improve performance

internal/playback/fmp4.go

@@ -1,9 +1,9 @@
 package playback
 
 import (
-	"bufio"
 	"bytes"
 	"errors"
+	"fmt"
 	"io"
 	"os"
 	"time"
@@ -33,27 +33,48 @@ func durationMp4ToGo(v uint64, timeScale uint32) time.Duration {
 
 var errTerminated = errors.New("terminated")
 
-func readInit(r io.ReadSeeker) ([]byte, error) {
-	br := bufio.NewReaderSize(r, 4096)
-	var out []byte
+func fmp4ReadInit(r io.ReadSeeker) ([]byte, error) {
+	buf := make([]byte, 8)
+	_, err := io.ReadFull(r, buf)
+	if err != nil {
+		return nil, err
+	}
 
-	for {
-		by, err := br.ReadByte()
-		if err != nil {
-			return nil, err
-		}
+	if !bytes.Equal(buf[4:], []byte{'f', 't', 'y', 'p'}) {
+		return nil, fmt.Errorf("ftyp box not found")
+	}
 
-		out = append(out, by)
+	ftypSize := uint32(buf[0])<<24 | uint32(buf[1])<<16 | uint32(buf[2])<<8 | uint32(buf[3])
 
-		if len(out) >= 8 {
-			if bytes.Equal(out[len(out)-8:], []byte{
-				'm', 'o', 'o', 'f', 0x00, 0x00, 0x00, 0x10,
-			}) {
-				out = out[:len(out)-12]
-				return out, nil
-			}
-		}
+	_, err = r.Seek(int64(ftypSize), io.SeekStart)
+	if err != nil {
+		return nil, err
 	}
+
+	_, err = io.ReadFull(r, buf)
+	if err != nil {
+		return nil, err
+	}
+
+	if !bytes.Equal(buf[4:], []byte{'m', 'o', 'o', 'v'}) {
+		return nil, fmt.Errorf("moov box not found")
+	}
+
+	moovSize := uint32(buf[0])<<24 | uint32(buf[1])<<16 | uint32(buf[2])<<8 | uint32(buf[3])
+
+	_, err = r.Seek(0, io.SeekStart)
+	if err != nil {
+		return nil, err
+	}
+
+	buf = make([]byte, ftypSize+moovSize)
+
+	_, err = io.ReadFull(r, buf)
+	if err != nil {
+		return nil, err
+	}
+
+	return buf, nil
 }
 
 func seekAndMuxParts(
@@ -377,7 +398,7 @@ func fmp4SeekAndMux(
 	}
 	defer f.Close()
 
-	init, err := readInit(f)
+	init, err := fmp4ReadInit(f)
 	if err != nil {
 		return 0, err
 	}

internal/playback/fmp4_test.go

@@ -0,0 +1,79 @@
+package playback
+
+import (
+	"io"
+	"os"
+	"testing"
+
+	"github.com/bluenviron/mediacommon/pkg/codecs/mpeg4audio"
+	"github.com/bluenviron/mediacommon/pkg/formats/fmp4"
+)
+
+func writeBenchInit(f io.WriteSeeker) {
+	init := fmp4.Init{
+		Tracks: []*fmp4.InitTrack{
+			{
+				ID:        1,
+				TimeScale: 90000,
+				Codec: &fmp4.CodecH264{
+					SPS: []byte{
+						0x67, 0x42, 0xc0, 0x28, 0xd9, 0x00, 0x78, 0x02,
+						0x27, 0xe5, 0x84, 0x00, 0x00, 0x03, 0x00, 0x04,
+						0x00, 0x00, 0x03, 0x00, 0xf0, 0x3c, 0x60, 0xc9,
+						0x20,
+					},
+					PPS: []byte{0x08},
+				},
+			},
+			{
+				ID:        2,
+				TimeScale: 90000,
+				Codec: &fmp4.CodecMPEG4Audio{
+					Config: mpeg4audio.Config{
+						Type:         mpeg4audio.ObjectTypeAACLC,
+						SampleRate:   48000,
+						ChannelCount: 2,
+					},
+				},
+			},
+		},
+	}
+
+	err := init.Marshal(f)
+	if err != nil {
+		panic(err)
+	}
+
+	_, err = f.Write([]byte{
+		'm', 'o', 'o', 'f', 0x00, 0x00, 0x00, 0x10,
+	})
+	if err != nil {
+		panic(err)
+	}
+}
+
+func BenchmarkFMP4ReadInit(b *testing.B) {
+	f, err := os.CreateTemp(os.TempDir(), "mediamtx-playback-fmp4-")
+	if err != nil {
+		panic(err)
+	}
+	defer os.Remove(f.Name())
+
+	writeBenchInit(f)
+	f.Close()
+
+	for n := 0; n < b.N; n++ {
+		func() {
+			f, err := os.Open(f.Name())
+			if err != nil {
+				panic(err)
+			}
+			defer f.Close()
+
+			_, err = fmp4ReadInit(f)
+			if err != nil {
+				panic(err)
+			}
+		}()
+	}
+}