Fix live stream presentation timestamps

Use capture presentation time directly for MoQ timestamps instead of adding composition time, which is already reflected in PTS.

machinery/src/cloud/livemoq/annexb.go

@@ -59,6 +59,16 @@ func BroadcastPath(prefix string, deviceKey string) string {
 	return prefix + "/" + strings.Trim(deviceKey, "/") + "/live.hang"
 }
 
+// TimestampUs converts the capture presentation timestamp from milliseconds.
+// CompositionTime must not be added: it is already represented in the PTS and
+// is only used by muxers to derive DTS for streams containing B-frames.
+func TimestampUs(presentationTimeMs int64) uint64 {
+	if presentationTimeMs < 0 {
+		return 0
+	}
+	return uint64(presentationTimeMs) * 1000
+}
+
 func hasAnnexBStartCode(payload []byte) bool {
 	return len(payload) >= 4 && payload[0] == 0 && payload[1] == 0 &&
 		((payload[2] == 0 && payload[3] == 1) || payload[2] == 1)

machinery/src/cloud/livemoq/annexb_test.go

@@ -72,3 +72,12 @@ func TestBroadcastPath(t *testing.T) {
 		t.Fatalf("BroadcastPath() default = %q", got)
 	}
 }
+
+func TestTimestampUs(t *testing.T) {
+	if got := TimestampUs(1234); got != 1_234_000 {
+		t.Fatalf("TimestampUs() = %d, want 1234000", got)
+	}
+	if got := TimestampUs(-1); got != 0 {
+		t.Fatalf("TimestampUs() negative = %d, want 0", got)
+	}
+}

machinery/src/cloud/livemoq_enabled.go

@@ -152,17 +152,13 @@ func publishLiveStreamMoQ(ctx context.Context, config liveMoQConfig) error {
 			writing = true
 			log.Log.Info("cloud.publishLiveStreamMoQ(): first H.264 keyframe received; broadcast is live")
 		}
-		presentationTimeMs := packet.Time + packet.CompositionTime
-		if presentationTimeMs < 0 {
-			presentationTimeMs = 0
-		}
 		payload, err := livemoq.NormalizeH264AccessUnit(packet.Data)
 		if err != nil {
 			return fmt.Errorf("normalize H.264 access unit: %w", err)
 		}
 		frame := moq.Frame{
 			Payload:     payload,
-			TimestampUs: uint64(presentationTimeMs) * 1000,
+			TimestampUs: livemoq.TimestampUs(packet.Time),
 		}
 		if err := stream.WriteFrame(frame); err != nil {
 			return fmt.Errorf("write H.264 access unit: %w", err)