+  }
 
   if ((flow_return = gst_pad_push (spc->srcpad, out)) != GST_FLOW_OK) {
     GST_DEBUG_OBJECT (spc, "pausing task, reason %s",
@@ -237,6 +440,11 @@ spc_play (GstPad * pad)
     }
   }
 
+  if (position >= end) {
+    gst_pad_pause_task (pad);
+    gst_pad_push_event (pad, gst_event_new_eos ());
+  }
+
   gst_object_unref (spc);
 
   return;
@@ -246,38 +454,69 @@ static gboolean
 spc_setup (GstSpcDec * spc)
 {
   guchar *data = GST_BUFFER_DATA (spc->buf);
-  gboolean text_format = FALSE;
 
   if (!spc_negotiate (spc)) {
     return FALSE;
   }
 
-  if (data[0x23] == 26) {
-    GstEvent *tagevent;
-    GstTagList *taglist = gst_tag_list_new ();
-
-    if (data[0xA0] == '/')
-      text_format = TRUE;
-
-    gchar spctitle[0x21];
-    gchar spcartist[0x21];
-    gchar spcgame[0x21];
-
-    strncpy (spctitle, (gchar *) & data[0x2E], 32);
-    strncpy (spcartist, (gchar *) & data[(text_format ? 0xB1 : 0xB0)], 32);
-    strncpy (spcgame, (gchar *) & data[0x4E], 32);
-
-    spctitle[0x20] = '\0';
-    spcartist[0x20] = '\0';
-    spcgame[0x20] = '\0';
-
-    gst_tag_list_add (taglist, GST_TAG_MERGE_APPEND,
-        GST_TAG_TITLE, spctitle,
-        GST_TAG_ARTIST, spcartist, GST_TAG_ALBUM, spcgame, NULL);
-
-    tagevent = gst_event_new_tag (taglist);
-    gst_element_found_tags_for_pad (GST_ELEMENT (spc), spc->srcpad, taglist);
+  spc_tag_info *info = &(spc->tag_info);
+
+  spc_tag_get_info (data, GST_BUFFER_SIZE (spc->buf), info);
+
+  GstTagList *taglist = gst_tag_list_new ();
+
+  if (info->title)
+    gst_tag_list_add (taglist, GST_TAG_MERGE_REPLACE, GST_TAG_TITLE,
+        info->title, NULL);
+  if (info->artist)
+    gst_tag_list_add (taglist, GST_TAG_MERGE_REPLACE, GST_TAG_ARTIST,
+        info->artist, NULL);
+  /* Prefer the name of the official soundtrack over the name of the game (since this is
+   * how track numbers are derived)
+   */
+  if (info->album)
+    gst_tag_list_add (taglist, GST_TAG_MERGE_REPLACE, GST_TAG_ALBUM,
+        info->album, NULL);
+  else if (info->game)
+    gst_tag_list_add (taglist, GST_TAG_MERGE_REPLACE, GST_TAG_ALBUM, info->game,
+        NULL);
+  if (info->year) {
+    GDate *date = g_date_new_dmy (1, 1, info->year);
+
+    gst_tag_list_add (taglist, GST_TAG_MERGE_REPLACE, GST_TAG_DATE, date, NULL);
+    g_date_free (date);
+  }
+  if (info->track) {
+    gst_tag_list_add (taglist, GST_TAG_MERGE_REPLACE, GST_TAG_TRACK_NUMBER,
+        info->track, NULL);
   }
+  if (info->comment)
+    gst_tag_list_add (taglist, GST_TAG_MERGE_REPLACE, GST_TAG_COMMENT,
+        info->comment, NULL);
+  if (info->disc)
+    gst_tag_list_add (taglist, GST_TAG_MERGE_REPLACE,
+        GST_TAG_ALBUM_VOLUME_NUMBER, info->disc, NULL);
+  if (info->publisher)
+    gst_tag_list_add (taglist, GST_TAG_MERGE_REPLACE, GST_TAG_ORGANIZATION,
+        info->publisher, NULL);
+  if (info->dumper)
+    gst_tag_list_add (taglist, GST_TAG_MERGE_REPLACE, GST_TAG_CONTACT,
+        info->dumper, NULL);
+  if (info->emulator)
+    gst_tag_list_add (taglist, GST_TAG_MERGE_REPLACE, GST_TAG_ENCODER,
+        info->emulator == EMU_ZSNES ? "ZSNES" : "Snes9x", NULL);
+
+  guint64 total_duration =
+      (guint64) (gst_spc_duration (spc) + gst_spc_fadeout (spc));
+
+  gst_tag_list_add (taglist, GST_TAG_MERGE_REPLACE,
+      GST_TAG_DURATION, total_duration,
+      GST_TAG_GENRE, "Game", GST_TAG_CODEC, "SPC700", NULL);
+
+  gst_element_found_tags_for_pad (GST_ELEMENT (spc), spc->srcpad, taglist);
+
+  /* spc_tag_info_free(&info); */
+
 
