Feature: Implement H.264 and AV1 hardware encoding for remote control

Remark: Need to update FFmpeg static libraries to take effort

server/go/protocol/commands.go

@@ -350,6 +350,69 @@ func IsH264Keyframe(data []byte) bool {
 	return false
 }
 
+// IsAnyKeyframe sniffs the codec from the first byte then dispatches to the
+// matching keyframe detector. H.264 Annex B always starts with 0x00 (start
+// code prefix); AV1 OBU headers have bit7=0 and bits[3:6]=obu_type in [1,15]
+// so the first byte is in [0x08,0x78] and never 0x00. Lets the server stay
+// codec-agnostic so the browser can run H.264 and AV1 sessions side by side.
+func IsAnyKeyframe(data []byte) bool {
+	if len(data) == 0 {
+		return false
+	}
+	if data[0] == 0x00 {
+		return IsH264Keyframe(data)
+	}
+	return IsAv1Keyframe(data)
+}
+
+// IsAv1Keyframe walks the OBU chain and returns true on the first
+// OBU_SEQUENCE_HEADER (type 1). FFmpeg's AV1 encoders prepend SEQ HDR to
+// every IDR, so seeing one is equivalent to "this packet contains a key
+// frame". Mirrors the C++ IsAv1Keyframe helper in ScreenSpyDlg.cpp.
+//
+// AV1 OBU header byte layout: 0|type:4|ext:1|size:1|reserved:1
+func IsAv1Keyframe(data []byte) bool {
+	n := len(data)
+	pos := 0
+	for pos < n {
+		hdr := data[pos]
+		obuType := (hdr >> 3) & 0x0F
+		hasExt := hdr&0x04 != 0
+		hasSize := hdr&0x02 != 0
+		if obuType == 1 { // OBU_SEQUENCE_HEADER
+			return true
+		}
+		pos++
+		if hasExt {
+			if pos >= n {
+				return false
+			}
+			pos++
+		}
+		if !hasSize {
+			return false // unsized OBU runs to end of packet
+		}
+		// LEB128 size
+		var sz uint64
+		for i := range 8 {
+			if pos >= n {
+				return false
+			}
+			b := data[pos]
+			pos++
+			sz |= uint64(b&0x7F) << (7 * i)
+			if b&0x80 == 0 {
+				break
+			}
+		}
+		if uint64(pos)+sz > uint64(n) {
+			return false
+		}
+		pos += int(sz)
+	}
+	return false
+}
+
 // LOGIN_INFOR structure size and offsets (matching C++ struct with default alignment)
 // Note: C++ struct uses default alignment (4-byte for uint32/int)
 const (