Refactored all MP4 code to better handle custom atoms
This commit is contained in:
David Howden
parent
e6dce4ae2a
commit
36d9163868
240
mp4.go
240
mp4.go
@ -21,6 +21,7 @@ var atomTypes = map[int]string{
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21: "uint8",
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}
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// NB: atoms does not include "----", this is handled separately
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var atoms = atomNames(map[string]string{
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"\xa9alb": "album",
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"\xa9art": "artist",
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@ -70,63 +71,9 @@ func ReadAtoms(r io.ReadSeeker) (Metadata, error) {
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return m, err
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}
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func readCustomAtom(r io.ReadSeeker, size uint32) (string, uint32, error) {
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var datasize uint32
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var datapos int64
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var name string
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var mean string
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for size > 8 {
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var subsize uint32
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err := binary.Read(r, binary.BigEndian, &subsize)
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if err != nil {
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return "----", size - 4, err
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}
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subname, err := readString(r, 4)
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if err != nil {
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return "----", size - 8, err
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}
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b, err := readBytes(r, int(subsize-8))
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if err != nil {
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return "----", size - subsize, err
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}
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// Remove the size of the atom from the size counter
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size -= subsize
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switch string(subname) {
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case "mean":
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mean = string(b[4:])
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case "name":
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name = string(b[4:])
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case "data":
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datapos, err = r.Seek(0, os.SEEK_CUR)
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if err != nil {
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return "----", size, err
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}
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datasize = subsize
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datapos -= int64(subsize)
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}
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}
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// there should remain only the header size
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if size != 8 {
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return "----", size, errors.New("---- atom out of bound")
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}
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if mean == "com.apple.iTunes" && datasize != 0 && name != "" {
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// we jump just before the data subatom
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_, err := r.Seek(datapos, os.SEEK_SET)
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if err != nil {
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return "----", size, err
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}
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return name, datasize + 8, nil
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}
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return "----", size, nil
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}
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func (m metadataMP4) readAtoms(r io.ReadSeeker) error {
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for {
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var size uint32
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ok := false
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err := binary.Read(r, binary.BigEndian, &size)
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name, size, err := readAtomHeader(r)
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if err != nil {
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if err == io.EOF {
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return nil
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@ -134,11 +81,6 @@ func (m metadataMP4) readAtoms(r io.ReadSeeker) error {
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return err
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}
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name, err := readString(r, 4)
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if err != nil {
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return err
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}
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switch name {
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case "meta":
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// next_item_id (int32)
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@ -147,81 +89,141 @@ func (m metadataMP4) readAtoms(r io.ReadSeeker) error {
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return err
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}
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fallthrough
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case "moov", "udta", "ilst":
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return m.readAtoms(r)
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case "free":
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_, err := r.Seek(int64(size-8), os.SEEK_CUR)
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if err != nil {
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return err
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}
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continue
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case "mdat": // skip the data, the metadata can be at the end
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_, err := r.Seek(int64(size-8), os.SEEK_CUR)
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if err != nil {
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return err
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}
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continue
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case "----":
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// Generic atom.
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// Should have 3 sub atoms : mean, name and data.
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// We check that mean=="com.apple.iTunes" and we use the subname as
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// the name, and move to the data atom.
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// If anything goes wrong, we jump at the end of the "----" atom.
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}
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_, ok := atoms[name]
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if name == "----" {
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name, size, err = readCustomAtom(r, size)
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if err != nil {
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return err
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}
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ok = (name != "----")
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default:
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_, ok = atoms[name]
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if name != "----" {
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ok = true
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}
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}
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b, err := readBytes(r, int(size-8))
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if err != nil {
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return err
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}
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// At this point, we allow all known atoms and the valid "----" atoms
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if !ok {
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_, err := r.Seek(int64(size-8), os.SEEK_CUR)
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if err != nil {
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return err
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}
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continue
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}
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// 16: name + size + "data" + size (4 bytes each), have already read 8
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b = b[8:]
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class := getInt(b[1:4])
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contentType, ok := atomTypes[class]
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if !ok {
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return fmt.Errorf("invalid content type: %v", class)
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}
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b = b[8:]
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switch name {
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case "trkn", "disk":
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m[name] = int(b[3])
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m[name+"_count"] = int(b[5])
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default:
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var data interface{}
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// 4: atom version (1 byte) + atom flags (3 bytes)
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// 4: NULL (usually locale indicator)
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switch contentType {
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case "text":
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data = string(b)
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case "uint8":
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data = getInt(b[:1])
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case "jpeg", "png":
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data = &Picture{
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Ext: contentType,
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MIMEType: "image/" + contentType,
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Data: b,
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}
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}
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m[name] = data
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err = m.readAtomData(r, name, size-8)
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if err != nil {
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return err
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}
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}
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}
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func (m metadataMP4) readAtomData(r io.ReadSeeker, name string, size uint32) error {
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b, err := readBytes(r, int(size))
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if err != nil {
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return err
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}
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// "data" + size (4 bytes each)
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b = b[8:]
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class := getInt(b[1:4])
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contentType, ok := atomTypes[class]
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if !ok {
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return fmt.Errorf("invalid content type: %v (%x) (%x)", class, b[1:4], b)
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}
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// 4: atom version (1 byte) + atom flags (3 bytes)
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// 4: NULL (usually locale indicator)
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b = b[8:]
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if name == "trkn" || name == "disk" {
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fmt.Printf("%#v: %x\n", name, b)
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m[name] = int(b[3])
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m[name+"_count"] = int(b[5])
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return nil
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}
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var data interface{}
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switch contentType {
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case "text":
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data = string(b)
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case "uint8":
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data = getInt(b[:1])
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case "jpeg", "png":
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data = &Picture{
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Ext: contentType,
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MIMEType: "image/" + contentType,
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Data: b,
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}
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}
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m[name] = data
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return nil
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}
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func readAtomHeader(r io.ReadSeeker) (name string, size uint32, err error) {
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err = binary.Read(r, binary.BigEndian, &size)
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if err != nil {
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return
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}
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name, err = readString(r, 4)
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return
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}
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// Generic atom.
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// Should have 3 sub atoms : mean, name and data.
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// We check that mean is "com.apple.iTunes" and we use the subname as
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// the name, and move to the data atom.
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// If anything goes wrong, we jump at the end of the "----" atom.
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func readCustomAtom(r io.ReadSeeker, size uint32) (string, uint32, error) {
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subNames := make(map[string]string)
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var dataSize uint32
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for size > 8 {
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subName, subSize, err := readAtomHeader(r)
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if err != nil {
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return "", 0, err
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}
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// Remove the size of the atom from the size counter
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size -= subSize
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switch subName {
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case "mean", "name":
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b, err := readBytes(r, int(subSize-8))
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if err != nil {
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return "", 0, err
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}
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subNames[subName] = string(b[4:])
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case "data":
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// Found the "data" atom, rewind
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dataSize = subSize + 8 // will need to re-read "data" + size (4 + 4)
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_, err := r.Seek(-8, os.SEEK_CUR)
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if err != nil {
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return "", 0, err
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}
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}
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}
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// there should remain only the header size
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if size != 8 {
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err := errors.New("---- atom out of bounds")
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return "", 0, err
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}
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if subNames["mean"] != "com.apple.iTunes" || subNames["name"] == "" || dataSize == 0 {
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return "----", 0, nil
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}
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return subNames["name"], dataSize, nil
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}
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func (metadataMP4) Format() Format { return MP4 }
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func (metadataMP4) FileType() FileType { return AAC }
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