X-Git-Url: http://git.tuebingen.mpg.de/?a=blobdiff_plain;f=mp4.c;h=5ca1307f680d366c155b2e98257ba807c5a4fb92;hb=HEAD;hp=7145a47a829695e2cf82a46f58b18aa743c30246;hpb=b96d1f30be6fda4b3d93aef19e66273260503cac;p=paraslash.git

diff --git a/mp4.c b/mp4.c
index 7145a47a..fe9d4b37 100644
--- a/mp4.c
+++ b/mp4.c
@@ -5,6 +5,15 @@
  * See file COPYING.
  */
 
+/** \file mp4.c Paraslash's internal mp4 parser. */
+
+/*
+ * This is a stripped down version of the former mp4ff library which used to be
+ * part of the faad decoder project but was removed from the faad code base in
+ * 2017. The original code has been cleaned up substantially and the public API
+ * has been documented. See the git commit log for details.
+ */
+
 #include <regex.h>
 
 #include "para.h"
@@ -122,36 +131,45 @@ static int read_int16(struct mp4 *f, uint16_t *result)
 	return ret;
 }
 
+/** \cond atom_items */
+/* A macro defining the atoms we care about. It gets expanded twice. */
 #define ATOM_ITEMS \
-	ATOM_ITEM(MOOV, 'm', 'o', 'o', 'v') \
-	ATOM_ITEM(TRAK, 't', 'r', 'a', 'k') \
-	ATOM_ITEM(MDIA, 'm', 'd', 'i', 'a') \
-	ATOM_ITEM(MINF, 'm', 'i', 'n', 'f') \
-	ATOM_ITEM(STBL, 's', 't', 'b', 'l') \
-	ATOM_ITEM(UDTA, 'u', 'd', 't', 'a') \
+	ATOM_ITEM(MOOV, 'm', 'o', 'o', 'v') /* movie (top-level container) */ \
+	ATOM_ITEM(TRAK, 't', 'r', 'a', 'k') /* container for a single track */ \
+	ATOM_ITEM(MDIA, 'm', 'd', 'i', 'a') /* media information */ \
+	ATOM_ITEM(MINF, 'm', 'i', 'n', 'f') /* extends mdia */ \
+	ATOM_ITEM(STBL, 's', 't', 'b', 'l') /* sample table container */ \
+	ATOM_ITEM(UDTA, 'u', 'd', 't', 'a') /* user data */ \
 	ATOM_ITEM(ILST, 'i', 'l', 's', 't') /* iTunes Metadata list */ \
-	ATOM_ITEM(ARTIST, 0xa9, 'A', 'R', 'T') \
-	ATOM_ITEM(TITLE, 0xa9, 'n', 'a', 'm') \
-	ATOM_ITEM(ALBUM, 0xa9, 'a', 'l', 'b') \
-	ATOM_ITEM(DATE, 0xa9, 'd', 'a', 'y') \
-	ATOM_ITEM(COMMENT, 0xa9, 'c', 'm', 't') \
+	ATOM_ITEM(ARTIST, 0xa9, 'A', 'R', 'T') /* artist */ \
+	ATOM_ITEM(TITLE, 0xa9, 'n', 'a', 'm') /* title */ \
+	ATOM_ITEM(ALBUM, 0xa9, 'a', 'l', 'b') /* album */ \
+	ATOM_ITEM(DATE, 0xa9, 'd', 'a', 'y') /* date */ \
+	ATOM_ITEM(COMMENT, 0xa9, 'c', 'm', 't') /* comment */ \
 	ATOM_ITEM(MDHD, 'm', 'd', 'h', 'd') /* track header */ \
 	ATOM_ITEM(STSD, 's', 't', 's', 'd') /* sample description box */ \
 	ATOM_ITEM(STTS, 's', 't', 't', 's') /* time to sample box */ \
 	ATOM_ITEM(STSZ, 's', 't', 's', 'z') /* sample size box */ \
 	ATOM_ITEM(STCO, 's', 't', 'c', 'o') /* chunk offset box */ \
 	ATOM_ITEM(STSC, 's', 't', 's', 'c') /* sample to chunk box */ \
-	ATOM_ITEM(MP4A, 'm', 'p', '4', 'a') \
+	ATOM_ITEM(MP4A, 'm', 'p', '4', 'a') /* mp4 audio */ \
 	ATOM_ITEM(META, 'm', 'e', 't', 'a') /* iTunes Metadata box */ \
 	ATOM_ITEM(DATA, 'd', 'a', 't', 'a') /* iTunes Metadata data box */ \
 
