Rewrite magic source

pkg/magic/producer.go

@@ -0,0 +1,40 @@
+package magic
+
+import (
+	"bytes"
+	"encoding/hex"
+	"errors"
+	"io"
+
+	"github.com/AlexxIT/go2rtc/pkg/core"
+	"github.com/AlexxIT/go2rtc/pkg/flv"
+	"github.com/AlexxIT/go2rtc/pkg/h264/annexb"
+	"github.com/AlexxIT/go2rtc/pkg/magic/bitstream"
+	"github.com/AlexxIT/go2rtc/pkg/magic/mjpeg"
+	"github.com/AlexxIT/go2rtc/pkg/mpegts"
+)
+
+func Open(r io.Reader) (core.Producer, error) {
+	rd := core.NewReadBuffer(r)
+
+	b, err := rd.Peek(4)
+	if err != nil {
+		return nil, err
+	}
+
+	switch {
+	case bytes.HasPrefix(b, []byte(annexb.StartCode)):
+		return bitstream.Open(rd)
+
+	case bytes.HasPrefix(b, []byte{0xFF, 0xD8}):
+		return mjpeg.Open(rd)
+
+	case bytes.HasPrefix(b, []byte(flv.Signature)):
+		return flv.Open(rd)
+
+	case b[0] == mpegts.SyncByte:
+		return mpegts.Open(rd)
+	}
+
+	return nil, errors.New("magic: unsupported header: " + hex.EncodeToString(b))
+}