EXT-X-START tag support (#31)

* add support for EXT-X-START tags

* warns about improper START tags

CHANGELOG.md

@@ -1,3 +1,7 @@
+## HEAD
+
+* added ability to parse EXT-X-START tags
+
 <a name="3.0.0"></a>
 # 3.0.0 (2017-06-09)
 

README.md

@@ -160,6 +160,7 @@ Manifest {
 * [EXT-X-DISCONTINUITY-SEQUENCE](http://tools.ietf.org/html/draft-pantos-http-live-streaming#section-4.3.3.3)
 * [EXT-X-ENDLIST](http://tools.ietf.org/html/draft-pantos-http-live-streaming#section-4.3.3.4)
 * [EXT-X-PLAYLIST-TYPE](http://tools.ietf.org/html/draft-pantos-http-live-streaming#section-4.3.3.5)
+* [EXT-X-START](http://tools.ietf.org/html/draft-pantos-http-live-streaming#section-4.3.5.2)
 
 ### Master Playlist Tags
 
@@ -235,7 +236,6 @@ Example media playlist using `EXT-X-CUE-` tags.
 * [EXT-X-SESSION-DATA](http://tools.ietf.org/html/draft-pantos-http-live-streaming#section-4.3.4.4)
 * [EXT-X-SESSION-KEY](http://tools.ietf.org/html/draft-pantos-http-live-streaming#section-4.3.4.5)
 * [EXT-X-INDEPENDENT-SEGMENTS](http://tools.ietf.org/html/draft-pantos-http-live-streaming#section-4.3.5.1)
-* [EXT-X-START](http://tools.ietf.org/html/draft-pantos-http-live-streaming#section-4.3.5.2)
 
 ## Including the Parser
 

src/parse-stream.js

@@ -363,6 +363,21 @@ export default class ParseStream extends Stream {
       this.trigger('data', event);
       return;
     }
+    match = (/^#EXT-X-START:?(.*)$/).exec(line);
+    if (match) {
+      event = {
+        type: 'tag',
+        tagType: 'start'
+      };
+      if (match[1]) {
+        event.attributes = parseAttributes(match[1]);
+
+        event.attributes['TIME-OFFSET'] = parseFloat(event.attributes['TIME-OFFSET']);
+        event.attributes.PRECISE = (/YES/).test(event.attributes.PRECISE);
+      }
+      this.trigger('data', event);
+      return;
+    }
     match = (/^#EXT-X-CUE-OUT-CONT:?(.*)?$/).exec(line);
     if (match) {
       event = {

src/parser.js

@@ -288,6 +288,18 @@ export default class Parser extends Stream {
               }
               this.manifest.totalDuration = entry.duration;
             },
+            start() {
+              if (!entry.attributes || isNaN(entry.attributes['TIME-OFFSET'])) {
+                this.trigger('warn', {
+                  message: 'ignoring start declaration without appropriate attribute list'
+                });
+                return;
+              }
+              this.manifest.start = {
+                timeOffset: entry.attributes['TIME-OFFSET'],
+                precise: entry.attributes.PRECISE
+              };
+            },
             'cue-out'() {
               currentUri.cueOut = entry.data;
             },

test/fixtures/m3u8/start.js

@@ -0,0 +1,35 @@
+{
+  "allowCache": true,
+  "mediaSequence": 0,
+  "playlistType": "VOD",
+  "segments": [
+    {
+      "duration": 10,
+      "timeline": 0,
+      "uri": "media-00001.ts"
+    },
+    {
+      "duration": 10,
+      "timeline": 0,
+      "uri": "media-00002.ts"
+    },
+    {
+      "duration": 10,
+      "timeline": 0,
+      "uri": "media-00003.ts"
+    },
+    {
+      "duration": 10,
+      "timeline": 0,
+      "uri": "media-00004.ts"
+    }
+  ],
+  "targetDuration": 10,
+  "endList": true,
+  "discontinuitySequence": 0,
+  "discontinuityStarts": [],
+  "start": {
+    "timeOffset": 10.3,
+    "precise": false
+  }
+}

test/fixtures/m3u8/start.m3u8

@@ -0,0 +1,13 @@
+#EXT-X-VERSION:3
+#EXT-X-PLAYLIST-TYPE:VOD
+#EXT-X-TARGETDURATION:10
+#EXT-X-START:TIME-OFFSET=10.3
+#EXTINF:10,
+media-00001.ts
+#EXTINF:10,
+media-00002.ts
+#EXTINF:10,
+media-00003.ts
+#EXTINF:10,
+media-00004.ts
+#EXT-X-ENDLIST

test/m3u8.test.js

@@ -731,6 +731,59 @@ QUnit.test('parses prefixed with 0x or 0X #EXT-X-KEY:IV tags', function(assert)
     0x90abcdef
   ]), 'parsed an IV value with 0X');
 });
+// #EXT-X-START
+QUnit.test('parses EXT-X-START tags', function(assert) {
+  const manifest = '#EXT-X-START:TIME-OFFSET=1.1\n';
+  let element;
+
+  this.parseStream.on('data', function(elem) {
+    element = elem;
+  });
+  this.lineStream.push(manifest);
+
+  assert.ok(element, 'an event was triggered');
+  assert.strictEqual(element.type, 'tag', 'the line type is tag');
+  assert.strictEqual(element.tagType, 'start', 'the tag type is start');
+  assert.strictEqual(element.attributes['TIME-OFFSET'], 1.1, 'parses time offset');
+  assert.strictEqual(element.attributes.PRECISE, false, 'precise defaults to false');
+});
+QUnit.test('parses EXT-X-START PRECISE attribute', function(assert) {
+  const manifest = '#EXT-X-START:TIME-OFFSET=1.4,PRECISE=YES\n';
+  let element;
+
+  this.parseStream.on('data', function(elem) {
+    element = elem;
+  });
+  this.lineStream.push(manifest);
+
+  assert.ok(element, 'an event was triggered');
+  assert.strictEqual(element.type, 'tag', 'the line type is tag');
+  assert.strictEqual(element.tagType, 'start', 'the tag type is start');
+  assert.strictEqual(element.attributes['TIME-OFFSET'], 1.4, 'parses time offset');
+  assert.strictEqual(element.attributes.PRECISE, true, 'parses precise attribute');
+});
+QUnit.test('flags missing EXT-X-START TIME-OFFSET attribute', function(assert) {
+  const parser = new Parser();
+
+  const manifest = [
+    '#EXT-X-VERSION:3',
+    '#EXT-X-TARGETDURATION:10',
+    '#EXT-X-START:PRECISE=YES',
+    '#EXTINF:10,',
+    'media-00001.ts',
+    '#EXT-X-ENDLIST'
+  ].join('\n');
+  let warning;
+
+  parser.on('warn', function(warn) {
+    warning = warn;
+  });
+  parser.push(manifest);
+
+  assert.ok(warning, 'a warning was triggered');
+  assert.ok((/ignoring start/).test(warning.message), 'message is about start tag');
+  assert.strictEqual(typeof parser.manifest.start, 'undefined', 'does not parse start');
+});
 
 QUnit.test('ignores empty lines', function(assert) {
   const manifest = '\n';