   if (OSPC_Init (GST_BUFFER_DATA (spc->buf), GST_BUFFER_SIZE (spc->buf)) != 0) {
     return FALSE;
@@ -288,9 +527,15 @@ spc_setup (GstSpcDec * spc)
 
   gst_pad_start_task (spc->srcpad, (GstTaskFunction) spc_play, spc->srcpad);
 
-  gst_buffer_unref (spc->buf);
-  spc->buf = NULL;
+  /* We can't unreference this buffer because we might need to re-initialize
+   * the emulator with the original data during a reverse seek
+   * gst_buffer_unref (spc->buf);
+   * spc->buf = NULL;
+   */
   spc->initialized = TRUE;
+  spc->seeking = FALSE;
+  spc->seekpoint = 0;
+  spc->byte_pos = 0;
   return spc->initialized;
 }
 
diff --git a/ext/spc/gstspc.h b/ext/spc/gstspc.h
index a1627997..e1740667 100644
--- a/ext/spc/gstspc.h
+++ b/ext/spc/gstspc.h
@@ -1,5 +1,6 @@
 /* Copyright (C) 2004-2005 Michael Pyne <michael dot pyne at kdemail net>
  * Copyright (C) 2004-2006 Chris Lee <clee at kde org>
+ * Copyright (C) 2007 Brian Koropoff <bkoropoff at gmail com>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ -24,6 +25,8 @@
 
 #include <openspc.h>
 
+#include "tag.h"
+
 G_BEGIN_DECLS
 
 #define GST_TYPE_SPC_DEC \
@@ -49,6 +52,12 @@ struct _GstSpcDec
 
   GstBuffer  *buf;
   gboolean    initialized;
+  gboolean    seeking;
+  guint32     seekpoint;
+  
+  spc_tag_info tag_info;
+  
+  guint32 byte_pos;
 };
 
