X-Git-Url: http://git.tuebingen.mpg.de/?a=blobdiff_plain;f=mp4.c;h=49b975047399384bace263a7bd6bf27e57005c11;hb=391f710903d9550b37db25c9ef41466cfbd629eb;hp=0956dff1152102b1462d23b90c558aa6355c7b1f;hpb=fd11b7738de8b2961774737731de6b1b084120c8;p=paraslash.git

diff --git a/mp4.c b/mp4.c
index 0956dff1..49b97504 100644
--- a/mp4.c
+++ b/mp4.c
@@ -12,47 +12,30 @@
 #include "string.h"
 #include "mp4.h"
 
-struct mp4ff_track {
-	int32_t type;
-	int32_t channelCount;
-	int32_t sampleSize;
+struct mp4_track {
+	bool is_audio;
+	uint16_t channelCount;
 	uint16_t sampleRate;
-	int32_t audioType;
-
-	/* stsd */
-	int32_t stsd_entry_count;
 
 	/* stsz */
-	int32_t stsz_sample_size;
-	int32_t stsz_sample_count;
-	int32_t *stsz_table;
+	uint32_t stsz_sample_size;
+	uint32_t stsz_sample_count;
+	uint32_t *stsz_table;
 
 	/* stts */
-	int32_t stts_entry_count;
-	int32_t *stts_sample_count;
-	int32_t *stts_sample_delta;
+	uint32_t stts_entry_count;
+	uint32_t *stts_sample_count;
+	uint32_t *stts_sample_delta;
 
 	/* stsc */
-	int32_t stsc_entry_count;
-	int32_t *stsc_first_chunk;
-	int32_t *stsc_samples_per_chunk;
-	int32_t *stsc_sample_desc_index;
+	uint32_t stsc_entry_count;
+	uint32_t *stsc_first_chunk;
+	uint32_t *stsc_samples_per_chunk;
+	uint32_t *stsc_sample_desc_index;
 
 	/* stsc */
-	int32_t stco_entry_count;
-	int32_t *stco_chunk_offset;
-
-	/* ctts */
-	int32_t ctts_entry_count;
-	int32_t *ctts_sample_count;
-	int32_t *ctts_sample_offset;
-
-	/* esde */
-	uint8_t *decoderConfig;
-	int32_t decoderConfigLen;
-
-	uint32_t maxBitrate;
-	uint32_t avgBitrate;
+	uint32_t stco_entry_count;
+	uint32_t *stco_chunk_offset;
 
 	uint32_t timeScale;
 	uint64_t duration;
@@ -60,51 +43,48 @@ struct mp4ff_track {
 
 #define MAX_TRACKS 1024
 
-struct mp4ff {
-	/* stream to read from */
-	struct mp4ff_callback *stream;
+struct mp4 {
+	const struct mp4_callback *cb;
 	int64_t current_position;
 
 	uint64_t moov_offset;
 	uint64_t moov_size;
 	uint8_t last_atom;
 	uint64_t file_size;
-	uint32_t error;
 
-	/* mvhd */
-	int32_t time_scale;
-	int32_t duration;
+	uint32_t read_error;
+	uint32_t error;
 
 	/* incremental track index while reading the file */
 	int32_t total_tracks;
 
 	/* track data */
-	struct mp4ff_track *track[MAX_TRACKS];
+	struct mp4_track *track[MAX_TRACKS];
 
 	/* metadata */
-	struct mp4ff_metadata tags;
+	struct mp4_metadata meta;
 };
 
-int32_t mp4ff_total_tracks(const struct mp4ff *f)
+int32_t mp4_total_tracks(const struct mp4 *f)
 {
 	return f->total_tracks;
 }
 
-static int32_t read_data(struct mp4ff *f, void *data, uint32_t size)
+static int32_t read_data(struct mp4 *f, void *data, uint32_t size)
 {
 	int32_t result = 1;
 
-	result = f->stream->read(f->stream->user_data, data, size);
+	result = f->cb->read(f->cb->user_data, data, size);
 
 	if (result < size)
-		f->stream->read_error++;
+		f->read_error++;
 
 	f->current_position += size;
 
 	return result;
 }
 
-static uint64_t read_int64(struct mp4ff *f)
+static uint64_t read_int64(struct mp4 *f)
 {
 	uint8_t data[8];
 
@@ -112,25 +92,11 @@ static uint64_t read_int64(struct mp4ff *f)
 	return read_u64_be(data);
 }
 
-/* comnapre 2 atom names, returns 1 for equal, 0 for unequal */
-static int32_t atom_compare(const int8_t a1, const int8_t b1,
-				  const int8_t c1, const int8_t d1,
-				  const int8_t a2, const int8_t b2,
-				  const int8_t c2, const int8_t d2)
+static bool atom_compare(int8_t a1, int8_t b1, int8_t c1, int8_t d1,
+		int8_t a2, int8_t b2, int8_t c2, int8_t d2)
 {
-	if (a1 == a2 && b1 == b2 && c1 == c2 && d1 == d2)
-		return 1;
-	else
-		return 0;
+	return a1 == a2 && b1 == b2 && c1 == c2 && d1 == d2;
 }
-
-enum tracks {
-	TRACK_UNKNOWN = 0,
-	TRACK_AUDIO  = 1,
-	TRACK_VIDEO = 2,
-	TRACK_SYSTEM = 3
-};
-
 enum atoms {
 	/* atoms with subatoms */
 	ATOM_MOOV = 1,
@@ -215,8 +181,7 @@ enum atoms {
 
 #define COPYRIGHT_SYMBOL ((int8_t)0xA9)
 
-static uint8_t atom_name_to_type(const int8_t a, const int8_t b,
-		const int8_t c, const int8_t d)
+static uint8_t atom_name_to_type(int8_t a, int8_t b, int8_t c, int8_t d)
 {
 	if (a == 'm') {
 		if (atom_compare(a, b, c, d, 'm', 'o', 'o', 'v'))
@@ -371,7 +336,7 @@ static uint8_t atom_name_to_type(const int8_t a, const int8_t b,
 }
 
 /* read atom header, return atom size, atom size is with header included */
-static uint64_t atom_read_header(struct mp4ff *f, uint8_t * atom_type,
+static uint64_t atom_read_header(struct mp4 *f, uint8_t * atom_type,
 				uint8_t * header_size)
 {
 	uint64_t size;
@@ -395,7 +360,7 @@ static uint64_t atom_read_header(struct mp4ff *f, uint8_t * atom_type,
 	return size;
 }
 
-static int64_t get_position(const struct mp4ff *f)
+static int64_t get_position(const struct mp4 *f)
 {
 	return f->current_position;
 }
@@ -421,15 +386,15 @@ static int need_parse_when_meta_only(uint8_t atom_type)
 	}
 }
 
-static int32_t set_position(struct mp4ff *f, const int64_t position)
+static int32_t set_position(struct mp4 *f, int64_t position)
 {
-	f->stream->seek(f->stream->user_data, position);
+	f->cb->seek(f->cb->user_data, position);
 	f->current_position = position;
 
 	return 0;
 }
 
-static void track_add(struct mp4ff *f)
+static void track_add(struct mp4 *f)
 {
 	f->total_tracks++;
 
@@ -438,17 +403,17 @@ static void track_add(struct mp4ff *f)
 		f->error++;
 		return;
 	}
-	f->track[f->total_tracks - 1] = para_calloc(sizeof(struct mp4ff_track));
+	f->track[f->total_tracks - 1] = para_calloc(sizeof(struct mp4_track));
 }
 
-static uint8_t read_char(struct mp4ff *f)
+static uint8_t read_char(struct mp4 *f)
 {
 	uint8_t output;
 	read_data(f, &output, 1);
 	return output;
 }
 
-static uint32_t read_int24(struct mp4ff *f)
+static uint32_t read_int24(struct mp4 *f)
 {
 	int8_t data[4];
 
@@ -456,7 +421,7 @@ static uint32_t read_int24(struct mp4ff *f)
 	return read_u24_be(data);
 }
 
-static uint32_t read_int32(struct mp4ff *f)
+static uint32_t read_int32(struct mp4 *f)
 {
 	int8_t data[4];
 
@@ -464,10 +429,10 @@ static uint32_t read_int32(struct mp4ff *f)
 	return read_u32_be(data);
 }
 
-static int32_t read_stsz(struct mp4ff *f)
+static int32_t read_stsz(struct mp4 *f)
 {
 	int32_t i;
-	struct mp4ff_track *t;
+	struct mp4_track *t;
 
 	if (f->total_tracks == 0)
 		return f->error++;
@@ -479,15 +444,15 @@ static int32_t read_stsz(struct mp4ff *f)
 	if (t->stsz_sample_size != 0)
 		return 0;
 	t->stsz_table = para_malloc(t->stsz_sample_count * sizeof(int32_t));
-	for (i = 0; i < t->stsz_sample_count && !f->stream->read_error; i++)
+	for (i = 0; i < t->stsz_sample_count && !f->read_error; i++)
 		t->stsz_table[i] = read_int32(f);
 	return 0;
 }
 
-static int32_t read_stts(struct mp4ff *f)
+static int32_t read_stts(struct mp4 *f)
 {
 	int32_t i;
-	struct mp4ff_track *t;
+	struct mp4_track *t;
 
 	/* CVE-2017-9223 */
 	if (f->total_tracks == 0)
@@ -504,45 +469,17 @@ static int32_t read_stts(struct mp4ff *f)
 	t->stts_sample_delta = para_malloc(t->stts_entry_count
 		* sizeof (int32_t));
 	/* CVE-2017-9254 */
-	for (i = 0; i < t->stts_entry_count && !f->stream->read_error; i++) {
+	for (i = 0; i < t->stts_entry_count && !f->read_error; i++) {
 		t->stts_sample_count[i] = read_int32(f);
 		t->stts_sample_delta[i] = read_int32(f);
 	}
 	return 1;
 }
 
