From 37bd9a1b98ce5847e209958e8e25b545738a9664 Mon Sep 17 00:00:00 2001
From: aler9 <46489434+aler9@users.noreply.github.com>
Date: Sun, 17 May 2020 16:47:05 +0200
Subject: [PATCH] add sdp functions

---
 go.mod               |  5 ++-
 go.sum               |  4 +++
 interleaved-frame.go |  2 +-
 sdp.go               | 77 ++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 86 insertions(+), 2 deletions(-)
 create mode 100644 sdp.go

diff --git a/go.mod b/go.mod
index f69a9976..2c496dcc 100644
--- a/go.mod
+++ b/go.mod
@@ -2,4 +2,7 @@ module github.com/aler9/gortsplib
 
 go 1.13
 
-require github.com/stretchr/testify v1.4.0
+require (
+	github.com/stretchr/testify v1.4.0
+	gortc.io/sdp v0.18.2
+)
diff --git a/go.sum b/go.sum
index 8fdee585..e62fffec 100644
--- a/go.sum
+++ b/go.sum
@@ -1,5 +1,7 @@
 github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
@@ -9,3 +11,5 @@ gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
+gortc.io/sdp v0.18.2 h1:w2L1h9rgMZwGQz/bYMxTQ36POQ114ETpYUX1pFfSsLg=
+gortc.io/sdp v0.18.2/go.mod h1:Oj8tpRIx+Zx6lyrQR9+HHegByfbaz92A9wPSWrQhTI4=
diff --git a/interleaved-frame.go b/interleaved-frame.go
index 63cd84a9..1da0bf97 100644
--- a/interleaved-frame.go
+++ b/interleaved-frame.go
@@ -8,7 +8,7 @@ import (
 )
 
 const (
-	_INTERLEAVED_FRAME_MAX_SIZE         =  512 * 1024
+	_INTERLEAVED_FRAME_MAX_SIZE         = 512 * 1024
 	_INTERLEAVED_FRAME_MAX_CONTENT_SIZE = (_INTERLEAVED_FRAME_MAX_SIZE - 4)
 )
 
diff --git a/sdp.go b/sdp.go
new file mode 100644
index 00000000..43ade655
--- /dev/null
+++ b/sdp.go
@@ -0,0 +1,77 @@
+package gortsplib
+
+import (
+	"fmt"
+	"strconv"
+
+	"gortc.io/sdp"
+)
+
+// SDPParse parses a SDP document.
+func SDPParse(in []byte) (*sdp.Message, error) {
+	s, err := sdp.DecodeSession(in, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	m := &sdp.Message{}
+	d := sdp.NewDecoder(s)
+	err = d.Decode(m)
+	if err != nil {
+		// allow empty Origins
+		if err.Error() != "failed to decode message: DecodeError in section s: origin address not set" {
+			return nil, err
+		}
+	}
+
+	if len(m.Medias) == 0 {
+		return nil, fmt.Errorf("no tracks defined")
+	}
+
+	return m, nil
+}
+
+// SDPFilter removes everything from a SDP document, except the bare minimum.
+func SDPFilter(msgIn *sdp.Message, byteIn []byte) (*sdp.Message, []byte) {
+	msgOut := &sdp.Message{}
+
+	msgOut.Name = "Stream"
+	msgOut.Origin = sdp.Origin{
+		Username:    "-",
+		NetworkType: "IN",
+		AddressType: "IP4",
+		Address:     "127.0.0.1",
+	}
+
+	for i, m := range msgIn.Medias {
+		var attributes []sdp.Attribute
+		for _, attr := range m.Attributes {
+			if attr.Key == "rtpmap" || attr.Key == "fmtp" {
+				attributes = append(attributes, attr)
+			}
+		}
+
+		// control attribute is mandatory, and is the path that is appended
+		// to the stream path in SETUP
+		attributes = append(attributes, sdp.Attribute{
+			Key:   "control",
+			Value: "trackID=" + strconv.FormatInt(int64(i), 10),
+		})
+
+		msgOut.Medias = append(msgOut.Medias, sdp.Media{
+			Bandwidths: m.Bandwidths,
+			Description: sdp.MediaDescription{
+				Type:     m.Description.Type,
+				Protocol: "RTP/AVP", // override protocol
+				Formats:  m.Description.Formats,
+			},
+			Attributes: attributes,
+		})
+	}
+
+	sdps := sdp.Session{}
+	sdps = msgOut.Append(sdps)
+	byteOut := sdps.AppendTo(nil)
+
+	return msgOut, byteOut
+}