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module github.com/rixtox/mp4dovi | ||
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go 1.17 |
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package main | ||
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import ( | ||
"encoding/binary" | ||
"fmt" | ||
"io" | ||
"log" | ||
"os" | ||
) | ||
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type FourCC [4]byte | ||
type BoxType FourCC | ||
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var ( | ||
MoovBoxType = BoxType{'m', 'o', 'o', 'v'} | ||
TrakBoxType = BoxType{'t', 'r', 'a', 'k'} | ||
MdiaBoxType = BoxType{'m', 'd', 'i', 'a'} | ||
MinfBoxType = BoxType{'m', 'i', 'n', 'f'} | ||
StblBoxType = BoxType{'s', 't', 'b', 'l'} | ||
StsdBoxType = BoxType{'s', 't', 's', 'd'} | ||
DvheBoxType = BoxType{'d', 'v', 'h', 'e'} | ||
Dvh1BoxType = BoxType{'d', 'v', 'h', '1'} | ||
) | ||
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const HeaderSize = 8 | ||
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type Header struct { | ||
Size uint32 | ||
Type BoxType | ||
} | ||
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func findHeader(r io.ReadSeeker, boxType BoxType, limit int64) (header *Header, err error) { | ||
var h Header | ||
for offset := int64(0); limit < 0 || offset < limit; offset += int64(h.Size) { | ||
if err = binary.Read(r, binary.BigEndian, &h); err != nil { | ||
return nil, fmt.Errorf(`failed reading box header: %w`, err) | ||
} | ||
if h.Type == boxType { | ||
return &h, nil | ||
} | ||
if _, err = r.Seek(int64(h.Size-HeaderSize), io.SeekCurrent); err != nil { | ||
return nil, fmt.Errorf(`failed seeking after box "%s": %s`, h.Type, err) | ||
} | ||
} | ||
return nil, fmt.Errorf(`cannot find box "%s"`, boxType) | ||
} | ||
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func forEachBox(r io.ReadSeeker, limit int64, fn func(header Header) error) (err error) { | ||
var h Header | ||
var start int64 | ||
if start, err = r.Seek(0, io.SeekCurrent); err != nil { | ||
return fmt.Errorf(`failed to get current offset with seek: %w`, err) | ||
} | ||
for offset := start; limit < 0 || offset < start+limit; offset += int64(h.Size) { | ||
if _, err = r.Seek(offset, io.SeekStart); err != nil { | ||
return fmt.Errorf(`failed to seek to offset: %w`, err) | ||
} | ||
if err = binary.Read(r, binary.BigEndian, &h); err != nil { | ||
return fmt.Errorf(`failed reading box header: %w`, err) | ||
} | ||
if err = fn(h); err != nil { | ||
return fmt.Errorf(`callback failed: %w`, err) | ||
} | ||
} | ||
return | ||
} | ||
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func sampleEntryHandler(rw *os.File) func(Header) error { | ||
return func(h Header) (err error) { | ||
if h.Type == DvheBoxType { | ||
if _, err = rw.Seek(-4, io.SeekCurrent); err != nil { | ||
return fmt.Errorf(`failed to seek back: %w`, err) | ||
} | ||
if err = binary.Write(rw, binary.BigEndian, Dvh1BoxType); err != nil { | ||
return fmt.Errorf(`failed to write box header type "%s": %w`, Dvh1BoxType, err) | ||
} | ||
fmt.Println(`Changed Dolby Vision codec from dvhe to dvh1`) | ||
} | ||
return | ||
} | ||
} | ||
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func trakHandler(rw *os.File) func(Header) error { | ||
return func(trak Header) (err error) { | ||
var h *Header | ||
var sampleEntryCount uint32 | ||
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if trak.Type != TrakBoxType { | ||
return | ||
} | ||
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if h, err = findHeader(rw, MdiaBoxType, int64(trak.Size-HeaderSize)); err != nil { | ||
return fmt.Errorf(`failed finding box "%s": %w`, MdiaBoxType, err) | ||
} | ||
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if h, err = findHeader(rw, MinfBoxType, int64(h.Size-HeaderSize)); err != nil { | ||
return fmt.Errorf(`failed finding box "%s": %w`, MinfBoxType, err) | ||
} | ||
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if h, err = findHeader(rw, StblBoxType, int64(h.Size-HeaderSize)); err != nil { | ||
return fmt.Errorf(`failed finding box "%s": %w`, StblBoxType, err) | ||
} | ||
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if h, err = findHeader(rw, StsdBoxType, int64(h.Size-HeaderSize)); err != nil { | ||
return fmt.Errorf(`failed finding box "%s": %w`, StsdBoxType, err) | ||
} | ||
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if _, err = rw.Seek(4, io.SeekCurrent); err != nil { | ||
return fmt.Errorf(`failed to seek: %w`, err) | ||
} | ||
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if err = binary.Read(rw, binary.BigEndian, &sampleEntryCount); err != nil { | ||
return fmt.Errorf(`failed to read sampleEntryCount: %w`, err) | ||
} | ||
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if err = forEachBox(rw, int64(h.Size-HeaderSize-8), sampleEntryHandler(rw)); err != nil { | ||
return fmt.Errorf(`failed processing sample entry list: %w`, err) | ||
} | ||
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return | ||
} | ||
} | ||
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func run(mp4file string) (err error) { | ||
var ( | ||
rw *os.File | ||
h *Header | ||
) | ||
if rw, err = os.OpenFile(mp4file, os.O_RDWR, 0); err != nil { | ||
return fmt.Errorf(`cannot open file "%s": %w`, mp4file, err) | ||
} | ||
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if _, err = rw.Seek(0, io.SeekStart); err != nil { | ||
return fmt.Errorf(`failed to seek: %w`, err) | ||
} | ||
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if h, err = findHeader(rw, MoovBoxType, -1); err != nil { | ||
return fmt.Errorf(`failed finding box "%s": %w`, MoovBoxType, err) | ||
} | ||
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if err = forEachBox(rw, int64(h.Size-HeaderSize), trakHandler(rw)); err != nil { | ||
return fmt.Errorf(`failed processing moov children: %w`, err) | ||
} | ||
return | ||
} | ||
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func help() { | ||
fmt.Println(`Usage: mp4dovi <file>`) | ||
} | ||
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func main() { | ||
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if len(os.Args) != 2 { | ||
help() | ||
os.Exit(1) | ||
} | ||
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if err := run(os.Args[1]); err != nil { | ||
log.Fatal(err) | ||
} | ||
} |