Add Common Encryption support to BMFF, including subsample decryption.

media/base/decrypt_config.h

 // 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.
 
 #ifndef MEDIA_BASE_DECRYPT_CONFIG_H_
 #define MEDIA_BASE_DECRYPT_CONFIG_H_
 
+#include <vector>

[xhwang, 2012/06/27 19:37:43]

nit: usually we have empty line after including c++ system files.

[strobe_, 2012/07/13 00:47:07]

Done.

[strobe_, 2012/07/13 00:47:07]

Done.

 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "media/base/media_export.h"
 
 namespace media {
 
+struct SubsampleEntry {
+  int clear_bytes;
+  int cypher_bytes;
+};
+

[xhwang, 2012/06/27 19:37:43]

Can we have more docs on this? Ideally, people should be able to implement the
decryptor only by looking at this file, not any specific container spec.

[ddorwin, 2012/07/03 21:03:47]

Docs on what? DecryptConfig, the parameters, or CENC?

[xhwang, 2012/07/03 21:17:12]

About SubsampleEntry.

[strobe_, 2012/07/13 00:47:07]

Done.

 // Contains all information that a decryptor needs to decrypt.
 class MEDIA_EXPORT DecryptConfig {
  public:
-  explicit DecryptConfig(const uint8* key_id, int key_id_size);
+  DecryptConfig(const uint8* key_id, int key_id_size,
+                const uint8* iv, int iv_size,
+                const SubsampleEntry* subsamples, int subsample_count);

[xhwang, 2012/06/27 19:37:43]

Can we just pass const std::vector<SubsampleEntry>& in?

[ddorwin, 2012/07/03 21:03:47]

Agreed, especially since we store and return it as a vector now.

[strobe_, 2012/07/13 00:47:07]

Done.

+
+  // TODO(strobe): This constructor implicitly sets CBC mode and uses a default
+  // IV, to preserve compatibility with an early implementation. It should be
+  // removed, along with CBC mode and the default IV, when
+  // https://chromiumcodereview.appspot.com/10535029 lands.
+  DecryptConfig(const uint8* key_id, int key_id_size);
+
   ~DecryptConfig();
 
   const uint8* key_id() const { return key_id_.get(); }
   int key_id_size() const { return key_id_size_; }
+  const uint8* iv() const { return iv_.get(); }
+  int iv_size() const { return iv_size_; }

[xhwang, 2012/06/27 19:37:43]

We have a plan to replace scoped_array with std::string (or vector) for key_id
and key since they
are relatively small (see
http://code.google.com/p/chromium/issues/detail?id=130689).

Similarly, I would be fine to use std::string for the IV if it's always small.

ddorwin@, what do you think?

+  const std::vector<SubsampleEntry>& subsamples() const { return subsamples_; }
+  bool use_cbc() const { return use_cbc_; }
+
+  std::vector<SubsampleEntry>* mutable_subsamples() { return &subsamples_; }
 
  private:
   scoped_array<uint8> key_id_;
   int key_id_size_;
+  scoped_array<uint8> iv_;
+  int iv_size_;
+  std::vector<SubsampleEntry> subsamples_;
+  // TODO(strobe): Remove when CBC is no longer used.
+  bool use_cbc_;
 
   DISALLOW_COPY_AND_ASSIGN(DecryptConfig);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_DECRYPT_CONFIG_H_