Initial implementation of Encrypted Media Extensions in Chrome.

webkit/media/key_systems.cc

+// Copyright (c) 2012 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 "webkit/media/key_systems.h"
+
+#include "third_party/WebKit/Source/WebKit/chromium/public/platform/WebString.h"
+
+namespace webkit_media {
+
+namespace key_systems {
+
+namespace {
+
+const char kClearKeyKeySystem[] = "webkit-org.w3.clearkey";

[darin (slow to review), 2012/04/18 23:57:40]

nit: should we be concerned about claiming "webkit.org" namespaced entities in
the chromium repository?  i'm not sure what this really means, who decides what
this string means, or how it is specified by content authors.

[ddorwin, 2012/04/19 00:52:54]

This is really a "webkit-" prefix to "org.w3.clearkey". The latter is part of
the EME proposal but I prefixed it (similar to the methods) since this yet an
official draft.

The WebKit layout tests use this string. However, the implementation of the key
systems is (likely to be) in the ports.

+
+struct MediaFormatAndKeySystem {
+  const char* mime_type;
+  const char* codec;
+  const char* key_system;
+};
+
+static const MediaFormatAndKeySystem
+supported_format_key_system_combinations[] = {
+  // TODO(ddorwin): Reconsider based on how usage of this class evolves.
+  // For now, this class is stateless, so we do not have the opportunity to
+  // build a list using ParseCodecString() like MimeUtil. Therfore, the

[darin (slow to review), 2012/04/18 23:57:40]

does "MimeUtil" in this comment refer to net/base/mime_util.cc?  may be good to
clarify.

[ddorwin, 2012/04/19 00:52:54]

Done.

+  // following line must be separate entries.
+  // { "video/webm", "vorbis,vp8,vp8.0", kClearKeyKeySystem },
+  { "video/webm", "vorbis", kClearKeyKeySystem },

[darin (slow to review), 2012/04/18 23:57:40]

do you intend for there to be other key_system values in the future?  this
currently seems like gratuitous infrastructure when the only valid key_system is
kClearKeyKeySystem.

[ddorwin, 2012/04/19 00:52:54]

Yes. We will add to this table when we add new key systems/CDMs.

+  { "video/webm", "vp8", kClearKeyKeySystem },
+  { "video/webm", "vp8.0", kClearKeyKeySystem },
+  { "audio/webm", "vorbis", kClearKeyKeySystem },
+  { "video/webm", "", kClearKeyKeySystem },
+  { "audio/webm", "", kClearKeyKeySystem }
+};
+
+bool IsSupportedKeySystemWithContainerAndCodec(const std::string& mime_type,
+                                               const std::string& codec,
+                                               const std::string& key_system) {
+  for (size_t i = 0;
+       i < arraysize(supported_format_key_system_combinations);
+       ++i) {
+    const MediaFormatAndKeySystem& combination =
+        supported_format_key_system_combinations[i];
+    if (combination.mime_type == mime_type &&
+        combination.codec == codec &&
+        combination.key_system == key_system)
+      return true;
+  }
+
+  return false;
+}
+
+}  // namespace
+
+bool IsSupportedKeySystem(const WebKit::WebString& key_system) {
+  if (key_system == kClearKeyKeySystem)
+    return true;
+  return false;
+}
+
+bool IsSupportedKeySystemWithMediaMimeType(
+    const std::string& mime_type,
+    const std::vector<std::string>& codecs,
+    const std::string& key_system) {
+  if (codecs.empty())
+    return IsSupportedKeySystemWithContainerAndCodec(mime_type, "", key_system);
+
+  for (size_t i = 0; i < codecs.size(); ++i) {
+    if (!IsSupportedKeySystemWithContainerAndCodec(
+            mime_type, codecs[i], key_system))
+      return false;
+  }
+
+  return true;
+}
+
+}  // namespace key_systems
+
+}  // namespace webkit_media