-static int32_t read_ctts(struct mp4ff *f)
-{
-	int32_t i;
-	struct mp4ff_track *t;
-
-	if (f->total_tracks == 0)
-		return f->error++;
-	t = f->track[f->total_tracks - 1];
-	if (t->ctts_entry_count)
-		return 0;
-
-	read_char(f);	/* version */
-	read_int24(f);	/* flags */
-	t->ctts_entry_count = read_int32(f);
-
-	t->ctts_sample_count = para_malloc(t->ctts_entry_count
-		* sizeof (int32_t));
-	t->ctts_sample_offset = para_malloc(t->ctts_entry_count
-		* sizeof (int32_t));
-
-	/* CVE-2017-9257 */
-	for (i = 0; i < t->ctts_entry_count && !f->stream->read_error; i++) {
-		t->ctts_sample_count[i] = read_int32(f);
-		t->ctts_sample_offset[i] = read_int32(f);
-	}
-	return 1;
-}
-
-static int32_t read_stsc(struct mp4ff *f)
+static int32_t read_stsc(struct mp4 *f)
 {
 	int32_t i;
-	struct mp4ff_track *t;
+	struct mp4_track *t;
 
 	if (f->total_tracks == 0)
 		return f->error++;
@@ -558,7 +495,7 @@ static int32_t read_stsc(struct mp4ff *f)
 		sizeof (int32_t));
 
 	/* CVE-2017-9255 */
-	for (i = 0; i < t->stsc_entry_count && !f->stream->read_error; i++) {
+	for (i = 0; i < t->stsc_entry_count && !f->read_error; i++) {
 		t->stsc_first_chunk[i] = read_int32(f);
 		t->stsc_samples_per_chunk[i] = read_int32(f);
 		t->stsc_sample_desc_index[i] = read_int32(f);
@@ -566,10 +503,10 @@ static int32_t read_stsc(struct mp4ff *f)
 	return 0;
 }
 
-static int32_t read_stco(struct mp4ff *f)
+static int32_t read_stco(struct mp4 *f)
 {
 	int32_t i;
-	struct mp4ff_track *t;
+	struct mp4_track *t;
 
 	if (f->total_tracks == 0)
 		return f->error++;
@@ -581,12 +518,12 @@ static int32_t read_stco(struct mp4ff *f)
 	t->stco_chunk_offset = para_malloc(t->stco_entry_count
 		* sizeof(int32_t));
 	/* CVE-2017-9256 */
-	for (i = 0; i < t->stco_entry_count && !f->stream->read_error; i++)
+	for (i = 0; i < t->stco_entry_count && !f->read_error; i++)
 		t->stco_chunk_offset[i] = read_int32(f);
 	return 0;
 }
 
-static uint16_t read_int16(struct mp4ff *f)
+static uint16_t read_int16(struct mp4 *f)
 {
 	int8_t data[2];
 
@@ -594,80 +531,12 @@ static uint16_t read_int16(struct mp4ff *f)
 	return read_u16_be(data);
 }
 
-static uint32_t read_mp4_descr_length(struct mp4ff *f)
-{
-	uint8_t b;
-	uint8_t numBytes = 0;
-	uint32_t length = 0;
-
-	do {
-		b = read_char(f);
-		numBytes++;
-		length = (length << 7) | (b & 0x7F);
-	} while ((b & 0x80) && numBytes < 4);
-
-	return length;
-}
-static int32_t read_esds(struct mp4ff *f)
-{
-	uint8_t tag;
-	uint32_t temp;
-	struct mp4ff_track *t;
-
-	if (f->total_tracks == 0)
-		return f->error++;
-	t = f->track[f->total_tracks - 1];
-	read_char(f);	/* version */
-	read_int24(f);	/* flags */
-	/* get and verify ES_DescrTag */
-	tag = read_char(f);
-	if (tag == 0x03) {
-		/* read length */
-		if (read_mp4_descr_length(f) < 5 + 15) {
-			return 1;
-		}
-		/* skip 3 bytes */
-		read_int24(f);
-	} else {
-		/* skip 2 bytes */
-		read_int16(f);
-	}
-
-	/* get and verify DecoderConfigDescrTab */
-	if (read_char(f) != 0x04) {
-		return 1;
-	}
-
-	/* read length */
-	temp = read_mp4_descr_length(f);
-	if (temp < 13)
-		return 1;
-
-	t->audioType = read_char(f);
-	read_int32(f);	//0x15000414 ????
-	t->maxBitrate = read_int32(f);
-	t->avgBitrate = read_int32(f);
-
-	/* get and verify DecSpecificInfoTag */
-	if (read_char(f) != 0x05) {
-		return 1;
-	}
-
-	/* read length */
-	t->decoderConfigLen = read_mp4_descr_length(f);
-	free(t->decoderConfig);
-	t->decoderConfig = para_malloc(t->decoderConfigLen);
-	read_data(f, t->decoderConfig, t->decoderConfigLen);
-	/* will skip the remainder of the atom */
-	return 0;
-}
-
-static int32_t read_mp4a(struct mp4ff *f)
+static int32_t read_mp4a(struct mp4 *f)
 {
 	int32_t i;
 	uint8_t atom_type = 0;
 	uint8_t header_size = 0;
-	struct mp4ff_track *t;
+	struct mp4_track *t;
 
 	if (f->total_tracks == 0)
 		return f->error++;
@@ -682,7 +551,7 @@ static int32_t read_mp4a(struct mp4ff *f)
 	read_int32(f);	/* reserved */
 
 	t->channelCount = read_int16(f);
-	t->sampleSize = read_int16(f);
+	read_int16(f);
 
 	read_int16(f);
 	read_int16(f);
@@ -692,16 +561,14 @@ static int32_t read_mp4a(struct mp4ff *f)
 	read_int16(f);
 
 	atom_read_header(f, &atom_type, &header_size);
-	if (atom_type == ATOM_ESDS)
-		read_esds(f);
 	return 0;
 }
 
-static int32_t read_stsd(struct mp4ff *f)
+static int32_t read_stsd(struct mp4 *f)
 {
-	int32_t i;
+	int32_t i, entry_count;
 	uint8_t header_size = 0;
-	struct mp4ff_track *t;
+	struct mp4_track *t;
 
 	/* CVE-2017-9218 */
 	if (f->total_tracks == 0)
@@ -711,127 +578,43 @@ static int32_t read_stsd(struct mp4ff *f)
 	read_char(f);	/* version */
 	read_int24(f);	/* flags */
 
-	t->stsd_entry_count = read_int32(f);
+	entry_count = read_int32(f);
 
 	/* CVE-2017-9253 */
-	for (i = 0; i < t->stsd_entry_count && !f->stream->read_error; i++) {
+	for (i = 0; i < entry_count && !f->read_error; i++) {
 		uint64_t skip = get_position(f);
 		uint64_t size;
 		uint8_t atom_type = 0;
 		size = atom_read_header(f, &atom_type, &header_size);
 		skip += size;
-
-		if (atom_type == ATOM_MP4A) {
-			t->type = TRACK_AUDIO;
+		t->is_audio = atom_type == ATOM_MP4A;
+		if (t->is_audio)
 			read_mp4a(f);
-		} else if (atom_type == ATOM_MP4V) {
-			t->type = TRACK_VIDEO;
-		} else if (atom_type == ATOM_MP4S) {
-			t->type = TRACK_SYSTEM;
-		} else {
-			t->type = TRACK_UNKNOWN;
-		}
 		set_position(f, skip);
 	}
 