 struct _GstSpcDecClass
diff --git a/ext/spc/tag.c b/ext/spc/tag.c
new file mode 100644
index 00000000..41ce812f
--- /dev/null
+++ b/ext/spc/tag.c
@@ -0,0 +1,353 @@
+/* Copyright (C) 2007 Brian Koropoff <bkoropoff at gmail com>
+ *
+ * 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 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 <glib/gstring.h>
+#include <glib/gtypes.h>
+#include <glib/gmem.h>
+#include <glib/gprintf.h>
+
+#include <tag.h>
+#include <string.h>
+#include <stdlib.h>
+
+
+#define EXTENDED_OFFSET 0x10200
+#define EXTENDED_MAGIC ((guint32) ('x' << 0 | 'i' << 8 | 'd' << 16 | '6' << 24))
+
+#define TYPE_LENGTH 0x0
+#define TYPE_STRING 0x1
+#define TYPE_INTEGER 0x4
+
+#define TAG_TITLE 0x01
+#define TAG_GAME 0x02
+#define TAG_ARTIST 0x03
+#define TAG_DUMPER 0x04
+#define TAG_DUMP_DATE 0x05
+#define TAG_EMULATOR 0x06
+#define TAG_COMMENT 0x07
+#define TAG_ALBUM 0x10
+#define TAG_DISC 0x11
+#define TAG_TRACK 0x12
+#define TAG_PUBLISHER 0x13
+#define TAG_YEAR 0x14
+#define TAG_INTRO 0x30
+#define TAG_LOOP 0x31
+#define TAG_END 0x32
+#define TAG_FADE 0x33
+#define TAG_MUTED 0x34
+#define TAG_COUNT 0x35
+#define TAG_AMP 0x36
+
+#define READ_INT8(data, offset) (data[offset])
+#define READ_INT16(data, offset) ((data[offset] << 0) + (data[offset+1] << 8))
+#define READ_INT24(data, offset) ((data[offset] << 0) + (data[offset+1] << 8) + (data[offset+2] << 16))
+#define READ_INT32(data, offset) ((data[offset] << 0) + (data[offset+1] << 8) + (data[offset+2] << 16) + (data[offset+3] << 24))
+
+static inline gboolean
+spc_tag_is_extended (guchar * data, guint length)
+{
+  // Extended tags come at the end of the file (at a known offset)
+  // and start with "xid6"
+  return (length > EXTENDED_OFFSET + 4
+      && READ_INT32 (data, EXTENDED_OFFSET) == EXTENDED_MAGIC);
+}
+
+static inline gboolean
+spc_tag_is_text_format (guchar * data, guint length)
+{
+  // Because the id666 format is brain dead, there's
+  // no definite way to decide if it is in text
+  // format.  This function implements a set of
+  // heuristics to make a best-effort guess.
+
+  // If the date field contains separators, it is probably text
+  if (data[0xA0] == '/' || data[0xA0] == '.')
+    return TRUE;
+  // If the first byte of the date field is small (but not 0,
+  // which could indicate an empty string), it's probably binary
+  if (data[0x9E] >= 1 && data[0x9E] <= 31)
+    return FALSE;
+
+  // If all previous tests turned up nothing, assume it's text
+  return TRUE;
+}
+
+static inline gboolean
+spc_tag_is_present (guchar * data, guint length)
+{
+  return data[0x23] == 26;
+}
+
+static inline GDate *
+spc_tag_unpack_date (guint32 packed)
+{
+  guint dump_year = packed / 10000;
+  guint dump_month = (packed % 10000) / 100;
+  guint dump_day = packed % 100;
+
+  if (dump_month == 0)
+    dump_month = 1;
+  if (dump_day == 0)
+    dump_day = 1;
+
+  if (dump_year != 0)
+    return g_date_new_dmy (dump_day, dump_month, dump_year);
+  else
+    return NULL;
+}
+
+void
+spc_tag_clear (spc_tag_info * info)
+{
+  info->title = info->game = info->publisher = info->artist = info->album =
+      info->comment = info->dumper = NULL;
+  info->dump_date = NULL;
+  info->time_seconds = 0;
+  info->time_fade_milliseconds = 0;
+  info->time_intro = 0;
+  info->time_end = 0;
+  info->time_loop = 0;
+  info->time_fade = 0;
+  info->loop_count = 0;
+  info->muted = 0;
+  info->disc = 0;
+  info->amplification = 0;
+}
+
+void
+spc_tag_get_info (guchar * data, guint length, spc_tag_info * info)
+{
+  spc_tag_clear (info);
+
+  if (spc_tag_is_present (data, length)) {
+    gboolean text_format = spc_tag_is_text_format (data, length);
+
