Parse WebVTT regions and styles.

This adds more generic settings for regions and CSS styles.  These are
global settings, so they go on the StreamInfo object.

Change-Id: Ibb76c060206152ccf8e9a067c09877226f67c927

packager/media/base/text_stream_info.h

@@ -8,12 +8,38 @@
 #define PACKAGER_MEDIA_BASE_TEXT_STREAM_INFO_H_
 
 #include "packager/media/base/stream_info.h"
+#include "packager/media/base/text_sample.h"
 
+#include <map>
 #include <string>
 
 namespace shaka {
 namespace media {
 
+struct TextRegion {
+  /// The width of the region; percent units are relative to the window.
+  TextNumber width{100, TextUnitType::kPercent};
+  /// The height of the region; percent units are relative to the window.
+  TextNumber height{100, TextUnitType::kPercent};
+
+  /// The x and y coordinates of the anchor point within the window.  Percent
+  /// units are relative to the window.  In WebVTT this is called the
+  /// "viewport region anchor".
+  TextNumber window_anchor_x{0, TextUnitType::kPercent};
+  TextNumber window_anchor_y{0, TextUnitType::kPercent};
+  /// The x and y coordinates of the anchor point within the region.  Percent
+  /// units are relative to the region size.  For example: if this is
+  /// (100, 100), then the bottom right of the region should be placed at the
+  /// window anchor point.
+  /// See https://www.w3.org/TR/webvtt1/#regions.
+  TextNumber region_anchor_x{0, TextUnitType::kPercent};
+  TextNumber region_anchor_y{0, TextUnitType::kPercent};
+
+  /// If true, cues are scrolled up when adding new cues; if false, cues are
+  /// added above existing cues or replace existing ones.
+  bool scroll = false;
+};
+
 class TextStreamInfo : public StreamInfo {
  public:
   /// No encryption supported.
@@ -42,8 +68,16 @@ class TextStreamInfo : public StreamInfo {
 
   uint16_t width() const { return width_; }
   uint16_t height() const { return height_; }
+  const std::map<std::string, TextRegion>& regions() const { return regions_; }
+  void AddRegion(const std::string& id, const TextRegion& region) {
+    regions_[id] = region;
+  }
+  const std::string& css_styles() const { return css_styles_; }
+  void set_css_styles(const std::string& styles) { css_styles_ = styles; }
 
  private:
+  std::map<std::string, TextRegion> regions_;
+  std::string css_styles_;
   uint16_t width_;
   uint16_t height_;
 

packager/media/formats/mp4/mp4_muxer.cc

@@ -579,7 +579,7 @@ bool MP4Muxer::GenerateTextTrak(const TextStreamInfo* text_info,
     webvtt.config.config = "WEBVTT";
     // The spec does not define a way to carry STYLE and REGION information in
     // the mp4 container.
-    if (!text_info->codec_config().empty()) {
+    if (!text_info->regions().empty() || !text_info->css_styles().empty()) {
       LOG(INFO) << "Skipping possible style / region configuration as the spec "
                    "does not define a way to carry them inside ISO-BMFF files.";
     }

packager/media/formats/webvtt/webvtt_muxer.cc

@@ -7,10 +7,12 @@
 #include "packager/media/formats/webvtt/webvtt_muxer.h"
 
 #include <memory>
+#include <regex>
 
 #include "packager/file/file.h"
 #include "packager/file/file_closer.h"
 #include "packager/media/base/muxer_util.h"
+#include "packager/media/base/text_stream_info.h"
 #include "packager/media/formats/webvtt/webvtt_utils.h"
 #include "packager/status_macros.h"
 
@@ -18,20 +20,13 @@ namespace shaka {
 namespace media {
 namespace webvtt {
 
-namespace {
-
-std::string ToString(const std::vector<uint8_t>& v) {
-  return std::string(v.begin(), v.end());
-}
-
-}  // namespace
-
 WebVttMuxer::WebVttMuxer(const MuxerOptions& options) : Muxer(options) {}
 WebVttMuxer::~WebVttMuxer() {}
 
 Status WebVttMuxer::InitializeMuxer() {
-  if (streams().size() != 1) {
+  if (streams().size() != 1 || streams()[0]->stream_type() != kStreamText) {
-    return Status(error::MUXER_FAILURE, "Incorrect number of streams");
+    return Status(error::MUXER_FAILURE,
+                  "Incorrect streams given to WebVTT muxer");
   }
 