 	return 0;
 }
 
-static int32_t read_mvhd(struct mp4ff *f)
-{
-	int32_t i;
-
-	read_char(f);	/* version */
-	read_int24(f);	/* flags */
-	read_int32(f); /* creation_time */
-	read_int32(f); /* modification_time */
-	f->time_scale = read_int32(f);
-	f->duration = read_int32(f);
-	read_int32(f); /* preferred_rate */
-	read_int16(f); /* preferred_volume */
-	for (i = 0; i < 10; i++)
-		read_char(f); /* reserved */
-	for (i = 0; i < 9; i++)
-		read_int32(f); /* matrix */
-	read_int32(f); /* preview_time */
-	read_int32(f); /* preview_duration */
-	read_int32(f); /* poster_time */
-	read_int32(f); /* selection_time */
-	read_int32(f); /* selection_duration */
-	read_int32(f); /* current_time */
-	read_int32(f); /* next_track_id */
-	return 0;
-}
-
-static int32_t tag_add_field(struct mp4ff_metadata *tags, const char *item,
+static int32_t tag_add_field(struct mp4_metadata *meta, const char *item,
 		const char *value, int32_t len)
 {
-	void *backup = (void *) tags->tags;
-
-	if (!item || (item && !*item) || !value)
-		return 0;
-
-	tags->tags = (struct mp4ff_tag *)realloc(tags->tags,
-		(tags->count + 1) * sizeof(struct mp4ff_tag));
-	if (!tags->tags) {
-		free(backup);
-		return 0;
+	meta->tags = para_realloc(meta->tags,
+		(meta->count + 1) * sizeof(struct mp4_tag));
+	meta->tags[meta->count].item = para_strdup(item);
+	meta->tags[meta->count].len = len;
+	if (len >= 0) {
+		meta->tags[meta->count].value = para_malloc(len + 1);
+		memcpy(meta->tags[meta->count].value, value, len);
+		meta->tags[meta->count].value[len] = 0;
 	} else {
-		tags->tags[tags->count].item = para_strdup(item);
-		tags->tags[tags->count].len = len;
-		if (len >= 0) {
-			tags->tags[tags->count].value = para_malloc(len + 1);
-			memcpy(tags->tags[tags->count].value, value, len);
-			tags->tags[tags->count].value[len] = 0;
-		} else {
-			tags->tags[tags->count].value = para_strdup(value);
-		}
-		tags->count++;
-		return 1;
-	}
-}
-
-static const char *ID3v1GenreList[] = {
-	"Blues", "Classic Rock", "Country", "Dance", "Disco", "Funk",
-	"Grunge", "Hip-Hop", "Jazz", "Metal", "New Age", "Oldies",
-	"Other", "Pop", "R&B", "Rap", "Reggae", "Rock",
-	"Techno", "Industrial", "Alternative", "Ska", "Death Metal", "Pranks",
-	"Soundtrack", "Euro-Techno", "Ambient", "Trip-Hop", "Vocal",
-	"Jazz+Funk", "Fusion", "Trance", "Classical", "Instrumental", "Acid",
-	"House", "Game", "Sound Clip", "Gospel", "Noise", "AlternRock", "Bass",
-	"Soul", "Punk", "Space", "Meditative", "Instrumental Pop",
-	"Instrumental Rock", "Ethnic", "Gothic", "Darkwave",
-	"Techno-Industrial", "Electronic", "Pop-Folk", "Eurodance", "Dream",
-	"Southern Rock", "Comedy", "Cult", "Gangsta", "Top 40",
-	"Christian Rap", "Pop/Funk", "Jungle", "Native American", "Cabaret",
-	"New Wave", "Psychadelic", "Rave", "Showtunes", "Trailer", "Lo-Fi",
-	"Tribal", "Acid Punk", "Acid Jazz", "Polka", "Retro", "Musical",
-	"Rock & Roll", "Hard Rock", "Folk", "Folk/Rock", "National Folk",
-	"Swing", "Fast-Fusion", "Bebob", "Latin", "Revival", "Celtic",
-	"Bluegrass", "Avantgarde", "Gothic Rock", "Progressive Rock",
-	"Psychedelic Rock", "Symphonic Rock", "Slow Rock", "Big Band",
-	"Chorus", "Easy Listening", "Acoustic", "Humour", "Speech", "Chanson",
-	"Opera", "Chamber Music", "Sonata", "Symphony", "Booty Bass", "Primus",
-	"Porn Groove", "Satire", "Slow Jam", "Club", "Tango", "Samba",
-	"Folklore", "Ballad", "Power Ballad", "Rhythmic Soul", "Freestyle",
-	"Duet", "Punk Rock", "Drum Solo", "A capella", "Euro-House",
-	"Dance Hall", "Goa", "Drum & Bass", "Club House", "Hardcore", "Terror",
-	"Indie", "BritPop", "NegerPunk", "Polsk Punk", "Beat",
-	"Christian Gangsta", "Heavy Metal", "Black Metal", "Crossover",
-	"Contemporary C", "Christian Rock", "Merengue", "Salsa", "Thrash Metal",
-	"Anime", "JPop", "SynthPop",
-};
-
-static const char *meta_index_to_genre(uint32_t idx)
-{
-	if (idx > 0 && idx <= sizeof (ID3v1GenreList) / sizeof (ID3v1GenreList[0])) {
-		return ID3v1GenreList[idx - 1];
-	} else {
-		return 0;
+		meta->tags[meta->count].value = para_strdup(value);
 	}
+	meta->count++;
+	return 1;
 }
 
-static char *read_string(struct mp4ff *f, uint32_t length)
+static char *read_string(struct mp4 *f, uint32_t length)
 {
 	char *str = para_malloc(length + 1);
 	if ((uint32_t)read_data(f, str, length) != length) {
@@ -842,239 +625,53 @@ static char *read_string(struct mp4ff *f, uint32_t length)
 	return str;
 }
 
-static int32_t set_metadata_name(const uint8_t atom_type, char **name)
+static const char *get_metadata_name(uint8_t atom_type)
 {
-	static char *tag_names[] = {
-		"unknown", "title", "artist", "writer", "album",
-		"date", "tool", "comment", "genre", "track",
-		"disc", "compilation", "genre", "tempo", "cover",
-		"album_artist", "contentgroup", "lyrics", "description",
-		"network", "show", "episodename",
-		"sorttitle", "sortalbum", "sortartist", "sortalbumartist",
-		"sortwriter", "sortshow",
-		"season", "episode", "podcast"
-	};
-	uint8_t tag_idx = 0;
-
 	switch (atom_type) {
-	case ATOM_TITLE:
-		tag_idx = 1;
-		break;
-	case ATOM_ARTIST:
-		tag_idx = 2;
-		break;
-	case ATOM_WRITER:
-		tag_idx = 3;
-		break;
-	case ATOM_ALBUM:
-		tag_idx = 4;
-		break;
-	case ATOM_DATE:
-		tag_idx = 5;
-		break;
-	case ATOM_TOOL:
-		tag_idx = 6;
-		break;
-	case ATOM_COMMENT:
-		tag_idx = 7;
-		break;
-	case ATOM_GENRE1:
-		tag_idx = 8;
-		break;
-	case ATOM_TRACK:
-		tag_idx = 9;
-		break;
-	case ATOM_DISC:
-		tag_idx = 10;
-		break;
-	case ATOM_COMPILATION:
-		tag_idx = 11;
-		break;
-	case ATOM_GENRE2:
-		tag_idx = 12;
-		break;
-	case ATOM_TEMPO:
-		tag_idx = 13;
-		break;
-	case ATOM_COVER:
-		tag_idx = 14;
-		break;
-	case ATOM_ALBUM_ARTIST:
-		tag_idx = 15;
-		break;
-	case ATOM_CONTENTGROUP:
-		tag_idx = 16;
-		break;
-	case ATOM_LYRICS:
-		tag_idx = 17;
-		break;
-	case ATOM_DESCRIPTION:
-		tag_idx = 18;
-		break;
-	case ATOM_NETWORK:
-		tag_idx = 19;
-		break;
-	case ATOM_SHOW:
-		tag_idx = 20;
-		break;
-	case ATOM_EPISODENAME:
-		tag_idx = 21;
-		break;
-	case ATOM_SORTTITLE:
-		tag_idx = 22;
-		break;
-	case ATOM_SORTALBUM:
-		tag_idx = 23;
-		break;
-	case ATOM_SORTARTIST:
-		tag_idx = 24;
-		break;
-	case ATOM_SORTALBUMARTIST:
-		tag_idx = 25;
-		break;
-	case ATOM_SORTWRITER:
-		tag_idx = 26;
-		break;
-	case ATOM_SORTSHOW:
-		tag_idx = 27;
-		break;
-	case ATOM_SEASON:
-		tag_idx = 28;
-		break;
-	case ATOM_EPISODE:
-		tag_idx = 29;
-		break;
-	case ATOM_PODCAST:
-		tag_idx = 30;
-		break;
-	default:
-		tag_idx = 0;
-		break;
-	}
-
-	*name = para_strdup(tag_names[tag_idx]);
-	return 0;
-}
-
-static uint32_t min_body_size(const uint8_t atom_type)
-{
-	switch(atom_type) {
-	case ATOM_GENRE2:
-	case ATOM_TEMPO:
-		return 10;
-	case ATOM_TRACK:
-		return sizeof (char) /* version */
-			+ sizeof(uint8_t) * 3 /* flags */
-			+ sizeof(uint32_t) /* reserved */
-			+ sizeof(uint16_t) /* leading uint16_t */
-			+ sizeof(uint16_t) /* track */
-			+ sizeof(uint16_t); /* totaltracks */
-	case ATOM_DISC:
-		return sizeof (char) /* version */
-			+ sizeof(uint8_t) * 3 /* flags */
-			+ sizeof(uint32_t) /* reserved */
-			+ sizeof(uint16_t) /* disc */
-			+ sizeof(uint16_t); /* totaldiscs */
-	default: assert(false);
+	case ATOM_TITLE: return "title";
+	case ATOM_ARTIST: return "artist";
+	case ATOM_ALBUM: return "album";
+	case ATOM_DATE: return "date";
+	case ATOM_COMMENT: return "comment";
+	default: return "unknown";
 	}
 }
 
