Generic metadata API.

avi is updated as example.
No version bump, the API still might change slightly ...
No update to ffmpeg.c as requested by aurel.

Originally committed as revision 16424 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/Makefile

@@ -14,6 +14,7 @@ OBJS = allcodecs.o                                                      \
        faanidct.o                                                       \
        imgconvert.o                                                     \
        jrevdct.o                                                        \
+       metadata.o                                                       \
        opt.o                                                            \
        parser.o                                                         \
        raw.o                                                            \

libavcodec/avcodec.h

@@ -400,6 +400,51 @@ enum SampleFormat {
  */
 #define FF_MIN_BUFFER_SIZE 16384
 
+
+/*
+ * public Metadata API.
+ * Important concepts, to keep in mind
+ * 1. keys are unique, there are never 2 tags with equal keys, this is also
+ *    meant semantically that is a demuxer should not knowingly produce
+ *    several keys that are litterally different but semantically identical,
+ *    like key=Author5, key=Author6.
+ *    All authors have to be placed in the same tag for the case of Authors.
+ * 2. Metadata is flat, there are no subtags, if you for whatever obscene
+ *    reason want to store the email address of the child of producer alice
+ *    and actor bob, that could have key=alice_and_bobs_childs_email_address.
+ * 3. A tag whichs value is translated has the ISO 639 3-letter language code
+ *    with a '-' between appended. So for example Author-ger=Michael, Author-eng=Mike
+ *    the original/default language is in the unqualified "Author"
+ *    A demuxer should set a default if it sets any translated tag.
+ */
+
+#define AV_METADATA_IGNORE_CASE     1
+#define AV_METADATA_IGNORE_SUFFIX   2
+
+typedef struct {
+    char *key;
+    char *value;
+}AVMetaDataTag;
+
+struct AVMetaData;
+
+/**
+ * gets a metadata element with matching key.
+ * @param prev set to the previous matching element to find the next.
+ * @param flags allows case as well as suffix insensitive comparissions.
+ * @return found tag or NULL, changing key or value leads to undefined behavior.
+ */
+AVMetaDataTag *
+av_metadata_get(struct AVMetaData *m, const char *key, const AVMetaDataTag *prev, int flags);
+
+/**
+ * sets the given tag in m, overwriting an existing tag.
+ * @param tag tag to add to m, key and value will be av_strduped.
+ * @return >= 0 if success otherwise error code that is <0.
+ */
+int av_metadata_set(struct AVMetaData **m, AVMetaDataTag tag);
+
+
 /**
  * motion estimation type.
  */

libavcodec/metadata.c

@@ -0,0 +1,75 @@
+/*
+ * copyright (c) 2009 Michael Niedermayer
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "metadata.h"
+
+AVMetaDataTag *
+av_metadata_get(struct AVMetaData *m, const char *key, const AVMetaDataTag *prev, int flags)
+{
+    unsigned int i, j;
+
+    if(!m)
+        return NULL;
+
+    if(prev) i= prev - m->elems + 1;
+    else     i= 0;
+
+    for(; i<m->count; i++){
+        const char *s= m->elems[i].key;
+        if(flags & AV_METADATA_IGNORE_CASE) for(j=0; toupper(s[j]) == toupper(key[j]) && key[j]; j++);
+        else                                for(j=0;         s[j]  ==         key[j]  && key[j]; j++);
+        if(key[j])
+            continue;
+        if(s[j] && !(flags & AV_METADATA_IGNORE_SUFFIX))
+            continue;
+        return &m->elems[i];
+    }
+    return NULL;
+}
+
+int av_metadata_set(struct AVMetaData **pm, AVMetaDataTag elem)
+{
+    struct AVMetaData *m= *pm;
+    AVMetaDataTag *tag= av_metadata_get(m, elem.key, NULL, 0);
+
+    if(!m)
+        m=*pm= av_mallocz(sizeof(*m));
+
+    if(tag){
+        av_free(tag->value);
+        av_free(tag->key);
+        *tag= m->elems[--m->count];
+    }else{
+        AVMetaDataTag *tmp= av_realloc(m->elems, (m->count+1) * sizeof(*m->elems));
+        if(tmp){
+            m->elems= tmp;
+        }else
+            return AVERROR(ENOMEM);
+    }
+    if(elem.value){
+        elem.key  = av_strdup(elem.key  );
+        elem.value= av_strdup(elem.value);
+        m->elems[m->count++]= elem;
+    }
+    if(!m->count)
+        av_freep(pm);
+
+    return 0;
+}

libavcodec/metadata.h

@@ -0,0 +1,38 @@
+/*
+ * copyright (c) 2009 Michael Niedermayer
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVCODEC_METADATA_H
+#define AVCODEC_METADATA_H
+
+/**
+ * @file metadata.h
+ * internal metadata API header
+ * see avcodec.h or the public API!
+ */
+
+
+#include "avcodec.h"
+
+struct AVMetaData{
+    int count;
+    AVMetaDataTag *elems;
+};
+
+#endif /* AVCODEC_METADATA_H */

libavformat/avformat.h

@@ -608,6 +608,8 @@ typedef struct AVFormatContext {
     struct AVPacketList *raw_packet_buffer_end;
 
     struct AVPacketList *packet_buffer_end;
+
+    struct AVMetaData *meta_data;
 } AVFormatContext;
 