+    info->title = g_new0 (gchar, 0x21);
+    info->game = g_new0 (gchar, 0x21);
+    info->artist = g_new0 (gchar, 0x21);
+    info->dumper = g_new0 (gchar, 0x10);
+    info->comment = g_new0 (gchar, 0x32);
+
+    strncpy (info->title, (gchar *) & data[0x2E], 32);
+    strncpy (info->artist, (gchar *) & data[(text_format ? 0xB1 : 0xB0)], 32);
+    strncpy (info->game, (gchar *) & data[0x4E], 32);
+    strncpy (info->dumper, (gchar *) & data[0x6E], 16);
+    strncpy (info->comment, (gchar *) & data[0x7E], 32);
+
+    if (text_format) {
+      gchar time[4];
+      gchar fade[6];
+      guint dump_year, dump_month, dump_day;
+
+      strncpy (time, (gchar *) data + 0xA9, 3);
+      strncpy (fade, (gchar *) data + 0xAC, 5);
+
+      time[3] = fade[5] = 0;
+
+      info->time_seconds = atoi (time);
+      info->time_fade_milliseconds = atoi (fade);
+
+      dump_year = (guint) atoi ((gchar *) data + 0x9E);
+      dump_month = (guint) atoi ((gchar *) data + 0x9E + 3);
+      dump_day = (guint) atoi ((gchar *) data + 0x9E + 3 + 3);
+
+      if (dump_month == 0)
+        dump_month = 1;
+      if (dump_day == 0)
+        dump_day = 1;
+      if (dump_year != 0)
+        info->dump_date = g_date_new_dmy (dump_day, dump_month, dump_year);
+
+      info->muted = READ_INT8 (data, 0xD1);
+      info->emulator = READ_INT8 (data, 0xD2);
+    } else {
+      info->time_seconds = READ_INT24 (data, 0xA9);
+      info->time_fade_milliseconds = READ_INT32 (data, 0xAC);
+      info->dump_date = spc_tag_unpack_date (READ_INT32 (data, 0x9E));
+      info->muted = READ_INT8 (data, 0xD0);
+      info->emulator = READ_INT8 (data, 0xD1);
+    }
+  }
+
+  if (spc_tag_is_extended (data, length)) {
+    guchar *chunk = data + EXTENDED_OFFSET + 8;
+    guint32 chunk_size = *((guint32 *) (data + EXTENDED_OFFSET + 4));
+
+    guchar *subchunk, *subchunk_next;
+
+    for (subchunk = chunk; subchunk < chunk + chunk_size;
+        subchunk = subchunk_next) {
+      guint8 tag = READ_INT8 (subchunk, 0);
+      guint8 type = READ_INT8 (subchunk, 1);
+      guint16 length = READ_INT16 (subchunk, 2);
+      guchar *value = subchunk + 4;
+
+      switch (type) {
+        case TYPE_LENGTH:
+        {
+          switch (tag) {
+            case TAG_TRACK:
+              info->track = READ_INT8 (subchunk, 2 + 1);
+              break;
+            case TAG_YEAR:
+              info->year = READ_INT16 (subchunk, 2);
+              break;
+            case TAG_COUNT:
+              info->loop_count = READ_INT8 (subchunk, 2);
+              break;
+            case TAG_EMULATOR:
+              info->emulator = READ_INT8 (subchunk, 2);
+              break;
+            case TAG_DISC:
+              info->disc = READ_INT8 (subchunk, 2);
+              break;
+            case TAG_MUTED:
+              info->muted = READ_INT8 (subchunk, 2);
+              break;
+            default:
+              break;
+          }
+
+          subchunk_next = subchunk + 4;
+          break;
+        }
+        case TYPE_STRING:
+        {
+          gchar *dest;
+
+          if (length <= 1)
+            dest = NULL;
+          else
+            switch (tag) {
+              case TAG_TITLE:
+                dest = info->title = g_renew (gchar, info->title, length);
+                break;
+              case TAG_GAME:
+                dest = info->game = g_renew (gchar, info->game, length);
+                break;
+              case TAG_ARTIST:
+                dest = info->artist = g_renew (gchar, info->artist, length);
+                break;
+              case TAG_ALBUM:
+                dest = info->album = g_renew (gchar, info->album, length);
+                break;