+/** \endcond atom_items */
+
+/** For the C enumeration we concatenate ATOM_ with the first argument. */
 #define ATOM_ITEM(_name, a, b, c, d) ATOM_ ## _name,
+/** The enumeration of interesting atoms. */
 enum atom {ATOM_ITEMS};
 #undef ATOM_ITEM
 
+/** A cpp version of read_u32_be(). */
+#define ATOM_VALUE(a, b, c, d) ((a << 24) + (b << 16) + (c << 8) + d)
+
 static uint8_t atom_name_to_type(uint8_t *p)
 {
-	#define ATOM_VALUE(a, b, c, d) ((a << 24) + (b << 16) + (c << 8) + d)
+	/** Expands to an instance of the following unnamed structure. */
 	#define ATOM_ITEM(_name, a, b, c, d) \
 		{.name = # _name, .val = ATOM_VALUE(a, b, c, d)},
 	static const struct {
@@ -225,7 +243,7 @@ static int read_stsz(struct mp4 *f)
 		return ret;
 	if (t->stsz_sample_size != 0)
 		return 1;
-	t->stsz_table = para_malloc(t->stsz_sample_count * sizeof(int32_t));
+	t->stsz_table = arr_alloc(t->stsz_sample_count, sizeof(int32_t));
 	for (uint32_t n = 0; n < t->stsz_sample_count; n++) {
 		ret = read_int32(f, &t->stsz_table[n]);
 		if (ret <= 0)
@@ -245,8 +263,7 @@ static int read_stts(struct mp4 *f)
 	ret = read_int32(f, &t->stts_entry_count);
 	if (ret <= 0)
 		return ret;
-	t->stts_sample_count = para_malloc(t->stts_entry_count
-		* sizeof(int32_t));
+	t->stts_sample_count = arr_alloc(t->stts_entry_count, sizeof(int32_t));
 	for (uint32_t n = 0; n < t->stts_entry_count; n++) {
 		ret = read_int32(f, &t->stts_sample_count[n]);
 		if (ret <= 0)
@@ -269,9 +286,9 @@ static int read_stsc(struct mp4 *f)
 	ret = read_int32(f, &t->stsc_entry_count);
 	if (ret <= 0)
 		return ret;
-	t->stsc_first_chunk = para_malloc(t->stsc_entry_count * sizeof(int32_t));
-	t->stsc_samples_per_chunk = para_malloc(t->stsc_entry_count
-		* sizeof (int32_t));
+	t->stsc_first_chunk = arr_alloc(t->stsc_entry_count, sizeof(int32_t));
+	t->stsc_samples_per_chunk = arr_alloc(t->stsc_entry_count,
+		sizeof (int32_t));
 	for (uint32_t n = 0; n < t->stsc_entry_count; n++) {
 		ret = read_int32(f, &t->stsc_first_chunk[n]);
 		if (ret <= 0)
@@ -295,8 +312,7 @@ static int read_stco(struct mp4 *f)
 	ret = read_int32(f, &t->stco_entry_count);
 	if (ret <= 0)
 		return ret;
-	t->stco_chunk_offset = para_malloc(t->stco_entry_count
-		* sizeof(int32_t));
+	t->stco_chunk_offset = arr_alloc(t->stco_entry_count, sizeof(int32_t));
 	for (uint32_t n = 0; n < t->stco_entry_count; n++) {
 		ret = read_int32(f, &t->stco_chunk_offset[n]);
 		if (ret <= 0)
@@ -381,7 +397,7 @@ static int parse_tag(struct mp4 *f, uint8_t parent, int32_t size)
 			goto fail;
 		len = subsize - (header_size + 8);
 		free(value);
-		value = para_malloc(len + 1);
+		value = alloc(len + 1);
 		ret = read_data(f, value, len);
 		if (ret <= 0)
 			goto fail;
@@ -566,6 +582,14 @@ static int parse_sub_atoms(struct mp4 *f, uint64_t total_size, bool meta_only)
 	return 1;
 }
 
