0.29.1原版

internal/motionphoto/motionphoto.go

@@ -0,0 +1,110 @@
+package motionphoto
+
+import (
+	"bytes"
+	"encoding/binary"
+	"regexp"
+	"strconv"
+)
+
+type Detection struct {
+	VideoStart              int
+	PresentationTimestampUs int64
+}
+
+var (
+	motionPhotoMarkerRegex = regexp.MustCompile(`(?i)(?:Camera:MotionPhoto|GCamera:MotionPhoto|MicroVideo)["'=:\s>]+1`)
+	presentationRegex      = regexp.MustCompile(`(?i)(?:Camera:MotionPhotoPresentationTimestampUs|GCamera:MotionPhotoPresentationTimestampUs)["'=:\s>]+(-?\d+)`)
+	microVideoOffsetRegex  = regexp.MustCompile(`(?i)(?:Camera:MicroVideoOffset|GCamera:MicroVideoOffset)["'=:\s>]+(\d+)`)
+)
+
+const maxMetadataScanBytes = 256 * 1024
+
+func DetectJPEG(blob []byte) *Detection {
+	if len(blob) < 16 || !bytes.HasPrefix(blob, []byte{0xFF, 0xD8}) {
+		return nil
+	}
+
+	text := string(blob[:min(len(blob), maxMetadataScanBytes)])
+	if !motionPhotoMarkerRegex.MatchString(text) {
+		return nil
+	}
+
+	videoStart := detectVideoStart(blob, text)
+	if videoStart < 0 || videoStart >= len(blob) {
+		return nil
+	}
+
+	return &Detection{
+		VideoStart:              videoStart,
+		PresentationTimestampUs: parsePresentationTimestampUs(text),
+	}
+}
+
+func ExtractVideo(blob []byte) ([]byte, *Detection) {
+	detection := DetectJPEG(blob)
+	if detection == nil {
+		return nil, nil
+	}
+
+	videoBlob := blob[detection.VideoStart:]
+	if !looksLikeMP4(videoBlob) {
+		return nil, nil
+	}
+
+	return videoBlob, detection
+}
+
+func detectVideoStart(blob []byte, text string) int {
+	if matches := microVideoOffsetRegex.FindStringSubmatch(text); len(matches) == 2 {
+		if offset, err := strconv.Atoi(matches[1]); err == nil && offset > 0 && offset < len(blob) {
+			start := len(blob) - offset
+			if looksLikeMP4(blob[start:]) {
+				return start
+			}
+		}
+	}
+
+	return findEmbeddedMP4Start(blob)
+}
+
+func parsePresentationTimestampUs(text string) int64 {
+	matches := presentationRegex.FindStringSubmatch(text)
+	if len(matches) != 2 {
+		return 0
+	}
+
+	value, err := strconv.ParseInt(matches[1], 10, 64)
+	if err != nil {
+		return 0
+	}
+	return value
+}
+
+func findEmbeddedMP4Start(blob []byte) int {
+	searchFrom := len(blob)
+	for searchFrom > 8 {
+		index := bytes.LastIndex(blob[:searchFrom], []byte("ftyp"))
+		if index < 4 {
+			return -1
+		}
+
+		start := index - 4
+		if looksLikeMP4(blob[start:]) {
+			return start
+		}
+
+		searchFrom = index - 1
+	}
+
+	return -1
+}
+
+func looksLikeMP4(blob []byte) bool {
+	if len(blob) < 12 || !bytes.Equal(blob[4:8], []byte("ftyp")) {
+		return false
+	}
+
+	size := binary.BigEndian.Uint32(blob[:4])
+	return size == 1 || size >= 8
+}

internal/motionphoto/motionphoto_test.go

@@ -0,0 +1,25 @@
+package motionphoto
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/usememos/memos/internal/testutil"
+)
+
+func TestDetectJPEG(t *testing.T) {
+	t.Parallel()
+
+	blob := testutil.BuildMotionPhotoJPEG()
+	detection := DetectJPEG(blob)
+	require.NotNil(t, detection)
+	require.Positive(t, detection.VideoStart)
+	require.EqualValues(t, 123456, detection.PresentationTimestampUs)
+
+	videoBlob, extracted := ExtractVideo(blob)
+	require.NotNil(t, extracted)
+	require.True(t, bytes.Equal(videoBlob[:4], []byte{0x00, 0x00, 0x00, 0x10}))
+	require.Equal(t, []byte("ftyp"), videoBlob[4:8])
+}