From 308b92d16e0c0abb660fbb8f35d568a800620041 Mon Sep 17 00:00:00 2001
From: KongQun Yang <kqyang@google.com>
Date: Mon, 16 Jul 2018 16:39:41 -0700
Subject: [PATCH] [WebVTT] support cues without payload

WebVTT cues without payload may not carry meaningful information, but it
is allowed by WebVTT specification [1]. It could also be useful
sometimes, e.g. to signal the time progression in live case.

Fixes #433.

[1] https://www.w3.org/TR/webvtt1/#types-of-webvtt-cue-payload

Change-Id: I9e31f4a3789cbdafb7667b64f4019834190ecfc0
---
 .../media/formats/webvtt/webvtt_parser.cc     |  5 +--
 .../formats/webvtt/webvtt_parser_unittest.cc  | 45 +++++++++++++++++++
 2 files changed, 47 insertions(+), 3 deletions(-)

diff --git a/packager/media/formats/webvtt/webvtt_parser.cc b/packager/media/formats/webvtt/webvtt_parser.cc
index 2e225a82e3..901cc6dccb 100644
--- a/packager/media/formats/webvtt/webvtt_parser.cc
+++ b/packager/media/formats/webvtt/webvtt_parser.cc
@@ -163,15 +163,14 @@ bool WebVttParser::Parse() {
     }
 
     // CUE with ID
-    if (block.size() > 2 && MaybeCueId(block[0]) &&
+    if (block.size() >= 2 && MaybeCueId(block[0]) &&
         IsLikelyCueTiming(block[1]) && ParseCueWithId(block)) {
       saw_cue = true;
       continue;
     }
 
     // CUE with no ID
-    if (block.size() > 1 && IsLikelyCueTiming(block[0]) &&
-        ParseCueWithNoId(block)) {
+    if (IsLikelyCueTiming(block[0]) && ParseCueWithNoId(block)) {
       saw_cue = true;
       continue;
     }
diff --git a/packager/media/formats/webvtt/webvtt_parser_unittest.cc b/packager/media/formats/webvtt/webvtt_parser_unittest.cc
index a4241a430c..1ed0d1b20c 100644
--- a/packager/media/formats/webvtt/webvtt_parser_unittest.cc
+++ b/packager/media/formats/webvtt/webvtt_parser_unittest.cc
@@ -214,6 +214,28 @@ TEST_F(WebVttParserTest, ParseOneCue) {
   ASSERT_OK(parser_->Run());
 }
 
+TEST_F(WebVttParserTest, ParseOneEmptyCue) {
+  const char* text =
+      "WEBVTT\n"
+      "\n"
+      "00:01:00.000 --> 01:00:00.000\n"
+      "\n";
+
+  ASSERT_NO_FATAL_FAILURE(SetUpAndInitializeGraph(text));
+
+  {
+    testing::InSequence s;
+    EXPECT_CALL(*Output(kOutputIndex),
+                OnProcess(IsStreamInfo(_, kTimeScale, !kEncrypted, _)));
+    EXPECT_CALL(
+        *Output(kOutputIndex),
+        OnProcess(IsTextSample(_, kNoId, 60000u, 3600000u, kNoSettings, "")));
+    EXPECT_CALL(*Output(kOutputIndex), OnFlush(_));
+  }
+
+  ASSERT_OK(parser_->Run());
+}
+
 TEST_F(WebVttParserTest, FailToParseCueWithArrowInId) {
   const char* text =
       "WEBVTT\n"
@@ -250,6 +272,29 @@ TEST_F(WebVttParserTest, ParseOneCueWithId) {
   ASSERT_OK(parser_->Run());
 }
 
+TEST_F(WebVttParserTest, ParseOneEmptyCueWithId) {
+  const char* text =
+      "WEBVTT\n"
+      "\n"
+      "id\n"
+      "00:01:00.000 --> 01:00:00.000\n"
+      "\n";
+
+  ASSERT_NO_FATAL_FAILURE(SetUpAndInitializeGraph(text));
+
+  {
+    testing::InSequence s;
+    EXPECT_CALL(*Output(kOutputIndex),
+                OnProcess(IsStreamInfo(_, kTimeScale, !kEncrypted, _)));
+    EXPECT_CALL(
+        *Output(kOutputIndex),
+        OnProcess(IsTextSample(_, "id", 60000u, 3600000u, kNoSettings, "")));
+    EXPECT_CALL(*Output(kOutputIndex), OnFlush(_));
+  }
+
+  ASSERT_OK(parser_->Run());
+}
+
 TEST_F(WebVttParserTest, ParseOneCueWithSettings) {
   const char* text =
       "WEBVTT\n"