Merge branch 'feat-hjj-FileExpand' into dev

pkg/service/file/file.go

@@ -484,6 +484,22 @@ func isLikelyMP4(b []byte) bool {
 		}
 		// 找到 ftyp 就放行（只做基本合法性检查）
 		if typ == "ftyp" {
+
+			major := b[i+int(hdr) : i+int(hdr)+4]
+			minor := binary.BigEndian.Uint32(b[i+int(hdr)+4 : i+int(hdr)+8])
+			compatStart := i + int(hdr) + 8
+			compatEnd := i + int(size)
+			if compatEnd > len(b) {
+				compatEnd = len(b)
+			}
+			brands := make([]string, 0, 5)
+			for j := compatStart; j+4 <= compatEnd && len(brands) < 5; j += 4 {
+				brands = append(brands, string(b[j:j+4]))
+			}
+			fmt.Printf("ftyp found: offset=%d size=%d hdr=%d major=%q minor=%d compatTop5=%v\n",
+				i, size, hdr, string(major), minor, brands,
+			)
+
 			if size < 16 {
 				return false
 			}
@@ -491,7 +507,6 @@ func isLikelyMP4(b []byte) bool {
 			if i+int(hdr)+8 > len(b) {
 				return false
 			}
-			major := b[i+int(hdr) : i+int(hdr)+4]
 			// fourcc 通常都是可打印字符（允许空格0x20）
 			for _, c := range major {
 				if c == 0x00 {