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mpegtsmuxer.go
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/
mpegtsmuxer.go
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package main
import (
"bufio"
"context"
"log"
"os"
"time"
"github.com/aler9/gortsplib/v2/pkg/codecs/h264"
"github.com/asticode/go-astits"
)
// mpegtsMuxer allows to save a H264 stream into a MPEG-TS file.
type mpegtsMuxer struct {
sps []byte
pps []byte
f *os.File
b *bufio.Writer
mux *astits.Muxer
dtsExtractor *h264.DTSExtractor
firstIDRReceived bool
startDTS time.Duration
}
// newMPEGTSMuxer allocates a mpegtsMuxer.
func newMPEGTSMuxer(sps []byte, pps []byte) (*mpegtsMuxer, error) {
f, err := os.Create("mystream.ts")
if err != nil {
return nil, err
}
b := bufio.NewWriter(f)
mux := astits.NewMuxer(context.Background(), b)
mux.AddElementaryStream(astits.PMTElementaryStream{
ElementaryPID: 256,
StreamType: astits.StreamTypeH264Video,
})
mux.SetPCRPID(256)
return &mpegtsMuxer{
sps: sps,
pps: pps,
f: f,
b: b,
mux: mux,
}, nil
}
// close closes all the mpegtsMuxer resources.
func (e *mpegtsMuxer) close() {
e.b.Flush()
e.f.Close()
}
// encode encodes H264 NALUs into MPEG-TS.
func (e *mpegtsMuxer) encode(nalus [][]byte, pts time.Duration) error {
// prepend an AUD. This is required by some players
filteredNALUs := [][]byte{
{byte(h264.NALUTypeAccessUnitDelimiter), 240},
}
nonIDRPresent := false
idrPresent := false
for _, nalu := range nalus {
typ := h264.NALUType(nalu[0] & 0x1F)
switch typ {
case h264.NALUTypeSPS:
e.sps = append([]byte(nil), nalu...)
continue
case h264.NALUTypePPS:
e.pps = append([]byte(nil), nalu...)
continue
case h264.NALUTypeAccessUnitDelimiter:
continue
case h264.NALUTypeIDR:
idrPresent = true
case h264.NALUTypeNonIDR:
nonIDRPresent = true
}
filteredNALUs = append(filteredNALUs, nalu)
}
nalus = filteredNALUs
if !nonIDRPresent && !idrPresent {
return nil
}
// add SPS and PPS before every group that contains an IDR
if idrPresent {
nalus = append([][]byte{e.sps, e.pps}, nalus...)
}
var dts time.Duration
if !e.firstIDRReceived {
// skip samples silently until we find one with a IDR
if !idrPresent {
return nil
}
e.firstIDRReceived = true
e.dtsExtractor = h264.NewDTSExtractor()
var err error
dts, err = e.dtsExtractor.Extract(nalus, pts)
if err != nil {
return err
}
e.startDTS = dts
dts = 0
pts -= e.startDTS
} else {
var err error
dts, err = e.dtsExtractor.Extract(nalus, pts)
if err != nil {
return err
}
dts -= e.startDTS
pts -= e.startDTS
}
oh := &astits.PESOptionalHeader{
MarkerBits: 2,
}
if dts == pts {
oh.PTSDTSIndicator = astits.PTSDTSIndicatorOnlyPTS
oh.PTS = &astits.ClockReference{Base: int64(pts.Seconds() * 90000)}
} else {
oh.PTSDTSIndicator = astits.PTSDTSIndicatorBothPresent
oh.DTS = &astits.ClockReference{Base: int64(dts.Seconds() * 90000)}
oh.PTS = &astits.ClockReference{Base: int64(pts.Seconds() * 90000)}
}
// encode into Annex-B
annexb, err := h264.AnnexBMarshal(nalus)
if err != nil {
return err
}
// write TS packet
_, err = e.mux.WriteData(&astits.MuxerData{
PID: 256,
AdaptationField: &astits.PacketAdaptationField{
RandomAccessIndicator: idrPresent,
},
PES: &astits.PESData{
Header: &astits.PESHeader{
OptionalHeader: oh,
StreamID: 224, // video
},
Data: annexb,
},
})
if err != nil {
return err
}
log.Println("wrote TS packet")
return nil
}