 typedef struct AVPacketList {

libavformat/avidec.c

@@ -216,13 +216,17 @@ static void clean_index(AVFormatContext *s){
     }
 }
 
-static int avi_read_tag(ByteIOContext *pb, char *buf, int maxlen,  unsigned int size)
+static int avi_read_tag(AVFormatContext *s, const char *key, unsigned int size)
 {
+    ByteIOContext *pb = s->pb;
+    uint8_t value[1024];
+
     int64_t i = url_ftell(pb);
     size += (size & 1);
-    get_strz(pb, buf, maxlen);
+    get_strz(pb, value, sizeof(value));
     url_fseek(pb, i+size, SEEK_SET);
-    return 0;
+
+    return av_metadata_set(&s->meta_data, (const AVMetaDataTag){key, value});
 }
 
 static int avi_read_header(AVFormatContext *s, AVFormatParameters *ap)
@@ -235,7 +239,6 @@ static int avi_read_header(AVFormatContext *s, AVFormatParameters *ap)
     int i;
     AVStream *st;
     AVIStream *ast = NULL;
-    char str_track[4];
     int avih_width=0, avih_height=0;
     int amv_file_format=0;
 
@@ -561,26 +564,25 @@ static int avi_read_header(AVFormatContext *s, AVFormatParameters *ap)
             url_fseek(pb, size, SEEK_CUR);
             break;
         case MKTAG('I', 'N', 'A', 'M'):
-            avi_read_tag(pb, s->title, sizeof(s->title), size);
+            avi_read_tag(s, "Title", size);
             break;
         case MKTAG('I', 'A', 'R', 'T'):
-            avi_read_tag(pb, s->author, sizeof(s->author), size);
+            avi_read_tag(s, "Artist", size);
             break;
         case MKTAG('I', 'C', 'O', 'P'):
-            avi_read_tag(pb, s->copyright, sizeof(s->copyright), size);
+            avi_read_tag(s, "Copyright", size);
             break;
         case MKTAG('I', 'C', 'M', 'T'):
-            avi_read_tag(pb, s->comment, sizeof(s->comment), size);
+            avi_read_tag(s, "Comment", size);
             break;
         case MKTAG('I', 'G', 'N', 'R'):
-            avi_read_tag(pb, s->genre, sizeof(s->genre), size);
+            avi_read_tag(s, "Genre", size);
             break;
         case MKTAG('I', 'P', 'R', 'D'):
-            avi_read_tag(pb, s->album, sizeof(s->album), size);
+            avi_read_tag(s, "Album", size);
             break;
         case MKTAG('I', 'P', 'R', 'T'):
-            avi_read_tag(pb, str_track, sizeof(str_track), size);
-            sscanf(str_track, "%d", &s->track);
+            avi_read_tag(s, "Track", size);
             break;
         default:
             if(size > 1000000){

libavformat/avienc.c

@@ -103,6 +103,15 @@ static void avi_write_info_tag(ByteIOContext *pb, const char *tag, const char *s
     }
 }
 
+static void avi_write_info_tag2(AVFormatContext *s, const char *fourcc, const char *key1, const char *key2)
+{
+    AVMetaDataTag *tag= av_metadata_get(s->meta_data, key1, NULL, AV_METADATA_IGNORE_CASE);
+    if(!tag && key2)
+        tag= av_metadata_get(s->meta_data, key2, NULL, AV_METADATA_IGNORE_CASE);
+    if(tag)
+        avi_write_info_tag(s->pb, fourcc, tag->value);
+}
+
 static int avi_write_counters(AVFormatContext* s, int riff_id)
 {
     ByteIOContext *pb = s->pb;
@@ -332,17 +341,13 @@ static int avi_write_header(AVFormatContext *s)
 
     list2 = start_tag(pb, "LIST");
     put_tag(pb, "INFO");
-    avi_write_info_tag(pb, "INAM", s->title);
-    avi_write_info_tag(pb, "IART", s->author);
-    avi_write_info_tag(pb, "ICOP", s->copyright);
-    avi_write_info_tag(pb, "ICMT", s->comment);
-    avi_write_info_tag(pb, "IPRD", s->album);
-    avi_write_info_tag(pb, "IGNR", s->genre);
-    if (s->track) {
-        char str_track[4];
-        snprintf(str_track, 4, "%d", s->track);
-        avi_write_info_tag(pb, "IPRT", str_track);
-    }
+    avi_write_info_tag2(s, "INAM", "Title", NULL);
+    avi_write_info_tag2(s, "IART", "Artist", "Author");
+    avi_write_info_tag2(s, "ICOP", "Copyright", NULL);
+    avi_write_info_tag2(s, "ICMT", "Comment", NULL);
+    avi_write_info_tag2(s, "IPRD", "Album", NULL);
+    avi_write_info_tag2(s, "IGNR", "Genre", NULL);
+    avi_write_info_tag2(s, "IPRT", "Track", NULL);
     if(!(s->streams[0]->codec->flags & CODEC_FLAG_BITEXACT))
         avi_write_info_tag(pb, "ISFT", LIBAVFORMAT_IDENT);
     end_tag(pb, list2);

libavformat/utils.c

@@ -21,6 +21,7 @@
 #include "avformat.h"
 #include "internal.h"
 #include "libavcodec/opt.h"
+#include "libavcodec/metadata.h"
 #include "libavutil/avstring.h"
 #include "riff.h"
 #include <sys/time.h>
@@ -2305,6 +2306,14 @@ void av_close_input_stream(AVFormatContext *s)
         av_free(s->chapters[s->nb_chapters]);
     }
     av_freep(&s->chapters);
+    if(s->meta_data){
+        while(s->meta_data->count--){
+            av_freep(&s->meta_data->elems[s->meta_data->count].key);
+            av_freep(&s->meta_data->elems[s->meta_data->count].value);
+        }
+        av_freep(&s->meta_data->elems);
+    }
+    av_freep(&s->meta_data);
     av_free(s);
 }