From 30c4379e6b738d15636f5987dc4bbc1df37e2ce2 Mon Sep 17 00:00:00 2001
From: Lysander <fraiic@163.com>
Date: Thu, 23 Nov 2023 05:42:36 +0800
Subject: [PATCH] support optional URI in EXT-X-MEDIA tag (#104)

* URI is OPTIONAL in EXT-X-MEDIA tag

* make URI mandatory in case of SUBTITLES

* adapt client in order to work with renditions without URLs

---------

Co-authored-by: aler9 <46489434+aler9@users.noreply.github.com>
---
 client_downloader_primary.go           | 42 ++++++++++++++------------
 pkg/playlist/multivariant_rendition.go | 34 +++++++++++++++------
 pkg/playlist/multivariant_test.go      |  2 +-
 3 files changed, 47 insertions(+), 31 deletions(-)

diff --git a/client_downloader_primary.go b/client_downloader_primary.go
index d36ca20..898b578 100644
--- a/client_downloader_primary.go
+++ b/client_downloader_primary.go
@@ -209,27 +209,29 @@ func (d *clientDownloaderPrimary) run(ctx context.Context) error {
 				return fmt.Errorf("audio playlist with id \"%s\" not found", leadingPlaylist.Audio)
 			}
 
-			u, err := clientAbsoluteURL(d.primaryPlaylistURL, audioPlaylist.URI)
-			if err != nil {
-				return err
+			if audioPlaylist.URI != "" {
+				u, err := clientAbsoluteURL(d.primaryPlaylistURL, audioPlaylist.URI)
+				if err != nil {
+					return err
+				}
+
+				ds := newClientDownloaderStream(
+					false,
+					d.httpClient,
+					d.onDownloadStreamPlaylist,
+					d.onDownloadSegment,
+					d.onDecodeError,
+					u,
+					nil,
+					d.rp,
+					d.onStreamTracks,
+					d.onSetLeadingTimeSync,
+					d.onGetLeadingTimeSync,
+					d.onData,
+				)
+				d.rp.add(ds)
+				streamCount++
 			}
-
-			ds := newClientDownloaderStream(
-				false,
-				d.httpClient,
-				d.onDownloadStreamPlaylist,
-				d.onDownloadSegment,
-				d.onDecodeError,
-				u,
-				nil,
-				d.rp,
-				d.onStreamTracks,
-				d.onSetLeadingTimeSync,
-				d.onGetLeadingTimeSync,
-				d.onData,
-			)
-			d.rp.add(ds)
-			streamCount++
 		}
 
 	default:
diff --git a/pkg/playlist/multivariant_rendition.go b/pkg/playlist/multivariant_rendition.go
index e83295d..fe3d4ac 100644
--- a/pkg/playlist/multivariant_rendition.go
+++ b/pkg/playlist/multivariant_rendition.go
@@ -111,22 +111,32 @@ func (t *MultivariantRendition) unmarshal(v string) error {
 		return fmt.Errorf("GROUP-ID missing")
 	}
 
-	if t.Type != MultivariantRenditionTypeClosedCaptions {
-		if t.URI == "" {
-			return fmt.Errorf("missing URI")
-		}
-
-		if t.InstreamID != "" {
-			return fmt.Errorf("INSTREAM-ID is forbidden with type %s", t.Type)
-		}
-	} else {
+	// If the TYPE is CLOSED-CAPTIONS, the URI
+	// attribute MUST NOT be present.
+	// The URI attribute of the EXT-X-MEDIA tag is REQUIRED if the media
+	// type is SUBTITLES, but OPTIONAL if the media type is VIDEO or AUDIO.
+	switch t.Type {
+	case MultivariantRenditionTypeClosedCaptions:
 		if t.URI != "" {
 			return fmt.Errorf("URI is forbidden for type CLOSED-CAPTIONS")
 		}
 
+	case MultivariantRenditionTypeSubtitles:
+		if t.URI == "" {
+			return fmt.Errorf("URI is required for type SUBTITLES")
+		}
+
+	default:
+	}
+
+	// This attribute is REQUIRED if the TYPE attribute is CLOSED-CAPTIONS
+	// For all other TYPE values, the INSTREAM-ID MUST NOT be specified.
+	if t.Type == MultivariantRenditionTypeClosedCaptions {
 		if t.InstreamID == "" {
 			return fmt.Errorf("missing INSTREAM-ID")
 		}
+	} else if t.InstreamID != "" {
+		return fmt.Errorf("INSTREAM-ID is forbidden with type %s", t.Type)
 	}
 
 	return nil
@@ -164,7 +174,11 @@ func (t MultivariantRendition) marshal() string {
 		ret += ",CHANNELS=\"" + t.Channels + "\""
 	}
 
-	ret += ",URI=\"" + t.URI + "\"\n"
+	if t.URI != "" {
+		ret += ",URI=\"" + t.URI + "\""
+	}
+
+	ret += "\n"
 
 	return ret
 }
diff --git a/pkg/playlist/multivariant_test.go b/pkg/playlist/multivariant_test.go
index bf9620d..9d98581 100644
--- a/pkg/playlist/multivariant_test.go
+++ b/pkg/playlist/multivariant_test.go
@@ -256,7 +256,7 @@ v2/prog_index.m3u8
 #EXT-X-MEDIA:TYPE="AUDIO",GROUP-ID="aud1",LANGUAGE="en",NAME="English",DEFAULT=YES,AUTOSELECT=YES,CHANNELS="2",URI="a1/prog_index.m3u8"
 #EXT-X-MEDIA:TYPE="AUDIO",GROUP-ID="aud2",LANGUAGE="en",NAME="English",DEFAULT=YES,AUTOSELECT=YES,CHANNELS="6",URI="a2/prog_index.m3u8"
 #EXT-X-MEDIA:TYPE="AUDIO",GROUP-ID="aud3",LANGUAGE="en",NAME="English",DEFAULT=YES,AUTOSELECT=YES,CHANNELS="6",URI="a3/prog_index.m3u8"
-#EXT-X-MEDIA:TYPE="CLOSED-CAPTIONS",GROUP-ID="cc1",LANGUAGE="en",NAME="English",DEFAULT=YES,AUTOSELECT=YES,URI=""
+#EXT-X-MEDIA:TYPE="CLOSED-CAPTIONS",GROUP-ID="cc1",LANGUAGE="en",NAME="English",DEFAULT=YES,AUTOSELECT=YES
 #EXT-X-MEDIA:TYPE="SUBTITLES",GROUP-ID="sub1",LANGUAGE="en",NAME="English",DEFAULT=YES,AUTOSELECT=YES,FORCED=NO,URI="s1/en/prog_index.m3u8"
 `,
 		Multivariant{