From 264705818bc35fe3dc0f512d331d8fe98225378c Mon Sep 17 00:00:00 2001
From: nareix <hi.nareix@gmail.com>
Date: Sun, 12 Jun 2016 08:52:20 +0800
Subject: [PATCH] change Streams()

---
 demuxer.go | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/demuxer.go b/demuxer.go
index e9e1a5e..72fd650 100644
--- a/demuxer.go
+++ b/demuxer.go
@@ -27,7 +27,11 @@ type Demuxer struct {
 	movieAtom *atom.Movie
 }
 
-func (self *Demuxer) Streams() (streams []av.CodecData) {
+func (self *Demuxer) Streams() (streams []av.CodecData, err error) {
+	if len(self.streams) == 0 {
+		err = fmt.Errorf("mp4: no streams")
+		return
+	}
 	for _, stream := range self.streams {
 		streams = append(streams, stream)
 	}