-static int32_t parse_tag(struct mp4ff *f, const uint8_t parent,
-		const int32_t size)
+static void parse_tag(struct mp4 *f, uint8_t parent, int32_t size)
 {
-	uint8_t atom_type;
-	uint8_t header_size = 0;
 	uint64_t subsize, sumsize;
-	char *name = NULL;
 	char *data = NULL;
-	uint32_t done = 0;
 	uint32_t len = 0;
 	uint64_t destpos;
 
 	for (
 		sumsize = 0;
-		sumsize < size && !f->stream->read_error; /* CVE-2017-9222 */
+		sumsize < size && !f->read_error; /* CVE-2017-9222 */
 		set_position(f, destpos), sumsize += subsize
 	) {
+		uint8_t atom_type;
+		uint8_t header_size = 0;
 		subsize = atom_read_header(f, &atom_type, &header_size);
 		destpos = get_position(f) + subsize - header_size;
-		if (done)
-			continue;
-		if (atom_type == ATOM_NAME) {
-			read_char(f);	/* version */
-			read_int24(f);	/* flags */
-			free(name);
-			name = read_string(f, subsize - (header_size + 4));
-			continue;
-		}
 		if (atom_type != ATOM_DATA)
 			continue;
 		read_char(f);	/* version */
 		read_int24(f);	/* flags */
 		read_int32(f);	/* reserved */
-
-		/* some need special attention */
-		if (parent == ATOM_GENRE2 || parent == ATOM_TEMPO) {
-			uint16_t val;
-			if (subsize - header_size < min_body_size(parent))
-				continue;
-			val = read_int16(f);
-			if (parent == ATOM_TEMPO) {
-				char temp[16];
-				sprintf(temp, "%.5u BPM", val);
-				tag_add_field(&(f-> tags), "tempo",
-					temp, -1);
-			} else {
-				const char *tmp = meta_index_to_genre(val);
-				if (tmp)
-					tag_add_field (&(f->tags),
-						"genre", tmp, -1);
-			}
-			done = 1;
-		} else if (parent == ATOM_TRACK || parent == ATOM_DISC) {
-			uint16_t index, total;
-			char temp[32];
-			if (subsize - header_size < min_body_size(parent))
-				continue;
-			read_int16(f);
-			index = read_int16(f);
-			total = read_int16(f);
-			if (parent == ATOM_TRACK)
-				read_int16(f);
-			sprintf(temp, "%d", index);
-			tag_add_field(&(f->tags), parent == ATOM_TRACK?
-				"track" : "disc", temp, -1);
-			if (total > 0) {
-				sprintf(temp, "%d", total);
-				tag_add_field(& (f-> tags),
-					parent == ATOM_TRACK?
-					"totaltracks" : "totaldiscs", temp, -1);
-			}
-			done = 1;
-		} else {
-			free(data);
-			data = read_string(f, subsize - (header_size + 8));
-			len = subsize - (header_size + 8);
-		}
-	}
-	if (data) {
-		if (!done) {
-			if (name == NULL)
-				set_metadata_name(parent , &name);
-			if (name)
-				tag_add_field(&(f->tags), name, data, len);
-		}
-
 		free(data);
+		data = read_string(f, subsize - (header_size + 8));
+		len = subsize - (header_size + 8);
 	}
-	free(name);
-	return 1;
+	if (!data)
+		return;
+	tag_add_field(&f->meta, get_metadata_name(parent), data, len);
+	free(data);
 }
 
-static int32_t read_mdhd(struct mp4ff *f)
+static int32_t read_mdhd(struct mp4 *f)
 {
 	uint32_t version;
-	struct mp4ff_track *t;
+	struct mp4_track *t;
 
 	/* CVE-2017-9221 */
 	if (f->total_tracks == 0)
@@ -1102,24 +699,34 @@ static int32_t read_mdhd(struct mp4ff *f)
 	return 1;
 }
 
-static int32_t parse_metadata(struct mp4ff *f, const int32_t size)
+static int32_t read_ilst(struct mp4 *f, int32_t size)
 {
-	uint64_t subsize, sumsize = 0;
-	uint8_t atom_type;
-	uint8_t header_size = 0;
+	uint64_t sumsize = 0;
 
 	while (sumsize < size) {
+		uint8_t atom_type;
+		uint64_t subsize, destpos;
+		uint8_t header_size = 0;
 		subsize = atom_read_header(f, &atom_type, &header_size);
 		if (subsize == 0)
 			break;
-		parse_tag(f, atom_type, (uint32_t)(subsize - header_size));
+		destpos = get_position(f) + subsize - header_size;
+		switch (atom_type) {
+		case ATOM_ARTIST:
+		case ATOM_TITLE:
+		case ATOM_ALBUM:
+		case ATOM_COMMENT:
+		case ATOM_DATE:
+			parse_tag(f, atom_type, subsize - header_size);
+		}
+		set_position(f, destpos);
 		sumsize += subsize;
 	}
 
 	return 0;
 }
 
-static int32_t read_meta(struct mp4ff *f, const uint64_t size)
+static int32_t read_meta(struct mp4 *f, uint64_t size)
 {
 	uint64_t subsize, sumsize = 0;
 	uint8_t atom_type;
@@ -1132,19 +739,17 @@ static int32_t read_meta(struct mp4ff *f, const uint64_t size)
 		subsize = atom_read_header(f, &atom_type, &header_size);
 		if (subsize <= header_size + 4)
 			return 1;
-		if (atom_type == ATOM_ILST) {
-			parse_metadata(f, (uint32_t) (subsize - (header_size + 4)));
-		} else {
+		if (atom_type == ATOM_ILST)
+			read_ilst(f, subsize - (header_size + 4));
+		else
 			set_position(f, get_position(f) + subsize - header_size);
-		}
 		sumsize += subsize;
 	}
 
 	return 0;
 }
 
-static int32_t atom_read(struct mp4ff *f, const int32_t size,
-		const uint8_t atom_type)
+static int32_t atom_read(struct mp4 *f, int32_t size, uint8_t atom_type)
 {
 	uint64_t dest_position = get_position(f) + size - 8;
 	if (atom_type == ATOM_STSZ) {
@@ -1153,9 +758,6 @@ static int32_t atom_read(struct mp4ff *f, const int32_t size,
 	} else if (atom_type == ATOM_STTS) {
 		/* time to sample box */
 		read_stts(f);
-	} else if (atom_type == ATOM_CTTS) {
-		/* composition offset box */
-		read_ctts(f);
 	} else if (atom_type == ATOM_STSC) {
 		/* sample to chunk box */
 		read_stsc(f);
@@ -1165,9 +767,6 @@ static int32_t atom_read(struct mp4ff *f, const int32_t size,
 	} else if (atom_type == ATOM_STSD) {
 		/* sample description box */
 		read_stsd(f);
-	} else if (atom_type == ATOM_MVHD) {
-		/* movie header box */
-		read_mvhd(f);
 	} else if (atom_type == ATOM_MDHD) {
 		/* track header */
 		read_mdhd(f);
@@ -1181,7 +780,7 @@ static int32_t atom_read(struct mp4ff *f, const int32_t size,
 }
 
 /* parse atoms that are sub atoms of other atoms */
-static int32_t parse_sub_atoms(struct mp4ff *f, const uint64_t total_size, int meta_only)
+static int32_t parse_sub_atoms(struct mp4 *f, uint64_t total_size, int meta_only)
 {
 	uint64_t size;
 	uint8_t atom_type = 0;
@@ -1215,14 +814,14 @@ static int32_t parse_sub_atoms(struct mp4ff *f, const uint64_t total_size, int m
 }
 
 /* parse root atoms */
-static int32_t parse_atoms(struct mp4ff *f, int meta_only)
+static int32_t parse_atoms(struct mp4 *f, int meta_only)
 {
 	uint64_t size;
 	uint8_t atom_type = 0;
 	uint8_t header_size = 0;
 
 	f->file_size = 0;
-	f->stream->read_error = 0;
+	f->read_error = 0;
 
 	while ((size =
 		atom_read_header(f, &atom_type, &header_size)) != 0) {
@@ -1248,84 +847,45 @@ static int32_t parse_atoms(struct mp4ff *f, int meta_only)
 	return 0;
 }
 
-void mp4ff_get_decoder_config(const struct mp4ff *f, const int track,
-				 unsigned char **ppBuf, unsigned int *pBufSize)
+struct mp4 *mp4_open_read(const struct mp4_callback *cb)
 {
-	if (track >= f->total_tracks) {
-		*ppBuf = NULL;
-		*pBufSize = 0;
-		return;
-	}
+	struct mp4 *f = para_calloc(sizeof(struct mp4));
 
-	if (f->track[track]->decoderConfig == NULL
-		|| f->track[track]->decoderConfigLen == 0) {
-		*ppBuf = NULL;
-		*pBufSize = 0;
-	} else {
-		*ppBuf = para_malloc(f->track[track]->decoderConfigLen);
-		memcpy(*ppBuf, f->track[track]->decoderConfig,
-			f->track[track]->decoderConfigLen);
-		*pBufSize = f->track[track]->decoderConfigLen;
+	f->cb = cb;
+	parse_atoms(f, 0);
+	if (f->error) {
+		free(f);
+		f = NULL;
 	}
+	return f;
 }
 
-struct mp4ff *mp4ff_open_read(struct mp4ff_callback *f)
-{
-	struct mp4ff *ff = para_calloc(sizeof(struct mp4ff));
-
-	ff->stream = f;
-
-	parse_atoms(ff, 0);
-
-	if (ff->error) {
-		free(ff);
-		ff = NULL;
-	}
-
-	return ff;
-}
-
-static int32_t tag_delete(struct mp4ff_metadata *tags)
-{
-	uint32_t i;
-
-	for (i = 0; i < tags->count; i++) {
-		free(tags->tags[i].item);
-		free(tags->tags[i].value);
-	}
-	free(tags->tags);
-	tags->tags = NULL;
-	tags->count = 0;
-
-	return 0;
-}
-
-void mp4ff_close(struct mp4ff *ff)
+void mp4_close(struct mp4 *f)
 {
 	int32_t i;
 
-	for (i = 0; i < ff->total_tracks; i++) {
-		if (ff->track[i]) {
-			free(ff->track[i]->stsz_table);
-			free(ff->track[i]->stts_sample_count);
-			free(ff->track[i]->stts_sample_delta);
-			free(ff->track[i]->stsc_first_chunk);
-			free(ff->track[i]->stsc_samples_per_chunk);
-			free(ff->track[i]->stsc_sample_desc_index);
-			free(ff->track[i]->stco_chunk_offset);
-			free(ff->track[i]->decoderConfig);
-			free(ff->track[i]->ctts_sample_count);
-			free(ff->track[i]->ctts_sample_offset);
-			free(ff->track[i]);
+	for (i = 0; i < f->total_tracks; i++) {
+		if (f->track[i]) {
+			free(f->track[i]->stsz_table);
+			free(f->track[i]->stts_sample_count);
+			free(f->track[i]->stts_sample_delta);
+			free(f->track[i]->stsc_first_chunk);
+			free(f->track[i]->stsc_samples_per_chunk);
+			free(f->track[i]->stsc_sample_desc_index);
+			free(f->track[i]->stco_chunk_offset);
+			free(f->track[i]);
 		}
 	}
-
-	tag_delete(&(ff->tags));
-	free(ff);
+	for (i = 0; i < f->meta.count; i++) {
+		free(f->meta.tags[i].item);
+		free(f->meta.tags[i].value);
+	}
+	free(f->meta.tags);
+	free(f);
 }
 