   // Only initialize the stream once we see a cue to avoid empty files.
@@ -39,9 +34,10 @@ Status WebVttMuxer::InitializeMuxer() {
                                  streams()[0]->time_scale(),
                                  MuxerListener::kContainerText);
 
-  buffer_.reset(
+  auto* stream = static_cast<const TextStreamInfo*>(streams()[0].get());
-      new WebVttFileBuffer(options().transport_stream_timestamp_offset_ms,
+  const std::string preamble = WebVttGetPreamble(*stream);
-                           ToString(streams()[0]->codec_config())));
+  buffer_.reset(new WebVttFileBuffer(
+      options().transport_stream_timestamp_offset_ms, preamble));
   last_cue_ms_ = 0;
 
   return Status::OK;

packager/media/formats/webvtt/webvtt_parser.cc

@@ -95,6 +95,24 @@ bool ParsePercent(const std::string& str, float* value) {
   return true;
 }
 
+bool ParseDoublePercent(const std::string& str, float* a, float* b) {
+  std::regex re(R"((\d+(?:\.\d+)?)%,(\d+(?:\.\d+)?)%)");
+  std::smatch match;
+  if (!std::regex_match(str, match, re)) {
+    return false;
+  }
+
+  double tempA, tempB;
+  base::StringToDouble(match[1], &tempA);
+  base::StringToDouble(match[2], &tempB);
+  if (tempA >= 100 || tempB >= 100) {
+    return false;
+  }
+  *a = tempA;
+  *b = tempB;
+  return true;
+}
+
 void ParseSettings(const std::string& id,
                    const std::string& value,
                    TextSettings* settings) {
@@ -174,12 +192,6 @@ void ParseSettings(const std::string& id,
   }
 }
 
-void UpdateConfig(const std::vector<std::string>& block, std::string* config) {
-  if (!config->empty())
-    *config += "\n\n";
-  *config += base::JoinString(block, "\n");
-}
-
 }  // namespace
 
 WebVttParser::WebVttParser() {}
@@ -250,7 +262,11 @@ bool WebVttParser::ParseBlock(const std::vector<std::string>& block) {
       LOG(WARNING)
           << "Found style block after seeing cue. Ignoring style block";
     } else {
-      UpdateConfig(block, &style_region_config_);
+      for (size_t i = 1; i < block.size(); i++) {
+        if (!css_styles_.empty())
+          css_styles_ += "\n";
+        css_styles_ += block[i];
+      }
     }
     return true;
   }
@@ -260,10 +276,10 @@ bool WebVttParser::ParseBlock(const std::vector<std::string>& block) {
     if (saw_cue_) {
       LOG(WARNING)
           << "Found region block after seeing cue. Ignoring region block";
-    } else {
-      UpdateConfig(block, &style_region_config_);
-    }
       return true;
+    } else {
+      return ParseRegion(block);
+    }
   }
 
   // CUE with ID
@@ -284,6 +300,93 @@ bool WebVttParser::ParseBlock(const std::vector<std::string>& block) {
   return false;
 }
 
