headers: support SSRCs with length < 4 (#396)

go.mod

@@ -5,7 +5,7 @@ go 1.15
 require (
 	github.com/alecthomas/template v0.0.0-20190718012654-fb15b899a751 // indirect
 	github.com/alecthomas/units v0.0.0-20190924025748-f65c72e2690d // indirect
-	github.com/aler9/gortsplib v0.0.0-20210529171927-4f595a1d0dd6
+	github.com/aler9/gortsplib v0.0.0-20210529202307-2c0d28ecb481
 	github.com/asticode/go-astits v0.0.0-00010101000000-000000000000
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/fsnotify/fsnotify v1.4.9

go.sum

@@ -4,8 +4,8 @@ github.com/alecthomas/units v0.0.0-20190924025748-f65c72e2690d h1:UQZhZ2O0vMHr2c
 github.com/alecthomas/units v0.0.0-20190924025748-f65c72e2690d/go.mod h1:rBZYJk541a8SKzHPHnH3zbiI+7dagKZ0cgpgrD7Fyho=
 github.com/aler9/go-astits v0.0.0-20210423195926-582b09ed7c04 h1:CXgQLsU4uxWAmsXNOjGLbj0A+0IlRcpZpMgI13fmVwo=
 github.com/aler9/go-astits v0.0.0-20210423195926-582b09ed7c04/go.mod h1:DkOWmBNQpnr9mv24KfZjq4JawCFX1FCqjLVGvO0DygQ=
-github.com/aler9/gortsplib v0.0.0-20210529171927-4f595a1d0dd6 h1:OJ2HRSMDf3Aw8JWzaTejck6kGTMY41BKIIo36Pw10eM=
-github.com/aler9/gortsplib v0.0.0-20210529171927-4f595a1d0dd6/go.mod h1:zVCg+TQX445hh1pC5QgAuuBvvXZMWLY1XYz626dGFqY=
+github.com/aler9/gortsplib v0.0.0-20210529202307-2c0d28ecb481 h1:KR8GchdFkhzZPSUt20Z3k92GBV6dmyTazWkJKJop8Ro=
+github.com/aler9/gortsplib v0.0.0-20210529202307-2c0d28ecb481/go.mod h1:zVCg+TQX445hh1pC5QgAuuBvvXZMWLY1XYz626dGFqY=
 github.com/aler9/rtmp v0.0.0-20210403095203-3be4a5535927 h1:95mXJ5fUCYpBRdSOnLAQAdJHHKxxxJrVCiaqDi965YQ=
 github.com/aler9/rtmp v0.0.0-20210403095203-3be4a5535927/go.mod h1:vzuE21rowz+lT1NGsWbreIvYulgBpCGnQyeTyFblUHc=
 github.com/asticode/go-astikit v0.20.0 h1:+7N+J4E4lWx2QOkRdOf6DafWJMv6O4RRfgClwQokrH8=