-static int32_t chunk_of_sample(const struct mp4ff *f, const int32_t track,
-		const int32_t sample, int32_t * chunk_sample, int32_t * chunk)
+static int32_t chunk_of_sample(const struct mp4 *f, int32_t track,
+		int32_t sample, int32_t *chunk_sample, int32_t *chunk)
 {
 	int32_t total_entries = 0;
 	int32_t chunk2entry;
@@ -1370,10 +930,10 @@ static int32_t chunk_of_sample(const struct mp4ff *f, const int32_t track,
 	return 0;
 }
 
-static int32_t chunk_to_offset(const struct mp4ff *f, const int32_t track,
-		const int32_t chunk)
+static int32_t chunk_to_offset(const struct mp4 *f, int32_t track,
+		int32_t chunk)
 {
-	const struct mp4ff_track *p_track = f->track[track];
+	const struct mp4_track *p_track = f->track[track];
 
 	if (p_track->stco_entry_count && (chunk > p_track->stco_entry_count)) {
 		return p_track->stco_chunk_offset[p_track->stco_entry_count -
@@ -1387,11 +947,11 @@ static int32_t chunk_to_offset(const struct mp4ff *f, const int32_t track,
 	return 0;
 }
 
-static int32_t sample_range_size(const struct mp4ff *f, const int32_t track,
-		const int32_t chunk_sample, const int32_t sample)
+static int32_t sample_range_size(const struct mp4 *f, int32_t track,
+		int32_t chunk_sample, int32_t sample)
 {
 	int32_t i, total;
-	const struct mp4ff_track *p_track = f->track[track];
+	const struct mp4_track *p_track = f->track[track];
 
 	if (p_track->stsz_sample_size) {
 		return (sample - chunk_sample) * p_track->stsz_sample_size;
@@ -1407,8 +967,8 @@ static int32_t sample_range_size(const struct mp4ff *f, const int32_t track,
 	return total;
 }
 
-static int32_t sample_to_offset(const struct mp4ff *f, const int32_t track,
-		const int32_t sample)
+static int32_t sample_to_offset(const struct mp4 *f, int32_t track,
+		int32_t sample)
 {
 	int32_t chunk, chunk_sample, chunk_offset1, chunk_offset2;
 
@@ -1420,33 +980,64 @@ static int32_t sample_to_offset(const struct mp4ff *f, const int32_t track,
 	return chunk_offset2;
 }
 
-void mp4ff_set_sample_position(struct mp4ff *f, const int32_t track,
-		const int32_t sample)
+/**
+ * Return the number of milliseconds of the given track.
+ *
+ * \param f As returned by \ref mp4_open_read(), must not be NULL.
+ * \param track Between zero and the value returned by \ref mp4_total_tracks().
+ *
+ * The function returns zero if the audio file is of zero length or contains a
+ * corrupt track header.
+ */
+uint64_t mp4_get_duration(const struct mp4 *f, int32_t track)
+{
+	const struct mp4_track *t = f->track[track];
+
+	if (t->timeScale == 0)
+		return 0;
+	return t->duration * 1000 / t->timeScale;
+}
+
+/**
+ * Check whether the given track number corresponds to an audio track.
+ *
+ * \param f See \ref mp4_get_duration().
+ * \param track See \ref mp4_get_duration().
+ *
+ * Besides audio tracks, an mp4 file may contain video and system tracks. For
+ * those the function returns false.
+ */
+bool mp4_is_audio_track(const struct mp4 *f, int32_t track)
+{
+	return f->track[track]->is_audio;
+}
+
+void mp4_set_sample_position(struct mp4 *f, int32_t track, int32_t sample)
 {
 	int32_t offset = sample_to_offset(f, track, sample);
 	set_position(f, offset);
 }
 
-int32_t mp4ff_get_sample_size(const struct mp4ff *f, int track, int sample)
+int32_t mp4_get_sample_size(const struct mp4 *f, int track, int sample)
 {
-	const struct mp4ff_track *t = f->track[track];
+	const struct mp4_track *t = f->track[track];
 
 	if (t->stsz_sample_size != 0)
 		return t->stsz_sample_size;
 	return t->stsz_table[sample];
 }
 
-uint32_t mp4ff_get_sample_rate(const struct mp4ff *f, const int32_t track)
+uint32_t mp4_get_sample_rate(const struct mp4 *f, int32_t track)
 {
 	return f->track[track]->sampleRate;
 }
 
-uint32_t mp4ff_get_channel_count(const struct mp4ff *f, const int32_t track)
+uint32_t mp4_get_channel_count(const struct mp4 *f, int32_t track)
 {
 	return f->track[track]->channelCount;
 }
 
-int32_t mp4ff_num_samples(const struct mp4ff *f, const int32_t track)
+int32_t mp4_num_samples(const struct mp4 *f, int32_t track)
 {
 	int32_t i;
 	int32_t total = 0;
@@ -1457,42 +1048,33 @@ int32_t mp4ff_num_samples(const struct mp4ff *f, const int32_t track)
 	return total;
 }
 
-struct mp4ff *mp4ff_open_read_metaonly(struct mp4ff_callback *f)
+struct mp4 *mp4_open_meta(const struct mp4_callback *cb)
 {
-	struct mp4ff *ff = para_calloc(sizeof(struct mp4ff));
-
-	ff->stream = f;
-
-	parse_atoms(ff, 1);
+	struct mp4 *f = para_calloc(sizeof(struct mp4));
 
-	if (ff->error) {
-		free(ff);
-		ff = NULL;
+	f->cb = cb;
+	parse_atoms(f, 1);
+	if (f->error) {
+		free(f);
+		f = NULL;
 	}
-
-	return ff;
+	return f;
 }
 
-int32_t mp4ff_meta_get_num_items(const struct mp4ff *f)
+/**
+ * Return the metadata of an mp4 file.
+ *
+ * \param f As returned by either \ref mp4_open_read() or \ref mp4_open_meta().
+ *
+ * The caller is allowed to add, delete or modify the entries of the returned
+ * structure in order to pass the modified version to \ref mp4_meta_update().
+ */
+struct mp4_metadata *mp4_get_meta(struct mp4 *f)
 {
-	return f->tags.count;
+	return &f->meta;
 }
 
-int32_t mp4ff_meta_get_by_index(const struct mp4ff *f, uint32_t index,
-				char **item, char **value)
-{
-	if (index >= f->tags.count) {
-		*item = NULL;
-		*value = NULL;
-		return 0;
-	} else {
-		*item = para_strdup(f->tags.tags[index].item);
-		*value = para_strdup(f->tags.tags[index].value);
-		return 1;
-	}
-}
-
-static uint32_t find_atom(struct mp4ff *f, uint64_t base, uint32_t size,
+static uint32_t find_atom(struct mp4 *f, uint64_t base, uint32_t size,
 			  const char *name)
 {
 	uint32_t remaining = size;
@@ -1521,7 +1103,7 @@ static uint32_t find_atom(struct mp4ff *f, uint64_t base, uint32_t size,
 	return 0;
 }
 
-static uint32_t find_atom_v2(struct mp4ff *f, uint64_t base, uint32_t size,
+static uint32_t find_atom_v2(struct mp4 *f, uint64_t base, uint32_t size,
 		const char *name, uint32_t extraheaders, const char *name_inside)
 {
 	uint64_t first_base = (uint64_t) (-1);
@@ -1561,119 +1143,74 @@ struct membuffer {
 	void *data;
 	unsigned written;
 	unsigned allocated;
-	unsigned error;
 };
 
 static struct membuffer *membuffer_create(void)
 {
-	const unsigned initial_size = 256;
-
-	struct membuffer *buf = para_malloc(sizeof(*buf));
-	buf->data = para_malloc(initial_size);
-	buf->written = 0;
-	buf->allocated = initial_size;
-	buf->error = buf->data == 0 ? 1 : 0;
+	struct membuffer *buf = para_calloc(sizeof(*buf));
 
+	buf->allocated = 256;
+	buf->data = para_malloc(buf->allocated);
 	return buf;
 }
 
-static unsigned membuffer_write(struct membuffer *buf, const void *ptr, unsigned bytes)
+static void membuffer_write(struct membuffer *buf, const void *ptr,
+		unsigned bytes)
 {
 	unsigned dest_size = buf->written + bytes;
 
-	if (buf->error)
-		return 0;
 	if (dest_size > buf->allocated) {
 		do {
 			buf->allocated <<= 1;
 		} while (dest_size > buf->allocated);
-
-		{
-			void *newptr = realloc(buf->data, buf->allocated);
-			if (newptr == 0) {
-				free(buf->data);
-				buf->data = 0;
-				buf->error = 1;
-				return 0;
-			}
-			buf->data = newptr;
-		}
+		buf->data = para_realloc(buf->data, buf->allocated);
 	}
 
 	if (ptr)
 		memcpy((char *) buf->data + buf->written, ptr, bytes);
 	buf->written += bytes;
-	return bytes;
 }
 
