Support for parsing encrypted WebM streams by src.

media/webm/webm_crypto_helpers.h

+// Copyright (c) 2013 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.
+
+#ifndef MEDIA_WEBM_WEBM_CRYPTO_HELPERS_H_
+#define MEDIA_WEBM_WEBM_CRYPTO_HELPERS_H_
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "media/base/decoder_buffer.h"
+
+namespace media {
+
+// TODO(xhwang): Figure out the init data type appropriately once it's spec'ed.

[ddorwin, 2013/03/10 21:29:39]

You could link to https://www.w3.org/Bugs/Public/show_bug.cgi?id=19096

[fgalligan1, 2013/03/12 00:42:42]

Done.

+const char kWebMEncryptInitDataType[] = "video/webm";
+

[ddorwin, 2013/03/10 21:29:39]

Should some of the existing Chunk Demuxer code be updated to use these?

[fgalligan1, 2013/03/12 00:42:42]

Done.

+// Generates a 16 byte CTR counter block. The CTR counter block format is a
+// CTR IV appended with a CTR block counter. |iv| is an 8 byte CTR IV.
+// |iv_size| is the size of |iv| in btyes. Returns a string of
+// kDecryptionKeySize bytes.
+std::string GenerateWebMCounterBlock(const uint8* iv, int iv_size);

[ddorwin, 2013/03/10 21:29:39]

This is not currently used outside the .cc file.

[fgalligan1, 2013/03/12 00:42:42]

Done.

+
+// Returns an initialized DecryptConfig, which can be sent to the Decryptor if
+// the stream has potentially encrypted frames. Every encrypted Block has a
+// signal byte, and if the frame is encrypted an IV, prepended to the frame.
+// Leaving the initialization vector empty will tell the decryptor that the
+// frame is unencrypted. Current encrypted WebM request for comments
+// specification is here
+// http://wiki.webmproject.org/encryption/webm-encryption-rfc
+scoped_ptr<DecryptConfig> WebMCreateDecryptConfig(
+    const uint8* data, int data_size,
+    const uint8* key_id, int key_id_size);
+
+}  // namespace media
+
+#endif  // MEDIA_WEBM_WEBM_CRYPT_HELPERS_H_