+bool WebVttParser::ParseRegion(const std::vector<std::string>& block) {
+  TextRegion region;
+  std::string region_id;
+  // Fill in defaults.  Some may already be this, but set them anyway.
+  // See https://www.w3.org/TR/webvtt1/#regions
+  region.width.value = 100;
+  region.width.type = TextUnitType::kPercent;
+  region.height.value = 3;
+  region.height.type = TextUnitType::kLines;
+  region.window_anchor_x.value = 0;
+  region.window_anchor_x.type = TextUnitType::kPercent;
+  region.window_anchor_y.value = 100;
+  region.window_anchor_y.type = TextUnitType::kPercent;
+  region.region_anchor_x.value = 0;
+  region.region_anchor_x.type = TextUnitType::kPercent;
+  region.region_anchor_y.value = 100;
+  region.region_anchor_y.type = TextUnitType::kPercent;
+
+  bool first = true;
+  for (const auto& line : block) {
+    // First line is "REGION", skip.
+    if (first) {
+      first = false;
+      continue;
+    }
+
+    base::StringPairs pairs;
+    if (!base::SplitStringIntoKeyValuePairs(line, ':', ' ', &pairs)) {
+      LOG(ERROR) << "Invalid WebVTT settings: " << line;
+      return false;
+    }
+    for (const auto& pair : pairs) {
+      const std::string& value = pair.second;
+      if (pair.first == "id") {
+        if (value.find("-->") != std::string::npos) {
+          LOG(ERROR) << "Invalid WebVTT REGION ID: " << value;
+          return false;
+        }
+        if (regions_.find(value) != regions_.end()) {
+          LOG(ERROR) << "Duplicate WebVTT REGION: " << value;
+          return false;
+        }
+        region_id = value;
+      } else if (pair.first == "width") {
+        if (!ParsePercent(value, &region.width.value)) {
+          LOG(ERROR) << "Invalid WebVTT REGION width: " << value;
+          return false;
+        }
+      } else if (pair.first == "lines") {
+        unsigned int temp;
+        if (!base::StringToUint(value, &temp)) {
+          LOG(ERROR) << "Invalid WebVTT REGION lines: " << value;
+          return false;
+        }
+        region.height.value = temp;
+      } else if (pair.first == "regionanchor") {
+        if (!ParseDoublePercent(value, &region.region_anchor_x.value,
+                                &region.region_anchor_y.value)) {
+          LOG(ERROR) << "Invalid WebVTT REGION regionanchor: " << value;
+          return false;
+        }
+      } else if (pair.first == "viewportanchor") {
+        if (!ParseDoublePercent(value, &region.window_anchor_x.value,
+                                &region.window_anchor_y.value)) {
+          LOG(ERROR) << "Invalid WebVTT REGION windowanchor: " << value;
+          return false;
+        }
+      } else if (pair.first == "scroll") {
+        if (value != "up") {
+          LOG(ERROR) << "Invalid WebVTT REGION scroll: " << value;
+          return false;
+        }
+        region.scroll = true;
+      } else {
+        LOG(ERROR) << "Unknown WebVTT REGION setting: " << pair.first;
+        return false;
+      }
+    }
+  }
+  if (region_id.empty()) {
+    LOG(ERROR) << "WebVTT REGION id is required";
+    return false;
+  }
+  regions_.insert(std::make_pair(region_id, std::move(region)));
+  return true;
+}
+
 bool WebVttParser::ParseCueWithNoId(const std::vector<std::string>& block) {
   return ParseCue("", block.data(), block.size());
 }
@@ -378,10 +481,14 @@ void WebVttParser::DispatchTextStreamInfo() {
   // The language of the stream will be overwritten by the Demuxer later.
   const char kNoLanguage[] = "";
 
-  std::vector<std::shared_ptr<StreamInfo>> streams;
+  const auto stream = std::make_shared<TextStreamInfo>(
-  streams.emplace_back(std::make_shared<TextStreamInfo>(
+      kTrackId, kTimescale, kDuration, kCodecWebVtt, kWebVttCodecString, "",
-      kTrackId, kTimescale, kDuration, kCodecWebVtt, kWebVttCodecString,
+      kNoWidth, kNoHeight, kNoLanguage);
-      style_region_config_, kNoWidth, kNoHeight, kNoLanguage));
+  stream->set_css_styles(css_styles_);
+  for (const auto& pair : regions_)
+    stream->AddRegion(pair.first, pair.second);
+
+  std::vector<std::shared_ptr<StreamInfo>> streams{stream};
   init_cb_.Run(streams);
 }
 

packager/media/formats/webvtt/webvtt_parser.h

@@ -7,10 +7,13 @@
 #ifndef PACKAGER_MEDIA_FORMATS_WEBVTT_WEBVTT_PARSER_H_
 #define PACKAGER_MEDIA_FORMATS_WEBVTT_WEBVTT_PARSER_H_
 
+#include <map>
 #include <string>
 #include <vector>
 
 #include "packager/media/base/media_parser.h"
+#include "packager/media/base/text_sample.h"
+#include "packager/media/base/text_stream_info.h"
 #include "packager/media/formats/webvtt/text_readers.h"
 
 namespace shaka {
@@ -31,6 +34,7 @@ class WebVttParser : public MediaParser {
  private:
   bool Parse();
   bool ParseBlock(const std::vector<std::string>& block);
+  bool ParseRegion(const std::vector<std::string>& block);
   bool ParseCueWithNoId(const std::vector<std::string>& block);
   bool ParseCueWithId(const std::vector<std::string>& block);
   bool ParseCue(const std::string& id,
@@ -43,7 +47,8 @@ class WebVttParser : public MediaParser {
   NewTextSampleCB new_text_sample_cb_;
 
