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stsz.go
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stsz.go
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package mp4
import (
"encoding/binary"
"io"
"io/ioutil"
)
// StszBox - Sample Size Box (stsz - mandatory)
//
// Contained in : Sample Table box (stbl)
//
// For each track, either stsz of the more compact stz2 must be present. stz2 variant is not supported.
//
// This table lists the size of each sample. If all samples have the same size, it can be defined in the
// SampleUniformSize attribute.
type StszBox struct {
Version byte
Flags uint32
SampleUniformSize uint32
SampleNumber uint32
SampleSize []uint32
}
// DecodeStsz - box-specific decode
func DecodeStsz(hdr *boxHeader, startPos uint64, r io.Reader) (Box, error) {
data, err := ioutil.ReadAll(r)
if err != nil {
return nil, err
}
versionAndFlags := binary.BigEndian.Uint32(data[0:4])
b := &StszBox{
Version: byte(versionAndFlags >> 24),
Flags: versionAndFlags & flagsMask,
SampleUniformSize: binary.BigEndian.Uint32(data[4:8]),
SampleNumber: binary.BigEndian.Uint32(data[8:12]),
SampleSize: []uint32{},
}
if len(data) > 12 {
for i := 0; i < int(b.SampleNumber); i++ {
sz := binary.BigEndian.Uint32(data[(12 + 4*i):(16 + 4*i)])
b.SampleSize = append(b.SampleSize, sz)
}
}
return b, nil
}
// Type - box-specific type
func (b *StszBox) Type() string {
return "stsz"
}
// Size - box-specific size
func (b *StszBox) Size() uint64 {
return uint64(boxHeaderSize + 12 + len(b.SampleSize)*4)
}
// GetSampleSize returns the size (in bytes) of a sample
func (b *StszBox) GetSampleSize(i int) uint32 {
if i > len(b.SampleSize) {
return b.SampleUniformSize
}
return b.SampleSize[i-1]
}
// Encode - write box to w
func (b *StszBox) 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)
sw.WriteUint32(b.SampleUniformSize)
if len(b.SampleSize) == 0 {
sw.WriteUint32(b.SampleNumber)
} else {
sw.WriteUint32(uint32(len(b.SampleSize)))
for i := range b.SampleSize {
sw.WriteUint32(b.SampleSize[i])
}
}
_, err = w.Write(buf)
return err
}
func (b *StszBox) Info(w io.Writer, specificBoxLevels, indent, indentStep string) error {
bd := newInfoDumper(w, indent, b, int(b.Version), b.Flags)
if b.SampleNumber == 0 { // No samples
return bd.err
}
if len(b.SampleSize) == 0 {
bd.write(" - sampleSize: %d", b.SampleUniformSize)
bd.write(" - sampleCount: %d", b.SampleNumber)
} else {
bd.write(" - sampleCount: %d", b.SampleNumber)
}
level := getInfoLevel(b, specificBoxLevels)
if level >= 1 {
for i := range b.SampleSize {
bd.write(" - sample[%d] size=%d", i+1, b.SampleSize[i])
}
}
return bd.err
}