fix: mvhd and tkhd timestamps

timestamps were off by one day.
Added methods to set and get creation and modification times
for mvhd and tkhd boxes with unix epoch reference.

CHANGELOG.md

@@ -7,7 +7,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
-- Nothing yet
+### Fixed
+
+- mvhd and tkhd timestamp was off by one day
+
+### Added
+
+- mvhd and tkhd methods to set and get creation and modification times
 
 ## [0.45.1] - 2024-07-12
 

mp4/mvhd.go

@@ -26,6 +26,9 @@ type MvhdBox struct {
 	Volume           Fixed16
 }
 
+// EpochDiffS is the difference in seconds between Jan 1, 1904 and Jan 1, 1970
+const EpochDiffS = int64((66*365 + 17) * 24 * 3600)
+
 // CreateMvhd - create mvhd box with reasonable values
 func CreateMvhd() *MvhdBox {
 	return &MvhdBox{
@@ -140,10 +143,29 @@ func (b *MvhdBox) Info(w io.Writer, specificBoxLevels, indent, indentStep string
 	return bd.err
 }
 
+// CraetionTimeS returns the creation time in seconds since Jan 1, 1970
+func (b *MvhdBox) CreationTimeS() int64 {
+	return int64(b.CreationTime) - EpochDiffS
+}
+
+// ModificationTimeS returns the modification time in seconds since Jan 1, 1970
+func (b *MvhdBox) ModificationTimeS() int64 {
+	return int64(b.ModificationTime) - EpochDiffS
+}
+
+// SetCreationTimeS sets the creation time from seconds since Jan 1, 1970
+func (b *MvhdBox) SetCreationTimeS(unixTimeS int64) {
+	b.CreationTime = uint64(unixTimeS + EpochDiffS)
+}
+
+// SetModificationTimeS sets the modification time from seconds since Jan 1, 1970
+func (b *MvhdBox) SetModificationTimeS(unixTimeS int64) {
+	b.ModificationTime = uint64(unixTimeS + EpochDiffS)
+}
+
 // Make time string from t which is seconds since Jan. 1 1904
 func timeStr(t uint64) string {
-	epochDiffS := int64((66*365 + 16) * 24 * 3600)
-	unixSeconds := int64(t) - epochDiffS
+	unixSeconds := int64(t) - EpochDiffS
 	if unixSeconds < 0 {
 		return "0"
 	}

mp4/mvhd_test.go

@@ -2,33 +2,43 @@ package mp4
 
 import (
 	"bytes"
-	"reflect"
+	"os"
 	"testing"
 )
 
 func TestMvhd(t *testing.T) {
-	var buf bytes.Buffer
+	mvhd := CreateMvhd()
+	boxDiffAfterEncodeAndDecode(t, mvhd)
 
-	mvhdCreated := CreateMvhd()
-	err := mvhdCreated.Encode(&buf)
-	if err != nil {
-		t.Error(err)
+	recentTime := int64(1721459921)
+	mvhd.SetCreationTimeS(recentTime)
+	mvhd.SetModificationTimeS(recentTime)
+	if mvhd.CreationTimeS() != recentTime {
+		t.Errorf("CreationTimeS %d not %d", mvhd.CreationTimeS(), recentTime)
 	}
-
-	if uint64(buf.Len()) != mvhdCreated.Size() {
-		t.Errorf("Mismatch bytes written %d not equal to size %d", buf.Len(), mvhdCreated.Size())
+	if mvhd.ModificationTimeS() != recentTime {
+		t.Errorf("ModificationTimeS %d not %d", mvhd.ModificationTimeS(), recentTime)
 	}
+}
 
-	reader := &buf
-	hdr, err := DecodeHeader(reader)
+func TestMvhdTimeDecodeS(t *testing.T) {
+	data, err := os.ReadFile("testdata/mvhd_1970.dat")
 	if err != nil {
 		t.Error(err)
 	}
-	mvhdRead, err := DecodeMvhd(hdr, 0, reader)
+	reader := bytes.NewReader(data)
+	box, err := DecodeBox(0, reader)
 	if err != nil {
 		t.Error(err)
 	}
-	if !reflect.DeepEqual(mvhdRead, mvhdCreated) {
-		t.Errorf("Mismatch mvhdCreated vs mvhdRead:\n%+v\n%+v", mvhdCreated, mvhdRead)
+	mvhd, ok := box.(*MvhdBox)
+	if !ok {
+		t.Errorf("Not a MvhdBox %+v", box)
+	}
+	if mvhd.CreationTimeS() != 0 {
+		t.Errorf("CreationTimeS %d not 0", mvhd.CreationTimeS())
+	}
+	if mvhd.ModificationTimeS() != 0 {
+		t.Errorf("ModificationTimeS %d not 0", mvhd.ModificationTimeS())
 	}
 }

mp4/testdata/golden_init_prog_mp4_dump.txt

@@ -7,26 +7,26 @@
   [mvhd] size=108 version=0 flags=000000
    - timeScale: 600
    - duration: 11520
-   - creation time: 2020-03-11T08:59:14Z
-   - modification time: 2020-03-11T08:59:14Z
+   - creation time: 2020-03-10T08:59:14Z
+   - modification time: 2020-03-10T08:59:14Z
   [iods] size=21
    - not implemented or unknown box
    - 000000001007004fffffff7fff
   [trak] size=4952
     [tkhd] size=92 version=0 flags=000001
      - trackID: 1
      - duration: 11520
-     - creation time: 2020-03-11T08:59:14Z
-     - modification time: 2020-03-11T08:59:14Z
+     - creation time: 2020-03-10T08:59:14Z
+     - modification time: 2020-03-10T08:59:14Z
      - Width: 960.0, Height: 540.0
     [edts] size=36
       [elst] size=28 version=0 flags=000000
       - entry[1]: segmentDuration=11520 mediaTime=4, mediaRateInteger=1 mediaRateFraction=0
     [mdia] size=4816
       [mdhd] size=32 version=0 flags=000000
        - timeScale: 100
-       - creation time: 2020-03-11T08:59:14Z
-       - modification time: 2020-03-11T08:59:14Z
+       - creation time: 2020-03-10T08:59:14Z
+       - modification time: 2020-03-10T08:59:14Z
        - language: und
       [hdlr] size=57 version=0 flags=000000
        - handlerType: vide

mp4/tkhd.go

@@ -151,3 +151,23 @@ func (b *TkhdBox) Info(w io.Writer, specificBoxLevels, indent, indentStep string
 	}
 	return bd.err
 }
+
+// CraetionTimeS returns the creation time in seconds since Jan 1, 1970
+func (b *TkhdBox) CreationTimeS() int64 {
+	return int64(b.CreationTime) - EpochDiffS
+}
+
+// ModificationTimeS returns the modification time in seconds since Jan 1, 1970
+func (b *TkhdBox) ModificationTimeS() int64 {
+	return int64(b.ModificationTime) - EpochDiffS
+}
+
+// SetCreationTimeS sets the creation time from seconds since Jan 1, 1970
+func (b *TkhdBox) SetCreationTimeS(unixTimeS int64) {
+	b.CreationTime = uint64(unixTimeS + EpochDiffS)
+}
+
+// SetModificationTimeS sets the modification time from seconds since Jan 1, 1970
+func (b *TkhdBox) SetModificationTimeS(unixTimeS int64) {
+	b.ModificationTime = uint64(unixTimeS + EpochDiffS)
+}