-static unsigned membuffer_write_atom_name(struct membuffer *buf, const char *data)
+static void membuffer_write_atom_name(struct membuffer *buf, const char *data)
 {
-	return membuffer_write(buf, data, 4) == 4 ? 1 : 0;
+	membuffer_write(buf, data, 4);
 }
 
-static unsigned membuffer_write_int16(struct membuffer *buf, uint16_t data)
-{
-	uint8_t temp[2];
-
-	write_u16_be(temp, data);
-	return membuffer_write(buf, temp, 2);
-}
-
-static unsigned membuffer_write_int32(struct membuffer *buf, uint32_t data)
+static void membuffer_write_int32(struct membuffer *buf, uint32_t data)
 {
 	uint8_t temp[4];
 	write_u32_be(temp, data);
-	return membuffer_write(buf, temp, 4);
-}
-
-static void membuffer_write_track_tag(struct membuffer *buf, const char *name,
-		uint32_t index, uint32_t total)
-{
-	membuffer_write_int32(buf,
-		8 /*atom header */  + 8 /*data atom header */  +
-		8 /*flags + reserved */  + 8 /*actual data */ );
-	membuffer_write_atom_name(buf, name);
-	membuffer_write_int32(buf,
-		8 /*data atom header */  +
-		8 /*flags + reserved */  + 8 /*actual data */ );
-	membuffer_write_atom_name(buf, "data");
-	membuffer_write_int32(buf, 0);	//flags
-	membuffer_write_int32(buf, 0);	//reserved
-	membuffer_write_int16(buf, 0);
-	membuffer_write_int16(buf, (uint16_t) index);	//track number
-	membuffer_write_int16(buf, (uint16_t) total);	//total tracks
-	membuffer_write_int16(buf, 0);
+	membuffer_write(buf, temp, 4);
 }
 
-static void membuffer_write_int16_tag(struct membuffer *buf, const char *name,
-		uint16_t value)
+static void membuffer_write_std_tag(struct membuffer *buf, const char *name,
+		const char *value)
 {
-	membuffer_write_int32(buf,
-		8 /*atom header */  + 8 /*data atom header */  +
-		8 /*flags + reserved */  + 2 /*actual data */ );
+	uint32_t len = strlen(value);
+	membuffer_write_int32(buf, 8 /* atom header */
+		+ 8 /* data atom header */
+		+ 8 /* flags + reserved */
+		+ len);
 	membuffer_write_atom_name(buf, name);
-	membuffer_write_int32(buf,
-		8 /*data atom header */  +
-		8 /*flags + reserved */  + 2 /*actual data */ );
+	membuffer_write_int32(buf, 8 /* data atom header */
+		+ 8 /* flags + reserved */
+		+ len);
 	membuffer_write_atom_name(buf, "data");
-	membuffer_write_int32(buf, 0);	//flags
-	membuffer_write_int32(buf, 0);	//reserved
-	membuffer_write_int16(buf, value);	//value
+	membuffer_write_int32(buf, 1);	/* flags */
+	membuffer_write_int32(buf, 0);	/* reserved */
+	membuffer_write(buf, value, len);
 }
 
-static uint32_t myatoi(const char *param)
+static unsigned membuffer_get_size(const struct membuffer *buf)
 {
-	return param ? atoi(param) : 0;
+	return buf->written;
 }
 
-static uint32_t meta_genre_to_index(const char *genrestr)
+static void *membuffer_detach(struct membuffer *buf)
 {
-	unsigned n;
-	for (n = 0; n < sizeof (ID3v1GenreList) / sizeof (ID3v1GenreList[0]); n++) {
-		if (!strcasecmp(genrestr, ID3v1GenreList[n]))
-			return n + 1;
-	}
-	return 0;
+	void *ret = para_realloc(buf->data, buf->written);
+	free(buf);
+	return ret;
 }
 
 struct stdmeta_entry {
@@ -1681,193 +1218,38 @@ struct stdmeta_entry {
 	const char *name;
 };
 
-struct stdmeta_entry stdmetas[] = {
-	{"\xA9" "nam", "title"},
-	{"\xA9" "ART", "artist"},
-	{"\xA9" "wrt", "writer"},
-	{"\xA9" "alb", "album"},
-	{"\xA9" "day", "date"},
-	{"\xA9" "too", "tool"},
-	{"\xA9" "cmt", "comment"},
-	{"cpil", "compilation"},
-	{"covr", "cover"},
-	{"aART", "album_artist"},
-};
-
-static const char *find_standard_meta(const char *name)	//returns atom name if found, 0 if not
+static const char *find_standard_meta(const char *name)
 {
-	unsigned n;
-	for (n = 0; n < sizeof (stdmetas) / sizeof (stdmetas[0]); n++) {
+	const struct stdmeta_entry stdmetas[] = {
+		{"\xA9" "nam", "title"},
+		{"\xA9" "ART", "artist"},
+		{"\xA9" "alb", "album"},
+		{"\xA9" "day", "date"},
+		{"\xA9" "cmt", "comment"},
+	};
+
+	for (unsigned n = 0; n < ARRAY_SIZE(stdmetas); n++)
 		if (!strcasecmp(name, stdmetas[n].name))
 			return stdmetas[n].atom;
-	}
-	return 0;
-}
-
-static void membuffer_write_std_tag(struct membuffer *buf, const char *name,
-		const char *value)
-{
-	uint32_t flags = 1;
-
-	/* special check for compilation flag */
-	if (strcmp(name, "cpil") == 0) {
-		flags = 21;
-	}
-
-	membuffer_write_int32(buf,
-		8 /*atom header */  + 8 /*data atom header */  +
-		8 /*flags + reserved */  + strlen(value));
-	membuffer_write_atom_name(buf, name);
-	membuffer_write_int32(buf,
-		8 /*data atom header */  +
-		8 /*flags + reserved */  + strlen(value));
-	membuffer_write_atom_name(buf, "data");
-	membuffer_write_int32(buf, flags);	//flags
-	membuffer_write_int32(buf, 0);	//reserved
-	membuffer_write(buf, value, strlen(value));
-}
-
-static void membuffer_write_custom_tag(struct membuffer *buf, const char *name,
-		const char *value)
-{
-	membuffer_write_int32(buf,
-		8 /*atom header */  +
-		0x1C /*weirdo itunes atom */  +
-		12 /*name atom header */  + strlen(name) +
-		16 /*data atom header + flags */  + strlen(value));
-	membuffer_write_atom_name(buf, "----");
-	membuffer_write_int32(buf, 0x1C);	//weirdo itunes atom
-	membuffer_write_atom_name(buf, "mean");
-	membuffer_write_int32(buf, 0);
-	membuffer_write(buf, "com.apple.iTunes", 16);
-	membuffer_write_int32(buf, 12 + strlen(name));
-	membuffer_write_atom_name(buf, "name");
-	membuffer_write_int32(buf, 0);
-	membuffer_write(buf, name, strlen(name));
-	membuffer_write_int32(buf,
-		8 /*data atom header */  +
-		8 /*flags + reserved */  + strlen(value));
-	membuffer_write_atom_name(buf, "data");
-	membuffer_write_int32(buf, 1);	//flags
-	membuffer_write_int32(buf, 0);	//reserved
-	membuffer_write(buf, value, strlen(value));
-}
-
-static unsigned membuffer_error(const struct membuffer *buf)
-{
-	return buf->error;
-}
-
-static void membuffer_free(struct membuffer *buf)
-{
-	free(buf->data);
-	free(buf);
-}
-
-static unsigned membuffer_get_size(const struct membuffer *buf)
-{
-	return buf->written;
-}
-
-static void *membuffer_detach(struct membuffer *buf)
-{
-	void *ret;
-
-	if (buf->error)
-		return 0;
-
-	ret = realloc(buf->data, buf->written);
-
-	if (ret == 0)
-		free(buf->data);
-
-	buf->data = 0;
-	buf->error = 1;
-
-	return ret;
+	return NULL;
 }
 
-static uint32_t create_ilst(const struct mp4ff_metadata *data, void **out_buffer,
+static uint32_t create_ilst(const struct mp4_metadata *meta, void **out_buffer,
 		uint32_t * out_size)
 {
 	struct membuffer *buf = membuffer_create();
 	unsigned metaptr;
-	char *mask = para_calloc(data->count);
-	const char *tracknumber_ptr = 0, *totaltracks_ptr = 0;
-	const char *discnumber_ptr = 0, *totaldiscs_ptr = 0;
-	const char *genre_ptr = 0, *tempo_ptr = 0;
-
-	for (metaptr = 0; metaptr < data->count; metaptr++) {
-		struct mp4ff_tag *tag = &data->tags[metaptr];
-		if (!strcasecmp(tag->item, "tracknumber")
-				|| !strcasecmp(tag->item, "track")) {
-			if (tracknumber_ptr == 0)
-				tracknumber_ptr = tag->value;
-			mask[metaptr] = 1;
-		} else if (!strcasecmp(tag->item, "totaltracks")) {
-			if (totaltracks_ptr == 0)
-				totaltracks_ptr = tag->value;
-			mask[metaptr] = 1;
-		} else if (!strcasecmp(tag->item, "discnumber")
-				|| !strcasecmp(tag->item, "disc")) {
-			if (discnumber_ptr == 0)
-				discnumber_ptr = tag->value;
-			mask[metaptr] = 1;
-		} else if (!strcasecmp(tag->item, "totaldiscs")) {
-			if (totaldiscs_ptr == 0)
-				totaldiscs_ptr = tag->value;
-			mask[metaptr] = 1;
-		} else if (!strcasecmp(tag->item, "genre")) {
-			if (genre_ptr == 0)
-				genre_ptr = tag->value;
-			mask[metaptr] = 1;
-		} else if (!strcasecmp(tag->item, "tempo")) {
-			if (tempo_ptr == 0)
-				tempo_ptr = tag->value;
-			mask[metaptr] = 1;
-		}
-	}
 