+/**
+ * Deallocate all resources associated with an mp4 file handle.
+ *
+ * \param f File handle returned by \ref mp4_open() or \ref mp4_open_meta().
+ *
+ * This frees the metadata items and various tables which were allocated when
+ * the file was opened. The given file handle must not be NULL.
+ */
 void mp4_close(struct mp4 *f)
 {
 	free(f->track.stsz_table);
@@ -586,7 +610,7 @@ static int open_file(const struct mp4_callback *cb, bool meta_only, struct mp4 *
 	int ret;
 	uint64_t size;
 	uint8_t atom_type, header_size;
-	struct mp4 *f = para_calloc(sizeof(*f));
+	struct mp4 *f = zalloc(sizeof(*f));
 
 	f->cb = cb;
 	while ((ret = atom_read_header(f, &atom_type, &header_size, &size)) > 0) {
@@ -620,6 +644,24 @@ fail:
 	return ret;
 }
 
+/**
+ * Read the audio track and the metadata of an mp4 file.
+ *
+ * \param cb Only the ->read() and ->seek() methods need to be supplied.
+ * \param result Initialized to a non-NULL pointer iff the function succeeds.
+ *
+ * This detects and parses the first audio track and the metadata information
+ * of the mp4 file. Various error checks are performed after the mp4 atoms have
+ * been parsed successfully.
+ *
+ * This function does not modify the file. However, if the caller intents to
+ * update the metadata later, the ->write() and ->truncate() methods must be
+ * supplied in the callback structure.
+ *
+ * \return Standard. Several errors are possible.
+ *
+ * \sa \ref mp4_open_meta().
+ */
 int mp4_open(const struct mp4_callback *cb, struct mp4 **result)
 {
 	struct mp4 *f;
@@ -664,9 +706,12 @@ static int32_t chunk_of_sample(const struct mp4 *f, int32_t sample,
 }
 
 /**
- * Return the number of milliseconds of the audio track.
+ * Compute the duration of an mp4 file.
+ *
+ * \param f See \ref mp4_close().
  *
- * \param f As returned by \ref mp4_open_read(), must not be NULL.
+ * \return The number of milliseconds of the audio track. This function never
+ * fails.
  */
 uint64_t mp4_get_duration(const struct mp4 *f)
 {
@@ -675,6 +720,17 @@ uint64_t mp4_get_duration(const struct mp4 *f)
 	return t->duration * 1000 / t->time_scale;
 }
 
+/**
+ * Reposition the read/write file offset.
+ *
+ * \param f See \ref mp4_close().
+ * \param sample The number of the sample to reposition to.
+ *
+ * The given sample number must be within range, i.e., strictly less than the
+ * value returned by \ref mp4_num_samples().
+ *
+ * \return Standard. The only possible error is an invalid sample number.
+ */
 int mp4_set_sample_position(struct mp4 *f, uint32_t sample)
 {
 	const struct mp4_track *t = &f->track;
@@ -700,6 +756,19 @@ int mp4_set_sample_position(struct mp4 *f, uint32_t sample)
 	return 1;
 }
 
+/**
+ * Look up and return the size of the given sample in the stsz table.
+ *
+ * \param f See \ref mp4_close().
+ * \param sample The sample number of interest.
+ * \param result Sample size is returned here.
+ *
+ * For the sample argument the restriction mentioned in the documentation of
+ * \ref mp4_set_sample_position() applies as well.
+ *
+ * \return Standard. Like for \ref mp4_set_sample_position(), EINVAL is the
+ * only possible error.
+ */
 int mp4_get_sample_size(const struct mp4 *f, uint32_t sample, uint32_t *result)
 {
 	const struct mp4_track *t = &f->track;
@@ -713,21 +782,65 @@ int mp4_get_sample_size(const struct mp4 *f, uint32_t sample, uint32_t *result)
 	return 1;
 }
 
+/**
+ * Return the sample rate stored in the stsd atom.
+ *
+ * \param f See \ref mp4_close().
+ *
+ * The sample rate is a property of the audio track of the mp4 file and is thus
+ * independent of the sample number.
+ *
+ * \return The function always returns a positive value because the open
+ * operation fails if the sample rate happens to be zero. A typical value is
+ * 44100.
+ */
 uint16_t mp4_get_sample_rate(const struct mp4 *f)
 {
 	return f->track.sample_rate;
 }
 