   BlockReader reader_;
-  std::string style_region_config_;
+  std::map<std::string, TextRegion> regions_;
+  std::string css_styles_;
   bool saw_cue_ = false;
   bool stream_info_dispatched_ = false;
   bool initialized_ = false;

packager/media/formats/webvtt/webvtt_parser_unittest.cc

@@ -4,12 +4,13 @@
 // license that can be found in the LICENSE file or at
 // https://developers.google.com/open-source/licenses/bsd
 
+#include "packager/media/formats/webvtt/webvtt_parser.h"
+
 #include <gtest/gtest.h>
 
 #include "packager/base/bind.h"
 #include "packager/media/base/stream_info.h"
 #include "packager/media/base/text_sample.h"
-#include "packager/media/formats/webvtt/webvtt_parser.h"
 
 namespace shaka {
 namespace media {
@@ -20,10 +21,6 @@ const uint32_t kTimeScale = 1000;
 
 const char* kNoId = "";
 
-std::string ToString(const std::vector<uint8_t>& v) {
-  return std::string(v.begin(), v.end());
-}
-
 void ExpectNoStyle(const TextFragmentStyle& style) {
   EXPECT_FALSE(style.underline);
   EXPECT_FALSE(style.bold);
@@ -210,7 +207,7 @@ TEST_F(WebVttParserTest, ParseOneCue) {
   EXPECT_EQ(settings.text_alignment, TextAlignment::kCenter);
 }
 
-TEST_F(WebVttParserTest, ParseOneCueWithStyleAndRegion) {
+TEST_F(WebVttParserTest, ParseOneCueWithStyle) {
   const uint8_t text[] =
       "WEBVTT\n"
       "\n"
@@ -219,7 +216,7 @@ TEST_F(WebVttParserTest, ParseOneCueWithStyleAndRegion) {
       "\n"
       "REGION\n"
       "id:scroll\n"
-      "scrol:up\n"
+      "scroll:up\n"
       "\n"
       "00:01:00.000 --> 01:00:00.000\n"
       "subtitle\n";
@@ -231,14 +228,9 @@ TEST_F(WebVttParserTest, ParseOneCueWithStyleAndRegion) {
 
   ASSERT_EQ(streams_.size(), 1u);
   ASSERT_EQ(samples_.size(), 1u);
+  auto* stream = static_cast<const TextStreamInfo*>(streams_[0].get());
 
-  EXPECT_EQ(ToString(streams_[0]->codec_config()),
+  EXPECT_EQ(stream->css_styles(), "::cue { color:lime }");
-            "STYLE\n"
-            "::cue { color:lime }\n"
-            "\n"
-            "REGION\n"
-            "id:scroll\n"
-            "scrol:up");
   EXPECT_EQ(samples_[0]->id(), kNoId);
   EXPECT_EQ(samples_[0]->start_time(), 60000u);
   EXPECT_EQ(samples_[0]->duration(), 3540000u);
@@ -314,7 +306,7 @@ TEST_F(WebVttParserTest, ParseOneEmptyCueWithId) {
   ExpectPlainCueWithBody(samples_[0]->body(), "");
 }
 
-TEST_F(WebVttParserTest, ParseOneCueWithSettings) {
+TEST_F(WebVttParserTest, ParseSettingSize) {
   const uint8_t text[] =
       "WEBVTT\n"
       "\n"
@@ -360,6 +352,46 @@ TEST_F(WebVttParserTest, ParseOneCueWithManySettings) {
   EXPECT_EQ(samples_[0]->settings().line->value, 5.0f);
 }
 
