mp4: read segment without init #115
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3052
changed the title
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I need to parse segment only: https://github.com/yapingcat/gomedia/files/13692755/index_video_5_0_1.zip and: |
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gomedia is used to extract video/audio frame from mp4,so gomedia need moov box to parse dash segment. |
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right, but with the current module, you have to parse the init data for EACH segment, which is really wasteful |
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OK I think this works, but it seems like bad code to have to call package sidx
import (
"bytes"
"crypto/aes"
"crypto/cipher"
"errors"
"fmt"
"github.com/yapingcat/gomedia/go-mp4"
"io"
"net/http"
)
// github.com/Eyevinn/mp4ff/blob/v0.40.2/mp4/crypto.go#L101
func Decrypt_CENC(sample []byte, key []byte, subSample *mp4.SubSample) error {
block, err := aes.NewCipher(key)
if err != nil {
return err
}
stream := cipher.NewCTR(block, subSample.IV[:])
if len(subSample.Patterns) != 0 {
var pos uint32 = 0
for j := 0; j < len(subSample.Patterns); j++ {
ss := subSample.Patterns[j]
nrClear := uint32(ss.BytesClear)
if nrClear > 0 {
pos += nrClear
}
nrEnc := ss.BytesProtected
if nrEnc > 0 {
stream.XORKeyStream(sample[pos:pos+nrEnc], sample[pos:pos+nrEnc])
pos += nrEnc
}
}
} else {
stream.XORKeyStream(sample, sample)
}
return nil
}
func get(url string, start, end uint32) ([]byte, error) {
req, err := http.NewRequest("GET", url, nil)
if err != nil {
return nil, err
}
req.Header.Set("Range", fmt.Sprintf("bytes=%v-%v", start, end))
fmt.Println(start, end)
res, err := http.DefaultClient.Do(req)
if err != nil {
return nil, err
}
defer res.Body.Close()
if res.StatusCode != http.StatusPartialContent {
return nil, errors.New(res.Status)
}
return io.ReadAll(res.Body)
}
func byte_ranges(r io.Reader, start uint32) ([][]uint32, error) {
sidx := mp4.SegmentIndexBox{
Box: &mp4.FullBox{
Box: &mp4.BasicBox{},
},
}
if _, err := sidx.Box.Box.Decode(r); err != nil {
return nil, err
}
if _, err := sidx.Decode(r); err != nil {
return nil, err
}
var rs [][]uint32
for _, e := range sidx.Entrys {
r := []uint32{start, start + e.ReferencedSize - 1}
rs = append(rs, r)
start += e.ReferencedSize
}
return rs, nil
}
func mux(
dst io.WriteSeeker,
url string,
start_sidx, start_segment uint32,
key []byte,
) error {
muxer, err := mp4.CreateMp4Muxer(dst)
if err != nil {
return err
}
vid := muxer.AddVideoTrack(mp4.MP4_CODEC_H264)
init, err := get(url, 0, start_sidx-1)
if err != nil {
return err
}
sidx, err := get(url, start_sidx, start_segment-1)
if err != nil {
return err
}
ranges, err := byte_ranges(bytes.NewReader(sidx), start_segment)
if err != nil {
return err
}
for _, r := range ranges {
segment, err := get(url, r[0], r[1])
if err != nil {
return err
}
segment = append(init, segment...)
demuxer := mp4.CreateMp4Demuxer(bytes.NewReader(segment))
if _, err := demuxer.ReadHead(); err != nil {
return err
}
demuxer.OnRawSample = func(_ mp4.MP4_CODEC_TYPE, sample []byte, subSample *mp4.SubSample) error {
return Decrypt_CENC(sample, key, subSample)
}
for {
pkg, err := demuxer.ReadPacket()
if err == io.EOF {
break
} else if err != nil {
return err
}
if err := muxer.Write(vid, pkg.Data, pkg.Pts, pkg.Dts); err != nil {
return err
}
}
}
return muxer.WriteTrailer()
} |
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other tools can read segment without init:
https://github.com/Eyevinn/mp4ff
https://github.com/abema/go-mp4
but this module cannot:
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