+/**
+ * Return the number of channels of the audio track.
+ *
+ * \param f See \ref mp4_close().
+ *
+ * \return The returned channel count is guaranteed to be positive because the
+ * open operation fails if the mp4a atom is missing or contains a zero channel
+ * count.
+ */
 uint16_t mp4_get_channel_count(const struct mp4 *f)
 {
 	return f->track.channel_count;
 }
 
+/**
+ * Return the number of samples of the audio track.
+ *
+ * \param f See \ref mp4_close().
+ *
+ * \return The sample count is read from the stsz atom during open.
+ */
 uint32_t mp4_num_samples(const struct mp4 *f)
 {
 	return f->track.stsz_sample_count;
 }
 
+/**
+ * Open an mp4 file in metadata-only mode.
+ *
+ * \param cb See \ref mp4_open().
+ * \param result See \ref mp4_open().
+ *
+ * This is similar to \ref mp4_open() but is cheaper because it only parses the
+ * metadata of the mp4 file. The only functions that can subsequently be called
+ * with the file handle returned here are \ref mp4_get_meta() and \ref
+ * mp4_update_meta().
+ *
+ * \return Standard.
+ *
+ * \sa \ref mp4_open(). The comment about ->write() and ->truncate() applies to
+ * this function as well.
+ */
 int mp4_open_meta(const struct mp4_callback *cb, struct mp4 **result)
 {
 	struct mp4 *f;
@@ -742,10 +855,15 @@ int mp4_open_meta(const struct mp4_callback *cb, struct mp4 **result)
 /**
  * Return the metadata of an mp4 file.
  *
- * \param f As returned by either \ref mp4_open_read() or \ref mp4_open_meta().
+ * \param f See \ref mp4_close().
  *
  * 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().
+ * structure with the intention to pass the modified version to \ref
+ * mp4_update_meta().
+ *
+ * \return This never returns NULL, even if the file contains no metadata tag
+ * items. However, the meta count will be zero and the ->tags pointer NULL in
+ * this case.
  */
 struct mp4_metadata *mp4_get_meta(struct mp4 *f)
 {
@@ -801,7 +919,7 @@ static void *modify_moov(struct mp4 *f, uint32_t *out_size)
 		new_ilst_size += TAG_LEN(strlen(f->meta.tags[n].value));
 	size_delta = new_ilst_size - (f->ilst_size - 8);
 	*out_size = total_size + size_delta;
-	out_buffer = para_malloc(*out_size);
+	out_buffer = alloc(*out_size);
 	p_out = out_buffer;
 	set_position(f, total_base);
 	ret = read_data(f, p_out, f->udta_offset - total_base);
@@ -867,6 +985,20 @@ static int write_data(struct mp4 *f, void *data, size_t size)
 	return 1;
 }
 
+/**
+ * Write back the modified metadata items to the mp4 file.
+ *
+ * This is the only public function which modifies the contents of an mp4 file.
+ * This is achieved by calling the ->write() and ->truncate() methods of the
+ * callback structure passed to \ref mp4_open() or \ref mp4_open_meta().
+ *
+ * \param f See \ref mp4_close().
+ *
+ * The modified metadata structure does not need to be supplied to this
+ * function because it is part of the mp4 structure.
+ *
+ * \return Standard.
+ */
 int mp4_update_meta(struct mp4 *f)
 {
 	void *new_moov_data;
@@ -907,15 +1039,15 @@ free_moov:
 /**
  * Return the value of the given tag item.
  *
- * \param f Must not be NULL.
+ * \param f See \ref mp4_close().
  * \param item "artist", "title", "album", "comment", or "date".
  *
- * \return The function always returns NULL if the given item is not in the
- * above list. Otherwise, if the file does not contain a tag for the given
- * item, the function also returns NULL. Otherwise a copy of the tag value is
- * returned and the caller should free this memory when it is no longer needed.
+ * \return The function returns NULL if the given item is not in the above
+ * list. Otherwise, if the file does not contain a tag for the given item, the
+ * function also returns NULL. Otherwise a copy of the tag value is returned
+ * and the caller should free this memory when it is no longer needed.
  */
-char *mp4_get_tag_value(const struct mp4 *f, const char *item)
+__malloc char *mp4_get_tag_value(const struct mp4 *f, const char *item)
 {
 	for (unsigned n = 0; n < f->meta.count; n++)
 		if (!strcasecmp(f->meta.tags[n].item, item))