Motown: Add examples/media_test, a command line media player app.

examples/media_test/media_test.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "examples/media_test/media_test.h"
+#include "mojo/services/media/common/cpp/linear_transform.h"
+#include "mojo/services/media/common/cpp/local_time.h"
+#include "mojo/services/media/control/interfaces/media_factory.mojom.h"
+
+namespace examples {
+
+// static
+std::unique_ptr<MediaTest> MediaTest::Create(
+    mojo::ApplicationImpl* app,
+    const std::string& input_file_name) {
+  return std::unique_ptr<MediaTest>(new MediaTest(app, input_file_name));
+}
+
+MediaTest::MediaTest(
+    mojo::ApplicationImpl* app,
+    const std::string& input_file_name) :
+    state_(mojo::media::MediaState::UNPREPARED) {
+  mojo::media::MediaFactoryPtr factory;
+  app->ConnectToService("mojo:media_factory", &factory);
+
+  factory->CreatePlayer(input_file_name, GetProxy(&media_player_));
+
+  HandleStatusUpdates();
+}
+
+MediaTest::~MediaTest() {}
+
+void MediaTest::RegisterUpdateCallback(const UpdateCallback& callback) {
+  update_callback_ = callback;
+}
+
+void MediaTest::Play() {
+  media_player_->Play();
+}
+
+void MediaTest::Pause() {
+  media_player_->Pause();
+}
+
+void MediaTest::Seek(int64_t position_ns) {
+  media_player_->Seek(position_ns);
+}
+
+mojo::media::MediaState MediaTest::state() const {
+  return state_;
+}
+
+int64_t MediaTest::position_ns() const {
+  if (!transform_) {
+    return 0;
+  }
+
+  // Create a linear transform that translates local time to presentation time.
+  // Note that 'reference' here refers to the presentation time, and 'target'
+  // refers to the local time.
+  mojo::media::LinearTransform transform(

[johngro, 2016/03/21 22:10:46]

transform_ does not appear to be getting used for much of anything else at the
moment.  As a minor optimization, consider making transform_ a LinearTransform
which gets reset during HandleStatusUpdate.  This will remove the need to reduce
the rate fraction every time position_ns gets called.

Also, if the LinearTransform instance gets initialized to 0 + 0/1 + 0, you don't
need to special case not having received a HandleStatusUpdate callback yet.

[dalesat, 2016/03/21 23:58:35]

Done.

+      transform_->quad->target_offset,
+      transform_->quad->reference_delta,
+      transform_->quad->target_delta,
+      transform_->quad->reference_offset);
+
+  // Apply the transform to the current time.
+  int64_t position;
+  transform.DoForwardTransform(
+      mojo::media::LocalClock::now().time_since_epoch().count(),
+      &position);
+
+  return position;

[johngro, 2016/03/21 22:10:46]

if you have an idea of what the asset's duration is, you should cap the reported
position to be <= the asset duration.

[dalesat, 2016/03/21 23:58:35]

Done.

+}
+
+const mojo::media::MediaMetadataPtr& MediaTest::metadata() const {
+  return metadata_;
+}
+
+void MediaTest::HandleStatusUpdates(
+    uint64_t version,
+    mojo::media::MediaPlayerStatusPtr status) {
+  if (status) {
+    // Process status received from the player.
+    state_ = status->state;
+    transform_ = status->timeline_transform.Pass();
+    metadata_ = status->metadata.Pass();
+    if (update_callback_ != nullptr) {
+      update_callback_();
+    }
+  }
+
+  // Request a status update.
+  media_player_->GetStatus(
+      version,
+      [this](uint64_t version, mojo::media::MediaPlayerStatusPtr status) {
+        HandleStatusUpdates(version, status.Pass());
+      });
+}
+
+}  // namespace examples