+TEST_F(WebVttParserTest, ParseRegions) {
+  const uint8_t text[] =
+      "WEBVTT\n"
+      "\n"
+      "REGION\n"
+      "id:foo\n"
+      "width:20%\n"
+      "lines:6\n"
+      "viewportanchor:25%,75%\n"
+      "scroll:up\n"
+      "\n"
+      "00:01:00.000 --> 01:00:00.000 region:foo\n"
+      "subtitle\n";
+
+  ASSERT_NO_FATAL_FAILURE(SetUpAndInitialize());
+
+  ASSERT_TRUE(parser_->Parse(text, sizeof(text) - 1));
+  ASSERT_TRUE(parser_->Flush());
+
+  ASSERT_EQ(streams_.size(), 1u);
+  ASSERT_EQ(samples_.size(), 1u);
+
+  auto* stream = static_cast<const TextStreamInfo*>(streams_[0].get());
+  const auto& regions = stream->regions();
+  ASSERT_EQ(regions.size(), 1u);
+  ASSERT_EQ(regions.count("foo"), 1u);
+
+  EXPECT_EQ(samples_[0]->settings().region, "foo");
+  const auto& region = regions.at("foo");
+  EXPECT_EQ(region.width.value, 20.0f);
+  EXPECT_EQ(region.width.type, TextUnitType::kPercent);
+  EXPECT_EQ(region.height.value, 6.0f);
+  EXPECT_EQ(region.height.type, TextUnitType::kLines);
+  EXPECT_EQ(region.window_anchor_x.value, 25.0f);
+  EXPECT_EQ(region.window_anchor_x.type, TextUnitType::kPercent);
+  EXPECT_EQ(region.window_anchor_y.value, 75.0f);
+  EXPECT_EQ(region.window_anchor_y.type, TextUnitType::kPercent);
+  EXPECT_TRUE(region.scroll);
+}
+
 // Verify that a typical case with mulitple cues work.
 TEST_F(WebVttParserTest, ParseMultipleCues) {
   const uint8_t text[] =

packager/media/formats/webvtt/webvtt_utils.cc

@@ -10,6 +10,7 @@
 #include <inttypes.h>
 
 #include <regex>
+#include <unordered_set>
 
 #include "packager/base/logging.h"
 #include "packager/base/strings/string_number_conversions.h"
@@ -260,5 +261,49 @@ std::string WebVttFragmentToString(const TextFragment& fragment) {
   return WriteFragment(fragment, &tags);
 }
 
+std::string WebVttGetPreamble(const TextStreamInfo& stream_info) {
+  std::string ret;
+  for (const auto& pair : stream_info.regions()) {
+    if (!ret.empty()) {
+      ret += "\n\n";
+    }
+
+    if (pair.second.width.type != TextUnitType::kPercent ||
+        pair.second.height.type != TextUnitType::kLines ||
+        pair.second.window_anchor_x.type != TextUnitType::kPercent ||
+        pair.second.window_anchor_y.type != TextUnitType::kPercent ||
+        pair.second.region_anchor_x.type != TextUnitType::kPercent ||
+        pair.second.region_anchor_y.type != TextUnitType::kPercent) {
+      LOG(WARNING) << "Unsupported unit type in WebVTT region";
+      continue;
+    }
+
+    base::StringAppendF(
+        &ret,
+        "REGION\n"
+        "id:%s\n"
+        "width:%f%%\n"
+        "lines:%d\n"
+        "viewportanchor:%f%%,%f%%\n"
+        "regionanchor:%f%%,%f%%",
+        pair.first.c_str(), pair.second.width.value,
+        static_cast<int>(pair.second.height.value),
+        pair.second.window_anchor_x.value, pair.second.window_anchor_y.value,
+        pair.second.region_anchor_x.value, pair.second.region_anchor_y.value);
+    if (pair.second.scroll) {
+      ret += "\nscroll:up";
+    }
+  }
+
+  if (!stream_info.css_styles().empty()) {
+    if (!ret.empty()) {
+      ret += "\n\n";
+    }
+    ret += "STYLE\n" + stream_info.css_styles();
+  }
+
+  return ret;
+}
+
 }  // namespace media
 }  // namespace shaka

packager/media/formats/webvtt/webvtt_utils.h

@@ -15,6 +15,7 @@
 
 #include "packager/base/strings/string_piece.h"
 #include "packager/media/base/text_sample.h"
+#include "packager/media/base/text_stream_info.h"
 
 namespace shaka {
 namespace media {
@@ -33,6 +34,10 @@ std::string WebVttSettingsToString(const TextSettings& settings);
 /// Converts the given TextFragment to a WebVTT cue body string.
 std::string WebVttFragmentToString(const TextFragment& fragment);
 
