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nmhd.go
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nmhd.go
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package mp4
import (
"io"
"io/ioutil"
)
// NmhdBox - Null Media Header Box (nmhd - often used instead ofsthd for subtitle tracks)
type NmhdBox struct {
Version byte
Flags uint32
}
// DecodeNmhd - box-specific decode
func DecodeNmhd(hdr *boxHeader, startPos uint64, r io.Reader) (Box, error) {
data, err := ioutil.ReadAll(r)
if err != nil {
return nil, err
}
s := NewSliceReader(data)
versionAndFlags := s.ReadUint32()
sb := &NmhdBox{
Version: byte(versionAndFlags >> 24),
Flags: versionAndFlags & flagsMask,
}
return sb, nil
}
// Type - box-specific type
func (b *NmhdBox) Type() string {
return "nmhd"
}
// Size - calculated size of box
func (b *NmhdBox) Size() uint64 {
return boxHeaderSize + 4 // FullBox
}
// Encode - write box to w
func (b *NmhdBox) Encode(w io.Writer) error {
err := EncodeHeader(b, w)
if err != nil {
return err
}
buf := makebuf(b)
sw := NewSliceWriter(buf)
versionAndFlags := (uint32(b.Version) << 24) + b.Flags
sw.WriteUint32(versionAndFlags)
_, err = w.Write(buf)
return err
}
func (b *NmhdBox) Info(w io.Writer, specificBoxLevels, indent, indentStep string) error {
bd := newInfoDumper(w, indent, b, int(b.Version), b.Flags)
return bd.err
}