+              case TAG_DUMPER:
+                dest = info->dumper = g_renew (gchar, info->dumper, length);
+                break;
+              case TAG_COMMENT:
+                dest = info->comment = g_renew (gchar, info->comment, length);
+                break;
+              case TAG_PUBLISHER:
+                dest = info->publisher =
+                    g_renew (gchar, info->publisher, length);
+                break;
+              default:
+                dest = NULL;
+                break;
+            }
+
+          if (dest)
+            strncpy (dest, (gchar *) value, length);
+
+          subchunk_next = value + length;
+          break;
+        }
+        case TYPE_INTEGER:
+        {
+          switch (tag) {
+            case TAG_INTRO:
+              info->time_intro = READ_INT32 (value, 0);
+              break;
+            case TAG_END:
+              info->time_end = READ_INT32 (value, 0);
+              break;
+            case TAG_FADE:
+              info->time_fade = READ_INT32 (value, 0);
+              break;
+            case TAG_LOOP:
+              info->time_loop = READ_INT32 (value, 0);
+              break;
+            case TAG_DUMP_DATE:
+              info->dump_date = spc_tag_unpack_date (READ_INT32 (value, 0));
+              break;
+            case TAG_AMP:
+              info->amplification = READ_INT32 (value, 0);
+              break;
+            default:
+              break;
+          }
+          subchunk_next = value + length;
+          break;
+        }
+        default:
+          subchunk_next = value + length;
+          break;
+      }
+    }
+  }
+
+  if (info->title && !*info->title) {
+    g_free (info->title);
+    info->title = NULL;
+  }
+  if (info->game && !*info->game) {
+    g_free (info->game);
+    info->game = NULL;
+  }
+  if (info->artist && !*info->artist) {
+    g_free (info->artist);
+    info->artist = NULL;
+  }
+  if (info->album && !*info->album) {
+    g_free (info->album);
+    info->album = NULL;
+  }
+  if (info->publisher && !*info->publisher) {
+    g_free (info->publisher);
+    info->publisher = NULL;
+  }
+  if (info->comment && !*info->comment) {
+    g_free (info->comment);
+    info->comment = NULL;
+  }
+  if (info->dumper && !*info->dumper) {
+    g_free (info->dumper);
+    info->dumper = NULL;
+  }
+}
+
+void
+spc_tag_free (spc_tag_info * info)
+{
+  if (info->title)
+    g_free (info->title);
+  if (info->game)
+    g_free (info->game);
+  if (info->artist)
+    g_free (info->artist);
+  if (info->album)
+    g_free (info->album);
+  if (info->publisher)
+    g_free (info->publisher);
+  if (info->comment)
+    g_free (info->comment);
+  if (info->dumper)
+    g_free (info->dumper);
+  if (info->dump_date)
+    g_date_free (info->dump_date);
+}
diff --git a/ext/spc/tag.h b/ext/spc/tag.h
new file mode 100644
index 00000000..5b795893
--- /dev/null
+++ b/ext/spc/tag.h
@@ -0,0 +1,37 @@
+/* Copyright (C) 2007 Brian Koropoff <bkoropoff at gmail com>
+ *
+ * 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 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 <glib/gtypes.h>
+#include <glib.h>
+
+typedef struct
+{
+	gchar *title, *game, *artist, *album, *publisher;
+	gchar *dumper, *comment;
+	enum { EMU_SNES9X = 2, EMU_ZSNES = 1, EMU_UNKNOWN = 0 } emulator;
+	guint8 track, disc, muted, loop_count;
+	guint16 year;
+	guint32 time_seconds, time_fade_milliseconds;
+	guint32 time_intro, time_loop, time_end, time_fade;
+	guint32 amplification;
+	GDate *dump_date;
+} spc_tag_info;
+
+void spc_tag_clear(spc_tag_info* info);
+void spc_tag_get_info(guchar* data, guint length, spc_tag_info* info);
+void spc_tag_free(spc_tag_info* info);