+/// Converts the common fields in the stream into WebVTT text.  This pulls out
+/// the REGION and STYLE blocks.
+std::string WebVttGetPreamble(const TextStreamInfo& stream_info);
+
 }  // namespace media
 }  // namespace shaka
 

packager/media/formats/webvtt/webvtt_utils_unittest.cc

@@ -224,5 +224,99 @@ TEST(WebVttUtilsTest, FragmentToString_HandlesNestedNewlinesWithStyle) {
   EXPECT_EQ(WebVttFragmentToString(frag), "<b>Hello</b>\n<b>World Now</b>");
 }
 
+TEST(WebVttUtilsTest, GetPreamble_BasicFlow) {
+  TextStreamInfo info(0, 0, 0, kCodecWebVtt, "", "", 0, 0, "");
+  info.set_css_styles("::cue { color: red; }");
+
+  TextRegion region;
+  region.width.value = 34;
+  region.height = TextNumber(56, TextUnitType::kLines);
+  region.window_anchor_x.value = 99;
+  region.window_anchor_y.value = 12;
+  region.region_anchor_x.value = 41;
+  region.region_anchor_y.value = 29;
+  info.AddRegion("foo", region);
+
+  EXPECT_EQ(WebVttGetPreamble(info),
+            "REGION\n"
+            "id:foo\n"
+            "width:34.000000%\n"
+            "lines:56\n"
+            "viewportanchor:99.000000%,12.000000%\n"
+            "regionanchor:41.000000%,29.000000%\n"
+            "\n"
+            "STYLE\n"
+            "::cue { color: red; }");
+}
+
+TEST(WebVttUtilsTest, GetPreamble_MultipleRegions) {
+  TextStreamInfo info(0, 0, 0, kCodecWebVtt, "", "", 0, 0, "");
+
+  TextRegion region1;
+  region1.width.value = 34;
+  region1.height = TextNumber(56, TextUnitType::kLines);
+  region1.window_anchor_x.value = 99;
+  region1.window_anchor_y.value = 12;
+  region1.region_anchor_x.value = 41;
+  region1.region_anchor_y.value = 29;
+  info.AddRegion("r1", region1);
+
+  TextRegion region2;
+  region2.width.value = 82;
+  region2.height = TextNumber(61, TextUnitType::kLines);
+  region2.window_anchor_x.value = 51;
+  region2.window_anchor_y.value = 62;
+  region2.region_anchor_x.value = 92;
+  region2.region_anchor_y.value = 78;
+  info.AddRegion("r2", region2);
+
+  EXPECT_EQ(WebVttGetPreamble(info),
+            "REGION\n"
+            "id:r1\n"
+            "width:34.000000%\n"
+            "lines:56\n"
+            "viewportanchor:99.000000%,12.000000%\n"
+            "regionanchor:41.000000%,29.000000%\n"
+            "\n"
+            "REGION\n"
+            "id:r2\n"
+            "width:82.000000%\n"
+            "lines:61\n"
+            "viewportanchor:51.000000%,62.000000%\n"
+            "regionanchor:92.000000%,78.000000%");
+}
+
+TEST(WebVttUtilsTest, GetPreamble_Scroll) {
+  TextStreamInfo info(0, 0, 0, kCodecWebVtt, "", "", 0, 0, "");
+
+  TextRegion region;
+  region.width.value = 37;
+  region.height = TextNumber(82, TextUnitType::kLines);
+  region.window_anchor_x.value = 32;
+  region.window_anchor_y.value = 66;
+  region.region_anchor_x.value = 95;
+  region.region_anchor_y.value = 72;
+  region.scroll = true;
+  info.AddRegion("foo", region);
+
+  EXPECT_EQ(WebVttGetPreamble(info),
+            "REGION\n"
+            "id:foo\n"
+            "width:37.000000%\n"
+            "lines:82\n"
+            "viewportanchor:32.000000%,66.000000%\n"
+            "regionanchor:95.000000%,72.000000%\n"
+            "scroll:up");
+}
+
+TEST(WebVttUtilsTest, GetPreamble_OnlyStyles) {
+  TextStreamInfo info(0, 0, 0, kCodecWebVtt, "", "", 0, 0, "");
+  info.set_css_styles("::cue { color: red; }");
+
+  EXPECT_EQ(WebVttGetPreamble(info),
+            "STYLE\n"
+            "::cue { color: red; }");
+}
+
 }  // namespace media
 }  // namespace shaka