-	if (tracknumber_ptr)
-		membuffer_write_track_tag(buf, "trkn", myatoi(tracknumber_ptr),
-			 myatoi(totaltracks_ptr));
-	if (discnumber_ptr)
-		membuffer_write_track_tag(buf, "disk", myatoi(discnumber_ptr),
-			 myatoi(totaldiscs_ptr));
-	if (tempo_ptr)
-		membuffer_write_int16_tag(buf, "tmpo", myatoi(tempo_ptr));
-
-	if (genre_ptr) {
-		uint32_t index = meta_genre_to_index(genre_ptr);
-		if (index == 0)
-			membuffer_write_std_tag(buf, "©gen", genre_ptr);
-		else
-			membuffer_write_int16_tag(buf, "gnre", index);
-	}
-	for (metaptr = 0; metaptr < data->count; metaptr++) {
-		struct mp4ff_tag *tag;
-		const char *std_meta_atom;
-
-		if (mask[metaptr])
-			continue;
-		tag = &data->tags[metaptr];
-		std_meta_atom = find_standard_meta(tag->item);
+	for (metaptr = 0; metaptr < meta->count; metaptr++) {
+		struct mp4_tag *tag = meta->tags + metaptr;
+		const char *std_meta_atom = find_standard_meta(tag->item);
 		if (std_meta_atom)
 			membuffer_write_std_tag(buf, std_meta_atom, tag->value);
 		else
-			membuffer_write_custom_tag(buf, tag->item, tag->value);
+			PARA_ERROR_LOG("invalid tag item: %s\n", tag->item);
 	}
-	free(mask);
-
-	if (membuffer_error(buf)) {
-		membuffer_free(buf);
-		return 0;
-	}
-
 	*out_size = membuffer_get_size(buf);
 	*out_buffer = membuffer_detach(buf);
-	membuffer_free(buf);
-
 	return 1;
 }
 
@@ -1884,42 +1266,30 @@ static void *membuffer_get_ptr(const struct membuffer *buf)
 	return buf->data;
 }
 
-static void membuffer_set_error(struct membuffer *buf)
-{
-	buf->error = 1;
-}
-
-static unsigned membuffer_transfer_from_file(struct membuffer *buf, struct mp4ff *src,
+static bool membuffer_transfer_from_file(struct membuffer *buf, struct mp4 *src,
 		unsigned bytes)
 {
-	unsigned oldsize;
-	void *bufptr;
-
-	oldsize = membuffer_get_size(buf);
-	if (membuffer_write(buf, 0, bytes) != bytes)
-		return 0;
+	unsigned oldsize = membuffer_get_size(buf);
+	char *bufptr;
 
+	membuffer_write(buf, 0, bytes);
 	bufptr = membuffer_get_ptr(buf);
-	if (bufptr == 0)
-		return 0;
-
-	if ((unsigned)read_data(src, (char *) bufptr + oldsize, bytes) !=
-		bytes) {
-		membuffer_set_error(buf);
-		return 0;
+	if (read_data(src, bufptr + oldsize, bytes) != bytes) {
+		free(buf->data);
+		free(buf);
+		return false;
 	}
-
-	return bytes;
+	return true;
 }
 
-static uint32_t create_meta(const struct mp4ff_metadata *data, void **out_buffer,
+static uint32_t create_meta(const struct mp4_metadata *meta, void **out_buffer,
 		uint32_t * out_size)
 {
 	struct membuffer *buf;
 	uint32_t ilst_size;
 	void *ilst_buffer;
 
-	if (!create_ilst(data, &ilst_buffer, &ilst_size))
+	if (!create_ilst(meta, &ilst_buffer, &ilst_size))
 		return 0;
 
 	buf = membuffer_create();
@@ -1930,18 +1300,17 @@ static uint32_t create_meta(const struct mp4ff_metadata *data, void **out_buffer
 
 	*out_size = membuffer_get_size(buf);
 	*out_buffer = membuffer_detach(buf);
-	membuffer_free(buf);
 	return 1;
 }
 
-static uint32_t create_udta(const struct mp4ff_metadata *data, void **out_buffer,
+static uint32_t create_udta(const struct mp4_metadata *meta, void **out_buffer,
 uint32_t * out_size)
 {
 	struct membuffer *buf;
 	uint32_t meta_size;
 	void *meta_buffer;
 
-	if (!create_meta(data, &meta_buffer, &meta_size))
+	if (!create_meta(meta, &meta_buffer, &meta_size))
 		return 0;
 
 	buf = membuffer_create();
@@ -1952,7 +1321,6 @@ uint32_t * out_size)
 
 	*out_size = membuffer_get_size(buf);
 	*out_buffer = membuffer_detach(buf);
-	membuffer_free(buf);
 	return 1;
 }
 
@@ -1961,8 +1329,7 @@ static uint32_t fix_byte_order_32(uint32_t src)
 	return read_u32_be(&src);
 }
 
-static uint32_t modify_moov(struct mp4ff *f, const struct mp4ff_metadata *data,
-		void **out_buffer, uint32_t * out_size)
+static void *modify_moov(struct mp4 *f, uint32_t *out_size)
 {
 	uint64_t total_base = f->moov_offset + 8;
 	uint32_t total_size = (uint32_t) (f->moov_size - 8);
@@ -1971,7 +1338,7 @@ static uint32_t modify_moov(struct mp4ff *f, const struct mp4ff_metadata *data,
 	uint32_t udta_size, meta_size, ilst_size;
 
 	uint32_t new_ilst_size;
-	void *new_ilst_buffer;
+	void *new_ilst_buffer, *out_buffer;
 
 	uint8_t *p_out;
 	int32_t size_delta;
@@ -1980,206 +1347,212 @@ static uint32_t modify_moov(struct mp4ff *f, const struct mp4ff_metadata *data,
 		struct membuffer *buf;
 		void *new_udta_buffer;
 		uint32_t new_udta_size;
-		if (!create_udta(data, &new_udta_buffer, &new_udta_size))
-			return 0;
+		if (!create_udta(&f->meta, &new_udta_buffer, &new_udta_size))
+			return NULL;
 
 		buf = membuffer_create();
 		set_position(f, total_base);
-		membuffer_transfer_from_file(buf, f, total_size);
-
+		if (!membuffer_transfer_from_file(buf, f, total_size)) {
+			free(new_udta_buffer);
+			return NULL;
+		}
 		membuffer_write_atom(buf, "udta", new_udta_size,
 			new_udta_buffer);
 
 		free(new_udta_buffer);
 
 		*out_size = membuffer_get_size(buf);
-		*out_buffer = membuffer_detach(buf);
-		membuffer_free(buf);
-		return 1;
-	} else {
-		udta_offset = get_position(f);
-		udta_size = read_int32(f);
-		if (!find_atom_v2 (f, udta_offset + 8, udta_size - 8, "meta", 4, "ilst")) {
-			struct membuffer *buf;
-			void *new_meta_buffer;
-			uint32_t new_meta_size;
-			if (!create_meta(data, &new_meta_buffer, &new_meta_size))
-				return 0;
-
-			buf = membuffer_create();
-			set_position(f, total_base);
-			membuffer_transfer_from_file(buf, f,
-				(uint32_t)(udta_offset - total_base));
-
-			membuffer_write_int32(buf, udta_size + 8 + new_meta_size);
-			membuffer_write_atom_name(buf, "udta");
-			membuffer_transfer_from_file(buf, f, udta_size);
-
-			membuffer_write_atom(buf, "meta", new_meta_size,
-				new_meta_buffer);
-			free(new_meta_buffer);
+		return membuffer_detach(buf);
+	}
+	udta_offset = get_position(f);
+	udta_size = read_int32(f);
+	if (!find_atom_v2 (f, udta_offset + 8, udta_size - 8, "meta", 4, "ilst")) {
+		struct membuffer *buf;
+		void *new_meta_buffer;
+		uint32_t new_meta_size;
 
-			*out_size = membuffer_get_size(buf);
-			*out_buffer = membuffer_detach(buf);
-			membuffer_free(buf);
-			return 1;
-		}
-		meta_offset = get_position(f);
-		meta_size = read_int32(f);
-		if (!find_atom(f, meta_offset + 12, meta_size - 12, "ilst"))
-			return 0;	//shouldn't happen, find_atom_v2 above takes care of it
-		ilst_offset = get_position(f);
-		ilst_size = read_int32(f);
+		if (!create_meta(&f->meta, &new_meta_buffer, &new_meta_size))
+			return NULL;
 
-		if (!create_ilst(data, &new_ilst_buffer, &new_ilst_size))
-			return 0;
+		buf = membuffer_create();
+		set_position(f, total_base);
+		if (!membuffer_transfer_from_file(buf, f,
+				udta_offset - total_base)) {
+			free(new_meta_buffer);
+			return NULL;
+		}
 
-		size_delta = new_ilst_size - (ilst_size - 8);
+		membuffer_write_int32(buf, udta_size + 8 + new_meta_size);
+		membuffer_write_atom_name(buf, "udta");
+		if (!membuffer_transfer_from_file(buf, f, udta_size)) {
+			free(new_meta_buffer);
+			return NULL;
+		}
 
-		*out_size = total_size + size_delta;
-		*out_buffer = para_malloc(*out_size);
-		p_out = (uint8_t *) * out_buffer;
+		membuffer_write_atom(buf, "meta", new_meta_size,
+			new_meta_buffer);
+		free(new_meta_buffer);
 
