mirror of
https://github.com/superseriousbusiness/gotosocial.git
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159 lines
4 KiB
Markdown
159 lines
4 KiB
Markdown
go-mp4
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------
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[](https://pkg.go.dev/github.com/abema/go-mp4)
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[](https://coveralls.io/github/abema/go-mp4)
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[](https://goreportcard.com/report/github.com/abema/go-mp4)
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go-mp4 is Go library which provides low-level I/O interfaces of MP4.
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This library supports you to parse or build any MP4 boxes(atoms) directly.
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go-mp4 provides very flexible interfaces for reading boxes.
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If you want to read only specific parts of MP4 file, this library extracts those boxes via io.ReadSeeker interface.
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On the other hand, this library is not suitable for complex data conversions.
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## Integration with your Go application
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### Reading
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You can parse MP4 file as follows:
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```go
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// expand all boxes
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_, err := mp4.ReadBoxStructure(file, func(h *mp4.ReadHandle) (interface{}, error) {
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fmt.Println("depth", len(h.Path))
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// Box Type (e.g. "mdhd", "tfdt", "mdat")
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fmt.Println("type", h.BoxInfo.Type.String())
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// Box Size
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fmt.Println("size", h.BoxInfo.Size)
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if h.BoxInfo.IsSupportedType() {
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// Payload
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box, _, err := h.ReadPayload()
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if err != nil {
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return nil, err
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}
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str, err := mp4.Stringify(box, h.BoxInfo.Context)
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if err != nil {
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return nil, err
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}
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fmt.Println("payload", str)
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// Expands children
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return h.Expand()
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}
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return nil, nil
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})
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```
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```go
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// extract specific boxes
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boxes, err := mp4.ExtractBoxWithPayload(file, nil, mp4.BoxPath{mp4.BoxTypeMoov(), mp4.BoxTypeTrak(), mp4.BoxTypeTkhd()})
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if err != nil {
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:
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}
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for _, box := range boxes {
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tkhd := box.Payload.(*mp4.Tkhd)
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fmt.Println("track ID:", tkhd.TrackID)
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}
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```
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```go
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// get basic informations
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info, err := mp4.Probe(bufseekio.NewReadSeeker(file, 1024, 4))
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if err != nil {
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:
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}
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fmt.Println("track num:", len(info.Tracks))
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```
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### Writing
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Writer helps you to write box tree.
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The following sample code edits emsg box and writes to another file.
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```go
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r := bufseekio.NewReadSeeker(inputFile, 128*1024, 4)
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w := mp4.NewWriter(outputFile)
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_, err = mp4.ReadBoxStructure(r, func(h *mp4.ReadHandle) (interface{}, error) {
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switch h.BoxInfo.Type {
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case mp4.BoxTypeEmsg():
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// write box size and box type
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_, err := w.StartBox(&h.BoxInfo)
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if err != nil {
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return nil, err
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}
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// read payload
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box, _, err := h.ReadPayload()
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if err != nil {
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return nil, err
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}
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// update MessageData
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emsg := box.(*mp4.Emsg)
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emsg.MessageData = []byte("hello world")
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// write box playload
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if _, err := mp4.Marshal(w, emsg, h.BoxInfo.Context); err != nil {
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return nil, err
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}
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// rewrite box size
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_, err = w.EndBox()
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return nil, err
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default:
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// copy all
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return nil, w.CopyBox(r, &h.BoxInfo)
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}
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})
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```
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### User-defined Boxes
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You can create additional box definition as follows:
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```go
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func BoxTypeXxxx() BoxType { return mp4.StrToBoxType("xxxx") }
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func init() {
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mp4.AddBoxDef(&Xxxx{}, 0)
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}
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type Xxxx struct {
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FullBox `mp4:"0,extend"`
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UI32 uint32 `mp4:"1,size=32"`
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ByteArray []byte `mp4:"2,size=8,len=dynamic"`
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}
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func (*Xxxx) GetType() BoxType {
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return BoxTypeXxxx()
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}
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```
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### Buffering
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go-mp4 has no buffering feature for I/O.
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If you should reduce Read function calls, you can wrap the io.ReadSeeker by [bufseekio](https://github.com/sunfish-shogi/bufseekio).
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## Command Line Tool
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Install mp4tool as follows:
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```sh
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go install github.com/abema/go-mp4/cmd/mp4tool@latest
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mp4tool -help
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```
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For example, `mp4tool dump MP4_FILE_NAME` command prints MP4 box tree as follows:
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```
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[moof] Size=504
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[mfhd] Size=16 Version=0 Flags=0x000000 SequenceNumber=1
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[traf] Size=480
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[tfhd] Size=28 Version=0 Flags=0x020038 TrackID=1 DefaultSampleDuration=9000 DefaultSampleSize=33550 DefaultSampleFlags=0x1010000
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[tfdt] Size=20 Version=1 Flags=0x000000 BaseMediaDecodeTimeV1=0
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[trun] Size=424 ... (use -a option to show all)
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[mdat] Size=44569 Data=[...] (use -mdat option to expand)
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```
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