[feature] Enable basic video support (mp4 only) (#1274)

* [feature] basic video support

* fix missing semicolon

* replace text shadow with stacked icons

Co-authored-by: f0x <f0x@cthu.lu>

vendor/github.com/abema/go-mp4/extract.go

@@ -0,0 +1,98 @@
+package mp4
+
+import (
+	"errors"
+	"io"
+)
+
+type BoxInfoWithPayload struct {
+	Info    BoxInfo
+	Payload IBox
+}
+
+func ExtractBoxWithPayload(r io.ReadSeeker, parent *BoxInfo, path BoxPath) ([]*BoxInfoWithPayload, error) {
+	return ExtractBoxesWithPayload(r, parent, []BoxPath{path})
+}
+
+func ExtractBoxesWithPayload(r io.ReadSeeker, parent *BoxInfo, paths []BoxPath) ([]*BoxInfoWithPayload, error) {
+	bis, err := ExtractBoxes(r, parent, paths)
+	if err != nil {
+		return nil, err
+	}
+
+	bs := make([]*BoxInfoWithPayload, 0, len(bis))
+	for _, bi := range bis {
+		if _, err := bi.SeekToPayload(r); err != nil {
+			return nil, err
+		}
+
+		var ctx Context
+		if parent != nil {
+			ctx = parent.Context
+		}
+		box, _, err := UnmarshalAny(r, bi.Type, bi.Size-bi.HeaderSize, ctx)
+		if err != nil {
+			return nil, err
+		}
+		bs = append(bs, &BoxInfoWithPayload{
+			Info:    *bi,
+			Payload: box,
+		})
+	}
+	return bs, nil
+}
+
+func ExtractBox(r io.ReadSeeker, parent *BoxInfo, path BoxPath) ([]*BoxInfo, error) {
+	return ExtractBoxes(r, parent, []BoxPath{path})
+}
+
+func ExtractBoxes(r io.ReadSeeker, parent *BoxInfo, paths []BoxPath) ([]*BoxInfo, error) {
+	if len(paths) == 0 {
+		return nil, nil
+	}
+
+	for i := range paths {
+		if len(paths[i]) == 0 {
+			return nil, errors.New("box path must not be empty")
+		}
+	}
+
+	boxes := make([]*BoxInfo, 0, 8)
+
+	handler := func(handle *ReadHandle) (interface{}, error) {
+		path := handle.Path
+		if parent != nil {
+			path = path[1:]
+		}
+		if handle.BoxInfo.Type == BoxTypeAny() {
+			return nil, nil
+		}
+		fm, m := matchPath(paths, path)
+		if m {
+			boxes = append(boxes, &handle.BoxInfo)
+		}
+
+		if fm {
+			if _, err := handle.Expand(); err != nil {
+				return nil, err
+			}
+		}
+		return nil, nil
+	}
+
+	if parent != nil {
+		_, err := ReadBoxStructureFromInternal(r, parent, handler)
+		return boxes, err
+	}
+	_, err := ReadBoxStructure(r, handler)
+	return boxes, err
+}
+
+func matchPath(paths []BoxPath, path BoxPath) (forwardMatch bool, match bool) {
+	for i := range paths {
+		fm, m := path.compareWith(paths[i])
+		forwardMatch = forwardMatch || fm
+		match = match || m
+	}
+	return
+}