-		set_position(f, total_base);
-		read_data(f, p_out,
-				(uint32_t) (udta_offset - total_base));
-		p_out += (uint32_t) (udta_offset - total_base);
-		*(uint32_t *) p_out = fix_byte_order_32(read_int32(f) + size_delta);
-		p_out += 4;
-		read_data(f, p_out, 4);
-		p_out += 4;
-		read_data(f, p_out,
-				(uint32_t) (meta_offset - udta_offset - 8));
-		p_out += (uint32_t) (meta_offset - udta_offset - 8);
-		*(uint32_t *) p_out = fix_byte_order_32(read_int32(f) + size_delta);
-		p_out += 4;
-		read_data(f, p_out, 4);
-		p_out += 4;
-		read_data(f, p_out,
-				(uint32_t) (ilst_offset - meta_offset - 8));
-		p_out += (uint32_t) (ilst_offset - meta_offset - 8);
-		*(uint32_t *) p_out = fix_byte_order_32(read_int32(f) + size_delta);
-		p_out += 4;
-		read_data(f, p_out, 4);
-		p_out += 4;
-
-		memcpy(p_out, new_ilst_buffer, new_ilst_size);
-		p_out += new_ilst_size;
-
-		set_position(f, ilst_offset + ilst_size);
-		read_data(f, p_out, (uint32_t) (total_size
-			- (ilst_offset - total_base) - ilst_size));
-
-		free(new_ilst_buffer);
+		*out_size = membuffer_get_size(buf);
+		return membuffer_detach(buf);
 	}
-	return 1;
-}
-
-static int32_t write_data(struct mp4ff *f, void *data, uint32_t size)
+	meta_offset = get_position(f);
+	meta_size = read_int32(f);
+ 	/* shouldn't happen, find_atom_v2 above takes care of it */
+	if (!find_atom(f, meta_offset + 12, meta_size - 12, "ilst"))
+		return NULL;
+	ilst_offset = get_position(f);
+	ilst_size = read_int32(f);
+	if (!create_ilst(&f->meta, &new_ilst_buffer, &new_ilst_size))
+		return NULL;
+	size_delta = new_ilst_size - (ilst_size - 8);
+	*out_size = total_size + size_delta;
+	out_buffer = para_malloc(*out_size);
+	p_out = out_buffer;
+	set_position(f, total_base);
+	read_data(f, p_out, (uint32_t) (udta_offset - total_base));
+	p_out += (uint32_t) (udta_offset - total_base);
+	*(uint32_t *)p_out = fix_byte_order_32(read_int32(f) + size_delta);
+	p_out += 4;
+	read_data(f, p_out, 4);
+	p_out += 4;
+	read_data(f, p_out, (uint32_t) (meta_offset - udta_offset - 8));
+	p_out += (uint32_t) (meta_offset - udta_offset - 8);
+	*(uint32_t *)p_out = fix_byte_order_32(read_int32(f) + size_delta);
+	p_out += 4;
+	read_data(f, p_out, 4);
+	p_out += 4;
+	read_data(f, p_out, (uint32_t) (ilst_offset - meta_offset - 8));
+	p_out += (uint32_t) (ilst_offset - meta_offset - 8);
+	*(uint32_t *)p_out = fix_byte_order_32(read_int32(f) + size_delta);
+	p_out += 4;
+	read_data(f, p_out, 4);
+	p_out += 4;
+	memcpy(p_out, new_ilst_buffer, new_ilst_size);
+	p_out += new_ilst_size;
+	set_position(f, ilst_offset + ilst_size);
+	read_data(f, p_out, (uint32_t) (total_size
+		- (ilst_offset - total_base) - ilst_size));
+	free(new_ilst_buffer);
+	return out_buffer;
+}
+
+static int32_t write_data(struct mp4 *f, void *data, uint32_t size)
 {
 	int32_t result = 1;
 
-	result = f->stream->write(f->stream->user_data, data, size);
+	result = f->cb->write(f->cb->user_data, data, size);
 
 	f->current_position += size;
 
 	return result;
 }
 
-static int32_t write_int32(struct mp4ff *f, const uint32_t data)
+static int32_t write_int32(struct mp4 *f, uint32_t data)
 {
 	int8_t temp[4];
 	write_u32_be(temp, data);
 	return write_data(f, temp, sizeof(temp));
 }
 
-static int32_t truncate_stream(struct mp4ff *f)
-{
-	return f->stream->truncate(f->stream->user_data);
-}
-
-int32_t mp4ff_meta_update(struct mp4ff_callback *f, const struct mp4ff_metadata *data)
+int32_t mp4_meta_update(struct mp4 *f)
 {
 	void *new_moov_data;
 	uint32_t new_moov_size;
 
-	struct mp4ff *ff = para_calloc(sizeof(struct mp4ff));
-	ff->stream = f;
-	set_position(ff, 0);
-
-	parse_atoms(ff, 1);
-
-	if (!modify_moov(ff, data, &new_moov_data, &new_moov_size)) {
-		mp4ff_close(ff);
+	set_position(f, 0);
+	new_moov_data = modify_moov(f, &new_moov_size);
+	if (!new_moov_data ) {
+		mp4_close(f);
 		return 0;
 	}
-
 	/* copy moov atom to end of the file */
-	if (ff->last_atom != ATOM_MOOV) {
+	if (f->last_atom != ATOM_MOOV) {
 		char *free_data = "free";
 
 		/* rename old moov to free */
-		set_position(ff, ff->moov_offset + 4);
-		write_data(ff, free_data, 4);
+		set_position(f, f->moov_offset + 4);
+		write_data(f, free_data, 4);
 
-		set_position(ff, ff->file_size);
-		write_int32(ff, new_moov_size + 8);
-		write_data(ff, "moov", 4);
-		write_data(ff, new_moov_data, new_moov_size);
+		set_position(f, f->file_size);
+		write_int32(f, new_moov_size + 8);
+		write_data(f, "moov", 4);
+		write_data(f, new_moov_data, new_moov_size);
 	} else {
-		set_position(ff, ff->moov_offset);
-		write_int32(ff, new_moov_size + 8);
-		write_data(ff, "moov", 4);
-		write_data(ff, new_moov_data, new_moov_size);
+		set_position(f, f->moov_offset);
+		write_int32(f, new_moov_size + 8);
+		write_data(f, "moov", 4);
+		write_data(f, new_moov_data, new_moov_size);
 	}
-
-	truncate_stream(ff);
-
-	mp4ff_close(ff);
+	free(new_moov_data);
+	f->cb->truncate(f->cb->user_data);
 	return 1;
 }
 
-/* find a metadata item by name */
-/* returns 0 if item found, 1 if no such item */
-static int32_t meta_find_by_name(const struct mp4ff *f, const char *item,
-		char **value)
+static char *meta_find_by_name(const struct mp4 *f, const char *item)
 {
 	uint32_t i;
 
-	for (i = 0; i < f->tags.count; i++) {
-		if (!strcasecmp(f->tags.tags[i].item, item)) {
-			*value = para_strdup(f->tags.tags[i].value);
-			return 1;
-		}
-	}
-
-	*value = NULL;
-
-	/* not found */
-	return 0;
+	for (i = 0; i < f->meta.count; i++)
+		if (!strcasecmp(f->meta.tags[i].item, item))
+			return para_strdup(f->meta.tags[i].value);
+	return NULL;
 }
 
-int32_t mp4ff_meta_get_artist(const struct mp4ff *f, char **value)
+/**
+ * Return the value of the artist meta tag of an mp4 file.
+ *
+ * \param f Must not be NULL.
+ *
+ * \return If the file does not contain this metadata tag, the function returns
+ * NULL. Otherwise, a copy of the tag value is returned. The caller should free
+ * this memory when it is no longer needed.
+ */
+char *mp4_meta_get_artist(const struct mp4 *f)
 {
-	return meta_find_by_name(f, "artist", value);
+	return meta_find_by_name(f, "artist");
 }
 
-int32_t mp4ff_meta_get_title(const struct mp4ff *f, char **value)
+/**
+ * Return the value of the title meta tag of an mp4 file.
+ *
+ * \param f See \ref mp4_meta_get_artist().
+ * \return See \ref mp4_meta_get_artist().
+ */
+char *mp4_meta_get_title(const struct mp4 *f)
 {
-	return meta_find_by_name(f, "title", value);
+	return meta_find_by_name(f, "title");
 }
 
-int32_t mp4ff_meta_get_date(const struct mp4ff *f, char **value)
+/**
+ * Return the value of the date meta tag of an mp4 file.
+ *
+ * \param f See \ref mp4_meta_get_artist().
+ * \return See \ref mp4_meta_get_artist().
+ */
+char *mp4_meta_get_date(const struct mp4 *f)
 {
-	return meta_find_by_name(f, "date", value);
+	return meta_find_by_name(f, "date");
 }
 
-int32_t mp4ff_meta_get_album(const struct mp4ff *f, char **value)
+/**
+ * Return the value of the album meta tag of an mp4 file.
+ *
+ * \param f See \ref mp4_meta_get_artist().
+ * \return See \ref mp4_meta_get_artist().
+ */
+char *mp4_meta_get_album(const struct mp4 *f)
 {
-	return meta_find_by_name(f, "album", value);
+	return meta_find_by_name(f, "album");
 }
 
-int32_t mp4ff_meta_get_comment(const struct mp4ff *f, char **value)
+/**
+ * Return the value of the comment meta tag of an mp4 file.
+ *
+ * \param f See \ref mp4_meta_get_artist().
+ * \return See \ref mp4_meta_get_artist().
+ */
+char *mp4_meta_get_comment(const struct mp4 *f)
 {
-	return meta_find_by_name(f, "comment", value);
+	return meta_find_by_name(f, "comment");
 }