1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef MEDIA_BASE_DECRYPT_CONFIG_H_ 6 #define MEDIA_BASE_DECRYPT_CONFIG_H_ 7 8 #include <string> 9 #include <vector> 10 11 #include "base/basictypes.h" 12 #include "base/memory/scoped_ptr.h" 13 #include "media/base/media_export.h" 14 15 namespace media { 16 17 // The Common Encryption spec provides for subsample encryption, where portions 18 // of a sample are set in cleartext. A SubsampleEntry specifies the number of 19 // clear and encrypted bytes in each subsample. For decryption, all of the 20 // encrypted bytes in a sample should be considered a single logical stream, 21 // regardless of how they are divided into subsamples, and the clear bytes 22 // should not be considered as part of decryption. This is logically equivalent 23 // to concatenating all 'cypher_bytes' portions of subsamples, decrypting that 24 // result, and then copying each byte from the decrypted block over the 25 // position of the corresponding encrypted byte. 26 struct SubsampleEntry { 27 uint32 clear_bytes; 28 uint32 cypher_bytes; 29 }; 30 31 // Contains all information that a decryptor needs to decrypt a media sample. 32 class MEDIA_EXPORT DecryptConfig { 33 public: 34 // Keys are always 128 bits. 35 static const int kDecryptionKeySize = 16; 36 37 // |key_id| is the ID that references the decryption key for this sample. 38 // |iv| is the initialization vector defined by the encrypted format. 39 // Currently |iv| must be 16 bytes as defined by WebM and ISO. Or must be 40 // empty which signals an unencrypted frame. 41 // |data_offset| is the amount of data that should be discarded from the 42 // head of the sample buffer before applying subsample information. A 43 // decrypted buffer will be shorter than an encrypted buffer by this amount. 44 // |subsamples| defines the clear and encrypted portions of the sample as 45 // described above. A decrypted buffer will be equal in size to the sum 46 // of the subsample sizes. 47 // 48 // |data_offset| is applied before |subsamples|. 49 DecryptConfig(const std::string& key_id, 50 const std::string& iv, 51 const int data_offset, 52 const std::vector<SubsampleEntry>& subsamples); 53 ~DecryptConfig(); 54 55 const std::string& key_id() const { return key_id_; } 56 const std::string& iv() const { return iv_; } 57 int data_offset() const { return data_offset_; } 58 const std::vector<SubsampleEntry>& subsamples() const { return subsamples_; } 59 60 private: 61 const std::string key_id_; 62 63 // Initialization vector. 64 const std::string iv_; 65 66 // TODO(fgalligan): Remove |data_offset_| if there is no plan to use it in 67 // the future. 68 // Amount of data to be discarded before applying subsample information. 69 const int data_offset_; 70 71 // Subsample information. May be empty for some formats, meaning entire frame 72 // (less data ignored by data_offset_) is encrypted. 73 const std::vector<SubsampleEntry> subsamples_; 74 75 DISALLOW_COPY_AND_ASSIGN(DecryptConfig); 76 }; 77 78 } // namespace media 79 80 #endif // MEDIA_BASE_DECRYPT_CONFIG_H_ 81
