diff --git a/ffmpeg/parse/parser.go b/ffmpeg/parse/parser.go
index 78bfe64f..5f54d68a 100644
--- a/ffmpeg/parse/parser.go
+++ b/ffmpeg/parse/parser.go
@@ -178,7 +178,11 @@ func (p *parser) Parse(line string) uint64 {
 		p.lock.log.Unlock()
 	}
 
-	if !p.prelude.done {
+	p.lock.prelude.Lock()
+	preludeDone := p.prelude.done
+	p.lock.prelude.Unlock()
+
+	if !preludeDone {
 		if isAVstreamProgress {
 			return 0
 		}